If you were anywhere in the Eastern United States today, chances are, you heard someone remark about the weather. New York hit three digits, Boston came darn close, and at every stop from Maine to Georgia, people were sweating through a humid, miserable day.

As the first heat wave of 2008 settles in, plenty of folks will think a bit harder about global warming, and hopefully even turn to the air-conditioned convenience of mass transit at the thought of pumping out more carbon while stuck traffic for hours at the end of a hot day.

But chances are, many will also continue in their habits, simply rolling up the windows and cranking the A/C, while more heat-trapping emissions slowly accumulate in the atmosphere. But despite perceptions you might have that the world is getting warmer, permanent ground-level environmental changes occur all but imperceptibly. No, instead the excess levels of urban auto emissions will register in a much more obvious and much more painful way: ozone.

Ozone is a gas, composed of three oxygen atoms; the gas in the air we breathe, generally referred to as oxygen, consists of just two atoms. Though known as early as the mid-1800s, ozone first entered the wider public consciousness in the 1970s, as widespread CFC use began to erode a protective layer of the gas in the Earth’s atmosphere.

Ozone does provide a valuable protective function high the atmosphere, absorbing energy from ultraviolet radiation and preventing much of it from reaching the Earth’s surface. Though it also has a small impact as a greenhouse gas, ozone’s primary negative effect is as a pollutant at ground level. Formed when certain volatile chemicals found in car exhaust and other industrial emissions react with the air in the presence of sunlight, ozone wreaks havoc on nearly everything surrounding it. 

It inflames the lungs and esophagus, making full, deep breaths nearly impossible without coughing. Concentrations of a mere two parts-per-million can irritate the eyes almost immediately. Even short-term exposure can degrade rubbers and plastics in a dramatic fashion, as well as deeply erode crop yields from agriculture in ozone-stricken areas.

Sadly, as it has on many other environmental issues, the current administration has taken a very passive approach to ozone regulation, with the EPA recently passing a regulatory standard far more lax than its own scientists recommended. But, to its credit, the EPA has also initiated a system in conjunction with local officials and news agencies to make the public aware of so-called “Ozone Action Days,” when the likelihood for ozone creation is high. This allows people to take personal steps to avoid releasing the volatile chemicals that help form ozone at ground level.

Still, considering the frequency and widespread nature of unacceptably high ozone concentrations, its clear that additional investments in cleaner vehicles and industrial methods must be made if fresh air is remain a sunny-day reality in urban areas across the United States.