In fact, indoor air pollution is now recognized as a serious source of respiratory diseases, including lung cancer. During fall and winter months, you're at greater risk, when windows are tightly shut and less fresh air can circulate.
The culprits? "Cigarette smoke is the biggest offender, and also the most fixable problem," says Karin Pacheco, MD, MSPH, a researcher in environmental and occupational health sciences at the National Jewish Medical and Research Center in Denver.
Radon (a cancer-causing radioactive gas) is a problem for many homes, both with and without basements. Bacteria and mold can breed in standing water and in uncleaned humidifiers, wet walls, and damp carpet. Household cleaners, adhesives, and paints also emit noxious fumes.
Good ventilation is the key with most indoor irritants, Pacheco tells WebMD. "Human beings are pretty sturdy, so using common sense will keep you plenty safe. We were meant to live in drafty caves. We need to keep our indoor air circulating - either by opening the windows or keeping ventilation systems running - when we have indoor irritants."
Are you at risk? This guide should help you assess your risk of health problems caused by indoor air pollution.
The No. 1 Culprit: Cigarette Smoke
Nearly 5,000 toxins make tobacco smoke the most toxic indoor pollutant. The greatest percentage of lung cancers is caused by cigarette smoke. Even secondhand smoke raises your risk of cancer, heart attack, and stroke.
"Children whose parents smoke have higher rates of asthma," Pacheco tells WebMD. In fact, smoking causes pneumonia, bronchitis, wheezing, coughing, excess phlegm, and ear infections in young children. In the past 15 years, the number of children with asthma has more than doubled - largely due to tobacco smoke exposure in the home.
The Risks From Sick Building Syndrome
If you've felt headachy and tired at work (and you've gotten plenty of sleep), you could be suffering from sick building syndrome. This term is used to describe symptoms that occur only at work that can't be linked with any illness or other cause. For some people, the symptoms are sore throat, burning eyes, itchy nose.
These symptoms are a reaction to indoor air pollutants - and "usually are a problem of large buildings with ventilation problems," Pacheco tells WebMD. "The classic case is a municipal building built in the 1970s that has been extensively renovated. When it was first built, it had adequate ventilation. But when they put up partitions, it changes the air flow."
New carpeting, adhesives, upholstery, copy machines, pesticides, and cleaning fluids can give off formaldehyde and other noxious compounds. Without adequate ventilation, these fumes can cause a variety of allergic reactions.
These irritants are "a real annoyance but will not result in permanent harm to your health," Pacheco says. "If you move in right after new carpeting has been installed, the smell will be irritating to eyes, noses, causing headaches, nausea. But it dissipates after a few weeks and shouldn't bother you after that."
In some buildings, a renovation has resulted in a badly routed ventilation system. You could be breathing exhaust fumes from trucks at your company's loading dock, says Pacheco. "Changing that kind of problem can be expensive, but not always. There may be a fairly simple solution. But if people are not reporting getting sick, nothing gets done."
The company's bottom line can suffer. "Employees who don't feel well are less productive than those who do," Pacheco notes. "Sick building syndrome has been well-documented, so it's clear that people aren't making it up. Employers should take it seriously. Some manipulations of the ventilation system can help significantly."
Invisible Risks: Bacteria, Molds, Viruses, and Radon
A humidifier with stagnant water, wet carpeting, and water-damaged walls - these are all breeding ground for bacteria, mold, and viruses. Anyone with asthma, allergies, or a hypersensitive reaction can be affected by these water-related problems, resulting in worse asthma attacks.
In fact, you can develop a mold allergy, which can lead to chronic sinusitis or asthma, says Pacheco. "If you have a water-damaged area, you need to fix it. If carpet has been completely soaked, you need to replace it. Regularly clean your humidifier, or you will release bacteria into the air whenever you use it."
Ventilating your attic and crawl space - and keeping humidity levels below 50% -- can help prevent moisture buildup in walls. Take steps to prevent water from leaking into a home.
Radon is a gas that exists in soil or rock containing uranium. The gas can infiltrate basements and crawl spaces of homes built on these deposits. Without a specific testing device, it's difficult to tell whether a home has a radon problem. This radioactive gas leaves no telltale signs; it is colorless and odorless. But exposure to radon is the second leading cause of lung cancer.
"Typically it's a ventilation issue," says Pacheco. "Improve the ventilation, and you've solved the problem. It's a very fixable problem."
Here are three other key risks you may not be aware of:
This common insulation material was used from the 1950s to 1970s to soundproof and cover floors, ceilings, water pipes, heating ducts, and water heaters.
"If you have asbestos around pipes or a water heater, that should be changed," says Pacheco. "But asbestos in tiles shouldn't bother you at all. It's only when you remove them that they will release airborne fibers - which cause health problems."
People misunderstand asbestos, she adds. "A lot of people have the impression that solid objects like these tiles have a little halo of asbestos around them. But it doesn't work that way. You have very limited exposure to the asbestos fibers until you start messing with them. That's when you release air particles into the air."
Household cleaners and hobby supplies can cause you problems -- but mostly, only when you're using them, says Pacheco. "Some glues can be bad for you and should be used only in a well-ventilated area, just like cleaning products. But just sitting there in a bottle or a can, they won't hurt you."
The classic at-home hazard: mixing ammonia and bleach, which produces chlorine gas. "That's really bad for you. It can really damage airways. That tops my list of list of hazards," she notes. "I understand why people want to do that, to clean an area, but it's not a good combination."
If wood stoves are not properly vented, they can give off particulates and nitrogen dioxide. "There's some evidence that asthmatics might have problems from wood stoves," says Pacheco. Improperly vented gas ranges can also cause respiratory problems. It's important to get these checked if there are signs of problems.