The transportation industry is the major source of air pollution in the United States. It causes more than half of carbon monoxide and nearly a third of nitrogen oxides emitted into the atmosphere. Hybrid cars do not completely eliminate pollution, but they do cut significantly the amount of carbon monoxide gas released to the environment.
The government can set rules that limit industries from engaging in practices that create pollution, for instance, industries directing their waste water to rivers. The regulations can include hefty fines for violations. The government could also step in and intervene on air pollution by raising fuel costs. This will reduce demand for fuel and encourage people to use public transportation, thereby reducing pollution. In the United States, the Clean Air Act of 1970 is a good example of a statute concerned with environmental protection.
Trees absorb pollutant gases through their stomata and convert them into utilizable nutrients; planted in urban centers, they decrease urban pollutants. According to calculations by the U.S. Forest Service, over a 50 year lifetime, a single tree produces $31,250 worth of oxygen and offers $62,000 worth of air pollution control.
Pollution in homes contributes significantly to the overall pollution of the urban areas. Sources of indoor pollution include combustion of fuels such as kerosene oil and coal. If consumers switched to more environmentally friendly fuels, like biogas, it would go a long way in controlling pollution. Even quitting smoking can mitigate urban pollution.