While asthma attacks can be triggered by cigarette smoke as well as allergens, such as pollen, the increase in diagnosis of asthma in children appears to be directly linked to exhaust fumes. Diane Bailey of the Natural Resources Defense Council reported that, "One major study found that components of diesel exhaust including particulate matter can cause biologic responses that are related to asthma; this exposure is associated with the inflammatory and immune responses involved in asthma."
Since many schools are located near major highways, the constant flow of diesel-fueled trucks and busses present a growing threat to the health of students, even when the students live in suburban or rural areas, as reported by Bailey. "A study of thirteen Southern California communities found that children exposed to traffic-related pollution in school were more likely to develop asthma irrespective of residential exposure."
In addition, studies taken in the Netherlands of over 1,000 children found that "asthma, wheezing, coughs, and runny nose were significantly more common in children living within 330 feet of freeways; and higher asthma rates were significantly associated with increasing levels of diesel truck traffic."
In England, a study of 10,000 children showed symptoms to be more likely if the child's home was near a main road, with the highest risk found in homes within 300 feet of the roadways. Again, diesel truck traffic played a significant role in the pollution levels.