As we enter smog season:

Pounds of smog-forming volatile organic gases produced annually by flatulence from each of the San Joaquin Valley's 2.5 million dairy cows, the California region's single largest source of smog-forming emissions contributing to its new ranking by the American Lung Association as having the dirtiest air in the nation: 20

Compare that with the average pounds of VOCs per car produced annually: 16

Interesting. Of course, there is more to the equation than just VOCs. Learn more about air quality and what you can do to make a difference at: http://www.epa.gov/otaq/