Environmental Illness

Overview

What is an environmental illness?

Chemicals, fumes, pollution, allergens, and other health hazards are common in our environment, and sometimes they can make us sick. Maybe you have mysterious headaches that only occur on weekends. Or you develop nausea and a rash after moving into a newly built home. Such symptoms can be caused by exposure to toxins commonly found in our homes, workplaces, and communities. For example:

• Those weekend headaches may be caused by a faulty furnace leaking carbon monoxide. Using a fireplace could create a back draft of furnace gases that can cause headaches. Replacing the furnace could make the headaches go away.
• Building materials in new homes-insulation, particleboard, carpet adhesive-emit formaldehyde, which can cause nausea and rashes. Also, the paper that makes up the outside layers of drywall provides the right conditions for the growth of mold. Exposure to these molds may cause respiratory problems and allergylike symptoms and may provoke asthma attacks.

You and your doctor may not know what is causing your illness, or it may be mistaken for another problem. Environmental hazards can cause or aggravate a wide range of common medical problems. A thorough evaluation of the environments in which you work, live, and play could reveal what is causing your illness.

What causes environmental illnesses?

Short- and long-term exposure to hazards such as chemicals, allergens, pollution, and other toxins can cause environmental illnesses. Chemicals in cigarettes are known to cause lung cancer. Exposure to asbestos, a common insulating material that can be found in older buildings, can cause tumors in the linings of the chest and abdomen, lung cancer, and other diseases. Wood-burning stoves and improperly vented gas ranges can cause respiratory problems. Drinking water from a rural well contaminated with pesticides or solvents from a nearby industrial plant could cause cancer or neurological problems. Inhalation of spores from molds that grow on building materials can cause respiratory problems and may make asthma more severe. Exposure to certain chemicals in the workplace may cause sterility, especially in men.

But often we don't know such exposures are causing our sickness. We don't know the types or amounts of chemicals to which we've been exposed, especially when the symptoms of disease or illness don't develop for years. For example, most cancers have a latent, or silent, period that can last a decade or more before symptoms develop.

What symptoms do environmental illnesses cause?

Symptoms depend on the environmental cause of the illness or disease. Common symptoms include headaches, cough, fatigue, and nausea. In some cases, you may not have any symptoms for years, until a disease progresses far enough for you to notice signs of it. In other instances, exposure may cause immediate allergic reactions, such as when contact with dust mites, cockroaches, pollen, or pets triggers an asthma attack. Or symptoms may emerge more gradually and become worse as the time of exposure continues.

For some people, going to work in a building with poor indoor air quality may cause headaches, coughs, dizziness, fatigue, and nausea. The building may be improperly ventilated, causing exposure to fumes from cleaning solvents or cigarette smoke. New buildings or new carpets emit formaldehyde, which is known to cause symptoms such as nausea, respiratory problems, dry or inflamed skin, and eye irritation. Buildings may have bacteria, molds, or viruses that have built up in heating and cooling ducts, carpets, ceiling tiles, or insulation and can cause fever, chills, muscle aches, cough, and other respiratory symptoms.

Symptoms of environmental illness are difficult to diagnose and may be mistaken for other medical problems. If you suspect exposure to toxins could be making you sick, it is important that you discuss your thoughts with a doctor.

What are the symptoms of environmental illness?

You or your doctor may not know your illness is related to a toxic exposure unless your symptoms won't go away or they appear only at specific times or places. Good detective work by you and your doctor will be needed to diagnose an environmental illness. For example, if you keep a log of your symptoms, you may discover that you feel nauseous and sluggish throughout your workweek, but you feel better on weekends and vacations. Poor indoor air quality, which some people call "sick building syndrome," may then be suspected as the cause of your illness. Your symptoms may go away when you are out of the environment that is making you sick, for example, a recent remodel of a room in your house or a new office building at work. But unless you discuss the variations in your symptoms with your doctor, it will be difficult for him or her to make such a connection.

Checking the walls of your home or workplace for efflorescence-a white, powdery or crystalline substance that accumulates on the surface of concrete, plaster, or masonry-can be a good first indicator of the presence of molds or moisture that can lead to molds. Air sampling, in which trained professionals analyze a sample of the air in a building, is another way to find out if molds are present.

Often, solving the mystery isn't so simple. A more serious illness may be caused by something to which you were exposed decades ago. Perhaps in the past you lived near a hazardous waste site, or you had a job remodeling old homes, which exposed you to asbestos. Before talking to your doctor, think about your history, previous jobs, homes, and activities.

How are environmental illnesses diagnosed?

Doctors and other health professionals can diagnose an environmental illness by taking an exposure history, which is a lengthy set of questions about your home, workplace, habits, occupations, lifestyle, family, and other matters. Your answers to the questions can help identify chemicals or other hazards to which you've been exposed recently or in the past and help your doctor decide whether you need specific tests to diagnose your illness.

How are environmental illnesses treated?

Initial treatment for an environmental illness includes eliminating or reducing your exposure to what is making you sick. For example, one of the most effective ways to improve air quality is to get rid of the source of the pollution. Gas stoves can be adjusted to reduce emissions or replaced with electric stoves. You can also increase the amount of fresh air coming into your home, change furnace and air-conditioning filters often, and make sure exhaust fans in the kitchen and bathroom are working. Furnaces can be placed outside of your main living areas or even in the garage.

One of the first and best steps you can take to clean the air in your house is to not allow smoking in your house-if smokers live in or visit your home, have them smoke outside.

Treatment beyond these first steps varies based on your symptoms, the cause of the illness, and what part of your body is affected.

The health effects of mold exposure are best treated by preventing or restricting further mold growth. Maintaining a dry environment indoors can help restrict the growth of molds. Humidity should be kept at less than 50%.¹ Though it may be difficult to do, it is important to eliminate exposure to molds that have already infected your home or workplace or your child's school. Molds should be removed from buildings by trained professionals, and you or your children should not return to the building until the removal process is complete.

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	Allergies: Avoiding indoor triggers

Frequently Asked Questions

Toxins in Our Environment

Indoor air pollution

Indoor air pollution can affect you at home, work, or even places you visit. It is a common source of respiratory diseases, including asthma, allergies, and lung cancer. It can be worse in winter, when windows are shut tight and less fresh air can circulate.

See tips for reducing indoor air pollution, such as not allowing anyone to smoke in your home.

• Cigarette smoke

One of the most common and toxic indoor air pollutants is cigarette smoke. Experts believe more than 87% of lung cancers are caused by cigarette smoke.² Smoking, or even inhaling secondhand smoke, increases your risk of heart attack and stroke.³

Tobacco smoke is a mixture of more than 4,700 compounds. Smoke from the smoldering end of a cigarette contains more cancer-causing chemicals than the smoke exhaled by a smoker.⁴ If you are a nonsmoker and household members or coworkers will not stop smoking around you, ask that they smoke only in well-ventilated or isolated areas. Never smoke around children or allow them to be exposed to cigarette smoke, especially if they have asthma or allergies.

Exposure to cigarette smoke causes wheezing, coughing, and extra mucus (phlegm) in many children. Secondhand smoke also can cause fluid to build up in the inner ear, which can cause ear infections. Lower respiratory infections, such as pneumonia and bronchitis, are also risks. Sometimes these types of infections become serious enough to require hospitalization, especially when they develop in babies and young children.⁵

Babies who are exposed to secondhand smoke are at increased risk for sudden infant death syndrome (SIDS).⁶

Cigarette smoke may cause thousands of children each year to develop asthma.⁶ Also, children with asthma who are exposed to cigarette smoke have more attacks and more severe symptoms than other children with asthma.⁶

See information on the increased impact of environmental illnesses on children. For example, in recent years, the number of children with asthma has more than doubled, and environmental causes are suspected.

• Woodstoves and gas ranges

Woodstoves that are not properly maintained and vented can give off gases, including carbon monoxide, nitrogen, particulates, and hydrocarbons. Children in homes heated with woodstoves are at increased risk for respiratory problems. Gas ranges, particularly when they are not well-vented or when they are used as a source of heat, may produce nitrogen dioxide, which can cause respiratory problems. Consider changing to an electric stove.

If your gas stove has a persistent yellow flame, it may be improperly adjusted. Ask your gas company to adjust the burners so the flame tips are blue. If you're planning to buy a new gas range or stove, consider one that does not use a pilot light.

If you use a woodstove, make sure the doors fit tightly. Only use aged or cured wood that is completely dry. Never burn pressure-treated wood because it is treated with chemicals.

Have chimneys, flues, and furnaces inspected each year.

For more information, see the topic Carbon Monoxide Poisoning.

• Building materials

Exposure to building materials, products used for home improvement, and textiles can cause health problems. For example, particleboard, insulation, carpet adhesives, and other household products emit formaldehyde, which can cause nausea, respiratory problems, dry or inflamed skin, and eye irritation. Newly built homes and the confined spaces of mobile homes can be a particular problem. Using environmentally safe products-such as paint that contains a low level of or no volatile organic compounds (VOCs)-can reduce the chemical load on your body.

• Sick building syndrome and building-related asthma

Experts coined the term "sick building syndrome" to describe acute symptoms that occur only during time spent in a particular building and that cannot be explained by any specific illness or cause. Symptoms include headache, dry cough, dry or itchy skin, dizziness, nausea, difficulty concentrating, fatigue, sensitivity to odors, and irritation of the eyes, nose, or throat. Typically the symptoms improve after you leave the building.

Poor ventilation that restricts fresh air flow inside can be a cause of sick building syndrome. Carpet, adhesives, upholstery, manufactured wood, copy machines, pesticides, and cleaning fluids can give off volatile organic compounds (VOCs), including formaldehyde. High concentrations of VOCs can cause cancer. Unvented gas and kerosene space heaters, woodstoves, fireplaces, and gas stoves can produce carbon monoxide and nitrogen dioxide.

Outdoor sources of chemicals can also cause sick building syndrome. Pollutants from cars and trucks and exhaust from plumbing vents and building machinery can enter a building through vents.

Building-related asthma, in contrast, is the term used when symptoms of a diagnosed illness can be linked directly to airborne contaminants within a building. Symptoms include cough, chest tightness, and wheezing. Leaving the building may not immediately improve the symptoms.

• Bacteria, molds, viruses, and other biological contaminants

Bacteria, molds, and viruses can breed in stagnant water that builds up in humidifiers, drain pans, and ducts, or where water collects on carpet, ceiling tiles, and insulation. Humidifier fever is an illness caused by toxins from microorganisms that grow in large heating and cooling systems in buildings, but they can also be found in home systems and humidifiers. Legionella pneumophila is an indoor bacterium that can cause Legionnaires' disease.

Pet dander, pollen, dust mites, molds, and rat and mouse urine are allergens that can cause asthma, allergic rhinitis, and other lung problems. Symptoms of illness caused by biological contaminants include sneezing, watery eyes, shortness of breath, lethargy, dizziness, and digestive problems.

Although studies so far have been inconclusive, evidence is accumulating that exposure to indoor allergens such as molds early in life can result in a persistent allergic reaction.⁷ Allergies to molds can also make asthma attacks worse or cause asthmalike symptoms.

Keep your home clean and as free from dust as possible to help reduce allergens. There are many ways to control dust and dust mites in your home, such as washing bedding in hot water to kill dust mites, and eliminating furnishings, such as drapes, that collect dust. Similarly, there are many steps you can take to control animal dander and other pet allergens.

Exhaust fans that vent to the outdoors and are installed in kitchens and bathrooms can help get rid of moisture that allows microorganisms, including molds, to grow. When modern building materials get wet, they provide an ideal environment for the growth of molds, which can make asthma attacks worse and may cause other respiratory symptoms. Ventilating attic and crawl spaces and keeping humidity levels below 50% can help prevent moisture buildup in building materials. There are other ways to control indoor molds, such as preventing leakage, removing wetted materials, storing fireplace wood outside the home, and using a dehumidifier during humid weather.

Keep humidifiers clean and refill them daily with fresh water. Frequently clean evaporation trays in air conditioners, dehumidifiers, and refrigerators. Water-damaged carpets and building materials can also have molds and bacteria in them. It is difficult to get rid of bacteria or molds, so, if possible, replace or remove water-damaged items from your home.

You can also:

• Remove carpets, and replace them with hardwood or tile floor.
• Have sofas with covers that can be removed and washed.
• Use blinds instead of drapes, because they collect less dust.
• Have air filters in some rooms, especially in the bedroom.

For more information, see:

Allergies: Avoiding indoor triggers.

• Household products

Many of the products you use to clean your home or use for hobbies and home improvement projects contain potentially hazardous chemicals. Some can be toxic and in sufficient doses can cause eye and respiratory problems, headaches, dizziness, visual problems, and memory impairment. One of the most important ways you can protect yourself is by following the instructions on the label. When using cleaning or other products, make sure to open windows or use an exhaust fan to provide good ventilation. Never mix household chemicals, such as chlorine and ammonia. Some mixtures can create toxic fumes that can be fatal.

It's better to use environmentally safe products. Vinegar, lemon juice, boric acid, or baking soda can be used instead of store-bought household cleaners-and they are less damaging to you and to the environment.

Be especially careful with products containing methylene chloride, including paint strippers, adhesive removers, and aerosol spray paints. If you use products that contain this chemical, make sure you have adequate ventilation or use them outdoors, if possible. Also, wear gloves to avoid skin contact. But whenever you can, use environmentally safe products instead.

Avoid exposure to benzene, which can cause cancer. Benzene is found in tobacco smoke, stored fuels, paint supplies, and vehicle exhaust inside garages. Also, try to limit your exposure to newly dry-cleaned clothing or furnishings. Dry-cleaned goods emit perchloroethylene (also known as tetrachloroethylene) and trichloroethylene. These chemicals cause skin rashes, headaches, and dizziness^{8, 9} If your clothes emit a strong odor when you pick them up from the cleaners, they may not have been dried properly and can release more of this chemical. After removing the protective plastic from the clothes, hang them outside, if possible. Consider finding a dry cleaner that uses less toxic chemicals.

• Asbestos

Asbestos is an insulating material commonly used from the 1950s to 1970s for soundproofing and to cover floors and ceilings, water pipes, and heating ducts. If it is in good condition, it's generally not a health risk, but when it becomes crumbly or frayed, asbestos fibers can be released into the air. Breathing asbestos fibers may cause lung cancer, asbestosis (scarring of the lung tissue), or mesothelioma.

• Radon

Radon is a colorless, odorless radioactive gas that can enter your home through cracks in concrete walls and floors and through floor drains. The most common source of radon is uranium that normally exists in the soil or rock on which homes are built. Problems arise when concentrations of radon build up in a home or building. Both old or new homes can have problems with radon even if they don't have a basement.

Exposure to radon gas is the second leading cause of lung cancer. (Tobacco smoke is the leading cause.) The risk of radon-associated lung cancer is 12 times higher for smokers than nonsmokers.¹⁰

You cannot smell or see radon, but it's easy to test for with a do-it-yourself kit available in hardware stores or through the U.S. Environmental Protection Agency (EPA). For more information, see the topic Radon.

Treatment for indoor air pollution

How you react to indoor air pollutants depends on your age, health, and how sensitive you are to certain chemicals or biological pollutants, such as bacteria. Treatment can be as simple as removing and limiting your exposure to toxins in your home. In some cases, serious illnesses-such as cancer, heart disease, and respiratory disease-can develop after long-term and repeated exposures. With such long-term exposures, treatment may be extensive, depending on the type of illness.

Outdoor air pollution

Polluted air comes from many sources, such as factories, cars, buses, trucks, and power plants. And there are other sources that you may not think of, such as dry cleaners, wildfires, and dust. Dirty air is a threat to your health, and it also damages crops, trees, water, and animals.

There are six major components of air pollution:

• Ozone. Ozone is a gas that exists at ground level as well as miles above the earth. It's made by a chemical reaction between nitrogen oxides and volatile organic compounds (VOCs) in the presence of heat and sunlight. "Good" ozone occurs naturally about 10 to 30 miles above the earth's surface. There, in the stratosphere, it forms a protective layer from the sun's harmful rays. At ground level, "bad" ozone (smog) exists. Exhaust from vehicles, industrial emissions, gasoline vapors, and chemical solvents are major sources of nitrogen oxides and VOCs. Add sunlight and hot weather to the mix, and harmful concentrations of ozone may develop. Because of the heat factor, ground-level ozone is a summertime air pollutant that can be dangerous, especially for people with respiratory illnesses. Problems include:
  • Irritation of the lungs that causes inflammation much like a sunburn.
  • Coughing, wheezing, and pain when taking a deep breath, and breathing problems while exercising.
  • Permanent lung damage from repeated exposure.
  • Aggravated asthma, increased susceptibility to pneumonia and bronchitis, and reduced lung capacity.
• Particulates. Particulates include dust, dirt, soot, smoke, and liquid droplets found in the air. They come from many sources, such as vehicles, factories, construction sites, unpaved roads, and wood burning. Other particulates are formed when gases from burning fuels react with water vapor and sunlight. This can result from the combustion of fuels in motor vehicles and from industrial and power plants. Particulates in the air you breathe can cause:
  • Aggravated asthma.
  • Coughing and difficult or painful breathing.
  • Chronic bronchitis.
  • Decreased lung function.
  • Eye, nose, and throat irritation.
• Carbon monoxide. In cities with lots of traffic, most of the carbon monoxide released into the air comes from vehicle exhaust. It also comes from manufacturing processes, wood burning, and forest fires. Indoor sources include cigarettes and space heaters. Carbon monoxide reduces the body's ability to deliver oxygen to tissues and organs, such as the heart and brain. It is especially dangerous for people who have heart problems. Carbon monoxide can be fatal to those exposed to extremely high levels. Every year carbon monoxide poisoning is a leading cause of toxin-related deaths. People with carbon monoxide poisoning may develop:
  • Headaches, irritability, or loss of consciousness.
  • Difficulty working, learning, or performing complex tasks.
  • Aggravation of heart problems, such as angina, heart failure, and coronary artery disease.
• Nitrogen dioxide. When mixed with other particles in the air, nitrogen dioxide can often be seen as a reddish brown layer over many urban areas. Sources are fuels burned by vehicles, electric utilities, and industrial plants. Nitrogen dioxide is one of the nitrogen oxides, a group of highly reactive gases that contain various amounts of nitrogen and oxygen. Nitrogen oxides cause several problems, including:
  • Respiratory problems associated with ground-level ozone.
  • Acid rain, which is created when nitrogen oxides and sulfur dioxide react with other substances in the air and form acids. The acids then fall to earth as rain, snow, dry particles, or fog.
  • Toxic chemicals. Nitrogen oxides mix with common organic chemicals and even ozone to create toxic chemicals that can cause biological mutations.
  • Visibility impairment. Nitrogen dioxide and nitrate particles block light transmission and reduce visibility in urban areas.
• Sulfur dioxide. These gases are formed when fuels containing sulfur are burned. Examples are coal and oil burning, the process of extracting gasoline from oil, or when metals are extracted from ore. Each year more than 13 million tons of sulfur dioxide are emitted into the air by electric utilities, especially those that burn coal. Other sources are industries that create products from metallic ore, coal, and crude oil or those that burn coal or oil, such as petroleum refineries or metal processing facilities. Sulfur dioxide causes:
  • Health problems for people with asthma and heart conditions.
  • Acid rain.
  • Damage to forests and crops.
  • Damage to fish in streams and lakes.
• Lead. Leaded gasoline used to be the main source of lead in the air, but because leaded fuels have been phased out, the main sources of lead emissions are metals-processing facilities, especially lead smelters. Lead may cause serious health problems, including:
  • Damage to kidneys, liver, brain, nerves, and other organs. Lead may also cause osteoporosis and reproductive problems. Excessive exposure can cause seizures, mental retardation, behavioral disorders, memory problems, and mood changes. Low levels of lead cause brain and nerve damage in young children and fetuses, which can lead to learning problems and low IQ.
  • High blood pressure and increases in heart disease.
  • Anemia.

For more information, see the topics Carbon Monoxide Poisoning and Lead Poisoning.

Pesticides

Exposure to pesticides may come from residual agricultural pesticides in foods or from household or workplace products used to control rodents, insects, and termites, and from disinfectants and fungicides. The most likely ways you are exposed are small quantities of pesticides in the foods you eat, and by direct contact with surfaces (such as plants, soils, or structures) where pesticides have been used.

If not used properly, both workplace and household pesticides can be dangerous. Exposure to high levels of some pesticides can cause headaches, dizziness, muscle twitching, nausea, weakness, and tingling sensations. Some experts believe that some pesticides may cause cancer or damage to the liver and central nervous system.¹¹ Pesticide exposure during pregnancy has been associated with miscarriage, fetal death, and early childhood cancers such as acute lymphoblastic leukemia (ALL). Indoor use of pesticides increases children's risk of brain tumors, ALL, and birth defects. Children can be poisoned by stored pesticides, so these should always be kept out of reach. For agricultural workers, exposure to pesticides has been associated with an increased risk of non-Hodgkin's lymphoma.¹²

See tips for reducing pesticide exposure in your home, such as reducing your use of lawn and garden pesticides and limiting your exposure to moth repellents.

Mercury in fish

For most people, the level of mercury absorbed by eating fish and shellfish is not a health concern. But in a fetus or young child, this can damage the brain and nerves (nervous system). Because of the mercury found in fish, the U.S. Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) advise women who may become pregnant, pregnant women, nursing mothers, and young children to avoid eating fish high in mercury and to eat limited amounts of fish and shellfish that are lower in mercury.¹³ For more information, see the topic Avoiding Mercury in Fish.

Who to Call

If you believe you have an environmental illness, first consider your symptoms. If your symptoms are severe (for example, you are having trouble breathing), you have ingested household chemicals, or you fear you may have a carbon monoxide leak in your home, call your Poison Control Center immediately. Otherwise, contact:

• A family medicine doctor.
• A doctor who specializes in occupational medicine and environmental medicine.
• A doctor who specializes in internal medicine or pediatrics.
• A regional clinic that is part of the Association of Occupational and Environmental Clinics (AOEC).

You may find it helpful to create a written exposure history to take to your doctor, to help identify the cause of your illness.

Other Places To Get Help

Online Resources

Organizations

Related Information

• Carbon Monoxide Poisoning
• Lead
• Lead Poisoning
• Radon

References

Citations

1. German JA, Michael B (2002). Environmental control of allergic diseases. American Family Physician, 66(3): 421-426.

2. Miller YE (2004). Lung cancer and other pulmonary neoplasms. In L Goldman, D Ausiello, eds., Cecil Textbook of Medicine, 22nd ed., pp. 1201-1208. Philadelphia: Saunders.

3. Pearson TA, et al. (2002). AHA guidelines for primary prevention of cardiovascular disease and stroke: 2002 update. Circulation, 106(3): 388-391.

4. Carter W, et al. (2000). Taking an Exposure History (ATSDR Publication No. ATSDR-HE-CS-2001-0002). Atlanta: U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry. Available online: http://www.atsdr.cdc.gov/HEC/CSEM/exphistory.

5. U.S. Environmental Protection Agency (2007). Smoke-free homes program. Available online: http://www.epa.gov/smokefree.

6. U.S. Environmental Protection Agency (2007). Health effects of exposure to secondhand smoke. Available online: http://www.epa.gov/smokefree/healtheffects.html.

7. Jacob B, et al. (2002). Indoor exposure to molds and allergic sensitization. Environmental Health Perspectives, 110(7): 647-653.

8. Agency for Toxic Substances and Disease Registry (1997, reaffirmed 2006). Toxicological profile for trichloroethylene: Public health statement for trichloroethylene. Available online: http://www.atsdr.cdc.gov/toxprofiles/phs19.html.

9. Schreiber JS, et al. (2002). Apartment residents' and day care workers' exposures to tetrachloroethylene and deficits in visual contrast sensitivity. Environmental Health Perspectives, 110(7): 655-664.

10. Field RW, et al. (2000). Residential radon gas exposure and lung cancer: The Iowa radon lung cancer study. American Journal of Epidemiology, 151(11): 1091-1102.

11. Arcury TA, Quandt SA (2003). Pesticides at work and at home: Exposure of migrant farmworkers. Lancet, 362(9400): 2021.

12. Sanborn MD, et al. (2002). Identifying and managing adverse environmental health effects: 4. Pesticides. Canadian Medical Association Journal, 166(11): 1431-1436.

13. U.S. Food and Drug Administration (2004). What you need to know about mercury in fish and shellfish: 2004 EPA and FDA advice for women who might become pregnant, women who are pregnant, nursing mothers, young children. Available online: http://www.epa.gov/waterscience/fish/advice.html.

Other Works Consulted

• Crinnion WJ (2006). Environmental medicine. In JE Pizzorno Jr, MT Murray, eds., Textbook of Natural Medicine, 3rd ed., pp. 339-353. Edinburgh: Churchill Livingstone.

• Hu H (2005). Heavy metal poisoning. In DL Kasper et al., eds., Harrison's Principles of Internal Medicine, 16th ed., vol. 1, pp. 2577-2580. New York: McGraw-Hill.

• Ruder AM (2006). Potential health effects of occupational chlorinated solvent exposure. Annals of the New York Academy of Sciences, 1076: 207-227.

• Seizer FE (2005). Environmental lung diseases. In DL Kasper et al., eds., Harrison's Principles of Internal Medicine, 16th ed., vol. 1, pp. 1521-1528. New York: McGraw-Hill.

• Swan SH, et al. (2005). Decrease in anogenital distance among male infants with prenatal phthalate exposure. Environmental Health Perspectives, 113(8): 1056-1061.

• Veraldi A, et al. (2006). Immunotoxic effects of chemicals: A matrix for occupational and environmental epidemiological studies. American Journal of Industrial Medicine, 49(12): 1046-1055.

• Centers for Disease Control and Prevention (2005). Third National Report on Human Exposure to Environmental Chemicals 2005: Executive summary (NCEH Publication No. 05-0725). Available online: http://www.cdc.gov/exposurereport.

• U.S. Department of Health and Human Services Office on Smoking and Health (2006). The health consequences of involuntary exposure to tobacco smoke: A report of the Surgeon General. Available online: http://www.surgeongeneral.gov/library/secondhandsmoke.

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