What is the key concept for this section? What is the major indoor air pollutant in many less-developed countries? What are the top three indoor air pollutants in the United States? List six sources...

What is the key concept for this section? What is the major indoor air pollutant in many less-developed countries? What are the top three indoor air pollutants in the United States? List six sources of common indoor air pollutants in a typical modern home. Give three reasons why they present a serious threat to human health. Explain why radon-222 is an indoor air pollution threat, how and where it occurs, and what can be done about it.