Irritation

LR2 (5% or 10% dissolved in distilled water, (Inveresk 1996) was found to be non-irritating in 36 human volunteers (26 female, 10 male) in a dermal patch test. Volunteers (age: 18–65 yr) were treated with approximately 20 µL of 0%, 5%, and 10% w/w LR2 in petrolatum, which was placed in Finn chambers and applied to their backs³. Forty-eight hr after application, the patches were removed and the application sites were rinsed. Application sites were evaluated 2 hr, 1 d, 2 d, and 5 d after patch removal. Two subjects showed what were reported as doubtful skin reactions to 10% LR2 at the 2-hr evaluation time point. No skin reactions to 5% or 10% LR2 were observed in the volunteers at later time points.

LR2 and LR4 were also non-irritating when applied to rabbits (Inveresk 1989, Safepharm 1993a). A single application of 0.5 mL (650 g) of LR2 in neat form (Inveresk 1989) or of 0.5 g of LR4 in 0.5 mL distilled water (Safepharm 1993 a) was applied to the dorsum of three male New Zealand White rabbits and covered for 4 hr. The patch was removed and the skin was evaluated for reactions after 1, 24, 48, and 72 hr. No erythema or edema was observed from LR2 exposure. Very slight erythema was observed from LR4 exposure in 2 of the 3 animals 1 hr after patch removal. There were no skin reactions to treatment with LR4 when the animals were evaluated after 24 and 72 hr.

No irritation was observed in one male and two female New Zealand White rabbits exposed topically to fabric treated with LR2 (Inveresk 1990a). The rabbits were exposed to fabric (approximately 2.5 cm×2.5 cm) “impregnated” with LR2 five times for 23 hr each. The amount of LR2 applied to or present in the fabric was not reported. The application sites were observed for skin reactions 1 hr after each application. No erythema or edema was observed following any of the exposures to the fabric.

Sensitization

LR2 was found to be a poor skin-sensitizing agent in the Magnusson and Kligman maximization test (Safepharm 1993b). Initially, 20 female Dunkin-Hartley guinea pigs were treated with three 0.1-mL injections containing (1) Freund's complete adjuvant plus water in a 1:1 ratio; (2) a 1% w/v dilution of test material in distilled water; and (3) a 1% w/v dilution of test material in Freund's complete adjuvant plus distilled water, respectively. Topical induction was attempted on d 7 with undiluted LR2 (0.2–0.3 mL) applied to filter paper placed over the injection sites and covered for 48 hr. Scattered mild redness was observed at the injection sites in 20/20 animals treated with LR2 1 hr after removal of the filter paper and in 2/20 animals after 24 hr of removal of the filter paper. The animals were then challenged on d 21 for 24 hr with filter paper patches containing 0.1–0.2 mL of 50% or 75% (v/v) solutions of LR2. None of the 20 animals developed a tissue reaction to 50% or 75% LR2 24 or 48 hr after challenge.

LR4 was also found to be a poor skin-sensitizing agent in the Magnusson and Kligman maximization test (Safepharm 1993c). Twenty female guinea pigs were initially injected intradermally with a 25% (w/v) solution of LR4. Topical induction was then attempted on d 7 with filter paper patches containing 75% (w/w) LR4 in distilled water. Only 1 of 20 animals had skin changes (scattered mild redness) at the application site 1 hr after removal of the patches. No animals had any visible skin reactions 24 hr after patch removal. None of the animals showed any tissue reaction either 24 or 48 hr after topical challenge with filter paper patches containing 50% or 75% solutions of LR4.

Systemic Effects

Acute dermal toxicity studies in Sprague-Dawley rats estimated the LD₅₀s for LR2 and LR4 to be>2,000 mg/kg (Safepharm 1994, 1993d). Animals were treated with 2,000 mg/kg of neat LR2 or LR4 (1.59 mL/kg) to a skin area of approximately 10% of the rat total body surface area and covered for 24 hr. The bandage was then removed and the test sites were observed for skin reactions for 14 d. There were no deaths, signs of systemic toxicity, or skin irritation, and weight gain was not affected in animals from either test group. No abnormalities were observed at necropsy.

Other Systemic Effects

No studies were identified that examined the effect of dermal exposure to APPs, ammonium ions, or polyphosphates on immunological, neurological, reproductive, or developmental parameters in humans or experimental animals. Additionally, no studies were identified that investigated the carcinogenicity of these compounds in humans or animals following dermal exposure.

Systemic Effects

Only one inhalation toxicity study was located for APPs. Five male and five female Sprague-Dawley rats were exposed to Amgard MC(M) at 5,090 mg/m³ (nose-only exposure) for 4 hr and monitored for 14 d (Safepharm 1993e). The mass median aerodynamic diameter (MMAD) of the APP particles was 5.8 µm, and their geometric standard deviation was 0.35 µm. No deaths occurred among the exposed animals and weight gain was normal over the 14-d observation period. Exposed animals developed a hunched posture, decreased respiratory rate, lethargy, and tiptoe gait 4 hr after exposure, but these symptoms were not evident after 3 d of exposure. The 4-hr-inhalation LC₅₀ for Amgard MC(M) was estimated to be >5,090 mg/m³ (>5.09 mg/L) for male and female rats.

Material Safety Data Sheets (MSDSs) report that exposure to LR2 or LR4 may cause nose and upper respiratory tract inflammation (Albright and Wilson 1998a, 1998b, 1998d, 1998e). The MSDSs for both LR2 and LR4 (Albright and Wilson 1998d, 1998e) report a 1-hr-inhalation LC₅₀ >20 mg/L (species and sex not reported). It is not known whether this is an experimentally determined or an estimated value.

No data on the inhalation toxicity of ammonium ions or of other polyphosphates were identified.

Other Systemic Effects

No studies were identified that examined the toxic effects of inhalation exposure to APPs, ammonium, or polyphosphates on immunological, neurological, reproductive, or developmental parameters in humans or laboratory animals. Additionally, no studies were identified that investigated the carcinogenic effects of these compounds following inhalation exposure.

Systemic Effects

No oral toxicity data for APPs were located for humans. Typical human dietary phosphorous levels are not harmful, especially in the presence of adequate calcium and vitamin D intake. The mean daily phosphorus dietary intake for adult males and females is estimated to be 1,500 mg/d and 1,000 mg/d, respectively. However, if the intake of phosphorus from processed foods was included in these values, the estimated dietary intake of phosphorous would be up to 20% higher.

It is known that high doses of ammonium ions can cause metabolic acidosis; persons with compromised liver function are at highest risk. Exposure to oral doses of 3.2 or 4.8 g ammonium/d as ammonium chloride for 5 d caused metabolic acidosis in two humans with compromised liver function (Sartorius et al. 1949). Effects secondary to acidosis include renal enlargement and demineralization of bone (ATSDR 1990).

The oral LD₅₀ for LR2 in rats was estimated to be >5,000 mg/kg (Inveresk 1990b). No deaths or clinical signs of toxicity were observed among five male and five female Sprague-Dawley rats given a single gavage dose of 5,000 mg/kg LR2 in distilled water and observed for 14 d. Weight-gain was normal in females during the second wk of the 2-wk observation period, but weight-gain in exposed males was reduced during the second wk. Gross post-mortem analysis of all dosed animals revealed no abnormalities.

No deaths or toxicity symptoms were observed among five male and five female Sprague-Dawley rats treated with a single gavage dose of 2,000 mg/kg LR4 in distilled water (Safepharm 1993f). Body weight gain was normal for all animals during both wk of the observation period and no gross abnormalities were detected at necropsy. Therefore, it was concluded that the LD₅₀ for LR4 in rats is >2,000 mg/kg.

JECFA (1974) summarized a number of toxicity studies on phosphates and polyphosphates (see Table 12–2). The primary effect identified in these studies is kidney calcification (nephrocalcinosis), resulting from the precipitation of calcium phosphate due to an upset in phosphate homeostasis. JECFA (1974) noted that it is difficult to identify an effect level for nephrocalcinosis in toxic ity studies because renal calcification occurs naturally to some extent in control rats which is determined by dietary intake of calcium and vitamin D.

TABLE 12–2

Summary of Oral Toxicity Studies on Polyphosphates.

Studies by van Esch et al. (1957, as cited in JECFA 1974) and Hodge (1964a, 1964b) suggest that chronic exposure to 0.5% polyphosphates in the diet may cause increased kidney weight but no kidney histopathology, while higher concentrations may cause kidney calcification when mineral levels are not equalized.

Reproductive and Developmental Effects

No information was found regarding the reproductive or developmental effects of APPs following oral exposure. Information on reproductive and developmental effects of ammonium ions was also not located.

A study conducted by van Esch et al. (1957, as cited in JECFA 1974) found decreased fertility in rats that were treated with a mixture of one-third Kurrol's salt and two-thirds diphosphate at a dietary concentration of 5%. No reproductive effects were reported at lower concentrations.

Lang (1959, as cited in JECFA 1974), found no effects on reproduction in three generations of rats, each fed diets containing 0.4% or 0.75% phosphoric acid for 90 wk.

No effects on fertility, litter size, neonate growth, or neonate survival was observed in a three-generation reproduction study in groups of rats administered 0.5% sodium tripolyphosphate or 0.5% sodium hexametaphosphate (Hodge 1964a, 1964b, and BIBRA 1964). There was also no apparent effect on the histopathology of major organs of the third generation.

Other Systemic Effects

No studies were identified that examined the immunological, neurological, or carcinogenic effects of oral exposure to APPs, ammonium ions, or polyphosphates. Ammonium ions and polyphosphates are unlikely to be carcinogenic, in light of the physiological roles of ammonium ions and phosphate in the body.

Dermal Assessment

There are no appropriate APP toxicity data available for deriving a dermal RfD.

Inhalation RfC

Only acute LC₅₀ data are available for APPs; these data are insufficient for the derivation of an RfC.

Oral RfD

There are no subchronic or chronic toxicity data for LR2 and LR4, therefore it is not possible to derive an oral RfD for these compounds.

IOM (1997) has developed a recommended dietary allowance (RDA) for phosphorous of 460 mg for children 1–3 yr old, 500 mg for children 4–8 yr old, 1,250 mg for ages 9–18 yr old, and 700 mg for ages 18 and older. The importance of the calcium:phosphate ratio was also noted; a ratio of less than 1:2 can cause resorption and loss of bone in animals.

The Joint Expert Committee on Food Additives (JECFA) of the Food and Agriculture Organization of the World Health Organization (FAO/WHO) has established a maximum tolerable daily intake for phosphates, including APP, of 70 mg phosphorus/kg (JECFA 1974). This value includes all phosphates including those in food and applies to diets that are sufficient in calcium.

The JECFA value of 70 mg/kg was derived from the lowest dietary concentration that produced nephrocalcinosis in the rat (1 % phosphorous) as described by van Esch et al. (1957, as cited in JECFA 1974). Extrapolation to the lowest phosphorous level that might conceivably cause nephrocalcinosis in humans was based on a daily food intake of 2,800 calories and a dietary phosphate level of 6,600 mg/d (JECFA 1974). Further details on the calculation were not provided.

The subcommittee chose to use the JECFA (1974) acceptable daily intake for phosphorous of 70 mg phosphorus/kg-d for deriving an oral RfD for APPs. The oral RfD was calculated by multiplying the approximate amount of phosphorous present, by weight, in LR2 and LR4. The solids portion of LR2 contains approximately 26% phosphorus, therefore, the oral RfD for LR2 is estimated to be 270 mg/kg-d (≈300 mg/kg-d). LR4 contains a minimum of 27% phosphorus by weight (Stewart Miller, Albright and Wilson, pers. commun., Nov. 1, 1999), corresponding to a minimal oral RfD of 260 mg/kg-d (≈300 mg/kg-d).

The U.S. EPA has developed an RfD for ammonium sulfamate (EPA 1999), but the subcommittee did not use this RfD for APPs because the primary toxic moiety of ammonium sulfamate may be the sulfamate ion, rather than the ammonium ion.

Dermal Exposure

The assessment of noncancer risk by the dermal route of exposure is based on the scenario described in Chapter 3. This exposure scenario assumes that an adult spends 1/4th of his or her time sitting on furniture upholstered with APPs, that 1/4th of the upper torso is in contact with the upholstery, and that clothing presents no barrier. APPs are considered to be ionic and are essentially not absorbed through the skin. However, to be conservative, the subcommittee assumed that ionized APPs permeate the skin at the same rate as water, with a permeability rate of 10⁻³ cm/hr (EPA 1992). Using that permeability rate, the highest expected application rate for APPs of 7.5 mg/cm², and Equation 1 in Chapter 3, the subcommittee calculated a dermal exposure level of 2.2 mg/kg-d. The oral RfD for APPs (300 mg/kg-d; see Oral RfD in Quantitative Toxicity section) was used as the best estimate of the internal dose from dermal exposure. Dividing the exposure level by the oral RfD yields a hazard index of 7.3 ×10⁻³. Thus it was concluded that APPs used as FRs in upholstery fabric are not likely to pose a noncancer risk from dermal exposure.

Inhalation Exposure

Oral Exposure

The assessment of noncancer toxicological risk for oral exposure to APPs is based on the oral exposure scenario described in Chapter 3. This scenario assumes a child is exposed to APPs by sucking on 50 cm² of fabric backcoated with APPs, 1 hr/d for 2 yr. The subcommittee estimated an upholstery application rate (S_a) for APPs of 7.5 mg/cm². Oral exposure was calculated using Equation 15 in Chapter 3. The extraction rate (µ_w) for APPs was estimated to be 0.038 based on extraction data for organic phosphates in polyester fiber (McIntyre et al. 1995). The release rate from the fiber for estimating extraction was 0.06/d at 28°C calculated using the equation 2d/2 πR (d=film thickness, R=fiber radius) with a correction from fiber to film of a factor of 0.63.

The worst-case average oral daily dose for APPs was estimated to be 0.059 mg/kg-d. Division of the oral dose estimate by the oral RfD for APPs of 300 mg/kg-d yields a hazard index of 2.0×10⁻⁴. These results indicate that under the given worst-case exposure scenario, oral exposure to APPs is not likely to pose a health risk to humans.