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Occup Environ Med. 2018 Feb;75(2):79-89. doi: 10.1136/oemed-2017-104431. Epub 2017 Aug 3.

Occupational pesticide exposure and subclinical hypothyroidism among male pesticide applicators.

Author information

1
Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, Maryland, USA.
2
Environmental Working Group, Washington, DC, USA.
3
Department of Public Health Sciences, The University of Chicago, Chicago, Illinois, USA.
4
National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA.
5
Department of Biology, Hood College, Frederick, Maryland, USA.

Abstract

OBJECTIVES:

Animal studies suggest that exposure to pesticides may alter thyroid function; however, few epidemiologic studies have examined this association. We evaluated the relationship between individual pesticides and thyroid function in 679 men enrolled in a substudy of the Agricultural Health Study, a cohort of licensed pesticide applicators.

METHODS:

Self-reported lifetime pesticide use was obtained at cohort enrolment (1993-1997). Intensity-weighted lifetime days were computed for 33 pesticides, which adjusts cumulative days of pesticide use for factors that modify exposure (eg, use of personal protective equipment). Thyroid-stimulating hormone (TSH), thyroxine (T4), triiodothyronine (T3) and antithyroid peroxidase (anti-TPO) autoantibodies were measured in serum collected in 2010-2013. We used multivariate logistic regression to estimate ORs and 95% CIs for subclinical hypothyroidism (TSH >4.5 mIU/L) compared with normal TSH (0.4-<4.5 mIU/L) and for anti-TPO positivity. We also examined pesticide associations with TSH, T4 and T3 in multivariate linear regression models.

RESULTS:

Higher exposure to the insecticide aldrin (third and fourth quartiles of intensity-weighted days vs no exposure) was positively associated with subclinical hypothyroidism (ORQ3=4.15, 95% CI 1.56 to 11.01, ORQ4=4.76, 95% CI 1.53 to 14.82, ptrend <0.01), higher TSH (ptrend=0.01) and lower T4 (ptrend=0.04). Higher exposure to the herbicide pendimethalin was associated with subclinical hypothyroidism (fourth quartile vs no exposure: ORQ4=2.78, 95% CI 1.30 to 5.95, ptrend=0.02), higher TSH (ptrend=0.04) and anti-TPO positivity (ptrend=0.01). The fumigant methyl bromide was inversely associated with TSH (ptrend=0.02) and positively associated with T4 (ptrend=0.01).

CONCLUSIONS:

Our results suggest that long-term exposure to aldrin, pendimethalin and methyl bromide may alter thyroid function among male pesticide applicators.

KEYWORDS:

agriculture; hypothyroidism; pesticides; thyroid disease; thyroid stimulating hormone

PMID:
28775130
PMCID:
PMC5771820
[Available on 2019-02-01]
DOI:
10.1136/oemed-2017-104431

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