Childhood exposure to metal neurotoxins can result in irreversible neuropsychological impairments. Metal exposures have declined in the general U.S. population and significant progress has been made in the reduction of certain metals in the environment through effective intervention strategies. However, this problem is far from solved.
In many parts of the world, particularly Low and Middle-income Countries (LMIC), the extent of exposure to and harm from metals is only now gaining recognition. Although most children are exposed to two or more metals at a time, for many years, researchers had focused on studying the effects of single metals on child development. The past 5-10 years, however, ushered an important shift in thinking, and studies now more commonly assess the impact of multiple metal exposures on child health. We still do not know how these multiple metals interact to increase toxicity or neurodevelopmental deficits. In the context of LMICs, children’s nutritional status (malnutrition or deficiency of nutrients like iron) may also play an important role in exacerbating metal toxicity. On the other hand, diet could both promote better metal excretion and be the source of metal exposure. These gaps in understanding how multiple metal exposures and diet/nutrition affect child development form the basis of an NIH-funded research program, Salud Ambiental Montevideo (SAM), led by Dr. Katarzyna Kordas in Uruguay.
Salud Ambiental Montevideo, which stands for Environmental Health Montevideo, has recruited families of first-grade children residing in geographic locations of Uruguay’s capital city with known or suspected sources of environmental metal exposure. Between 2009 and 2013, 357 children were enrolled for a cross-sectional study on multiple metals and diet. Data collection based on questionnaires, neuropsychological tests, home visits, and direct measures was performed. Children’s exposure to metals was assessed in hair, blood and urine; nutritional status was assessed through measures of height and weight and the collection of dietary recalls; a comprehensive battery of neuropsychological tests was administered. The battery included tests of memory, executive functioning, attention, visuo-motor coordination, general cognitive ability, and academic proficiency. This broad collection of measurements gives SAM the ability to fully evaluate multiple metal exposures on a variety of child developmental outcomes. Like in many industrialized countries, children in SAM have low exposure to multiple metals, which allows SAM researchers to make contributions to the understanding of how much of a developmental impact these low-level metals have when they occur together, in a “mixture”. Many children (~40%) also have iron deficiency (ID), allowing for a study of nutrient-metal interactions.
Diet and metal exposures:
Metals and oxidative stress:
Metals, cognition and behavior:
Since 2015, recruitment of additional first-graders has been ongoing, and these children are being followed until 5th grade, with further assessments anticipated beyond elementary school. Through this longitudinal study, we will assess trajectories of cognitive and behavioral development in children exposed to multiple metals. We are also working to incorporate biomarkers and direct measures of exposures to other toxicants with the hope of contributing to the understanding of the totality of children’s environmental exposures during early school years.
We welcome collaborations from colleagues and students that will foster research on the developmental effects of toxicants among children in Uruguay and elsewhere.
Elena I Queirolo, MD
Gabriel Barg, PhD
Fabiana Peregalli, MS
Epidemiology and Environmental Health
Epidemiology and Environmental Health