Cancer incidence among pesticide applicators exposed to permethrin in the Agricultural Health Study.
BACKGROUND
Permethrin is a synthetic pyrethroid insecticide widely used in agriculture, in public health, and in many U.S. homes and gardens.


OBJECTIVE
In this study we evaluated the incidence of cancer among pesticide applicators exposed to permethrin in the Agricultural Health Study (AHS).


METHODS
A total of 49,093 pesticide applicators were included in this analysis of the AHS, a prospective cohort study of licensed pesticide applicators in Iowa and North Carolina. Detailed information on pesticide exposure and lifestyle factors was obtained from self-administered questionnaires completed in 1993-1997. Average length of follow-up since applicator enrollment in the cohort was 9.14 years. We used two permethrin exposure metrics: a) lifetime days applicators personally mixed or applied permethrin and b) intensity-weighted lifetime days (lifetime days weighted by estimated intensity of exposure). We used Poisson regression analysis to estimate relative risks (RRs) and 95% confidence intervals (CIs) for malignancies by tertiles of exposure.


RESULTS
We found no associations between permethrin and all malignant neoplasms combined, or between permethrin and melanoma, non-Hodgkin lymphoma, leukemia, or cancers of the colon, rectum, lung, or prostate. We found elevated and statistically significant risks for multiple myeloma in the highest tertiles of both lifetime exposure-days (RR = 5.72; 95% CI, 2.76-11.87) and intensity-weighted lifetime exposure-days (RR = 5.01; 95% CI, 2.41-10.42), compared with applicators reporting they never used permethrin; these results are based on only 15 exposed cases. These findings were similar across a variety of alternative exposure metrics, exposure categories, and reference groups.


CONCLUSIONS
This study found no association with most cancers analyzed. Although the suggested association with multiple myeloma was based on a small number of cases, it warrants further evaluation.
Rusiecki
Jennifer A
JA
Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799 , USA. jrusiecki@usuhs.mil
Patel
Rahulkumar
R
Koutros
Stella
S
Beane-Freeman
Laura
L
Landgren
Ola
O
Bonner
Matthew R
MR
Coble
Joseph
J
Lubin
Jay
J
Blair
Aaron
A
Hoppin
Jane A
JA
Alavanja
Michael C R
MC
D000328:Adult; D005260:Female; D006801:Humans; D015994:Incidence; D007306:Insecticides; D007484:Iowa / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000453:epidemiology*; D009657:North Carolina / Q000453:epidemiology; D016273:Occupational Exposure / Q000706:statistics & numerical data; D026023:Permethrin
D007306:Insecticides; D026023:Permethrin