ORIGINAL ARTICLE

Use of a crop and job specific exposure matrix for estimating cumulative exposure to triazine herbicides among females in a case-control study in the Central Valley of California

H A Young¹, P K Mills², D Riordan³ and R Cress⁴

¹ The George Washington University School of Public Health and Health Services Department of Epidemiology and Biostatistics, Washington, DC, USA
² Cancer Registry of Central California/Public Health Institute and University of California San Francisco Fresno Medical Education Program, California, USA
³ Cancer Registry of Central California/Public Health Institute, California, USA
⁴ California Cancer Registry Cancer/Public Health Institute, California, USA

Correspondence to:
Correspondence to:
Dr H A Young
George Washington University School of Public Health and Health Services, 2300 Eye Street, NW, Ross Hall 120A, Washington, DC 20037, USA; bschay{at}gwumc.edu

Aims: To determine if a job exposure matrix (JEM) could be developed using the California Department of Pesticide Regulation Pesticide Usage Database in conjunction with crop, time, and county specific self reported work history and to determine if this was a feasible method to obtain exposure estimates to triazine herbicides.

Methods: Agricultural work histories were gathered from women enrolled in a population based case-control study of ovarian cancer cases and random controls. The work histories were used in conjunction with the database to construct job exposure matrices which took into account weightings for job type, work location, and crop.

Results: Cumulative exposure estimates were determined for 98 study subjects. Mean exposure estimates were similar for cases and controls. The exposure estimates were robust and insensitive to varying job weight assumptions. The estimates from the original weights were highly correlated with those constructed using the conservative and maximum weights. Estimates from all three schemes produced similar multivariate age adjusted odds ratios comparing cases and controls. There was a high degree of agreement in categorised quartiles of exposure between the original and conservative, and original and maximum weights.

Conclusions: The exposure estimate from the JEM provides a ranking of exposure within the study population that can be utilised as an "exposure score" with which to compare groups. Although it is not an absolute exposure measurement, it does offer a substantial advance over dichotomous categories based on self report of herbicide use, particularly when subjects are unlikely to recall specific names and dates of use of herbicides.

Abbreviations: CI, confidence interval; DPR, Department of Pesticide Regulation; EOC, epithelial ovarian cancer; JEM, job exposure matrix; OR, odds ratio

Keywords: pesticides; herbicides; exposure assessment; agriculture; job exposure matrix

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