Pesticide Exposure and Respiratory Health

Although there are few animal and human studies in the literature on this subject, exposure to pesticides in the course of agricultural activities can produce a range of respiratory illnesses including irritant-induced asthma and persistent wheeze. Case reports also exist regarding the respiratory health effects of pesticides in occupational cohorts exposed to organophosphates or paraquat. For example, depressions in acetylcholinesterase levels were found in Kenyan farmers exposed to organophosphate pesticides. A case series observed the development of persistent irritant asthma in individuals exposed to methylisothiocyanate during a metam-sodium pesticide spill in the Sacramento River in California. A study of grain farmers in Ohio found that increased cough was associated with mixing and applying pesticides more frequently. Among Iowa farmers, increased phlegm and wheeze was associated with insecticide application to animals, even after controlling for the animal exposures themselves. In aerial applicators, increased wheeze was found compared to control subjects (122-131).

The Agricultural Health Study is an ongoing study of licensed pesticide applicators consisting mainly of farmers in North Carolina and Iowa in the United States. In this cohort, 19% of farmers reported wheeze over the previous year, which is higher than the 12% background rate of wheeze in the general United States population. Eleven of 40 pesticides used by farmers were associated with wheeze and specific organophosphates (Parathion, malathion, chlorpyriphos), one thiocarbamate (s-ethyl-dipropylthiocarba-mate), and herbicides (glyphosate), paraquat, and atrazine) were associated with wheeze (132,133).

Chronic low-level pesticide exposures may also result in respiratory illness. For instance, chronic low-level occupational exposures to paraquat in Nicaraguan banana farmers found an association of wheeze among highly exposed groups. Another study in South African farm workers found more arterial desaturation among people working with paraquat (134,135).

Rural populations may also be at increased risk for respiratory effects from pesticide exposures. In China, an increased prevalence of wheeze was found in persons who applied organophosphate and pyrethroid/pyrethrins insecticides in the home. In Ethiopia, insecticide use at home was associated with increased skin sensitivity and increased wheeze; malathion was the pesticide most often involved (136,137).

Some strategies to reduce the likelihood of respiratory exposures to pesticides among agricultural populations include choosing pesticides with lower volatility, lower concentrations of active ingredients, and using equipment designed to minimize exposures (138).

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