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Occupational determinants of serum cholinesterase inhibition among organophosphate-exposed agricultural pesticide handlers in Washington State
  1. Jonathan N Hofmann*,
  2. Matthew C Keifer,
  3. Anneclaire J De Roos,
  4. Richard A Fenske,
  5. Clement E Furlong,
  6. Gerald van Belle,
  7. Harvey Checkoway
  1. University of Washington, United States
  1. Correspondence to: Jonathan N Hofmann, Epidemiology, University of Washington, Department of Epidemiology, Box 357236, Seattle, WA, United States; hofmann{at}


Objective: To identify potential risk factors for serum cholinesterase (BuChE) inhibition among agricultural pesticide handlers exposed to organophosphate (OP) and N-methyl-carbamate (CB) insecticides.

Methods: We conducted a longitudinal study among 154 agricultural pesticide handlers who participated in the Washington State cholinesterase monitoring program in 2006 and 2007. BuChE inhibition was analyzed in relation to reported exposures before and after adjustment for potential confounders using linear regression. Odds ratios estimating the risk of ‘BuChE depression’ (>20% from baseline) were also calculated for selected exposures based on unconditional logistic regression analyses.

Results: An overall decrease in mean BuChE activity was observed among study participants at the time of follow-up testing during the OP/CB spray season relative to pre-season baseline levels (mean decrease of 5.6%, P < 0.001). Score for estimated cumulative exposure to OP/CB insecticides in the past 30 days was a significant predictor of BuChE inhibition (coefficient = -1.74, P < 0.001). Several specific work practices and workplace conditions were associated with greater BuChE inhibition, including mixing/loading pesticides and cleaning spray equipment. Factors that were protective against BuChE inhibition included full-face respirator use, wearing chemical-resistant boots, and storing personal protective equipment in a locker at work.

Conclusions: Despite existing regulations, agricultural pesticide handlers continue to be exposed to OP/CB insecticides at levels resulting in BuChE inhibition. These findings suggest that modifying certain work practices could potentially reduce BuChE inhibition. Replication from other studies will be valuable.

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