Many people left homeless by Hurricane Katrina in 2005 survived that storm only to suffer another setback. Soon after moving into government-provided trailers, they began experiencing a range of health problems, from headaches and runny noses to difficulty breathing. Upon further exploration, tests revealed that the trailers had levels of formaldehyde as high as 50 times the U.S. Environmental Protection Agency's "elevated" level of 5 parts per million [source: Brunker]. It seems that the carcinogen was leaching from the composite wood and plywood panels used in the trailers. After years of insisting that the trailers were safe, the U.S. Federal Emergency Management Agency finally had the residents evacuated in early 2008.
Similar, though less attention-grabbing, occurrences happen every day. Health effects from indoor air pollution can be immediate and short-lived, or they may be severe and not show up until years after repeated exposures. The most common symptoms are sore throat, headache and persistent cough, as well as itchy, running eyes and nose. More severe symptoms include chronic breathing problems, heart disease and cancer.
Perhaps one of the most visible indoor air pollutants is environmental tobacco smoke, or secondhand smoke, which contains 200 known poisons and at least 43 compounds known to cause cancer. Even if you don't smoke, you may be subject to secondhand smoke if you live or work with someone who does. So-called "passive smoking" is responsible for around 3,000 lung cancer deaths and 35,000 to 50,000 heart disease deaths each year in nonsmoking adults. It also causes between 150,000 and 300,000 respiratory infections in infants each year and worsens the asthma of up to 1 million asthmatics [source: American Lung Association, EPA].
Other indoor air pollutants, like the ones in the following list, are largely invisible, but just as dangerous. Consider:
- Indoor radon exposure is the second-leading cause of lung cancer in the U.S., causing between 15,000 and 21,000 deaths each year [source: American Lung Association]. Radon can enter your house through the foundation.
- Exposure to formaldehyde irritates the mucous membranes and eyes, and can provoke asthma and impair the central nervous system.
- Biological contaminants can transmit illnesses like the flu and measles, trigger allergic reactions and cause digestive problems.
- Combustion gases impede the flow of oxygen through your body. High levels can cause unconsciousness and death, while lower levels create headaches, dizziness, weakness, confusion and fatigue. Some can lead to lung diseases like emphysema.
- High exposure to chemicals in household products and pesticides can irritate the respiratory tract; cause headaches, dizziness and vision problems; impair memory function and may cause cancer.
You can learn more about many of these pollutants in the HowStuffWorks articles A Guide to Home Safety and How to Allergy-Proof Your Home. Learn about ways to reduce indoor air pollution on the next page.