British and American researchers warn that there are silent killers in your home, including scented candles and air fresheners, that add toxic chemicals to the air which can cause a multitude of health problems, including cancer.

While most people realize that outdoor air pollution, which mainly comes from vehicle exhausts, is dangerous, many people don't understand the dangers of indoor pollutants. A study from South Carolina State University found that burning candles released several chemicals that pollute indoor air and have harmful effects on human health.

A report issued by the Royal College of Physicians says that while air pollution has an impact on everyone's health, the very young, elderly, and those with chronic health problems are particularly vulnerable.

Much of indoor pollution is the result of trying to cut energy bills by insulating homes to keep out drafts and keeping windows shut, but the result is a toxic brew of chemicals that we constantly breathe.

"When you seal your home to make it energy-efficient, you trap all of the chemicals that cause health problems inside your home," Dr. Bill Wolverton, a retired NASA senior research scientist who helped develop NASA's BioHome, told Newsmax Health. "Some of these chemicals are known carcinogens."

Air pollution has an impact on many areas of health, said the British committee, including lung and cardiovascular disease, diabetes, obesity, dementia, asthma, and cancer, as well as adverse effects on developing fetuses.

In the United States, pollution from both indoor and outdoor sources contributes to 200,000 early deaths each year, according to a study from the Massachusetts Institute of Technology.

Indoor pollutants come from gas heaters, indoor wood fires, second-hand tobacco smoke, chemicals used in the manufacture of flooring and furniture, and chemicals from personal care and cleaning products.

Even the lemon and pine scents used in cleaning products as well as candles and air fresheners can cause toxic fumes. A chemical called limonene is used in air fresheners and scented candles to give a lemony citrus smell.

When limonene mixes with other airborne contaminants, it can form the carcinogen formaldehyde, which can increase the risk of throat and nose cancers. A study conducted in York, England, found that for every two molecules of limonene released into the air, a molecule of formaldehyde was created.

Limonene isn't the only problem with candles. According to the Environmental Protection Agency, candles are usually made from petrochemicals that can release benzene, lead, and other chemicals into the air. Scented candles are worse than unscented, says the EPA, because they emit more particles known to cause breathing problems.

You can cut down on indoor pollution by following these steps:

1. Add indoor plants. Common houseplants can help purify air by using their natural ability to absorb toxins through their leaves and roots and turn them into nutrients. Dr. Wolverton recommends bamboo palm (chamaedorea seifritzii), Chinese evergreen (aglaonema modestum), English ivy (hedera helix), and gerbera daisy (gerbera jamesonii).

2. Use environmentally friendly cleaning supplies. Consider any product unsafe if it carries a warning.

3. Buy "green" products. Some products, such as low-emission carpets, paint, and building materials, have special labels that identify them as among those that give off the least chemicals. Low-emission carpets, for example, are labeled Green Label and Green Label Plus.