How to Beat Summer Smog

Smog may be a constant problem in the Houston area, but in the summer, levels of ozone and other pollutants can go sky-high. Dr. Tom Stock, an associate professor of environmental sciences at The University of Texas-Houston School of Public Health, says the culprit is the increase in ultraviolet light that comes with longer days.

"UV light is the main ingredient for what's known as photochemical smog," says Dr. Stock. "It combines with volatile organic compounds (VOC) and nitrogen oxides from industry and auto emissions to create ozone." The higher temperatures of summer also add to the mix.

Although ozone levels can be high sporadically throughout the year in Houston, Dr. Stock says the high ozone "season" typically runs from May through October. Most of the ozone alerts issued by pollution control agencies occur during this period, as well as the greatest number of days when the city is out of compliance with federal ozone standards. Smog is usually the worst during the afternoon hours, peaking at about 2 p.m. Much lower levels of pollutants occur early in the morning and late at night.

The only way to completely avoid smog in the summer is to stay indoors in an air-conditioned building. Obviously, joggers and others who exercise outside can't do that, but there are ways to avoid the highest levels of smog and ozone. "Morning and evening rush hours are the absolute worst times to run, especially if the trail is adjacent to a roadway, like the tracks around Rice University and Memorial Park," says Dr. Stock.

Surprisingly, jogging tracks near roadways experience lower levels of ozone. Dr. Stock says nitric oxide from automobile tailpipes mixes with ozone and reduces it to oxygen. On the other hand, levels of particulate matter, carbon dioxide and VOCs from automobiles are much higher. "I would not advise exercising near traffic," says Dr. Stock. "You would probably be better off breathing ozone than that other stuff."

Lawn mowers, edgers and other gas-powered tools, which get a lot of use in the summer months, emit significant levels of pollutants. Although no studies have been done yet, Dr. Stock says the Environmental Protection Agency is looking at regulating small engines to meet a federally mandated deadline for compliance with the Clean Air Act after the turn of the century.

To avoid the worst of summer smog:

• Schedule outdoor exercise between 5 and 7 a.m. or after 6 p.m.
  
  
• Avoid exercising in areas with high volumes of vehicle traffic.
  
  
• Stay in an air-conditioned environment during peak smog hours (from 10 a.m. to 3 p.m.) If your home doesn't have air conditioning, go to a shopping mall.
  
  
• Consider using electrically powered lawn tools.

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©2006 Texas Medical Center

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