Studies in Montreal and Santiago, Chile, found an increase in headache-induced hospital visits when nitrogen dioxide and carbon monoxide levels were especially high. Scientists point to pollutants' inflammatory effects on blood vessels.
The chemicals from fuel combustion have been shown to cause inflammation in general, which could help explain why a group of Canadian researchers found evidence that air pollution may trigger appendicitis.
High Blood Pressure
When University of Michigan researcher Robert Brook, MD, exposed healthy adults to particulate matter levels common on a typical day in Detroit, their diastolic blood pressure shot up several points—and the effects lasted up to 24 hours. The pollutants are thought to trigger a fight-or-flight-like response in the nervous system; as arteries constrict, blood pressure spikes.
Type II Diabetes
A study published in 2010 followed 1,775 middle-aged women in Germany's Rurh district, which is home to heavy traffic. After 16 years, the women were most likely to develop type II diabetes if they lived within 100 yards of a busy road.
Scientists in Canada have discovered that postmenopausal women living in areas with high levels of nitrogen dioxide may face at least a 25 percent higher chance of contracting the disease. Other research suggests that prolonged exposure to toxic emissions around the time of a woman's first period or first pregnancy may also increase risk.
Next: What you can do to avoid inhaling noxious fumes
Avoid the Heat
Air quality is lowest when the temperature is highest. Plan outdoor physical activity for morning or evening.
Avoid walking or biking along busy streets, where levels of pollutants tend to be higher.
Go to airnow.gov to check the EPA's daily air quality forecast for more than 300 cities.
Home air filters can block particulate matter. Make sure yours rate 9 or higher on the MERV scale (the industry standard for filter efficiency). When sitting in traffic, use the recycled-air setting on your A/C so you don't suck in fumes.
Listen to Your Body
If you're exercising outside on a smoggy day and you feel tightness in your chest, or if your eyes are teary, itchy, or red, "don't push it," Edelman says.
Eat Clean Cuisine
Stock up on foods high in antioxidants, like cherries, kale, and tomatoes. Antioxidants trap free radicals, which help pollutants do their dirty work in the body.
Keep Your Family Healthy