Occupation and thyroid cancer.

Numerous occupational and environmental exposures have been shown to disrupt thyroid hormones, but much less is known about their relationships with thyroid cancer. Here we review the epidemiology studies of occupations and occupational exposures and thyroid cancer incidence to provide insight into preventable risk factors for thyroid cancer. The published literature was searched using the Web of Knowledge database for all articles through August 2013 that had in their text 'occupation' 'job' 'employment' or 'work' and 'thyroid cancer'. After excluding 10 mortality studies and 4 studies with less than 5 exposed incident cases, we summarised the findings of 30 articles that examined thyroid cancer incidence in relation to occupations or occupational exposure. The studies were grouped by exposure/occupation category, study design and exposure assessment approach. Where available, gender-stratified results are reported. The most studied (19 of 30 studies) and the most consistent associations were observed for radiation-exposed workers and healthcare occupations. Suggestive, but inconsistent, associations were observed in studies of pesticide-exposed workers and agricultural occupations. Findings for other exposures and occupation groups were largely null. The majority of studies had few exposed cases and assessed exposure based on occupation or industry category, self-report, or generic (population-based) job exposure matrices. The suggestive, but inconsistent findings for many of the occupational exposures reviewed here indicate that more studies with larger numbers of cases and better exposure assessment are necessary, particularly for exposures known to disrupt thyroid homeostasis.