In a recent publication, PROTECT researchers found that toxic and essential metals are present at higher levels in pregnant Puerto Rican women compared to those from the general US population. Researchers identified that diet, water sources, and smoking were predictors and sources of these metals exposure. Amongst these predictors, smoking was the most significant predictor of blood cadmium, while the consumption of several food items (meat, tomato, collard) were additional predictors of cadmium exposure. Fish was one of the main predictors of blood mercury levels along with canned food and tomatoes, while fish and rice are significant positive predictors of arsenic levels. While blood lead concentrations in the study population were relatively low overall, researchers found that those who drink AAA public water have higher levels of blood lead compared to those who mostly drink from bottled water. Additionally, those that used metal cisterns to store water had elevated levels of urinary cadmium while water treatment was inversely associated with blood manganese levels.


The finding of fish and rice predicting arsenic is consistent with studies reporting increased exposure and possible health risks associated with consuming contaminated arsenic rice. Fish and canned food (especially canned tuna) are food groups known to be potentially high in mercury. At the same time, fish and seafood are one of the healthiest food pregnant women can eat because they are a great source of protein, micronutrients, and healthy fats. Therefore, pregnant women can selectively avoid consuming larger and longer-lived fish that contain the most mercury, including swordfish, fresh tuna, marlin, and king mackerel, and choose to eat lower-mercury and high-nutrient fish/seafood, such as salmon, shrimp, cod, and sardines.

In this study researchers evaluated all 1040 pregnant women within our cohort and collected urine, blood, and questionnaire data on demographics, product use, food consumption, and water usage over three clinical visits. The levels of 14 toxic and essential metals were measured in the urine and blood samples collected from those women and compared to the levels of metals in the US general female population. The metal levels changes across pregnancy and over years were also measured along with the relationship between different metals. Lastly, the important predictors of each metal were identified in blood and urine samples. For this approach, statistical tools such as linear mixed models (LMM) and multivariable linear mixed models with LASSO were used to fully utilize the repeated data collected on both metals and the potential predictor variables such as demographics, product use, food consumption, and water usage.


Metals like cadmium, mercury, and lead are non-essential to human health and toxic to the human body even in very low amounts. Metals like manganese and zinc play key roles in human physiology and are considered essential to human health—but even these can be toxic at high concentrations. Both types of metals can be environmental toxicants at high concentrations in our ecosystems and our bodies. “Because of the long-standing history of contamination with environmental chemicals in Puerto Rico, the risk of human exposure to certain chemicals, including metals, is high. However, very little is known regarding the extent and specific sources of human metal exposure on the island,” explains author Pahriya Ashrap. “This is the first study to examine levels, time trends, and predictors of urinary and blood metal biomarkers measured at multiple times during pregnancy among women living in Northern Puerto Rico. Understanding how metal biomarkers changed over time and identifying important predictors and sources to metals may inform risk evaluations in epidemiology and help design approaches to reduce metal exposure.”