Exposure to diesel-engine air pollution may plague allergy patients with certain genetic traits. In a small study of 19 individuals allergic to ragweed, the researchers tested the participants' DNA to figure out which forms of the GSTM1 and GSTP1 genes they had. These genes are responsible for producing enzymes that help the lungs detoxify pollutants and defuse oxidants before they can cause damage.
The GSTM1 gene comes in 2 forms: present and null. The null form of the gene is unable to produce the protective enzymes. About 50% of people have the null form of the gene. The GTSP1 gene can occur with a variation that makes it produce a less effective enzyme, which occurs in about 40% of people.
In the study, the participants were twice given 2 treatments: nose spray with either a dose of ragweed allergen and diesel-exhaust particles or spray with ragweed allergen and a placebo. The results showed that people who had the null form of GSTM1 had a greater allergic response to the diesel particles, compared with others in the study. In fact, a significant allergic response was seen in those who had both the null form of GSTM1 and the GSTP1 gene variation. (The findings were published recently in The Lancet)