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Occupational determinants of serum cholinesterase inhibition among organophosphate-exposed agricultural pesticide handlers in Washington State
  1. Jonathan N Hofmann1,
  2. Matthew C Keifer2,
  3. Anneclaire J De Roos1,3,
  4. Richard A Fenske2,
  5. Clement E Furlong4,5,
  6. Gerald van Belle2,6,
  7. Harvey Checkoway1,2
  1. 1Department of Epidemiology, University of Washington, Seattle, Washington, USA
  2. 2Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA
  3. 3The Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
  4. 4Department of Medicine - Division of Medical Genetics, University of Washington, Seattle, Washington, USA
  5. 5Department of Genome Sciences, University of Washington, Seattle, Washington, USA
  6. 6Department of Biostatistics, University of Washington, Seattle, Washington, USA
  1. Correspondence to Dr Jonathan N Hofmann, Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 6120 Executive Blvd, EPS 8109, MSC 7240, Bethesda, MD 20892-7240, USA; hofmannjn{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 analysed in relation to reported exposures before and after adjustment for potential confounders using linear regression. ORs 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 (β=−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.

  • Cholinesterases
  • organophosphates
  • pesticides
  • agricultural workers
  • occupational exposure

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  • Funding Financial support for this project was provided by U.S. CDC/NIOSH grants #1 U50 OH07544 and #1 T42 OH008433-01, and U.S. NIEHS grants #P30 ES07033, #P42 ES04696 and #T32 ES07262.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the University of Washington Institutional Review Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.