American Journal of Epidemiology 2005 161(1):102-103; doi:10.1093/aje/kwi010
Copyright © 2005 by the Johns Hopkins Bloomberg School of Public Health
THE AUTHORS REPLY
Won Jin Lee1,
Jane A. Hoppin2,
Aaron Blair1,
Jay H. Lubin3,
Mustafa Dosemeci1,
Dale P. Sandler2 and
Michael C. R. Alavanja1
1 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
2 Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC
3 Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Rockville, MD
We thank Poole et al. (1) for their comments on our manuscript (2). As we stated, we made certain decisions prior to our analysis that were designed to optimize the comparability of exposure categories in our exposure-response evaluation of alachlor and also to optimize statistical power. These decisions are standard methods (3) and include using the low-exposure group as a reference when substantial demographic differences exist between the exposed category and the nonexposed category, and aggregating disease entities that may be etiologically similar. However, since a plausible counterargument can be made for inclusion of nonexposed cohort members as a reference group and disaggregation of the group "lymphohematopoietic cancers" into its component parts, as suggested by Poole et al., we show the results of these analyses in table 1. While overall risk of all neoplasms is not elevated, as in our earlier analysis, a significant trend in leukemia risk is observed with an increase in alachlor use with either lifetime alachlor exposure days or intensity-weighted exposure days. No meaningful trend was seen for non-Hodgkin’s lymphoma or multiple myeloma at this time. As stated in our original manuscript, our results do suggest a possible association between alachlor application and incidence of lymphohematopoietic cancers among applicators in the Agricultural Health Study, which we will continue to monitor as cases continue to accumulate. If these preliminary associations are real, we expect that the strength of the exposure-response association with alachlor will increase as we further refine our disease classification by cell type and genotype.
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TABLE 1. Rate ratios for selected cancers by lifetime exposure days and intensity-weighted exposure days to alachlor among Agricultural Health Study applicators
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REFERENCES
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- Poole C, Cullen M, Irons R, et al. Re: "Cancer incidence among pesticide applicators exposed to alachlor in the Agricultural Health Study." (Letter). Am J Epidemiol 2004;161:000–00.
- Lee WJ, Hoppin JA, Blair A, et al. Cancer incidence among pesticide applicators exposed to alachlor in the Agricultural Health Study. Am J Epidemiol 2004;159:373–80.[Abstract/Free Full Text]
3. Rothman KJ, Greenland S, eds. Modern epidemiology. 2nd ed. Philadelphia, PA: Lippincott-Raven, 1998:316–17.
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