Browse http://www.epa.gov/ for comprehensive information.
Ozone, O3, aka smog, increases allergic reactions, shortness of breath, and susceptibility to infections. Smog "sears the nasal passages and hurts the lung's linings like a tinge of sunburn. The combination is especially bad for people with asthma," (New York Times, "An Ill Wind Blows at Vacation Sites," front page & p. A11, Friday, August 6, 1999). Repeated exposure to low levels of ozone may lead to chronic impairment. "A caustic irritant that essentially burns the tissues of the respiratory tract, ozone causes short-term inflammation and may lead to eventual scarring of the lungs." (American Lung Association brochure #0196)
Particulate matter, PM10, "Particulates have been associated with increased respiratory diseases (asthma, bronchitis, emphysema), cardiopulmonary disease (heart attack), and cancer." (1996 Illinois Annual Air Quality Report, p. 3) Diesel truck exhaust contributes "90% of soot from all vehicle sources." (From an Action Alert, American Lung Association, Metropolitan Chicago. 3/11/99) [Personal experience: when PSI is 60+ for PM10, I experience chill, fatigue, and indecisiveness. Wearing a Honeycomb Mask with an Activated Carbon Filter restores my body warmth, energy, clarity of mind and decisiveness within minutes.]
Sulfur dioxide, SO2, plus high humidity produces sulfuric acid droplets, about 5 to 20% of the brownish haze we see and breathe, irritating and inflaming tissue it directly contacts (in nose, throat, lungs). (IAAQR pp. 6&7) "Perhaps more important is evidence of impaired small airways mucociliary clearance after exposure of normal volunteers to as little as 100 ug/m3 of aerosolized H2SO4 for 1 hr." (Health Effects, p. 6) [Personal experience: On a humid morning when the haze is evident, my lungs constrict and my legs feel heavy, I put on an I Can Breathe! Silk Multipurpose Mask. The relief is immediate. I have energy and can walk briskly.]
Carbon monoxide, CO, invisible, "reduces oxygen carrying capacity of blood," decreases vigilance, and increases risk of heart attack. (IAAQR, pp. 4-5) "Some exposures during urban activities may adversely affect heart, brain, and central nervous system." (Health Effects, p. 484)
"Although dramatic air pollution episodes associated with readily evident excess mortality now are unlikely in much of the world, ozone, acid aerosols, and total particles may be responsible for adverse health effects at current levels of exposure. As the twentieth century ends, many respiratory hazards have been recognized and controlled in the United States and other developed countries. Concern remains, however, about the safety provided by existing standards for environmental exposures and the risks of new and unevaluated agents." (Health Effects, p. 4)
To detect airborne triggers of your symptoms, try a 24 hour test: Wear filtration masks for 24 hours to see if screening the air provides relief from your symptoms, increases energy and improves level of functioning. 2 levels: dust mask (dust, pollen, mold, dander) or an activated carbon filter (soot, diesel, gasoline, perfume, ink, formaldehyde).
Bibliography: 1996 Illinois Annual Air Quality Report (IAAQR)
"State of the Art Health Effects of Outdoor Air Pollution: Parts I and II," Committee of the Environmental and Occupational Health Assembly of the American Thoracic Society, R. Bascom, chair, et al, American Journal of Respiratory and Critical Care Medicine, Vol. 153, Numbers 1 and 2, January and February 1996, (Health Effects)