Pendimethalin exposure and cancer incidence among pesticide applicators.
BACKGROUND
Pendimethalin, a widely used herbicide, has been classified as a group C possible human carcinogen by the U.S. Environmental Protection Agency. We evaluated the incidence of cancer in relation to reported pendimethelin use among pesticide applicators in the Agricultural Health Study, a prospective cohort of licensed pesticide applicators in Iowa and North Carolina.


METHODS
Information on pesticide use came from two questionnaires (enrollment and take-home). The present analysis includes 9089 pendimethalin-exposed and 15,285 nonpendimethalin-exposed pesticide applicators with complete information on pendimethalin use and covariates from a take-home questionnaire. We conducted Poisson regression analyses to evaluate the association of pendimethalin exposure with cancer incidence (mean follow-up = 7.5 years) using two exposure metrics: tertiles of lifetime days of exposure and tertiles of intensity-weighted lifetime days of exposure.


RESULTS
Overall cancer incidence did not increase with increasing lifetime pendimethalin use, and there was no clear evidence of an association between pendimethalin use and risks for specific cancers. The risk for rectal cancer rose with increasing lifetime pendimethalin exposure when using nonexposed as the reference (rate ratio = 4.3; 95% confidence interval = 1.5-12.7 for the highest exposed subjects; P for trend = 0.007), but the association was attenuated when using the low exposed as the referent group (P for trend = 0.08). Similar patterns for rectal cancer were observed when using intensity-weighted exposure-days. The number of rectal cancer cases among the pendimethalin-exposed was small (n = 19). There was some evidence for an elevated risk for lung cancer, but the excess occurred only in the highest exposure category for lifetime pendimethalin exposure. The trends for lung cancer risk were inconsistent for different exposure metrics.


CONCLUSIONS
We did not find a clear association of lifetime pendimethalin exposure either with overall cancer incidence or with specific cancer sites.
Hou
Lifang
L
Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Rockville, MD 20852, USA.
Lee
Won Jin
WJ
Rusiecki
Jennifer
J
Hoppin
Jane A
JA
Blair
Aaron
A
Bonner
Matthew R
MR
Lubin
Jay H
JH
Samanic
Claudine
C
Sandler
Dale P
DP
Dosemeci
Mustafa
M
Alavanja
Michael C R
MC
D000328:Adult; D000814:Aniline Compounds / Q000506:poisoning*; D015331:Cohort Studies; D004781:Environmental Exposure / Q000032:analysis; D005260:Female; D006801:Humans; D007484:Iowa / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000453:epidemiology*; D009657:North Carolina / Q000453:epidemiology; D011446:Prospective Studies; D011795:Surveys and Questionnaires
D000814:Aniline Compounds; C030856:pendimethalin