Dog days of summer.

Those grim last days of summer--it seems as if it has never been anything but hot. Grit sticks to your clammy skin. The pavement radiates ripples of heat into the air. When the air you fill your lungs with is hotter than your own body temperature and about as clean as what comes out the back of your car, running can be more of a challenge than usual. Even taking out the trash can be more of a challenge than usual. Summer atmospheric inversions can raise pollution levels and when the air is bad, even without the heat, performance suffers.

Researchers in Israel assessed the effects of exposure to low levels of carbon monoxide on exercise performance, similar to levels found in all urban areas even when the authorities aren't issuing "Code Red" warnings. After exposure to carbon monoxide, carboxyhemoglobin levels (this is what the pathologist looks for when someone dies from carbon monoxide poisoning) rose from less than 1% to over 5%, and both duration of the exercise test and the measure of maximum effort were reduced as compared to controls. Researchers concluded that pollution of air by carbon monoxide impairs skeletal muscles and decreases exercise performance.

You know how bad you feel when the air is bad, so it is no surprise that bad air impairs running performance. What may be worse, of course, is the effect of air pollution on your overall health and well being, especially because you are being exposed to a host of pollutants like ozone, particulates, sulfur dioxide, nitrogen dioxide, and many others along with carbon monoxide. In a recent study, levels of particulate matter (one of the leading pollutants) was associated with an increased risk of death from all causes and from cardiovascular and respiratory illness. Ozone levels in the summer show similar associations. Air pollution is a trigger for asthma, may increase lung cancer risk, heart attack risk, can cause headaches, and can just make you feel toxic, tired, and lousy. When you run, you are processing huge volumes of that foul air and by breathing through your mouth you bypass natural scrubbing by the nasal mucosal membranes. So what's a runner to do? There are options to limit your exposure to bad air.

When air quality is poor, work out indoors if possible. If you have access to a treadmill, use it. If you must work out outdoors, do it early in the morning when the air will be cleaner than when traffic and industry increase the levels of pollutants. Run in a park, away from traffic-the air will be somewhat better than along the roads. If it's really bad and authorities are warning people to stay in, let it go. Use the day for cross training, flexibility exercises, strength training, or for rest and recovery. Running when the air is toxic isn't admirable--it's foolish. Cool weather will be here soon, turning those atmospheric inversions upside down again.

(New England Journal of Medicine, 2000, Vol. 343, No. 24, pp. 1742-1749; Occupational and Environmental Medicine, 1999, Vol. 56, No. 8, pp. 535-538)

RELATED ARTICLE: Can't Use Sunscreen on Your Eyeballs

Two large, important studies, the Beaver Dam Eye Study and the Salisbury Eye Evaluation project revealed the link between lifetime sun exposure and the development of early age-related maculopathy as well as cataracts. Both are vision robbers and you can limit your risk by using sunglasses and hats whenever you're outdoors.

(Arch of Ophthalmology, 2001, Vol. 119, No. 2, pp. 280. No. 246-250; JAMA, 1198, Vol. 280, No. 8, pp. 714-718)