Environmental Exposures to Metal Toxins as a Risk Factor for Colorectal Cancer: A Case-Control Study

Colorectal cancer (CRC) is the third most common and third most deadly cancer in the United States The role environmental toxins may contribute to CRC incidence is unknown. Cadmium and arsenic are known human carcinogens, although previous data have primarily focused on occupational exposures only. There are no studies on the relationship between environment metal exposures and the incidence of CRC using individual-level measurements from biospecimens.

A pilot case-control study was conducted. Urine and blood specimens were collected. Arsenic and cadmium were measured via inductively coupled plasma mass spectrometry. Logistic regression was used to estimate Odds Ratios of CRC incidence and 95% Confidence Intervals (CI) adjusted for age, gender, family history and smoking or urinary cotinine. Each metal was modeled as a binary variable (high versus low) based on the controls' median value or the limit of detection values.

Seventy-nine urine and 84 blood specimens were analyzed. Compared to those with low metal levels, the adjusted odds of incident CRC were 1.77 times higher (95% CI: 0.62-5.00), 1.90 times higher (95% CI: 0.68-5.31), and 1.29 times higher (95% CI:0.45-3.72), for those with higher urinary arsenic, urinary cadmium, and blood arsenic, respectively.

This is the first study evaluating individual-level measurements of environmental exposures to metal carcinogens and their association with CRC incidence. These pilot results are not statistically significant, although the mildly positive associations may become more profound as recruitment continues. Continued evaluation of environmental toxins and CRC incidence remains warranted.