# Trace Element Concentrations of Arsenic and Selenium in Toenails and Risk of Prostate Cancer among Pesticide Applicators

## TL;DR

This study found that higher levels of arsenic and selenium in toenails are linked to an increased risk of prostate cancer among pesticide applicators in Iowa.

## Contribution

The study provides new evidence linking toenail concentrations of arsenic and selenium to prostate cancer risk in a pesticide applicator population.

## Key findings

- High arsenic levels in toenails were associated with a 3.4-fold increased risk of prostate cancer.
- High selenium levels in toenails were associated with a 2.0-fold increased risk of prostate cancer.
- Over 50% of toenail samples had detectable levels for 14 of 22 trace elements analyzed.

## Abstract

Prostate cancer is a common cancer among males in the US, but little is known about its risk factors, including trace elements. The primary aim of this study was to examine prostate cancer and its association with arsenic and selenium in toenails. We conducted a small, nested case-control study of men residing in Iowa within the Agricultural Health Study cohort, where we also collected toenail samples to test for arsenic and other trace elements. Toenail samples were sent for neutron activation analysis aimed at long-lived trace elements, including arsenic. Logistic regression was used to estimate odds ratios (ORs) for trace element exposures and prostate cancer. A total of 66 prostate cancer cases and 173 healthy controls returned questionnaires, over 99% of which included toenail samples. An increased risk was seen for the highest levels of arsenic (OR = 3.4 confidence interval (CI) of 1.3–8.6 and OR = 2.2, 95% CI of 0.9–5.6) and the highest level of selenium (2.0, 95% CI of 1.0–4.0). These data also show detectable levels of over 50% for 14 of 22 elements detected in the toenails. The association seen here with arsenic and prostate cancer further supports ecological studies finding an association with community levels of arsenic and prostate cancer incidence and mortality.