Mr. Portnoy and Mr. Williams said the discovery of airborne latex might offer at least a partial explanation for the worldwide rise in asthma cases, a medical mystery that has puzzled doctors for two decades. Since the late 1970s, asthma cases and deaths from asthma have increased steadily in the United States, particularly in urban areas. Similar increases have been reported in other countries, including England and Australia. The increases have persisted despite improved treatments and drugs and as environmental regulations have cleared away much of the air pollution in U.S. cities. Although living conditions vary from country to country, one thing they have had in common, Mr. Portnoy and Mr. Williams suggest, is increasing car traffic and greater use of radial tires.
Radials are more likely to produce airborne particles than the older bias ply tires.
Mr. Portnoy, who is collaborating with Mr. Williams on additional research, added tire fragment counts to his daily mold spore and pollen counts in August, making Kansas City the first metropolitan area to routinely monitor levels of these particles. His preliminary findings, which he will present this week to the annual meeting of the American College of Allergy, Asthma and Immunology in Dallas, point strongly to tires as the source of this airborne material. Particle levels in Kansas City rise on weekdays both in the morning and in the evening, coinciding with rush-hour traffic, Mr. Portnoy found. On weekends, when traffic slackens, levels tend to be low. So far, laboratory experiments conducted by Mr. Williams and by researchers in California have shown that airborne tire particles do react to antibodies taken from people with latex allergies.