Environment and Breast Cancer: Science Review

Evidence From Humans
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Body mass index, agricultural pesticide use, and cancer incidence in the Agricultural Health Study cohort
Andreotti, G., Hou, L., Beane Freeman, L. E., Mahajan, R., Koutros, S., Coble, J., Lubin, J., Blair, A., Hoppin, J. A., Alavanja, M. Cancer Causes Control. 2010. 21:11, 1759-75.
Topic area
Environmental pollutant - Pesticides Body size
Study design
Prospective cohort
Funding agency
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Stratified analysis based on menopausal status
Number in Cohort
Cohort: 67,947
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Participants were from the Agricultural Health Study cohort, which is composed of almost 90,000 participants, including licensed private pesticide applicators and their spouses residing in Iowa and North Carolina, and commercial applicators residing in Iowa. Cancers diagnosed between enrollment and 2005 were included (median 10 year follow-up), and participants diagnosed prior to enrollment were excluded from analysis.
Comment about participation selection
This is a large cohort with high participation rates, and the prospective design minimized the likelihood of recall bias.
Exposure Investigated
Exposures investigated
For postmenopausal women, interaction between BMI and pesticide exposure was analyzed. BMI groups were <25, 25-29.9, >30, and pesticide exposure was classified as ever/never exposed to organochlorines, organophosphates, malathion, diazinon, carbaryl, and
How exposure was measured
Anthropomorphic measurement, self-administered Questionnaire, self-administered Questionnaire, by telephone
Exposure assessment comment
At enrollment, pesticide applicators completed questionnaires on ever/never use of 50 pesticides, and detailed information on 22 of the 50, including number of days and years pesticides were applied, use of personal protective equipment, and application methods. 44% of the applicators returned take-home questionnaires with detailed information on the remaining 28 pesticides. The authors state no meaningful differences were found between those who completed the take-home questionnaire and those who didn't, but there could be an unidentified confounder influencing a reporting bias.
Breast cancer outcome investigated
Primary incident breast cancer
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
race, state of residence, education, smoking status, alcohol intake, hypertension, diabetes, family history, meat intake, fruit intake, vegetable intake, vitamin supplement, leisure-time exercise, menopause status, parity.
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Strength of associations reported
Among postmenopausal women with BMI>30 compared to BMI<25:
No exposure to organochlorines: aHR 1.52 (95% CI 1.09-2.12)
Exposure to organochlorines: aHR 1.23 (95% CI 0.55-2.76)

No exposure to organophosphates: aHR 1.76 (95% CI 1.23-2.54)
Exposure to organophosphates: aHR 0.99 (95% CI 0.56-1.75)

No exposure to malathion: aHR 1.68 (95% CI 1.18-2.40)
Exposure to malathion: aHR 1.00 (95% CI 0.53-1.84)

No exposure to diazinon: aHR 1.49 (95% CI 1.07-2.07)
Exposure to diazinon: aHR 1.59 (95% CI 0.65-3.88)

No exposure to carbaryl: aHR 1.50 (95% CI 1.04-2.15)
Exposure to carbaryl: aHR 1.41 (95% CI 0.79-2.53)

Among postmenopausal women with BMI between 25 and 29.9 compared to BMI<25:
Exposure to carbaryl: aHR 1.64 (95% CI 1.02-2.65)
Results Comments
The number of postmenopausal women with breast cancer who were ever exposed to organochlorines or organophosphates is relatively small, compared to those women who were not exposed. This reduces the statistical power of the analyses.
Author address
Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, DHHS, 6120 Executive Blvd., EPS 8011, MSC 7240, Bethesda, MD 20892, USA. andreotg@mail.nih.gov
Reviewers Comments
The positive association between BMI and pesticide use and postmenopausal breast cancer was not specific to a particular pesticide, which suggests some uncontrolled difference between women who applied and did not apply pesticides. The authors state there could be a protective effect of working on a farm, such as physical activity, or vitamin D exposure.