Arsenic-treated wood is the result of a chemical process in which wood is treated with a pesticide/preservative called chromated copper arsenate (CCA) to prevent rotting in lumber designed for outdoor use. CCA contains arsenic, chromium, and copper and was widely used for residential purposes in the United States from the 1970s until EPA phased it out in 2003.

CCA-treated wood can be hazardous to human health because arsenic is classified as a known carcinogen. Exposure to arsenic can cause cancer of the lung, bladder, skin, kidney, prostate, and nasal passage. Data released in November 2003 by the US Environmental Protection Agency (EPA) show that 90 percent of children repeatedly exposed to arsenic-treated wood face a greater than one-in-one million risk of cancer. (One-in-one million is the EPA’s historic threshold of concern about the carcinogenic effects of toxic chemicals.) Arsenic exposure can also lead to nerve damage, dizziness, and numbness. Arsenic has been linked to immune diseases, cardiovascular disease, diabetes, and changes in hormone function. Lung and bladder cancer are the two health effects most often related to exposure to CCA-treated wood. For information on other cancer risks in the home environment, please see Cancer Risks.

Exposure to lead in housing poses a significant health risk to young children. Lead is a heavy metal used in many materials and products. When absorbed into the body, it is highly toxic to many organs and systems and seriously hinders the body’s neurological development. Lead is most harmful to children under age six because it is easily absorbed into their growing bodies and interferes with the developing brain and other organs and systems. Pregnant women and women of child-bearing age are also at increased risk, because lead ingested by the mother can cross the placenta and affect the unborn fetus.

Lead poisoning causes irreversible health effects and there is no cure for lead poisoning. At very low levels of exposure in children, lead causes reduced IQ and attention span, hyperactivity, impaired growth, reading and learning disabilities, hearing loss, insomnia, and a range of other health, intellectual, and behavioral problems. At low levels, lead poisoning may not present identifiable symptoms, and a blood test is the only way to know if a child is poisoned. At very high levels of exposure, which are now very rare in the U.S., lead poisoning can cause mental retardation, coma, convulsions, and even death.

The major remaining cause of lead poisoning is lead-based paint in housing, especially housing built before 1950, when lead paint was commonly used. Most children with elevated lead levels are poisoned in their own homes by peeling lead-based paint and the lead dust it generates. The mere presence of lead-based paint in a home is not a hazard, as about 40 percent of all U.S. housing contains some leaded paint, and the vast majority of children live safely in these homes and apartments.

Housing age is an important predictor of risk, because the lead content of paint varied substantially over the past century. During the first half of the twentieth century, the lead content of paint was marketed as a measure of its quality—the more lead the better. Prior to about 1940, leaded paints typically contained high amounts of lead, ranging from 10 percent to as much as 50 percent. Lead was added to make paint durable, so lead paint was frequently used in high-traffic and high-moisture areas, including kitchens and bathrooms, exterior siding and trim, window and door trim, stairs, porches, etc. In the early 1950s, the paint industry began reducing lead content, although many paints still contained harmful amounts of lead. Federal regulations limited lead content in 1972 and effectively banned lead in residential paints in 1978.

Exposure to rodents (mice and rats) has been linked to increased asthma symptoms among laboratory workers who handle rodents and are sensitized to them. Other studies have established links between rodent allergies and asthmatic symptoms in lab workers. Research published in 2004 found similar linkages in residential settings. Rodent allergens are likely from rodent urine, saliva, or skin.

It is clear that many inner-city residents are exposed to and allergic to rodents. A major study on asthma among inner-city children found that nearly 20 percent of asthmatic children had been sensitized to rats and 15 percent were sensitized to mice. This is important to note, as research has found mouse allergen in 82 percent of US homes.

Rodents can also expose humans to diseases such as hantavirus. Exposure to such disease vectors is rare but can cause severe health problems.

Pesticides are substances designed to kill, repel, or mitigate pests. They include a number of chemical and biological agents commonly used in and around the home to control a broad range of pests: insecticides (for insects, including cockroaches, ants, and termites), rodenticides (for mice and rats), fungicides (for mold and fungi), herbicides (for plants), and antimicrobials (for bacteria and viruses).

Use and Exposure

Approximately 4.4 billion pesticide applications are made each year to American homes, gardens, and yards. According to surveys by the Environmental Protection Agency (EPA), more than three-quarters of U.S. households use pesticides, with 66 percent treating major living areas in the home one or more times per year. Cockroaches and ants are the most common targets. More than one-third of households used insecticides in the absence of a major insect problem.

Molds are simple, microscopic organisms that can grow virtually anywhere, both in homes and outdoors. Along with mushrooms, yeasts, and mildew, molds are classified as fungi. Molds typically consist of a network of threadlike filaments that infiltrate the surface on which the mold is growing. Molds reproduce by releasing spores, which are lightweight and small enough to travel through the air. Spores can resist dry, adverse environmental conditions, allowing them to outlive the mold that produced them.Molds play an important ecological role in breaking down dead organic matter and returning nutrients to the environment. They require moisture and food to grow, and they typically thrive in warm, moist environments. Moisture is the key factor determining mold growth in the home, influencing both the types of mold present and the extent of mold colonization. A variety of materials found in the home, including insulation, wallpaper, glues used to affix carpet, backing paper on drywall, dust, and dirt, can serve as a food source for mold. Mold colonies can go dormant under adverse conditions and revive when favorable conditions return.

Mold growth often appears as green, gray, black, brown, or other discoloration. Eventually, mold growth results in the breakdown of the substrate. More than 1,000 types of molds have been found in US homes.

Exposure and Health Impacts

The concept of “essential maintenance practices” (EMPs) was developed to deal with lead-based paint in older housing in recognition that “an ounce of prevention is worth a pound of cure.” While some homes need dedicated “lead abatement projects” by certified contractors, in most cases, hazards can be avoided in the first place through good maintenance and common sense safeguards. Some EMPs are specific to lead safety, such as avoiding paint removal practices that generate and spread dangerous lead dust. Others address conditions that can cause multiple problems. For example, water leaks, water damage, and excessive moisture can encourage the growth of mold, mildew, and pests, which can cause asthma and other health problems, in addition to causing paint to deteriorate. Periodic visual inspections can identify clues to and causes of water leaks and moisture problems so that low-cost repairs “nip problems in the bud.” The concept of “enlightened maintenance practices” is at the foundation of healthy homes. The EPA/HUD five-hour training course in lead-safe work practices (LSWP) offers a model for conveying practical information to existing trades and can benefit all those whose work encounters painted surfaces in older housing.

Essential Maintenance Practices to Reduce Lead Hazards

Cockroaches in homes are a health hazard to many children and families because of the risks cockroach antigens pose to asthma sufferers. Traditionally, cockroaches were controlled because they are offensive, leave behind an awful smell, and cause gastrointestinal and respiratory illness. However, research shows that cockroach debris (old shells, saliva, body parts, and droppings) triggers asthma attacks in people who are sensitized to cockroach antigen (proteins found in the debris). In homes where several allergens are present, including dust mites, mold, furry pets, tobacco smoke, and certain chemicals, children may experience severe and frequent asthma attacks from high airborne concentrations of these allergens.

Any home with food or moisture can have cockroaches. Kitchens and bathrooms typically have the highest number of cockroaches due to the presence of food products and moisture from plumbing fixtures. Apartment buildings often have the worst infestations. The goal is to keep cockroaches out of the home and to eliminate existing pests. Reaching this goal is not always easy, especially in multi-unit housing that is already infested. For most apartment buildings, the landlord must take a building-wide approach to controlling these pests. Moreover, a coordinated effort by the landlord and all tenants is required to eliminate cockroaches.