How Indoor Air Pollution Works

Formaldehyde, PCB, asbestos: These are words that you don't want associated with your living space. Yet odds are that you encounter at least one of these chemicals in your home every day. If not, you're not out of the woods just yet. Indoor air pollutants can be released at high levels in short bursts, like when you use spray paint, or at lower levels over time, like chemicals leaching out of your carpet.

Both the formaldehyde and polychlorinated biphenyl (PCB) mentioned are found in common household products. PCB was banned from production in the U.S. in 1970 but persists in wire coatings, sealants, paints and wood floor finishes. Asbestos, another source of indoor air pollution that has been banned from widespread use, also still lingers in older homes, insulation materials, textured paints and floor tiles.

Formaldehyde is widely used by industries that make building materials and household goods. It is most commonly found in pressed wood products that are used for things like subflooring, shelving, cabinets and furniture, but it is also common in permanent-press fabrics, adhesives and paints.

Let's look at a few of the other causes of indoor air pollution and see where they originate:

The potential for harm from any of these pollutants depends partly on our individual sensitivity. The elderly, the young and those with compromised immune systems tend to be more susceptible. Ventilation also plays a role in how these pollutants harm you. If fresh air frequently circulates throughout the area, the culprits won't have as much time to accumulate and reach dangerous levels. Going back to the bathtub analogy, ventilation is like slowly draining out the oily bathtub water and adding clean water in its place: Eventually, the oil will become less and less of a problem. But if you keep the plug in and do nothing, you're going to have one nasty bathtub ring. Unfortunately, many newer, energy-efficient buildings are practically airtight -- they're like the plugged-up bathtub.

Find out how living in a poorly ventilated, contaminated indoor air space affects you on the next page.

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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:

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.

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If you suspect your living space is polluted, don't despair. You can easily implement several solutions. If you're unsure of whether your home has a problem, ask yourself these questions:

Answering "yes" to these questions doesn't necessarily mean you have indoor air pollution, but it's a good indication. An easy experiment is to try some of the solutions for indoor air pollution listed on this page and see if you notice a difference.

As you might expect, one of the cheapest and most effective ways to reduce indoor air pollution is to attack the problem at its source. Some sources, like those that contain asbestos, can simply be sealed to prevent exposure, while others, like pesticides, you may want to eliminate.

Some polluting sources like a gas-cooking stove or fuel-burning space heater may not be feasible for you to remove, but you can minimize your risk by always operating those devices according to the manufacturer's directions and being sure to ventilate well.

In fact, as you learned on the first page, ventilation is helpful at decreasing all indoor pollutants. Since most heating and cooling systems simply recirculate air rather than bring in fresh air, you'll want to open windows and doors when the weather is nice, operate window or attic fans, and run bathroom and kitchen fans that exhaust outdoors. You especially want to follow these steps when you're using items with potentially harmful chemicals like paints.

Increasing ventilation does have one caveat. If you live in a place with high outdoor humidity or high concentrations of outdoor pollutants, increased ventilation may actually worsen indoor air pollution. If the outdoor air you're pulling in is filtered to remove harmful particles, you have little to worry about. If it's not, you may want to settle on moderate ventilation rates.

Aside from ventilation, you can minimize the biological contaminants in your home by maintaining a humidity level of 30 to 50 percent. Higher levels encourage dust mites and mold growth. Keeping carpets clean and dry, and simply maintaining a clean house also discourage biological contaminants.

If you're worried about the potential harm from household cleaners, you have two options. The first is to carefully follow the instructions on the label, use them in well-ventilated areas, and store and dispose of them safely. The second is to pick a product that is made with benign ingredients. If you're unsure, read the label: If a product doesn't list its ingredients or has any "warnings," it's probably not safe.

The sources of indoor air pollution are many and varied, but so are the solutions. To learn more about this topic, be sure to look into the links on the following page.

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