One more study has shown that farmworkers are being exposed to dangerous levels of pesticide exposure. The matter is of especial concern in the agricultural season (May-August), say US researchers in their study of the scene in North Carolina.
As farmworkers can be exposed to a wide variety of pesticides, Sara A. Quandt from the Wake forest school of medicine and others sought to assess cholinesterase activity over time and that way monitor exposure to organophosphorus and carbamate pesticides.
Particularly they wanted to explore the association of cholinesterase depression with pesticide exposure across the agricultural season.
Cholinesterase, an enzyme in the brain, breaks apart the neurotransmitter acetylcholine, which is vital for the transmission of nerve impulses.
In disorders such as Alzheimer disease, Lewy body disease, and vascular dementia, the production of acetylcholine is decreased. As a result, nerve communication is less efficient, with consequent problems of memory and other brain and body functions.
A previous study had found that pesticides most frequently associated with cholinesterase depressions exceeding California threshold values included mevinphos (Phosdrin), oxydemeton methyl (Metasystox-R), methomyl (Lannate), and acephate (Orthene); these pesticides included organophosphates in toxicity categories I and II and one carbamate in toxicity category I.
Also farmworkers have reported many pesticide exposures that violate state and federal regulations.
Wakefield researchers collected dried blood samples from 231 migrant farmworkers and analyzed the samples for cholinesterase activity. The urine samples of workers were analyzed for metabolites of organophosphorus and carbamate pesticides. Reductions of 15% or more from an individual's highest value were identified and considered evidence of meaningful cholinesterase activity depression.
The average cholinesterase activity levels were lowest in June, with significantly higher mean values in July and August, the researchers found. When adjusted for age, gender, minutes waited to shower, and days worked in the fields, the number of organophosphorus and carbamate pesticides detected in urine predicted reductions in cholinesterase activity.
These data demonstrate that workers are experiencing pesticide exposure. Greater enforcement of existing safety regulations or strengthening of these regulations may be warranted, the researchers stressed.
Their findings have been published in Environmental Health Perspectives.