Hardening processes of glues

The difference in use of various glues can be influenced by their hardening process. For instance, water-based glues function by dehydration (water evaporates slowly or diffuses into the material). Solvent-based glues harden by evaporation of the solvent. Two-component glues function by chemical reaction, similar to certain one-component glues where UV-light is a catalyst in the chemical reaction. In addition, there are pressure bindings (contact glue) and hot melts.

The hardening process plays a major role in how a subject may be exposed to the chemicals present in that glue and is therefore considered in the following paragraphs.

Categorisation of glues

In Table 6, glues are categorised according to their main purpose (please note that this is not a complete list of glues). Exposure to glues and its constituents can also be categorised according to the way the glues are used, and hence to user exposure (e.g., grouping all tube glues into one category). In most cases, however, there are several alternatives for a specific task. At the same time, multi-purpose glues can also be used for various tasks. Describing a single default for such a glue would not cover all uses. It is therefore necessary to think carefully about the task, the type of glue, and its container before a default scenario is selected to determine exposure to that glue.

For this Fact Sheet, glues have been categorised on the basis of their container type. By grouping glues this way, glues are also grouped in terms of exposure and use. This is an alternative categorisation to the one shown in Table 6. For example, universal glues are contained in tubes, bottles, spray cans, and glue guns. The use (and hence the exposure scenario) varies for glues contained in different containers because the glues are handled differently; moreover its constituents may differ from each other. Please note that while some glues are kept in similar containers, their use is dissimilar, for example tile glue and carpet glue. In those cases, separate product categories were described. All glues are described with just a few scenarios in order to keep the Fact Sheet concise and easy to use.

The following scenarios for glues have been chosen: tube glue, bottled glue, super glue, two-component glue, wood parquet glue, carpet glue, tile glue, wallpaper glue, hot-melt adhesives, and spray glue, as described in Table 6.

Table 6

Glues sorted by purpose.

Use

Many glues are contained in (small) tubes. These glues are taken as one category since the way they are used is very similar. Hence, it is expected that the exposure is also similar. These glues are: universal glues (including hobby and household glues) and contact glue. Keep in mind that these glues may also be contained in other types of containers and do not reflect the entire segment of universal glues.

The tubes vary in size and range from 5 ml to 125 ml glue per tube. The glues are liquids or gels with moderate viscosities. They are used for many purposes, but generally for small tasks, e.g., crafting or gluing photos. The glue is simply put on the surface to be attached. It is then spread out (with a tool, finger, or the tip of the tube; not always necessary for smaller surfaces) to cover the surface and dried for a few minutes. According to the instructions on the container, one should check whether the glue will attach properly using one’s finger. Then, the other object is pushed against the surface and the objects are clamped tightly together. For somewhat smaller surfaces, simply holding the surfaces together should be sufficient.

Contact glues often require two-sided application of the glue, so that the adhesion is glue-glue. This increases the chance that an individual will be dermally exposed (assumed to be twofold).

Scenario for tube glue

In this scenario, two small objects are glued together with universal glue from a tube. The ConsExpo inhalation – exposure to vapour – evaporation – release area mode: increasing model is used to estimate inhalation exposure. Dermal exposure can occur when glues are spread out with the fingers or when excess glue is removed manually. The exposure duration will not be much longer than the application duration, because individuals will wash off glue immediately after use. The exposure is estimated using the ConsExpo dermal – direct product contact – instant application model because the task is rather small and therefore of short duration.

Frequency

Taking into account the information provided by a survey for the use frequency of universal glue by consumers, the default for this parameter is set to 36 times per year (see Annex II A.4.2). Because universal glue is assumed to be a common product distributed in tubes in the glue sector, the default seems appropriate in this scenario. A Q-factor of 2 is assigned because data is sufficient albeit limited.

Exposure duration

The period of time during which volatile compounds can evaporate may be longer than the application duration (see below) because the glue needs to harden. Assuming that a person stays in the room after use, an exposure duration of 240 minutes will be used as a default. The Q-factor is set to 1 because underpinning data is currently not available.

Product amount – inhalation

The amount of glue also depends on the surface being glued. In the report by Magré (2005), conclusions considering the product amount used per square metre were not drawn. In a consumer survey conducted in Germany in 2019, a 75^th percentile of 6 g for the used product amount was documented (see Annex II A.4.2). According to the directions for use of the products per 100 ml, a surface of 0.2 m² can be treated (see Annex II, product data collection Table 85). Assuming that a surface of 0.02 m² (small task) has to be treated with glue, 10 ml will be sufficient in this scenario. As in the consumer survey the treated surface was not further specified (e.g., size), it is assumed that considering the product information will provide a more conservative result. Therefore, this option is preferred.

Taking into account a product density of 0.9 g/cm³, the default for the product amount is set to 9 g. The Q-factor is set to 2 because there is underpinning data from the BfR market analysis for several products.

Room volume and ventilation rate

A room volume of 20 m³ and a ventilation rate of 0.6 per hour are used in this case because the room the user is working in is not specified (te Biesebeek et al., 2014).

Release area

The release area is interpreted here as the surface that is glued with the product amount used. According to the product information, 10 ml of universal glue (=9 g) is sufficient to treat an area of 200 cm², which is set as a default for this scenario. The Q-factor is set to 1 because underpinning data for this value is currently not available at the moment.

Application duration

According to an observational study about consumer use of DIY products (Magré, 2005), the average duration for a glue job for small surfaces amounts to approximately 6.5 minutes. Although this figure includes glues for other uses, it is also considered indicative for the use of tube glues. Time spent on gluing is heavily dependent on the surface area to be treated and not on what kind of glue is used (except for super glue due to its very short application time). According to information acquired during a consumer survey (including protocols), the application duration of universal glue can range from 1 minute to a maximum of 266 minutes. The 75^th percentile is 36 minutes (see Annex II A.4.2). As this value is more conservative and based on a more robust and extended data set, it is preferred here as an indicative value. Therefore, a default application duration of 36 minutes is taken into consideration. The Q-factor is set to 2 because the underpinning data is sufficient, albeit limited.

Exposed area – dermal

In general, only the fingertips of one hand are used to spread out tube glue. The surface area of one fingertip or rather one top phalanx of a finger is approximately 15 cm² (see subsection 4.1.1). It is assumed that only one side of a fingertip is used to spread out or remove the glue. Fifty percent of the surface area of one phalanx is 7.5 cm². Assuming the user applies two fingertips to this task, a dermal exposure area of 15 cm² is provided. The Q-factor is set to 1, because the underpinning data is quantitatively rich but rather compromised by the calculation in subsection 4.1.1.

Product amount – dermal

Spills can occur on the skin or while the glue is spread out. According to our own experiments (see Annex A.2), two performed trials yielded a mean of 0.06 g and a maximum of 0.09 g for the product amount on the skin. Therefore, as a conservative default, a product amount of 0.08 g is taken into account The Q-factor is set to 1 because the experiment was only conducted twice, which can provide an impression for the dimensions of the dermal product amount but is not sufficient for the default to be rated higher.

Table 8

Default values for tube glue.

Use

The bottles or jars contain glue in the range of 25 to 1000 g. In general, these glues are used for larger surfaces than tube glues. The most commonly known bottled glue is wood glue, which is used for various glue jobs ranging from small to large. The glue is easily squeezed from the bottle onto the objects and spread out with one’s finger, tool or with the nozzle. To keep the glues free from fungi and bacteria, preservatives are added. In addition, additives may be present to make the glue water-resistant. Hobby or universal glues also display a wide range of uses and are used similarly to wood glues (see Table 9).

Table 9

Possible applications of different types of bottled glue; please note that this list is not complete but can be considered in order to get an overview of possible applications (see Annex II A.5, Table 84, Table 85 and Table 86).

The exposure duration is not expected to be much longer than the one estimated for tube glues. One does not have to work precisely in this case and that saves time. Although bottled glues are taken up as one category, their uses and hence exposure may vary considerably. Therefore, two scenarios will be described with specific defaults for universal/wood glue and for construction glue, respectively.

For PVC glue (for hard plastics), no separate scenario is described. To calculate inhalation exposure, the default parameters for universal/wood glue can be used. PVC glue is applied with a brush, which is attached to the lid. Glue is applied to both ends of PVC pipes, which are then stuck together. Dermal exposure will be lower than is expected for other bottled glues and therefore considered negligible.

Scenario for universal/wood glue

The default scenario for this product category is gluing together two slides of wood. The inhalation exposure to bottled glues occurs from the (open) bottle itself, during and after application. For this task, the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: increasing and dermal – direct product contact – instant application models are used to estimate the expected exposure.

Frequency

As shown in Table 10, glues sold in bottles are mainly universal glue, wood glue, construction glue and PVC glue. Information regarding the use frequencies of universal and wood glue per year is provided in Annex II A.4.1 Table 74 Wood glue is used 6.3 times per year whereas universal glue is used up to 13 times per year. According to information acquired during a consumer survey regarding the use of universal glue, it is used up to 36 times per year (Annex II A.4.2). The latter value is used as a default for this scenario, following a more conservative approach. A Q-factor of 2 is assigned because underpinning data is sufficient albeit limited.

Exposure duration

It is expected that the individual will stay in the room after the application of the glue. A default of 240 minutes (4 hours) is stated. The Q-factor is set to 1 because underpinning data is currently not available.

Product amount – inhalation

The applied amount varies per task and the surface to be treated. According to product information 200 g wood glue are sufficient to treat a 1 m² surface (see Annex II, product data collection Table 86). For this scenario, a smaller surface of 0.05 m² is taken into account because it fits the usage pattern for wood glue from bottles. Excessively larger tasks (e.g., laying wood parquet) would be conducted using wood glue from buckets applied with a brush or a roller. For the referred surface, 10 g glue has to be used. As described in subsection 6.2, a recently conducted survey documented a used product amount of 6 g (see Annex II A.4.2). However, because the survey data was not specifically gathered for tube glue and the product information indicates a more conservative product consumption, the latter value (10 g) will be preferred as a default. The Q-factor is set to 2 because underpinning data is sufficient to derive a default, albeit limited.

Room volume and ventilation rate

Given the various types of tasks that could be conducted in nearly any indoor environment, it is assumed that a task is carried out in an unspecified room (20 m³ room volume with a ventilation rate of 0.6 per hour) (te Biesebeek et al., 2014).

Release area

The default for the used product amount is set to 10 g glue. Taking into account the results of the BfR-market analysis (see Annex II; product data collection Table 86), this relates to a surface area of 0.05 m² according to product information, which will be used as a default for the scenario. The Q-factor is set to 1 because the release area itself is an assumption and cannot be supported by underpinning data.

Application duration

According to the report by Magré (Magré, 2005), the average application duration for small surfaces is 6.5 minutes. As described previously in subsection 6.2, the results provided by a consumer survey lead to an application duration of 36 minutes (see Annex II A.4.2) for universal glue. However, in this survey, the size of the treated surface was not further specified by the users. Therefore, in accordance with the scenario for tube glue (approximately the same product amount), the default for the application duration is set at 36 minutes (estimation) for wood glue and universal/hobby glue alike. The Q-factor is set to 1 because the underpinning data by Magré (2005) and the survey (see Annex II A.4.2) are not specifically gathered for bottled/wood glue.

Exposed area – dermal

Dermal exposure occurs when the glue is spread out with one’s finger. Assuming that one uses only two fingertips of one hand, and only one side of each fingertip is exposed, a dermal exposure area of 15 cm² is used (see subsection 6.2). The Q-factor is set to 1, because the underpinning data for the surface area of a fingertip is quantitatively rich but rather compromised by the calculation in subsection 4.1.1. Furthermore, the assumption that the front side of two fingertips will be exposed is based on expert judgement.

Product amount – dermal

Spills can occur on the skin or while the glue is spread out. According to our own experiments (see Annex A.2), two performed trials yielded a mean of 0.06 g and a maximum of 0.09 g for the product amount on the skin. Therefore, as a conservative default, a product amount of 0.08 g is taken into account (see also subsection 6.2). It is assumed that the glue will be immediately removed after the task is completed. The Q-factor is set to 1 because the experiment was only conducted twice, which can provide an impression for the dimensions of the product amount but is not sufficient for the default to be rated higher.

Table 10

Default values for bottled glue: universal/wood glue.

Scenario for construction glue

Construction glue is used more often for larger tasks than wood glue, here the construction of a closet is described as the default scenario. Construction glues are often water-resistant, possess a high initial adhesion (150-200 kg/m²) and final strength, and have filling properties (up to a gap size of 20 mm), which make them suitable for specific tasks (connecting wooden or metallic plates, gluing heavy objects to a surface for example a mirror, etc.). The manner of application is different from the manner of application of wood glue. It needs more precision because removal of construction glue from surfaces is more difficult. This means that exposure is expected to be different from exposure for universal or wood glue.

Inhalation exposure may occur during application and hardening of the glue, which occurs under atmospheric humidity (reaction with water in air). Inhalation exposure is estimated using the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: increasing model. When no evaporation is expected, based on the constituents, inhalation exposure will be negligible. Dermal exposure, which is estimated using the ConsExpo dermal – direct product contact – instant application model, occurs during application of the glue, when spreading it with one’s fingers, or is caused by spills during clamping of materials.

Frequency

The frequency of these kinds of tasks is much lower in comparison to the use of universal or wood glue (e.g., for crafting) because they are far more specific and somehow more complex. A frequency of twice a year is assumed and a Q-factor of 1 is assigned because the value relies on expert judgement.

Exposure duration

Partially, the different parts of the closet have to be clamped or nailed together in order to give the glue the opportunity to harden without the parts coming apart. Such procedures take time. Additionally, assuming the user will stay in the room after he or she assembled the closet, an exposure duration of 240 minutes (4 hours) is set as a default. A Q-factor of 1 is assigned because the default relies on expert judgement.

Product amount – inhalation

Considering the area that has to be treated with glue (1 m²), a product amount of 250 g will be sufficient to fulfil the task according to the product information acquired in the BfR market analysis (see Annex II, product data collection Table 87). A Q-factor of 2 is assigned because the underpinning data is limited.

Room volume and ventilation rate

Because no room is specified to build a closet there or conduct a construction task that mainly consists of gluing, the default values for an unspecified room are set as defaults. A room size of 20 m³ and a ventilation rate of 0.6 per hour are assumed (te Biesebeek et al., 2014).

Release area

The product amount used is sufficient to treat a surface area of 1 m². Therefore, this value will be set as the default for the release area. As the dimension of the treated area (release area) is directly linked to the product consumption and vice versa, the underpinning data for the used product amount seems adequate to justify a Q-factor of 2 for the release area too.

Application duration

Assembling a closet is considered to be a rather big and complicated task even if the used product amount is comparatively low. The user has to work precisely to achieve a decent result. It is assumed that these kinds of tasks take 90 minutes of actual gluing. The Q-factor here is set to 1 because the value is based on expert judgement.

Exposed area – dermal

Dermal exposure will, in this case, occur from holding the glued materials with one hand while putting the counterpart of the closet in place and, if necessary, clamping the two parts together. This can lead to accidental contact with the applied glue and results in a potential exposed area of the palm of one hand, which equals 225 cm². The Q-factor is set to 2 because the underpinning data for the size of one palm is quantitatively rich, but the assumption that only this surface area of the hands will be exposed is based on expert judgement (see also subsection 4.5).

Product amount – dermal

According to Project in Annex II, when a palm is completely covered with glue, the amount of glue is approximately 1 g. Because the glue is hard to remove and the accompanying product information often advises wearing gloves, it can be assumed that subjects will cautious. Therefore, it is expected that the palm is only covered by 25%, hence 0.25 g is assumed as a default. The Q-factor is set to 1 since the assumption of 25% coverage relies solely on expert judgement.

Table 11

Default values for bottled glue: construction glue.

Use

Because of their high curing speed, super glues are mainly used for very small surfaces that need to be glued very securely and fast. According to information acquired during the BfR market analysis, super glues are contained in small tubes or dosage pens of 1-10 g per product (see Annex II, product data collection Table 88), which make it easy to dose small amounts of glue. An example of the use of super glue are the repairs on a mug that has lost its handle (ear). One droplet per end of the handle should be sufficient to reattach the handle to the mug. The mug and handle have to be pressed together and kept in place for a period of time ranging from a few seconds to two minutes at most. During this time, the glue polymerises to a solid synthetic resin. After 24 hours, the glue has attained its full strength. Product information warns about the fast and strong adhesive properties (super glue adheres very strongly to skin), but it is not advised to wear gloves. Furthermore, product information warns of inhalation exposure, even if the used product amount will be low, because super glues contain cyanoacrylate, which can cause irritation to the airways.

Scenario for super glue

As indicated in the prior paragraph, the reattachment of a displaced handle to a mug will be used as the default scenario for the use of super glue. Because the expected release area and product amount are very small, the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: constant and dermal – direct product contact – instant application models were chosen to assess the exposure from super glues.

Frequency

Because of their fast curing speed, which doesn’t provide much time for the user to make amendments, super glues aren’t used in as many situations as universal glues are. According to the information and results provided in Annex II A.4 Table 75, the default for the use frequency of super glue is set to 9 times per year. A Q-factor of 2 is assigned because of the limitations that are also explained in the afore-named Annex section.

Exposure duration

Assuming the subject stays in the room after finishing the task, which has to be conducted with precision, but also quickly (curing time), the exposure duration is set to 240 minutes with a Q-Factor of 1 because the value relies on personal judgement.

Product amount – inhalation

Per event, it is expected that an individual will not use more than a few droplets of glue. According to a letter from APA (Aromatic Product Association, 1998; as cited in (EU, 2003b)), the amount used for this type of glue will be 0.5 g per event. As a default parameter, 0.5 g glue per event will be assumed, with an assigned Q-factor of 2.

Room volume and ventilation rate

Because this kind of task could be conducted in nearly any indoor surroundings, it is assumed that it is carried out in an unspecified room (20 m³ room volume with a ventilation rate of 0.6 per hour) (te Biesebeek et al., 2014).

Release area

According to the product information acquired in the preparation phase for writing the 2007 DIY-Fact Sheet (ter Burg, 2007), 0.5 g super glue is sufficient to treat a surface of at least 2 cm², which will be used as a default for the release area. The Q-factor is set to 2 because the underpinning data is limited, but sufficient.

Emission duration

The emission duration is defined here as a reasonable estimate of the time during which the substance in question is released from the product. At most, it will take five minutes to glue a handle to a mug. A source depletion in this short time period is not expected. Surplus glue that may ooze when both surfaces (mug and handle) are pressed together will be immediately removed before it can harden and is therefore negligible for the emission duration default. A value of 5 minutes is therefore set as a default. A Q-factor of 1 is assigned because it is based on an estimate.

Exposed area – dermal

Although product information warns the user against letting the glue contact the skin because it will adhere very strongly, dermal exposure may occur because of spills or accidental touching of the glued surfaces. It is assumed that 50% of the surface area of two fingertips (see subsection 6.2) will be exposed during the task. 15 cm² is set as the default for the exposed area, with the Q-factor set to 1, because the underpinning data for the surface area of a fingertip is quantitatively rich but rather compromised by the calculation in subsection 4.1.1. However, individuals will try to avoid any dermal contact since the glue is difficult to remove and stuck fingers are hard to separate.

Product amount – dermal

Dermal exposure may occur, because objects may be very small making it easier to spill glue. Furthermore, it is advised by product information to remove surplus glue from the dosing tip with a cloth in order to prevent the tube from getting blocked. The amount that is spilt from surplus glue during application and the following clean-up phase will be very low, because the total amount used is already low. Half a droplet size (0.025 g) is considered as a default. A Q-factor of 1 is advised because the value is mainly based on expert judgement.

Table 12

Default values for super glue.

6.5.1. Liquid in tubes

Ingredients

Liquid two-component glues are composed of two separated formulations that have to be mixed together prior to use. Their ingredients are different from all the other types of glues. They consist of two components: i.e., a resin and a siccative (hardener). The chemical reaction between the two components provides the glue’s strength. Liquid two-component glues are used for many specific purposes that require fast and strong binding. In general, liquid two-component glues are resistant against water, cold, heat and chemicals.

Use

There are two kinds of liquid two-component glues available: glue based on polyurethane (PU) and glue based on epoxy resins. PU-based glues are well suited for binding wood, concrete, stone, ceramics and different kinds of plastics. Epoxy-based glues are more suitable for metals, pottery, porcelain, glass, ivory and plastics (Vereniging Nederlandse Lijmindustrie, 1999). However, the purposes of the liquid two-component glues may overlap, because there is no rule which glue is to be used for a specific task.

Liquid two-component glues are most often contained in duo-syringes or in tubes, and sometimes in buckets or cans (for larger tasks). There are very small duo-syringes that ensure the correct ratio between resin and siccative, which are used for optimal adhesion and are therefore easy to use. The duo-syringe contains approximately 60 g glue (both resin and siccative together). Besides syringes, separate tubes (of 100 ml each) are also used, where the products are designed in such a manner that an identical length of the lines of glue will provide the optimum volume ratio for optimal adhesive power. The resin and siccative are then mixed together (a mixing cup and a spatula are provided) until a homogeneous colour or mass is obtained. The mixing ratio of resin and siccative has a direct impact on the properties of the resulting glue product. A 2:1-ratio (Resin: siccative; epoxy-based) results in a very hard end product that is strongly resistant to outside influences. If the siccative percentage increases, the end product becomes more flexible but loses resistance.

The mixture is manageable for approximately 15 minutes (polyurethane-based) to 90 minutes (epoxy resin-based) before the mixture will harden. It is therefore important that the resin and siccative remain separated until usage. Before hardening, solvents such as acetone and MEK (methyl ethyl ketone) can be used to remove spilled glue. After hardening, the mixture can only be removed by mechanical force. Dermal contact is to be avoided and according to product information, the use of gloves is advised. However, accidental dermal contact to the mixture may still occur.

In general, liquid two-component glues are used for moderate-sized surfaces. Epoxy resin-based liquid two-component glues are manageable for longer periods of time and may be more suitable for larger surfaces. Then again, some PU- based liquid two-component glues are used to glue parquet and are used for a large surface size.

The mixing and loading process and the application (hence the exposure) are similar for both kinds of liquid two-component glues. Furthermore, no clear distinction can be made in the product amount or treated surface size between the uses of either liquid two-component glue. For these reasons, one default scenario will be described for the use of liquid two-component glue.

Scenario for liquid two-component glue

The scenario of gluing a large broken vase with a liquid two-component glue is described here. Assuming the vase has broken into several parts, this leads to an overall surface area of 500 cm² to be treated.

Mixing and loading: liquid two-component glue

When one of the products (resin or siccative) contains volatile agents, the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: constant model should be used to estimate the inhalation exposure. The formation of volatile substances during the chemical reaction between resin and siccative is unlikely (see section 4.1.1). Because the task’s duration is rather short, the ConsExpo dermal – direct product contact – instant application model is used to estimate dermal exposure (see subsection 4.1.1).

Frequency

According to the information provided in Annex II A.4 Table 75, a default of 7 times per year is assumed. A Q-factor of 2 is assigned because of the limitations explained in the afore-named Annex section.

Exposure duration

The exposure duration from the mixing and loading process is estimated to be 5 minutes due to the low product amount that has to be mixed. A Q-factor of 1 is assigned because the default is based on personal judgement.

Product amount – inhalation

For a surface area of 500 cm², approximately 20 g glue is needed, according to product information explained in the 2007 DIY-Fact Sheet (ter Burg, 2007). In contrast, the amount of glue used for the gluing events observed by Magré (Magré, 2005) was very low (< 0.5 g and 4 g). The surfaces that were treated were correspondingly small; the task consisted of gluing the ear of a mug and a broken dinner plate. However, 20 g mixed product amount is considered as a default here in order to follow a conservative approach. The Q-factor is set to 2 because the underpinning data is sufficient to derive a default but limited.

Release area

Evaporation takes place from a constant surface area, i.e., the mixing cup. The surface area is calculated using the radius of a small mixing cup (=4.5 cm) as it is usually sold in German DIY markets, resulting in a release area of approximately 60 cm². A Q-factor of 2 is assigned because the size of a mixing cup is easily traceable through market research.

Emission duration

The emission duration in this case equals the exposure duration (see above) because it is assumed that the VOC substance in question is released during the entire mixing and loading process and a source depletion is not expected in this short period. The Q-factor is set to 1 because the value was derived by expert judgement.

Exposed area – dermal

It is expected that 50% of the surface area of two phalanges, 15 cm², of the fingers are exposed while mixing because of spills or residues on the mixing tool (see subsection 4.1.1). The Q-factor is set to 1 because the underpinning data for the surface area of a fingertip is quantitatively rich but rather compromised by the calculation in subsection 4.1.1.

Product amount – dermal

The product amount contacting the skin is assumed to be low. Based on the results of the glue project explained in Annex II, A.2, it is assumed that in total, one drop of glue will remain on the fingertips: 0.05 g. A Q-factor of 1 is assigned because the value is mainly based on assumptions.

Table 13

Default values for mixing and loading: liquid two-component glue.

Application

The resin and siccative are put in a mixing cup in the proper ratio. With a matchstick or small spatula, the components are mixed before being applied to the surface with the same matchstick or spatula. Because the composition of liquid two-component glues is not completely known, inhalation exposure cannot be ignored. If there is evidence to suggest that the inhalation exposure to liquid two-component glues is negligible, one can leave out this route of exposure. For now, the model used to estimate inhalation exposure is the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: increasing model.

Dermal exposure is estimated using the ConsExpo dermal – direct product contact – instant application model because the task itself and the used product amount are relatively small.

Exposure duration

In the EU RAR on bisphenol A, an exposure duration of 210 minutes was estimated for the application of two-component glue. Here, the exposure duration is set at 240 minutes as a default, which is the time a subject stays in the room during and after application. A Q-factor of 1 is assigned because the underpinning data is limited and is supplemented with assumptions.

Room volume and ventilation rate

No room was specified or is preferred for such a task. Thus, the specifications of an `unspecified room´ are considered as defaults. The parameters for an unspecified room are 20 m³ for room volume and 0.6 per hour for ventilation rate. (te Biesebeek et al., 2014)

Release area

It is assumed that a vase that has broken in half provides a surface area of 500 cm² that has to be treated with glue in order to repair the object. The Q-factor is set to 1 because the value is based on personal judgement.

Application duration

The application duration is estimated to be 30 minutes. This is not comparable with the application durations observed by Magré (Magré, 2005), which covered time spans of 2 and 12 minutes per event, respectively. The tasks Magré observed were smaller, which may explain the difference. The Q-factor is set to 1 because the value is based on expert judgement.

Exposed area

Dermal exposure can occur during application when the parts are pressed together; surplus glue can be spilled on the hands. For consumers, the EU RAR document on bisphenol A (EU, 2003a) (constituent of epoxy resin) departed from a surface area of 54 cm² (=5% of the total surface of both hands = 1075 cm²) for its dermal exposure assessment for bisphenol A. The figure of 5% surface area is not related to the manner of use, but merely based on assumptions. In the scenario of holding the materials while applying the glue mixture, spills on the palm of one hand may occur. Assuming that approximately 20% of one palm (te Biesebeek et al., 2014) is exposed results in a surface area of 45 cm². This value is preferred to the EU assumption, because it is more related to the manner of use. A Q-factor of 2 is assigned because the underpinning data for the size of one palm is quantitatively rich but the assumption that only this surface area of the hands will be exposed is based on expert judgement (see also subsection 4.5).

Product amount – dermal

The product amount is not assumed to be high because relatively low amounts are used in the first place. Referring to the considerations explained in subsection 4.2.3, a palm provides space for approximately 1 g glue. As mentioned in the previous paragraph, it is assumed that 20% of the palm of a hand is exposed during this task. Adapting this for the product amount contacting the skin, a value of 0.2 g has to be considered. The Q-factor is set to 1 because the value relies heavily on assumptions.

Table 14

Default values for liquid two-component glue.

6.5.2. Adhesive putty

Product amount – dermal

As mentioned before, dermal exposure is expected to be significant. Both palms may potentially be covered with product residue. The product amount contacting the skin is calculated on the basis of the assumption that the exposed skin area is covered with a homogeneous layer of product with a layer thickness of 0.01 cm. Taking into account a skin area of 450 cm² and a density of 1.95 g/cm³ (for both, see above) the resulting product amount is approximately 9 g (0.01 cm × 450 cm² × 1.95 g/cm³ = 8.775 g ~ 9 g).

The default is therefore set to 9 g with a Q-factor of 1 because the calculation is based on assumptions.

Table 15

Default values for adhesive putty.

Use

These glues are used to glue wood parquet, where the parquet is meant to lie on top of the surface (the parquet is glued onto the floor) or to float above it (individual parts are glued together, but not glued onto the floor). Because the application of the two parquet glues is different, the product (amount) used may differ significantly. Furthermore, for parquet glued onto the floor, there are also two-component glues, which need to be mixed and loaded before they can be used. The application of the two-component glue is regarded as similar to parquet glue that is used to glue parquet onto a surface. The application of glue for floating parquet is entirely different, which results in different exposure. For this reason, two scenarios and related defaults will be described.

Scenario for parquet glued to surface

Gluing parquet onto a surface in the living room was selected as a default scenario. Inhalation exposure during mixing and loading may occur because of volatiles evaporating from the opened bucket (component A) and can (component B) the product is delivered in. In addition, evaporation is expected from the product surface in the mixing bucket while the two components are homogenised. Dermal exposure is expected because of spatters and spills first, while pouring the two components into the mixing bucket, and subsequently while the resin and the siccative are mixed. Consequently, inhalation and dermal exposure are estimated in accordance with the generic scenario for mixing two-component products (see subsection 4.1.1).

Mixing and loading: two-component parquet glue

When one of the products (resin or siccative) contains volatile agents, the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: constant model should be used to estimate inhalation exposure. However, formation of volatile substances during the chemical reaction between resin and siccative is considered very unlikely (see subsection 4.1.1). Dermal exposure during the mixing and loading phase is estimated using the dermal – direct product contact – instant application model and the default parameters described in subsection 4.1.1.

Frequency

The endurance of such a floor is estimated to be 30 years, which is considered to be the lifetime of massive parquet floors. However, people tend to redecorate. According to the information acquired in a consumer survey and explained in Annex II A.4, a frequency of once in 2 years is set as a default for this scenario.

The product amount required for this task is very high (25.3 kg, see below). The mixing and loading step will need to be repeated approximately 3 times, because the product amount is simply too much to handle in one step. As a result, the default for the frequency of the mixing and loading phase is set to 3 times a day (once every 2 years). A Q-factor of 2 is assigned because of the limitations, which are also explained in Annex II A.4.

Exposure duration

Because the amount that has to be mixed is rather large (approximately 8.5 kg per repetition) the mixing duration/exposure duration is assumed to be extensive in order to achieve a homogenous mass in the end. A duration of 10 minutes should be sufficient for this purpose. The Q-factor is set to 1 because the default is the result of assumptions.

Product amount – inhalation

The product information acquired in the BfR market analysis shows a consumption rate of 1150 g per m² (see Annex II, product data collection Table 90). Extrapolating from this and keeping in mind the 22 m² of floor that has to be treated in an average living room (te Biesebeek et al., 2014), the result is a total product amount of 25.3 kg wood parquet glue, which should be sufficient for the task. In each mixing and loading repetition an amount of 8.5 kg product is mixed. This value is used as the default here. A Q-factor of 3 is assigned because the underpinning data is sufficient to derive a default, albeit limited. Please note that in most cases, the task is performed by professionals, but this scenario relates to non-professional users.

Release area

The mixing and loading is done in a bucket. The bucket has a capacity of 20 l which is sufficient for the task and a diameter of approximately 37.5 cm. This leads to a surface area of 1100 cm² from which evaporation can be expected. A Q-factor of 2 is assigned because several bucket products with these specifications are available on the market. For the common user, a 20 l bucket will be sufficient for most tasks.

Emission duration

The emission duration in this case equals the exposure duration (see above) because it is assumed that VOC/SVOC substances are released during the entire mixing and loading process if present and a source depletion is not expected. The Q-factor is set to 1 because the value relies on personal judgement.

Product amount – dermal

The amount of product contacting the skin during mixing and loading through spatters and spills is considered to be comparatively high because of the high product amount that has to be mixed and the three repetitions which always include the pouring of the components into the mixing bucket. The dermal product amount is set at 0.5 g by estimation. A Q-factor of 1 is assigned because this value is based on expert judgement.

Table 16

Default values for mixing and loading: two-component parquet glue.

Application

After the parquet glue has been mixed, it has to be spread out on a segment of the floor by means of a tool. Afterwards, the parquet is put in place and is kept there by putting heavy objects on top, thereby preventing the parquet from warping. This is repeated several times until the floor is completely covered. Once the task is finished, it takes approximately 48 hours for the parquet floor to settle. During this period, one should not walk on the floor.

Exposure to parquet glue may occur via inhalation and by dermal contact. Inhalation exposure is estimated using the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: constant model, taking into account the simplification explained in subsection 4.2.2 and in the explanation regarding the release area default below. The dermal – direct product contact – constant rate model will be used to describe the dermal exposure.

Frequency

The endurance of such a floor is estimated to be 30 years, which is considered to be the lifetime of massive parquet floors. However, people tend to redecorate. According to the information acquired in a consumer survey and explained in Annex II A.4, a frequency of once every 2 years is set as a default for this scenario. A Q-factor of 2 is assigned because of the limitations also explained in Annex II A.4.

Exposure duration

By estimation, it takes individuals an entire day to lay a parquet floor, as was also seen in the EU RAR draft report on MDI (EU, 2003c). For this reason, an exposure duration of 480 minutes (8 hours) is taken into account. Once the task is completed, there will be no after-use activity, because the parquet has to settle, and any spills or surplus glue have to be removed immediately after they occur. The Q-factor is set to 2 because the supporting data is sufficient to derive a default, albeit limited.

Room volume and ventilation rate

According to the General Fact Sheet (te Biesebeek et al., 2014), a living room has a volume of 58 m³ with a floor surface area of 22 m² and a ventilation rate of 0.5 per hour.

Release area

An alternative description of the release area is required because exposure to a very high product amount released from large areas is not considered realistic. Furthermore, ConsExpo Web is not able to integrate exposure intervals. This scenario would lead to erroneous estimates. Instead, the release area is set to be equal to the surface area that can be treated per interval. It is assumed that an individual treats 1 m² per interval (see subsection 4.2.2). Subsequently, the surface is covered, and the user’s inhalation exposure will be negligible compared with the newly treated surface (nonetheless, please note that inhalation exposure to volatile substances is possible over a long time, weeks or maybe months, after application which can lead to chronic effects). These steps are repeated until the task is completed, comprising 22 repetitions. The inhalation exposure is described by evaporation of the total amount rather than by the adjusted amount from a constant surface area, i.e., 1 m². This simplification of the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: constant model is necessary, because otherwise, depletion of the source can occur. 1 m² is set as the default for the release area in this scenario. Because of this simplification, a Q-factor of 1 is assigned.

Emission duration

As a simplification, it is assumed that the task is divided into 1 m² sections (see above) that are treated with glue. On that basis, a reasonable estimate would be that a VOC substance is released during the entire period it takes to conduct the task, if present. Therefore, the emission duration is set on the same level as the exposure duration, which is 480 minutes (see above). A Q-factor of 1 is assigned because the value is based mainly on assumptions.

Exposed area – dermal

Exposure to parquet glue may occur through inhalation and by dermal contact. It is assumed that approximately 50% of both hands (450 cm²) will be exposed (te Biesebeek et al., 2014). The Q-factor is set to 2 because the underpinning data for the surface size of the hands is quantitatively rich but compromised by assumptions regarding the dimensions of the affected skin area (see also subsection 4.5).

Release duration – dermal

The substance is applied during the entire task because it is assumed that it is divided into sections of 1 m². Dermal exposure may also occur when the user is placing the parquet elements in their final position. Repetitive cleaning of the hands may lead to a fluctuation of the dermal exposure, but the user will not tend to completely remove all of the product from the skin because it is too time-consuming with a rather small benefit (hands will be exposed again in a short time). Therefore, the release duration is set to be equal to the exposure duration. A Q-factor of 2 is assigned because the underpinning data is sufficient to derive a default, albeit limited.

Table 17

Default values for parquet glue: gluing on surface.

Scenario for floating parquet

The task of constructing a floating parquet floor is considered easier than constructing a parquet floor onto the surface. The glue is applied to the groove joints and tongue of the parquet elements. The glue is allowed to be absorbed for 2-3 minutes before the next element is placed and tapped with a rubber mallet.

Assuming the same indoor environment as above (scenario for parquet glued to surface) for constructing floating parquet; it will take less time and far less glue to conduct the task.

Frequency

According to the Dutch Environmental Information Centre (Milieu Centraal), the durability of laminate or thin parquet is ten years at most, and the durability of use for an average floor cover in the Netherlands is eight years (Milieu Centraal, 2005). Nowadays, laminate that can be clicked together is more common than laminate that requires gluing. Considering a person who prefers parquet, the frequency of laying parquet may be higher. This is supported by the information provided in Annex II A.4 Table 75. A frequency of once every two years for constructing floating parquets will be considered as a default. A Q-factor of 2 is assigned because of the limitations also explained in the afore-named Annex section.

Exposure duration

The task is estimated to take 240 minutes while the construction itself is performed in intervals. Hence, the exposure duration and emission duration are the same. The Q-factor is set to 1 because the default is based on expert judgement.

Product amount – inhalation

According to the product information 37.5 g is sufficient to treat the groove joints of 1 m² of floating parquet (see Annex II, product data collection Table 91). For an area of 22 m² it is derived that 825 g glue is used. A Q-factor of 3 is considered because underpinning data is limited but sufficient.

Room volume and ventilation rate

According to the General Fact Sheet (te Biesebeek et al., 2014), a living room has a volume of 58 m³ with a floor surface area of 22 m² and a ventilation rate of 0.5 per hour.

Release area

It is assumed that 1 m² is treated per interval which will be set as the default for the effective release area (see subsection 4.2.2). This interval is repeated 22 times to complete the task (see also application scenario for parquet glued to surface). A Q-factor of 1 is assigned because the default is derived using assumptions that are based on expert judgement.

Emission duration

The emission duration is estimated to be as long as the exposure duration (240 minutes). The task is conducted in intervals (see application scenario for parquet glued to surface). Therefore, it is assumed that evaporation processes can occur during the entire parquet laying task, because the emission source is constantly renewed. A Q-factor of 1 is assigned because there is currently no underpinning data available.

Exposed area – dermal

Surplus glue must be removed with a moist cloth as soon as possible. The container is a flask with a nozzle, which indicates that the glue can be administered precisely to the groove joints. Spills may occur when the parts are pressed together. The exposure area will be approximately 50% of one palm (112.5 cm²) (te Biesebeek et al., 2014). The Q-factor is set to 2 because the underpinning data for the surface size of the hands is quantitatively rich but compromised by assumptions regarding the dimensions of the affected skin area (see also subsection 4.5).

Product amount – dermal

The product amount contacting the skin is estimated to be 0.5 g by expert judgement. A Q-factor of 1 is assigned because no data source is given.

Table 18

Default values for parquet glue: floating parquet.

Scenario for carpet glue

Carpet glue is used to keep floor covers in place and prevent them from warping. Carpet glue can be used for several kinds of floor covers such as carpets, carpet tiles, and PVC floor covers. Here, the laying of a carpet floor in the living room is considered.

During this process, individuals may be exposed through inhalation or by the dermal route. For inhalation exposure, the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: constant model is used. Additionally, the dermal – direct product contact – constant rate model is used to estimate dermal exposure.

Frequency

The durability of the carpet is heavily dependent on the type of carpet and its quality. The average durability according to the Environmental Information Centre (Milieu Centraal, 2005) is eight years. The results from a consumer survey explained in Annex II A.4 and summarised in Table 75, lead to a default for the use frequency of carpet glue of once every four years. A Q-factor of 2 is assigned because of the limitations also explained in the afore-named Annex section.

Exposure duration

The glue is spread across the surface using a glue spatula. A manageable time for this specific glue is 40 minutes (flash-off time according to product information). An alternative description of exposure is required, because exposure to a very high product amount released from large release areas is not realistic in this case. Instead, the release area is set to be equal to the surface area one can treat per interval. It is assumed that 4 m² per interval can be treated, which is assumed to take 15 minutes per effort. Assuming that the carpet is already cut to size and is only moved to fit, an exposure duration of 90 minutes will be considered in order to complete the task for the entire surface area of 22 m² (see below). The Q-factor is set to 1 for this default because it relies on expert judgement.

Product amount – inhalation

According to product information, 650 g product is sufficient for laying 1 m² of carpet (see Annex II, product data collection Table 92). To treat the entire surface area of 22 m² (see below), a total amount of 14.3 kg carpet glue will be required. This value will be used as a default for this scenario. A Q-factor of 3 is assigned because the underpinning data is sufficient to derive a default, albeit limited.

Room volume and ventilation rate

A room volume of 58 m³, a floor surface area of 22 m² and a ventilation rate of 0.5 per hour are selected as defaults in accordance with the General Fact Sheet (te Biesebeek et al., 2014).

Release area

As described above in the exposure duration section, the surface area a user can treat per interval is assumed to be 4 m². This will serve as the default value for the release area in this scenario. The Q-factor for this default is set to 1 because it strongly depends on assumptions that are based on expert judgement.

Emission duration

The emission duration is set to equal the total exposure duration because the task is conducted in intervals. Therefore, the potential evaporating source is constantly renewed. A Q-factor of 1 is assigned because no underpinning data is available.

Exposed area – dermal

The affected skin surface area is assumed to be approximately 50% of one palm, resulting in 112.5 cm² contact area (te Biesebeek et al., 2014). The Q-factor is set to 2 because the underpinning data for the surface size of a palm is quantitatively rich but compromised by assumptions regarding the dimensions of the affected skin area (see also subsection 4.5).

Release duration – dermal

It is assumed that the user will clean his or her hands during the task in order to not leave behind stains of glue on the top side of the carpet pieces when they are put in place. Nevertheless, the user is not expected to be able to totally remove all the product contacting his skin because it would be too time-consuming and elaborate. Therefore, a release duration of 90 minutes is estimated. Since this default is based on assumptions and expert judgement, the Q-factor is set to 1.

Table 19

Default values for carpet glue.

Use

Tile glues are glues for wall and floor tiles that must be attached to all kinds of surfaces, such as cement walls, concrete, wood, chipboards, other tiles et cetera. Tile glues can be used to cover floors in the living room, hall and kitchens or covering walls in, for instance, kitchens and bathrooms. Tile glues are available in paste form, which are ready to use, and as powder. In general, the pastes are used to attach tiles to absorbing surfaces, while the powders are used to attach tiles to non-absorbing surfaces. The powder is diluted with water until the desired ratio for the job is obtained. Tile glue (paste or obtained paste) is applied and spread out using a glue spatula. Wet stains or spills can be removed with water; hardened stains or spills must be removed mechanically (see product information).

Scenario for tile glue

The scenario selected for tile glue is for two walls in a bathroom, amounting to a surface area of 10 m² (two bathroom walls of 2 m wide and 2.5 m high) in total. Tile glues are available as pastes, primarily based on styrene acrylate dispersions, or as powders. During the task, the glue is applied to the tile or directly onto the surface using a glue spatula. The tiles are then attached by pressing them while shifting the tile into the right position. This must be done within a 15-minute time frame when the glue is still manageable.

Mixing and loading: tile glue

Mixing the powders, which have a mortar and a cement base, with water provides a paste that is applied in a manner similar to the ready-to-use products. Additional dermal/inhalation exposure from the mixing and loading process may occur. According to product information, a product consumption of 2.5 kg/m² (tile teeth of 6 mm) is sufficient (see Annex II; product data collection Table 93). Additionally, 1 kg powder has to be mixed with 0.3 l water in order to achieve the required texture. Therefore, the total product amount (powder mixed with water) will be 32.5 kg. This is obtained by mixing 25 kg powder with 7.5 l water. The mixing and loading process is repeated 5 times; otherwise, the quantity is too large to mix. The product amount is 32.5 kg, divided by 5 (= 6.5 kg) per mixing and loading event.

The inhalation exposure from mixing and loading DIY powders is estimated using the ConsExpo inhalation – exposure to spray – instantaneous release model. For dermal exposure, the direct product contact – constant rate model (see subsection 4.1.3) is advised. Defaults for the parameters product amount for inhalation exposure, room volume, exposed area (dermal) and dermal contact rate are chosen in accordance with the generic scenario for loading powders (see subsection 4.1.3).

Frequency

Covering walls or floors with tiles is not expected to occur at high frequency. The information extracted from a consumer survey and explained in Annex II A.4, leads to a default of once every two years. A Q-factor of 2 is assigned because of the limitations also explained in the above-named Annex section. Because the required product amount for this task is simply too much to handle (32.5 kg in total; 25 kg powder and 7.5 kg water; see above) in one mixing step, five repetitions are estimated to be required.

Exposure duration

According to product information, every mixing interval consists of pouring the right amount of powder into the water, homogenisation of the two components using a suitable mixing tool (e.g., a driller with attachment) for at least 3 minutes, a maturing time of five minutes and a concluding mixing effort in the end (see Annex II; product data collection, Table 93). Summing up the four phases leads to the estimate that the exposure duration is set to a default of 15 minutes. The Q-factor is set to 1 because underpinning data is only available for two of the 4 phases.

Released mass

In each repetition, 5 kg powder is mixed with 1.5 l water. Referring to the considerations in subsection 4.1.3, the default for the released mass is set to 8.3 µg per 200 g powder. Taking into account a product amount of 5 kg, a total amount of 207.5 µg is released into the air and will therefore be taken as a default. The Q-factor is set to 1 as explained in subsection 4.1.3.

Release duration – dermal

The release duration is assumed to be as long as the exposure duration because the user is not expected to clean his or her hands during the mixing task. Therefore, dermal exposure is not intermittent, and the default is set to 15 minutes with a Q-factor of 1 because underpinning data are not available for the entire mixing task (see the paragraph about exposure duration above)

Table 20

Default values for mixing and loading: tile glue.

Application

Although no solvents are present in tile glue, inhalation exposure may occur from other materials present. If there are sufficient arguments that inhalation exposure is negligible, the inhalation route can be ruled out. Otherwise, the inhalation exposure can be described by assuming an effective release area of 1 m² during the entire task. This is the surface a subject is assumed to cover per interval for this scenario (for an explanation, see subsection 4.2.2). Thus, the release area from which evaporation can be expected stays the same during the entire application phase. The inhalation exposure will consequently be estimated using the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: constant model. Because the source strength is renewed per interval the product amount is considered to be the amount required for the entire task. Therefore, the total product amount is taken to prevent an underestimation of exposure due to source depletion. For dermal exposure, the ConsExpo dermal – direct product contact – constant rate model is applied because it is assumed that individuals will clean their hands during the task.

Exposure duration

Because this task is rather big and has to be conducted with a high level of diligence in order to place the tiles straight, it is assumed that a time period of 360 minutes will be sufficient to treat the entire wall. The Q-factor is 1 because the default depends strongly on assumptions that are based on expert judgement only.

Amount of solution used

The product amount used whilst conducting this task depends on the size of the tiles and the resulting tile teeth (thickness of the glue layer). 6-mm tile teeth is sufficient for tiles with an edge length of 10 cm, which seems adequate for this scenario. According to product information, a product amount of 2.5 kg/m² is required for a task with these preferences. Therefore, 25 kg powder have to be mixed with 7.5 l water (0.3 l/kg powder) resulting in a solution with a total amount of 32.5 kg (see Annex II, product data collection Table 93). A Q-factor of 3 is assigned, because the underpinning data is sufficient to derive a default, albeit limited.

Dilution

The dilution in number of times is defined here as the inverse of the product concentration of tile glue powder in the water in the mixing vessel. According to the above given information about the used product amount, 25 kg powder are mixed with 7.5 l water. Therefore, the ultimately mixed solution amounting to roughly 32.5 kg contains 25 kg powder, which leads to a dilution factor of: 32.5 kg / 25 kg = 1.3. The Q-factor is set to 3 because the data used for this calculation is limited.

Room volume and ventilation rate

According to the information provided in the General Fact Sheet, a bathroom has a default room volume of 10 m³. The ventilation rates are generally high in bathrooms. A default of 2 per hour was derived (te Biesebeek et al., 2014).

Release area

In this case, the release area is considered to be the area treated with tile glue. Because the task is conducted in intervals, as was mentioned above, a release area of 1 m² will be used as the default value (for an explanation, see subsection 4.2.2). The Q-factor is considered to be 1 because the value strongly depends on assumptions that are based on expert judgement.

Emission duration

The emission duration is interpreted here as the time during which evaporation from the surface of the glue is possible because it is not covered with a tile and the emission source is not depleted. Because the task is conducted in intervals, a constant (i.e., constantly renewed) release area of 1 m² of glue-treated surface is ‘open’ and allowing evaporation. Therefore, the emission duration equals the exposure duration and is set to 360 minutes. The Q-factor is considered to be 1 because no underpinning data is available.

Exposed area – dermal

Dermal exposure results from spills or surplus glue removal. An exposure area of two palms (0.5 × 900 cm² from General Fact Sheet (te Biesebeek et al., 2014)) will be considered as a default. A Q-factor of 2 is assigned because the underpinning data for the surface size of two palms is quantitatively rich but compromised by assumptions regarding the dimensions of the affected skin area (see also subsection 4.5).

Release duration – dermal

The user needs to work precisely during the entire task. In order to prevent the hands from getting too sticky because of surplus glue, it is assumed that the user will clean his hands from time to time. However, a release duration of 360 minutes is estimated because dermal exposure is likely to occur during the entire task. The Q-factor is set to 1 because the value is based on expert judgement.

Table 21

Default values for application of tile glue.

Use

Wallpaper glues are available as powder or as flakes, which have to be mixed with water before use. The powder may contain poly anionic cellulose (PAC), methyl cellulose or polyvinyl acetate (PVAc) and does not normally contain any solvents. The adhesive powder is poured into cold water in the proper ratio (according to use directions) and stirred until there is a solution without any lumps. According to product information, 125 g glue powder can be mixed in 6 l to 10 l water (this is for normal wallpaper); there are also special (e.g., fleece wallpaper) and heavy wallpapers for which alternative wallpaper glue is used (in different mixing ratios). Although heavy wallpaper glue is based on the same constituents, it is likely to have other volume percentages. The obtained mix can be used for surfaces ranging from 30m² to 50 m², depending on the type of wallpaper. After the powder is mixed in, the mixture can be easily applied to the wallpaper using a brush. The wallpaper covered with glue is folded to make sure it is properly soaked with glue and left to rest before attaching it to the wall.

Scenario for wallpaper glue

In the default scenario, the walls in a living room will be covered with normal wallpaper. According to the General Fact Sheet (te Biesebeek et al., 2014), the volume and surface area are 58 m³ and 22 m², respectively. A total surface area of 40 m² for the walls (corrected for doors and windows) is assumed for hanging wallpaper.

Mixing and loading: wallpaper glue

The inhalation exposure from mixing and loading DIY powders is estimated using the ConsExpo inhalation – exposure to spray – instantaneous release model. For dermal exposure, the direct product contact – constant rate model (see subsection 4.1.3) is advised. Defaults for the parameters exposure duration, release duration (dermal), product amount for inhalation exposure (released mass), room volume, exposed area (dermal) and dermal contact rate are chosen in accordance with the generic scenario for loading powders (see subsection 4.1.3).

Frequency

Applying wallpaper is a rather big task that, in most cases, requires elaborate preparation and diligent execution. According to the information provided in Annex II A.4, wallpaper glue is used approximately 4 times per year, which will be set as a default. A Q-factor of 2 is assigned because of the limitations also explained in the above-named Annex section.

Exposure duration

The mixing duration of wallpaper glue powder with water was documented during a consumer survey as described in Annex II A.4.2. The duration varies from 1 minute up to 60 minutes with a 75^th percentile of 19.5 minutes. As this information is specifically gathered for this product category, this value will be preferred instead of the generic default described in subsection 4.1.3. A Q-factor of 2 is assigned because underpinning data is sufficient, albeit limited.

Released mass

For normal wallpaper and a surface area of 40 m², a 7.5 l mixture (125 g wall-paper glue mixed with 7.5 l water) must be made according to product information (see Annex II; product data collection Table 94). A recently conducted consumer survey (including protocol documentation) delivered results which indicates that a product amount (powder) of 271.3 g (75^th percentile) ~ 270 g wallpaper remover is used by a common consumer (see Annex II A.4.2). As this value is more conservative than the product information, it will be used in the following considerations. Referring to subsection 4.1.3, a default value of 11.2 µg released mass is set for a powder amount of 270 g. The Q-factor is set to 1, as described in subsection 4.1.3.

Released duration

The release duration is assumed to be similar to the exposure duration explained above. It is unlikely that the user will interrupt the mixing process in order to clean his hands before the mixture is homogenised. A Q-factor of 2 is assigned because underpinning data is limited.

Table 22

Default values for mixing and loading: wallpaper glue.

Application

The obtained mixture is applied with a brush after which the wallpaper is folded to allow it to soak properly. Afterwards, the wallpaper can be attached to the wall. Surplus glue should be removed instantly, using a moist cloth.

Because exposure to a very high product amount from a large surface is not realistic, it is assumed for this scenario that the task is conducted in segments of 1 m² (see descriptions in subsections 4.2.2 and 6.7).

In contrast to the considerations of the previous DIY Products Fact Sheet (ter Burg, 2007), inhalation exposure to substances evaporating from wallpaper glue will be taken into account at this point. New data acquired during the screening of the products available on the DIY market (see Annex II, product data collection Table 94 lead to the conclusion that wallpaper glue may contain VOC substances. The inhalation exposure is estimated using the ConsExpo inhalation – exposure to vapour – evaporation – release area mode: constant model because the task is conducted in intervals and the considered size of the release area (1 m²) is constant (while the source strength is renewed) throughout the task. For dermal exposure the dermal – direct product contact – constant rate model is applied.

Exposure duration

Covering the walls of a living room with wallpaper is a task that has to be conducted precisely in order to achieve acceptable and sustainable results. According to the information provided in Annex II A.4.2 from a consumer survey regarding the exposure duration (including mixing, application and staying in the same room after use) of wallpaper glue, a 75^th percentile of 498 minutes (~500 minutes) is derived. Therefore, 500 minutes will be used as a default for this scenario. A Q-factor of 2 is assigned because the data set is rather limited.

Amount of solution used

The entire amount of mixture used of ~ 16.5 kg (16.2 l water and 270 g product powder mixed with an approximate density of 1 g/cm³), as indicated by product information (7.5 l water per 125 g powder product; see Annex II; product data collection Table 94) and by a consumer survey (75^th percentile of amount used: 270 g; see Annex II A.4.2) is considered here because the source evaporation potential is restored in every interval. This prevents an underestimation of exposure through source depletion. A Q-factor of 3 is assigned because the underpinning data is sufficient to derive a default, albeit limited.

Dilution

The dilution as described in subsection 4.2.4 has to be considered in this scenario in order to properly assess the inhalation exposure. It is defined as the inverse of the product concentration of wallpaper glue powder in the water in the mixing vessel. As mentioned above, 270 g product has to be mixed with 16.2 l water, which yields a dilution factor of 16470 g / 270 g = 61 times. This value will be used as a default for the scenario, with a Q-factor of 3 because the calculation can be underpinned by limited quantitative data.

Room volume and ventilation rate

According to the General Fact Sheet, a living room has a room volume of 58 m³ and a ventilation rate of 0.5 per hour (te Biesebeek et al., 2014).

Release area

In accordance with the application scenario for tile glue (see subsection 6.7) and the explanations given in subsection 4.2.2, the effective release area in this case is assumed to be 1 m² (= one strip of wallpaper) throughout the task because this is the surface a user is able to treat per interval. The Q-factor is considered to be 1 because the value strongly depends on assumptions that are based on expert judgement.

Emission duration

The emission duration is estimated to be as long as the exposure duration (500 minutes). Because of the interval approach, it is assumed that, due to the constant renewal of the emission source, no depletion should be expected. The Q-factor is 1 because the default depends strongly on assumptions that are based on expert judgement.

Exposed area – dermal

Dermal exposure is expected to occur during application. The spreading of the glue and the folding and hanging of wallpaper will cause spills on both hands. The dermal exposure can be significant, depending on how the subject handles the wallpaper. Since wallpaper glue is not considered harmful and is easy to remove afterwards, subjects tend to be more careless and both hands will be exposed (= 900 cm²) (te Biesebeek et al., 2014). A Q-factor of 2 is assigned because the underpinning data for the surface size of both hands is quantitatively rich but compromised by assumptions regarding the dimensions of the affected skin area (see also subsection 4.5).

Release duration – dermal

The exposure duration is set at 500 minutes. The release duration is set to be equal to the exposure duration because it is assumed that the user is dermally exposed, throughout application, because a high product amount is used and lastly because of possible carelessness while handling the glue. It is also assumed as a conservative approach that the user will not clean the exposed body parts until he or she leaves the room. Nevertheless, a Q-factor of 1 is assigned for this default because it is based on assumptions.

Table 23

Default values for application of wallpaper glue.

Use

Hot-melt adhesives are solidified glues that are primarily for hobby use. They have a wide range of application and are used mainly for small surfaces, such as connections of model parts and flowers for decorative purposes. The adhesive agent is a thermoplastic, such as ethylene vinyl acetate (EVA). A glue gun is required to use a hot-melt adhesive. The glue gun is an electric device which heats up the solidified glue bar (20 g; see Annex II, product data collection Table 95). There are two variations of hot-melt adhesives available on the consumer market. The conventional hot-melt adhesive is manageable at a temperature range from 150 °C to 200 °C and more commonly used. The low-melt version works at a temperature level of 110 °C and is predominantly used for crafting or decorating tasks. The main advantage of this technology is its ability to also connect polystyrene and soft PVC, for which the 200 °C version of the glue is too hot. The glue is inserted in the rear and then heated up for approximately 5 minutes. As a result, the glue bar will melt inside the glue gun. By triggering the glue gun, the melted glue is squeezed out onto the surface. The parts must then be attached to each other within 15 to 20 seconds; otherwise, the glue has cooled down too much.

Scenario for hot-melt adhesives

The scenario of gluing the soles of the shoes (surface area approximately 100 cm²) with a hot-melt adhesive is described here. The effective release area, however, is much lower due the gradual release of the hot-melt in combination with the cooling down of the glue. The effective release area is estimated to be approximately 5 cm².

Exposure to a hot-melt adhesive takes place during the heating of the adhesive. Inhalation exposure may be caused by a chemical reaction due to heating, or from evaporation at high temperature. ConsExpo does not include models to evaluate chemical reactions. An estimate of the amount of chemical produced in the reaction has to be made separately. The exposure can then be calculated using the instantaneous release model. Similarly, the evaporation models in ConsExpo do not include an option where the evaporation takes place at a different (much higher, in this case) temperature than the surrounding space (room temperature). As the evaporation in this case is likely to be much higher than evaporation at room temperature, the use of the ConsExpo inhalation – exposure to vapour – evaporation model could lead to an underestimation of the exposure. Therefore, it is advised to use the inhalation – exposure to vapour – instantaneous release model in this case as well. The modelled concentration can be limited to the vapour pressure of the substance at room temperature to prevent the occurrence of unrealistically high concentration levels that may arise from the immediate release of the substance. Ticking the box: ‘limit the air concentration to the vapour pressure of pure substance’ in ConsExpo is required.

Inhalation exposure takes place when the glue is being heated or melted.

Due to the temperature of the glue after heating, the user tends to be very cautious during its use. Dermal exposure is therefore expected to be rather low and will predominantly occur when the glue stick is inserted prior to use. It is estimated using the ConsExpo dermal – direct product contact – instant application model.

Frequency

Because of its wide range of application, the frequency of use of hot-melt adhesives could be assumed to be rather high. The information provided in Annex II A.4 indicates that this kind of glue is used by the consumer 6 times per year, which will be used as the default. The Q-factor is set to 2 because of the limitations also explained in the above-named Annex section.

Exposure duration

In total, an application duration of 25 minutes will be taken into account for this task, which is spread over a longer period of time (gluing occurs in intervals). The default for the exposure duration is also set at 25 minutes due to the rapid cooling of the glue. The Q-factor is considered to be 1 since there is no underpinning data available.

Product amount – inhalation

According to assumptions, during this task, a total product amount of 60 g will be consumed equalling three commonly used glue bars. This value relies on expert judgement resulting in a Q-factor of 1.

Room volume and ventilation rate

The task is conducted in an unspecified room. This room is therefore defined to have a volume of 20 m³ and a ventilation rate of 0.6 per hour (te Biesebeek et al., 2014).

Exposed area – dermal

Dermal exposure during use is considered negligible, because one can work very precisely with a glue gun and, moreover, the glue is too hot to spread over the surface of the skin after heating up. Before use, there is dermal contact when the glue bar is inserted. Assuming that only one hand will be used to insert the glue bar; 20% of a palm will be exposed. This equals a contact surface of 45 cm² (te Biesebeek et al., 2014). A Q-factor of 2 is assigned because the underpinning data for the surface size of one palm is quantitatively rich but compromised by assumptions regarding the dimensions of the affected skin area (see also subsection 4.5).

Product amount – dermal

The product amount contacting the skin will be low because the glue is still solid at room temperature. The glue is more or less rubbed off the glue bar during the insertion of the glue bar into the device. The product amount is estimated to be of the order of 0.1 g. In the EU RAR on MDI (EU, 2003c), a similar product amount was provided (65 g), resulting in an estimated dermal exposure of 168 mg from MDI alone, which was a conservative estimation. For this default, a Q-factor of 2 is assigned because the underpinning data is limited and supplemented with estimations.

Table 24

Default values for hot-melt adhesive.

Use

Apart from glues in tubes, bottles, cartridges, syringes and canisters, glue is also available as sprays. Generally, glue spray is used on materials such as paper, cardboard, photos, textiles, cork and metal foils. Glue spray is also suitable for temporary attachment of materials. The glue is applied on both surfaces that are to be attached, except when porous materials are used, in those cases only one side should be sprayed with glue.

Scenario for glue spray

The scenario of gluing a poster to a wall or door, or mounting a poster in a frame, is described here. The inhalation exposure to the fraction of the non-volatile substances in the product can be estimated using the ConsExpo inhalation – exposure to spray – spraying model while the inhalation exposure to the volatile substances can be assessed using the inhalation – exposure to vapour – instantaneous release model. The defaults for the parameters exposure duration, room volume, ventilation and inhalation rate described for non-volatiles in sprays are used in the exposure estimation of both volatile and non-volatile substances. Defaults for the mass generation rate and the density of non-volatiles in the product are applicable only to the non-volatile substances and comply with the generic scenario for spray application (4.2.1). For the dermal exposure, however, the dermal – direct product contact – constant rate model is used.

Frequency

Glue spray is a product that is relatively easy to handle and has multifunctional application options. According to the information provided and explained in Annex II A.4, it is used by consumers at a frequency of 6 times per year. The Q-factor is considered to be 2 in this case because of the limitations also explained in Annex II A.4.

Spray duration

The surface of the poster is assumed to be 1.5 m². According to product information, 440 ml (375 g; product density =0.85 g/cm³; see Annex II, product data collection Table 96) is required to glue the poster onto a surface with application both on the poster and, for example, on a door. Using the mass generation rate for aerosol spray cans explained in subsection 4.2.1 (1.2 g/sec) provides a spraying duration of 315 seconds. A Q-factor of 2 is assigned in this case because the data basis for the product consumption is limited but sufficient.

Exposure duration

The exposure duration is the time that a person stays in the room during and after the task. The total exposure duration is set at 240 minutes as an estimation with the assumption that the user won’t leave the room once the task is conducted. Therefore, the Q-factor is considered to be 1.

Ventilation rate, room volume and height

The room is not specified. The default values for room volume, room height and ventilation rate from the General Fact Sheet for an unspecified room are considered in this case. These values are 20 m³, 2.5 m, and 0.6 per hour, respectively (te Biesebeek et al., 2014).

Product amount (default needed for the exposure assessment for volatile substances)

The product amount required for a 1.5 m² surface (poster) is 375 g according to the product information. A Q-factor of 3 is assigned here because the source data is sufficient to derive a default, albeit limited.

Exposed area – dermal

Dermal exposure may occur during the process of spraying because spray particles that bounce back from the treated surface or miss it can disperse in the room air and settle on the skin of the user. Furthermore, the user may accidently have dermal contact with surfaces already treated with glue while putting the object (the poster in this case) in position. The exposed area is assumed to be the surface of both hands (900 cm²) (te Biesebeek et al., 2014). A Q-factor of 2 is assigned because the underpinning data for the surface size of both hands is quantitatively rich but compromised by assumptions regarding the dimensions of the affected skin area (see also subsection 4.5).

Release duration – dermal

The release duration is the time during which the substance is present on the skin, resulting in dermal exposure. In this case, the release duration is assumed to equal the spray duration because intermittent spraying is not expected due to the small area that has to be treated. Furthermore, the user is not expected to work very precisely on this kind of task, which leads to the assumption that he will cover both surfaces with glue with just one short break when he switches between the wall and the poster. After spraying, the user tend to clean his hands in order to properly put the object in position without leaving behind stains of glue in undesired spots. The Q-factor is set to 2 because the data set for the derivation of the duration is limited but sufficient.

Table 25

Default values for glue spray.