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  • BMJ Publishing Group  (2)
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  • 1
    Publication Date: 2018-01-17
    Description: 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 (OR Q3 =4.15, 95% CI 1.56 to 11.01, OR Q4 =4.76, 95% CI 1.53 to 14.82, p trend 〈0.01), higher TSH (p trend =0.01) and lower T4 (p trend =0.04). Higher exposure to the herbicide pendimethalin was associated with subclinical hypothyroidism (fourth quartile vs no exposure: OR Q4 =2.78, 95% CI 1.30 to 5.95, p trend =0.02), higher TSH (p trend =0.04) and anti-TPO positivity (p trend =0.01). The fumigant methyl bromide was inversely associated with TSH (p trend =0.02) and positively associated with T4 (p trend =0.01). Conclusions Our results suggest that long-term exposure to aldrin, pendimethalin and methyl bromide may alter thyroid function among male pesticide applicators.
    Print ISSN: 1351-0711
    Electronic ISSN: 1470-7926
    Topics: Medicine
    Published by BMJ Publishing Group
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  • 2
    Publication Date: 2018-02-16
    Description: Objectives The previously observed inverse association between hog farming and risk of lung cancer in the Agricultural Health Study (AHS) has been attributed to endotoxin exposure, the levels of which are particularly high in industrial hog confinement facilities. We conducted an investigation to explore the potential biological mechanisms underlying this association, as well as other immunological changes associated with hog farming. Methods Serum immune marker levels were measured using a multiplexed bead-based assay in 61 active hog farmers and 61 controls matched on age, phlebotomy date and raising cattle. Both groups comprised non-smoking male AHS participants from Iowa. We compared natural log-transformed marker levels between hog farmers and controls using multivariate linear regression models. Results Circulating levels of macrophage-derived chemokine (CCL22), a chemokine previously implicated in lung carcinogenesis, were reduced among hog farmers (17% decrease; 95% CI –28% to –4%), in particular for those with the largest operations (〉6000 hogs: 26% decrease; 95% CI –39% to –10%; p trend =0.002). We also found that hog farmers had elevated levels of other immune markers, including macrophage inflammatory protein-3 alpha (MIP-3A/CCL20; 111% increase, 95% CI 19% to 273%), basic fibroblast growth factor (FGF-2; 93% increase, 95% CI 10% to 240%) and soluble interleukin-4 receptor (12% increase, 95% CI 1% to 25%), with particularly strong associations for MIP-3A/CCL20 and FGF-2 in winter. Conclusions These results provide insights into potential immunomodulatory mechanisms through which endotoxin or other exposures associated with hog farming may influence lung cancer risk, and warrant further investigation with more detailed bioaerosol exposure assessment.
    Print ISSN: 1351-0711
    Electronic ISSN: 1470-7926
    Topics: Medicine
    Published by BMJ Publishing Group
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