Winter 2012

Dialogue | What is ground-level ozone and why is it harmful to human health?

Ground-level ozone, or smog, results from a chemical reaction between nitrogen oxides (emitted from cars and power plants) and volatile organic compounds (emitted from paints and solvents) in the presence of heat and sunlight. Ozone causes or aggravates asthma and other respiratory illnesses, leading to more emergency room visits, lost school days, and even premature death.

Because heat is a key ingredient in ozone formation, it is critical that we take action today to curb global warming. UCS research shows that warmer summers will likely produce more bad air-quality days in many parts of the country—especially in urban areas where car- and smokestack-related emissions tend to be higher—making ozone-related health impacts and their associated costs much worse.

Unfortunately, federal emissions-reduction policies continue to stagnate: the Obama administration delayed the release of a revised national ozone standard until at least 2013, and the Environmental Protection Agency also delayed its draft rule for reducing global warming emissions from power plants. Because heat-trapping gases such as carbon dioxide linger in the atmosphere for decades, these delays allow emissions to continue to build, guaranteeing at least some additional increase in temperatures and making future emissions reductions more difficult and costly.

To learn more about the connection between global warming and ozone pollution, and what UCS is doing to help reduce the risks, visit


Also in this issue of Earthwise:

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Gas-Free—and Loving It