Risk factors of thyroid tumors: role of environmental and occupational exposures to chemical pollutants

Abstract

Background: The rising incidence of thyroid cancer observed during the last few decades in most western countries is explained in large part by increasing numbers of diagnoses due to changes in medical screening practices. However, beside radiation exposure, exposure to environmental chemicals may also play a role in thyroid cancer etiology and in the increased incidence. This paper presents the main chemicals suspected to induce thyroid tumorigenesis, and epidemiological results on the association between chemical exposure and thyroid tumors.

Methods: We reviewed experimental studies to identify the main chemicals possibly involved in thyroid tumorigenesis. We also reviewed the main epidemiological studies investigating the association between environmental chemical exposure and thyroid neoplasm in humans.

Results: Environmentally abundant chemicals may disrupt thyroid function and/or play a role in tumorigenesis through a variety of mechanisms. Epidemiological results provide insufficient evidence of a causal link between exposure to environmental chemicals and thyroid tumors, but raise the hypothesis of an increased risk of thyroid neoplasm for workers in the leather, wood, and paper industries, and those exposed to certain solvents and pesticides.

Conclusion: This paper highlights the need for large epidemiological studies evaluating the exposure to various groups of environmental chemicals and its impact on the thyroid gland.