Document Type

Capstone Experience

Graduation Date

8-2023

Degree Name

Master of Public Health

Department

Environmental, Agricultural & Occupational Health

First Committee Member

Aaron Yoder

Second Committee Member

Shinobu Watanabe-Galloway

Third Committee Member

Daisy Dai

Abstract

Thyroid cancer is one of the fastest growing cancers in the United States, with the rate of new cases increasing from 5.2 per 100,000 in 1985 to 13.8 per 100,000 in 2019, with a peak of 14.5 per 100,000 in 2015. Increased thyroid cancer incidence is associated with certain occupations, including healthcare and agriculture. Most existing literature on occupational exposures and thyroid cancer evaluate their association in terms of occupation type and thyroid cancer, rather than specific occupational exposures and thyroid cancer. This study sought to utilize the wide range of occupational exposure data in the Integrated Cancer Center Repository for Cancer Research(iCaRe2) to address this research gap by examining the relationship between selected occupational exposures and thyroid cancer incidence. Aims of this study were to: 1) examine the association between occupational exposures and thyroid cancer incidence, and 2) examine the association between occupational exposures and benign thyroid nodule incidence.

An exploratory case-control study was conducted with thyroid cancer cases (n=462) and high-risk enrollees (n=462) from the Thyroid Tumor and Cancer Collaborative Registry (TCCR) and controls (n=218) from the Great Plains Health Informatics Database (GPHID). Occupational exposures of the two TCCR groups were compared to the GPHID control group using multivariable logistic regression to calculate crude odds ratios, adjusted odds ratios (AORs), and 95% Confidence Intervals. AORs were adjusted for Body Mass Index (BMI), age, gender, and education.

Thyroid cancer cases had higher odds of prior exposure to insecticides/pesticides/herbicides (ORAdj=1.66 [95% CI: 1.15, 2.39]), radiation (ORAdj=1.60 [95%: 1.01, 2.52]), and radon (ORAdj=2.31 [95% CI: 1.10, 4.86]) compared to controls. High-risk cases had higher odds of exposure to paint thinners (ORAdj=1.82 [95% CI: 1.24, 2.69]) and floor cleaning agents (ORAdj=1.50 [95% CI: 1.01, 2.24]) compared to controls. Thyroid cancer cases had lower odds of having been exposed to dye chemicals compared to benign thyroid nodule incidence (ORAdj=0.41 [95% CI: 0.19, 0.86]) and higher odds of having been exposed to radiation (ORAdj=1.65 [95% CI: 1.13, 2.41]).

Thyroid cancer enrollees had higher odds of having been exposed to radiation, radon, and insecticides/pesticides/herbicides compared to controls and to radiation compared to high-risk enrollees. Thyroid nodule enrollees had higher odds of having been exposed to floor cleaning agents and paint thinners compared to controls and dye chemicals compared to the cancer group. These potential risk factors for thyroid cancer should be explored further in research evaluating more specific classes of occupational exposure than are available in iCaRe2. A better understanding of the relationship between occupational exposures and thyroid cancer is critical for guiding workplace safety and exposure policies.

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