Carbon monoxide Vehicle exhausts, cigarette smoke, gas stoves, wood stoves, oil heaters, kerosene heaters, unvented fuel burning appliances, faulty chimneys. Carbon dioxide Poor ventilation, fuel stoves and heaters, faulty chimneys, respiration. Nitrogen dioxide Car exhausts, industrial emissions, fuel burning appliances, gas stoves and heaters, faulty chimneys. Environmental tobacco smoke Tobacco products. Tobacco smoke can contain 3800 compounds, many of which are carcinogens and mutagens.
Asbestos is a known human carcinogen.
Environmental Protection Agency. Introduction to Indoor Air Quality.