A variety of human activities produce pollutants, many of which pose risks to human health, the natural environment, and the Earth’s biosphere. These activities, however, may have important economic and social purposes. For example, coal-fired utility plants emit a range of dangerous substances from their tall smokestacks, many of which fall back to Earth hundreds of miles downwind. These pollutants make breathing difficult for people who have asthma and heart disease, and they damage forests, lakes, rivers, and the ecosystems of which they are a part. Yet, the electrical power generated at these plants is used to run factories, provide heat and air conditioning for office buildings, light homes, and sustain the Internet. Likewise, the internal combustion engines in automobiles and trucks emit harmful pollutants from their exhaust pipes that cause smog in urban areas and contribute to global climate change. Yet these vehicles give people the means to travel, conduct their social lives, commute to work, and move goods to markets. These two examples illustrate the underlying contradictions, tensions, and fault lines upon which environmental politics, policy, and administration are built. Human activities that generate pollutants create benefits and impose costs. The distribution of those benefits and costs differs by areas of the country, by sectors of the economy, and among many groups and individuals within our society. For example, oil companies, automobile manufacturers, and private utility companies that own coal-fired power plants have traditionally been among the fiercest opponents of efforts to limit pollutants that degrade air quality. Environmental groups, public health groups, and elected officials in urban areas and the states of the Northeast and West Coast have been among the strongest supporters of air pollution controls. Opponents of efforts to limit pollution generally contend that such limits lead to increased prices and lost jobs. Utility companies do incur costs when they purchase and install air pollution control equipment. Those costs are passed on to manufacturing firms, tenants in office buildings, and homeowners in the form of higher electricity bills.