AP Environmental Science

Answer: A - Smoking is the most significant air pollutant in the United States in terms of its impact upon public health.

Key Takeaway: By far, smoking is the most significant air pollutant in the United States in terms of public health. Although smoking has decreased in recent years due to smoking bans and a general public dislike, it is still estimated that smoking and the diseases that result from it cause 20 percent of the deaths in the United States each year. Only very recently did obesity and its related diseases officially outrank smoking as a public health hazard.