Date of Award

January 2016

Document Type

Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Yawei Zhang

Second Advisor

Nicole Deziel

Abstract

While incident thyroid cancer diagnoses continue to increase at a rate faster than any other cancer in the US, questions about environmental exposures’ link to small malignancy increases persist. Nitrate consumption as a predictor for thyroid cancer has become a topic of interest due to their ubiquitous contamination of water and food supplies. No epidemiological studies have looked at the correlation of residential water source over an entire lifetime and its relation to thyroid cancer. A Connecticut based case-control study conducted in 2010-2011, including 462 histologically confirmed incident thyroid cancer cases and 498 Connecticut based controls used multivariate unconditional logistic regression models to estimate associations between types of lifetime residential water source, duration of private well water source, depth of private well, first lifetime drinking water source, and thyroid cancer risk. Controlling for several confounding factors, including dietary nitrate consumption, lifetime water source history was not associated with an increased risk of thyroid cancer. Amongst those diagnosed with papillary or follicular tumor type with size ≤10mm, reporting at least 20 years of private well water source and at least 20 years of community water source was associated with an increased risk of thyroid cancer (OR = 3.30, 95% CI: 1.49-7.31, p-value 0.0096). No other statistically significant associations were found between several history types, by tumor type, or tumor size, as well as across well depth, duration of private well use, and first water source. This study provides the first look at lifetime water source as a proxy to drinking water nitrate exposures and thyroid cancer risk. The finding of long-term private well and community water source exposure related to small malignancy warrants further investigation of how environmental exposures may impact small tumor size as opposed to large.

Comments

This thesis is restricted to Yale network users only. It will be made publicly available on 06/07/2018

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