The study presented Sunday was conducted by researcher Jane Hoppin of the US National Institute of Environmental Health Sciences. It examined 20,183 male farmers in the US states of Iowa and North Carolina.
“This is a breakthrough: never before has a large-scale study demonstrated that farmers’ exposure to insecticides, fungicides and herbicides can contribute to the prevalence of asthma, independently of other risk factors,” a statement from the European Respiratory Society’s annual congress said.
The study group was exposed to 48 different pesticides and asthma was found to be linked to the use of 16 of them, a “quite alarming” discovery, the statement said.
“Asthma was linked to specific chemicals since we did not identify a link either with particular pesticide classes or with a particular method of use,” Hoppin said.
“In addition, we show that a history of high pesticide exposure event was associated with a doubling of asthma risk,” she added.
Of the 452 farmers who developed asthma after the age of 20, 129 had allergic asthma while the remaining 323 had the non-allergic version.
Some pesticides led to a 30- to 40-percent increase in the prevalence of asthma, while some led to a two-fold increase.
Six of the 16 pesticides are no longer sold in the United States.
A similar study concerning female farmers is underway.
Some 300 million people worldwide suffer from asthma, according to the World Health Organisation.
A total of 15,000 clinical doctors, researchers, physiotherapists and medical and pharmaceutical industry workers from more than 100 countries are attending the European Respiratory Society’s 17th annual congress, which concludes on Wednesday.