How Indoor Air Quality Affects Health

Poor indoor air quality can contribute to symptoms ranging from eye, nose, and throat irritation to chronic conditions. Pollution sources such as wood smoke, natural gas combustion, or cigarette smoking that release gases or particles into the air can contribute to indoor air quality problems in homes. For example, secondhand smoke can cause respiratory and heart disease, whereas radon causes cancer. Inadequate ventilation also contributes to poor indoor air quality. High temperature and humidity levels can also increase concentrations of some pollutants. In addition, the use of candles, incense, or home deodorizers can increase symptoms in individuals with preexisting respiratory conditions (National Institute of Building Sciences 2005).

Radon Gas

Radon is a naturally occurring radioactive gas emitted by the normal decay of uranium, which is found in most soils; some soils have higher levels than others (Centers for Disease Control and Prevention and U.S. Department of Housing and Urban Development 2006). Radon is the leading cause of lung cancer among nonsmokers, causing an estimated 15,400–21,800 lung cancer deaths annually (Committee on Health Risks of Exposure to Radiation [BEIR VI] 1999; Frumkin and Samet 2001; U.S. Environmental Protection Agency 2003). Nearly one in 15 homes in the United States have radon levels above 4 picocuries per liter (pCi/L), the level at which the U.S. Environmental Protection Agency (EPA) recommends taking specific steps to reduce radon levels in the home (U.S. Environmental Protection Agency undated a). Radon gas can enter the home through structural deficiencies such as gaps between basement walls or large cracks in the foundation, and its presence can be detected through a simple test (Field et al. 2000). A house in an upper Midwest or Eastern state, for example, is more likely to have an elevated level of radon compared with a house in the South or on the West Coast (U.S. Environmental Protection Agency undated b). A study in one Midwestern state found that radon levels in 60% of the houses tested exceeded the EPA’s action level of 4 pCi/L (Field et al. 2000).

Map of the United States identifying risk for radon.

Allergens and Asthma

The predominant health outcome studied in conjunction with allergens in the home is asthma. Nearly 15 million asthma-related physician and outpatient hospital visits and almost 2 million asthma-related emergency department visits occurred in 2004. Environmental factors in homes that can contribute to the occurrence or severity of asthma include exposure to pests and pet dander (Akinbami and Schoendorf 2002), airborne and settled dust, dust mites (Institute of Medicine 2004), mold, and other conditions such as excess moisture. Studies show that 84% of U.S. homes have a bedroom with detectable levels of dust mite allergens; many of these have levels that can contribute to allergies or asthma (Arbes et al. 2003). Similarly, 82% of dwellings in the United States have detectable levels of mouse allergens (Cohn et al. 2004), and 63% have detectable levels of cockroach allergens (Cohn et al. 2006). Low-income households and older homes are also among the factors frequently associated with U.S. residences having high concentrations of mouse and cockroach allergens (Cohn et al. 2004, 2006).

Mouse eating a cupcake.

Dampness and the presence of mold are also associated with asthma and other respiratory health complaints. Exposure to dampness and mold in homes is estimated to contribute to approximately 21% of current asthma cases in the United States, at an annual cost of $3.5 billion (Mudarri and Fisk 2007). Moisture in homes supports the growth of mites and mold and the infestation of roaches, rats, and mice—all of which produce allergens that aggravate asthma and other preexisting chronic respiratory conditions, although it is not clear at what levels these contaminants cause allergic sensitization (Bornehag et al. 2004; Institute of Medicine 2004; Krieger and Higgins 2002; Mudarri and Fisk 2007).

How Water Quality Affects Health

In the United States, an estimated 4 million to 33 million cases of gastrointestinal illness associated with public drinking water systems occur annually (Colford et al. 2006; Messner et al. 2006). The presence of contaminants in water can lead to other adverse health effects; for example, pesticides can cause reproductive problems (Casarett and Doull 1991), polychlorinated biphenyls and lead can cause neurological disorders (Chevrier et al. 2007), and nitrates can cause methemoglobinemia or “blue baby syndrome” (Greer et al. 2005). Water contamination has many sources, including naturally occurring chemicals and minerals (e.g., arsenic, radon, uranium), local land-use practices (e.g., fertilizers, nitrates, pesticides, concentrated animal feeding operations), manufacturing processes, sewer overflow, and malfunctioning wastewater treatment systems (e.g., septic systems).

A particular area of concern with respect to water quality is the approximately 40–45 million persons in the United States who rely on private household wells for drinking water. Such systems are more commonly found in rural and suburban communities. Drinking water from public water systems is regulated by EPA, but private wells and small public water systems are unregulated, and testing for contaminants typically is left to homeowners. These wells can be contaminated with biological agents such as Cryptosporidium, E. coli O157:H7, and norovirus, all of which cause gastrointestinal illness. These wells can also be contaminated by chemicals, including pesticides and arsenic (U.S. Environmental Protection Agency undated c). Contamination of a private well is not only the concern of the household served by the well; it is also of concern to households using other nearby water supplies, including those that draw water from an aquifer. The safety of private wells can be improved by attention to issues including proper design, structure, installation, testing, and maintenance (Anderson et al. 2003; Centers for Disease Control and Prevention 1995).

How Residential Chemicals Affect Health

Chemicals in and around the home can contribute to poisonings and other health effects. Every 13 seconds, a poison control center in the United States fields a call about a potential poison exposure; more than 90% of these exposures occur in the home (Watson et al. 2004). Non-pharmaceutical products account for most poison exposures among children (McDonald et al. 2006). Most common among adult exposures are pain relievers, prescription medications, sedatives, cleaning products, and antidepressants (McDonald and Gielen 2006).

The long-term health effects of pesticide exposure are unknown (Lu et al. 2001), but some studies suggest links between chronic exposure to pesticides and attention and behavioral problems and other neuropsychologic deficits as well as increased risk for asthma among children exposed during the first year of life (Chanda and Pope 1996; Rice and Barone 2000; Salam et al. 2004). In an estimated 74% of U.S. households, pesticides are used to prevent or exterminate insects and rodents (U.S. Environmental Protection Agency 2004). No national estimates of home pesticide exposure prevalence are available (U.S. Environmental Protection Agency 2007). However, in Washington State, 48% of reported pesticide-related health complaints were the result of pesticide use in and around the home or on food (Washington State Department of Health 1998).

In general, household cleaning products are safe when used as directed. Still, even when used as intended, detergents, bleaches, and a variety of other household cleaning products represent chemical exposure and may contribute to poor indoor air quality. For many household chemicals, a “safe” frequency and quantity of use in homes has not been established.

Infants and young children are most susceptible to the adverse health effects from use of household chemicals because they may be more likely to be exposed—they spend more time indoors, they have more hand to mouth behaviors—and their smaller and still developing bodies may be more susceptible (U.S. Environmental Protection Agency 1998). Under the age of thirteen, more males are victims of poison exposures, but among teenagers and adults, more females are involved (McDonald and Gielen 2006).

How Housing Structure and Design Affect Health

A home provides shelter, privacy, and safety and protects our physical and mental health. A residence that fails to offer these essentials through adequately designed and properly maintained interiors and exteriors is not healthy housing. How homes are designed, constructed, and maintained; their physical characteristics; and the presence or absence of safety devices have many effects on injury, illness, and mental health. Home conditions also influence the ability of people to participate fully in their community.

Elevated Lead Levels

Between 1999 and 2004, an estimated 240,000 children 1–5 years of age had blood lead levels ≥ 10 micrograms per deciliter (μg/dL), and most of these elevated levels were a result of lead paint hazards in and around their homes ( Jones et al. 2009). Lead exposure can result in lasting impairment of a child’s development and behavior such as decreased IQ and attention span and increased risk for delinquent behavior (Centers for Disease Control and Prevention 2005d). Although in the United States lead has been banned from paint intended for residential purposes since 1978, older houses with lead paint remain. These homes can expose children to lead when maintenance is deferred and the paint deteriorates, or when the property is renovated or painted without using lead-safe work practices to control dust and soil contamination. In the United States in 2000, an estimated 1.2 million housing units with lead-based paint hazards were home to children younger than 6 years of age ( Jacobs et al. 2002). Other sources of lead exposure in the home include lead water pipes and solder used in plumbing, as well as toys and ceramics (Levin et al. 2008). Children of minority race/ethnicity and children whose families are poor are much more likely to be exposed to lead in their homes.

Outdoor stairs to a house featuring a banister with badly peeling paint.

Mental Health

Poor housing conditions, including crowding and inadequate lighting, are associated with risk for poor mental health. Poor-quality, overcrowded, multifamily homes are associated with outcomes that include aggression and withdrawal, lower general health status (Dunn et al. 2004; Evans et al. 1996; Lepore et al. 1992; Regeoczi 2003), and psychological distress, particularly among women and children (Evans et al. 2001). Lack of light (e.g., from inadequate number and placement of windows) is related to depression (Golden et al. 2005; Kripke 1998). Although some studies have suggested an association of dampness or mold with depression (Shenassa et al. 2007), the Institute of Medicine concluded that evidence is insufficient to determine whether an association exists between either damp indoor environment or presence of mold and neuropsychiatric symptoms (Institute of Medicine 2004).

Structural Deficiencies

In 2005, about 2 million people in the United States lived in severely inadequate homes (U.S. Department of Housing and Urban Development 2007). The U.S. Census Bureau defines severely inadequate housing as homes without heat, hot water, or electricity, or housing with significant upkeep problems and structural defects (U.S. Census Bureau 2006). Although wear typically increases as homes age, these problems are not limited to older homes. Some modern building practices, inferior building construction, and poor building design also can exacerbate conditions that threaten health. For example, water incursions in structures that lack adequate ventilation and drainage increase the risk for mold growth, which is associated with increased risk for asthma and perhaps other health problems (Institute of Medicine 2000, 2004; U.S. Department of Health and Human Services 2005a). Poor design and maintenance of both old and new homes can result in injuries, poisoning, and poor mental and physical health.

Accessibility

For the elderly and for persons with disabilities, home design and construction can hamper—sometimes substantially—ease of mobility and interfere with access to important features of the house like toilets, sinks and bathtubs, and shelving in cupboards and closets. Approximately 5.5 million disabled persons in the United States face barriers to community participation because of building design or because of the absence of sidewalks (Hendershot 2004). Additionally, inappropriate design and construction can increase the possibility of injury from falls among older adults and can deny some the opportunity to remain at home and more comfortably “age in place” rather than move to an assisted-living facility or nursing home.

How Behaviors Contribute to Adverse Health Related to Homes

Individual resident behavior is an important aspect of healthy and safe home environments. Yet a large gap exists between what we know about how to make homes healthier, and what we actually do. For example, research indicates that although parents say they support injury-prevention behaviors, their home lives do not reflect adequate injury-prevention practices (Gielen et al. 1995). In a survey of parents, 59% reported they did not use stair gates; only 37% had their water heater temperature set at 125°F or less, and 27% did not have smoke alarms (Gielen et al. 1995).

Disparities in Access to Safe and Healthy Homes

Many of the disparities in health status among subpopulations may be linked to poor access to safe and healthy homes, which is most prevalent among lower income populations, populations with disabilities, and minority populations. In 2005, 6% of all U.S. residents and 14% of low-income renters lived in homes with severe or moderate physical problems, such as water leaks that can cause mold growth and trigger allergic reactions and asthma attacks (U.S. Census Bureau 2006). Low-income minority renters in nonmetropolitan areas have a higher incidence of housing quality problems compared to other renters or homeowners ( Joint Center for Housing Studies of Harvard University 2008). Minority parents also are substantially less likely than are white parents to have safety measures in their homes such as stair gates, safety latches on cabinets, or lower hot-water thermostat settings (Flores et al. 2005).

Housing-related illness and injury are not, however, the exclusive domain of lower-income groups. Higher income populations also experience housing-related health problems. In some communities, more than 40% of the middle-class suburban population lives in homes with elevated levels of cockroach allergens (Matsui et al. 2003). High-density housing may be associated with negative psychological consequences for the affluent, as well as for poorer populations (Evans et al. 2000).

Venn diagram describing rent burden and inadequate homes showing the intersection between unassisted very-low-income renters and (a) renters with severely inadequate housing, (b) renters with severe rent burden, and (c) the worst case needs, the majority of whom are unassisted very-low-income renters.

Relationships among Community Characteristics, Health, and Homes

Broader community characteristics have important effects on homes and their residents. Homes also have effects on the broader environment.

Housing Instability and Homelessness

People with low-household incomes, the elderly, people with disabilities, and minority populations are least likely to have access to safe, healthy, affordable, and accessible homes. Each year in the United States, an estimated 2.1 million adults and 1.3 million children are homeless (Burt et al. 2001). For those who are homeless, the lack of a place to live is a daily, distressing fact of life. For approximately 2 million families at the bottom of the socioeconomic ladder, housing is so severely deficient that it is barely adequate ( Joint Center for Housing Studies of Harvard University 2004). For nearly 18 million Americans, more than 50% of family income is consumed by housing costs. Consequently, these families cannot meet expenses for other basic needs such as medical care, childcare, heating and gasoline, and food ( Joint Center for Housing Studies of Harvard University 2008), and with fuel costs rising, their ability to meet these expenses may be further compromised.

People with low incomes may not be able to secure adequate, affordable homes and may be forced to move often. This housing instability also contributes to adverse health outcomes, including increased asthma morbidity, tuberculosis, and developmental delay, as well as school failure and delinquency (Buckner 2008). Those who are both homeless and chronically ill are confronted by a unique set of problems as they try to maintain medical regimes related to asthma, diabetes, or AIDS (Leaver et al. 2007; Matte and Jacobs 2000). Without an adequate supply of affordable homes, healthy homes cannot be achieved.