List the major indoor pollutants and their sources.

There are several indoor pollutants to consider, including polychlorinated biphenyls (PCBs), volatile organic compounds (VOCs), carbon monoxide (CO), lead, mold and bacteria, radon, secondhand smoke, asbestos, and formaldehyde.

PCBs are found in some older buildings, especially in the insulating fluid for ceiling electrical fixtures. VOCs can come from a variety of products, including paints, cleaning supplies, and air fresheners. Carbon monoxide can be produced by unvented kerosene and gas space heaters, gas stoves, and car exhaust from attached garages. Lead was commonly used in house paint and gasoline and may still be found in homes built before the late 1970s. Mold and bacteria can accumulate anywhere there is moisture such as in bathrooms and in homes with poor ventilation. Radon is a naturally occurring radioactive gas that can cause lung cancer and enters indoors through cracks and other holes in the foundation. Secondhand smoke comes from the burning of tobacco products. Asbestos was commonly used in a variety of building construction materials for insulation and as a fire-retardant. Lastly, formaldehyde can come from pressed wood products (hardwood plywood wall paneling, particleboard, and fiber-board) and certain insulation materials.

The pollutants and sources can be visualized in a table, where one column lists the pollutants and another lists the sources. Of particular importance is to note the potential overlap of sources and pollutants, emphasizing how multiple pollutants can come from a single source and one pollutant could be produced by several sources.