The Association between Metals and Thyroid Cancer in Puerto Rico—A National Health and Nutrition Examination Survey Analysis and Ecological Study

Abstract

Thyroid cancer rates have risen globally over the past four decades, with Puerto Rico experiencing a particularly pronounced increase. This may be linked to higher metal exposure, as some metals are endocrine disruptors and carcinogens. Currently, certain regions of Puerto Rico have Superfund programs because of high concentrations of metals in the soil. Therefore, we investigated the association between thyroid cancer incidence and three metals (lead, cadmium, and mercury) with known endocrine-disrupting properties and increased levels in soil samples in Puerto Rico. We used the National Health and Nutrition Examination Survey (NHANES) data for heavy metal levels and the thyroglobulin antibody (TgAb) as a thyroid cancer marker. Additionally, we performed an ecological study using data from the Environmental Protection Agency (EPA) report on Metals from Natural and Anthropogenic Sources in Puerto Rico Soils and data from the Puerto Rico Central Cancer Registry on age-adjusted thyroid cancer incidence rates from 2015 to 2019. Through NHANES analysis, we found a significant negative association between mercury and TgAb. Through our ecological study, we observed higher thyroid cancer incidence rates and increased metal levels in the soil in the northern parts of Puerto Rico. Our heterogenous results necessitate further research on this topic.