Introduction

Most of us are surprised to learn that indoor air pollution has been ranked among the top five risks to our health. The air within homes and buildings may be more seriously polluted than the outdoor air, even in large cities. It is estimated that most people spend approximately 90 percent of their time indoors and 65 percent of that time is at home.

Poor indoor air quality can contribute to the development of chronic respiratory problems and disease. It can also cause nausea, fatigue, dizziness, headaches, nasal congestion, and irritation of the eyes, nose, and throat. While children, older adults, persons with lung disease, and others who spend the most time indoors are at greater risk for health problems caused by indoor air pollution, each of us can be susceptible to these adverse health effects.

It can be difficult to detect exposure to some indoor air pollutants. Many of the substances give no warning - they can't be seen or smelled. These substances may produce symptoms that are difficult to recognize or link to a specific cause. Further, some health effects may not appear until years later.

Listed below are steps that service providers can take to reduce the risks associated with existing sources of indoor air pollution and prevent new health problems from developing.

Biological Pollutants

Biological pollutants are present to some degree in every home and building. This includes molds, mildew, bacteria, pollen, house dust mites, cockroaches, and animal dander. High humidity levels, standing water, wet surfaces, and water-damaged materials are factors that allow growth of contaminants. Heating and cooling systems can become breeding grounds for mold and mildew and other contaminants. These contaminants can travel through the air and are usually inhaled, either alone or by attaching themselves to particles of dust. To reduce exposure to biological pollutants:

• Keep the house (or work area) clean. Many allergy-causing contaminants like dust mites, pollens, and animal dander can be reduced through regular cleaning.
• Prevent moisture buildup. Use exhaust fans vented to the outdoors in bathrooms and kitchens. Vent clothes dryers to the outdoors. Ventilate the attic and crawl spaces.
• Respond immediately when carpet or building materials are water-damaged. Thoroughly clean and dry water-damaged carpet and materials (within 24 hours) or consider removal and replacement.
• Frequently clean evaporation trays in air conditioners, refrigerators, and dehumidifiers. If cool mist or ultrasonic humidifiers are used, these appliances should be cleaned according to the manufacturer's instructions and refilled with fresh water daily.

Stoves, Heaters, Fireplaces, and Chimneys

Heating systems and other home appliances like stoves, heaters, fireplaces, water heaters and dryers using gas, fuel or wood can produce carbon monoxide, nitrogen dioxide, and particles that can be very dangerous. Carbon monoxide and nitrogen dioxide are odorless and colorless. Chimneys and flues not properly installed or maintained are hazardous. To reduce exposure to carbon monoxide, nitrogen dioxide and fuel particles:

• Have central air systems, including furnaces, flues and chimneys inspected annually by a trained professional. Promptly repair cracks or damaged parts.
• Use exhaust fans over gas cooking stoves and ovens and keep burners properly adjusted. Do not use stoves or ovens if the flame tip is always yellow or orange - ask the gas company to adjust the burner so the flame tip is blue. Never use a gas stove or oven to heat the home.
• Take special precautions when using unvented gas heaters or vent-free gas fireplaces. When using these heaters or fireplaces, follow the manufacturer's instructions, open a door from the room where the heater is located and open a window slightly for fresh air.
• Change filters on central air systems and air cleaners frequently according to manufacturer's instructions.
• Install carbon monoxide alarms.

Household Chemicals

Organic chemicals that release gases are in many household products. These include paints, paint strippers and other painting supplies; chlorine bleach, cleaners, disinfectants, and waxes; moth balls and air fresheners; aerosol propellants; and pesticides. Health effects caused by these chemicals can vary greatly and depend upon the level and amount of exposure. People using products with organic chemicals can expose themselves and others to high pollution levels. To reduce exposure to household chemicals:

• Always follow label instructions carefully. If a label says to use the product in a well-ventilated area, go outdoors. Otherwise, open windows to provide as much outdoor air as possible.
• Store all products safely and out of reach of children and pets. Some products such as paint and pesticides should be stored in well-ventilated areas outside the home.
• Buy limited quantities and throw away old or unneeded products safely. Gases can leak even from closed containers. Follow product label instructions about safe disposal.
• Use non-chemical methods of pest control when possible. Examples of these methods include electronic or radio frequency insect repellant devices and 'bug lights'. Physical barriers are created by using window and door screens and applying weather stripping. Replacing damaged wood and repairing leaking faucets and pipes are also helpful. Storing food in tightly sealed containers and washing indoor plants and pets are additional ways of addressing pest control in your household.
• Avoid exposure to paint strippers, adhesive removers, and aerosol spray paints. Many of these products contain methylene chloride that is especially hazardous.
• Minimize exposure to newly dry-cleaned materials. The chemical most often used in dry cleaning can be hazardous. Do not accept dry-cleaned materials when you pick them up from a commercial cleaner if they have a strong chemical odor; request the materials be properly dried.
• Keep exposure to moth repellants to a minimum. If it is necessary to use moth repellants with clothes, store these items in separately ventilated areas if possible.

Radon

Radon is a colorless and odorless gas from uranium in the soil or rock underneath homes and buildings. Radon gas enters through cracks in floors, walls, foundations, and floor drains. Any home or building, whether new or old, may have a radon problem. Radon is a serious health problem when it accumulates to high levels. Indoor radon exposure is the second-leading cause of lung cancer. Smokers exposed to radon substantially increase their risk of lung cancer. To reduce exposure to radon:

• Test the radon level in the house or building. This is the only way to determine if there is a problem. Radon test kits are simple to use, inexpensive and may be purchased at your local hardware store.
• Reduce indoor radon levels. Use a contractor trained to fix radon problems if radon is above acceptable levels. Lowering radon levels requires special knowledge and skills.

Formaldehyde

Formaldehyde is widely used to make building materials and household products. Sources of formaldehyde inside the home include pressed wood products such as particle board, hardwood plywood paneling and medium density fiber board. These products may be used as sub-flooring, shelving and in cabinets and furniture. Formaldehyde also is used in glues and adhesives, as a paint preservative, and in adding permanent-press features to clothing and draperies. To reduce exposure to formaldehyde:

• Ask about the formaldehyde content of pressed wood products found in building materials, furniture and cabinetry before they are purchased. If possible, use "exterior-grade" pressed wood products (these use different resins that have lower levels of formaldehyde).
• Increase ventilation, particularly after bringing new sources of formaldehyde into the home.
• Use air conditioning and dehumidifiers if needed to maintain moderate temperatures and reduce humidity levels. Heat and humidity increase the rate at which formaldehyde is released from materials.

Asbestos

Asbestos is a mineral fiber that was commonly used to insulate hot water pipes and furnaces in homes built between 1920 and 1972. It was also used in building construction as a component in shingles, textured ceilings, joint finishing and patching compound, and in the backing of vinyl, asphalt, and rubber flooring. Older homes and buildings may have asbestos that can become hazardous as the materials begin to deteriorate and become airborne. To reduce exposure to asbestos:

• Find out whether asbestos materials are present before you remodel an older home.
• Do not cut, rip, or sand asbestos-containing materials. Usually it is best to leave asbestos material that is in good condition undisturbed as it will not release asbestos fiber.
• Use a professionally trained contractor if asbestos needs to be removed or cleaned up.

Lead

The harmful effects of lead have been recognized for a long time. People are exposed to lead through air, drinking water, food, contaminated soil, deteriorating paint, and dust. Homes built before 1978 may have lead-based paint. Homes built before 1950 may have lead plumbing pipes. Harmful exposure to lead occurs when lead paint is improperly removed from surfaces.

Children may be exposed when they place hands or toys with lead dust on them in their mouths or when they eat lead paint chips. Lead dust from outdoor sources may be tracked inside homes and buildings. To reduce exposure to lead:

• Discuss lead screening with consumers' pediatricians. Children should be tested for lead exposure. See this month's article for Consumers & Families for specific information regarding children and lead.
• Tests for lead should be performed on older homes.
• Do not remove lead paint yourself. Lead paint in good condition usually should be left undisturbed. Do not scrape, sand or burn off lead paint. If lead paint needs to be removed, use a professional with special training.
• Keep children away from peeling paint.
• Wash children's hands frequently, especially before they eat.
• Do not bring lead dust into the home. Use doormats to wipe feet before entering the home. Wet mop floors and wipe furniture, window sills, and other dusty surfaces.

For additional information

• The information in this article was adapted in part from The Inside Story: A Guide to Indoor Air Quality, U.S. Environmental Protection. This document was prepared by the U.S. Environmental Protection Agency, and the Consumer Product Safety Commission Office of Radiation and Indoor Air.