Chemical mixtures and children's health

Abstract

Purpose of Review Humans are routinely exposed to multiple chemicals simultaneously or sequentially. There is evidence that the toxicity of individual chemicals may depend on the presence of other chemicals. Studies on chemical mixtures are limited, however, due to lack of sufficient exposure data, limited statistical power, and difficulty in the interpretation of multi-dimensional interactions. This review summarizes the recent literature examining chemical mixtures and pediatric health outcomes, with an emphasis on metal mixtures. Recent Findings Several studies report significant interactions between metals in relation to pediatric health outcomes. Two prospective studies found interactive effects of early life lead and manganese exposures on cognition. In two different cohorts, interactions between lead and cadmium exposures were reported on reproductive hormone levels and on neurodevelopment. Effects of lead exposure on impulsive behavior and cognition were modified by mercury exposure in studies from Canada and Denmark. However, there is little consistency related to exposure indicators and statistical approaches for evaluating interaction. Summary Several studies suggest that metals interact to cause health effects that are different from exposure to each metal alone. Despite the nearly infinite number of possible chemical combinations, mixtures research represents real life exposure scenarios and warrants more attention, particularly in the context of uniquely vulnerable children.

Urinary levels of trace elements among primary school-aged children from Italy: The contribution of smoking habits of family members

“…Since all the threats related to trace elements exposure, the increasing of urinary excretion of these compounds should be not overlooked. Also, notice that the simultaneous exposure to a great number of metals and other elements from ETS can lead to interactive effects between metals, that has been linked to several pediatric health outcomes (Claus Henn et al, 2014).…”

Perinatal and Childhood Exposure to Cadmium, Manganese, and Metal Mixtures and Effects on Cognition and Behavior: A Review of Recent Literature

“…3 or more chemicals). This may be due at least in part to challenges related to choosing a biomarker or measure of exposure that is appropriate for all metals of interest, difficulties related to collecting multiple biomarkers, the cost of analyzing multiple metals and/or multiple exposure measures, and statistical challenges such as limited power and analysis of highly correlated data [14]. In the present mixtures literature, there is little consistency in terms of metals evaluated, measures of exposure used for each metal, and statistical approach employed for analyzing joint or interactive effects.…”

“…Metal co-exposure also poses a critical threat to pediatric health [14]. The central nervous system is a common target organ for many environmental metals, leading to the natural question: what happens under joint exposure?…”

“…We focus on Cd and Mn because they are pervasive metals with biological properties that could produce neurotoxic effects and they have not been reviewed recently. We also provide an updated summary of the rapidly growing mixtures literature focused on neurodevelopmental outcomes, and include a wider range of publication dates than previously reported [14]. We focus on early life, which we differentiate in this paper into two distinct windows – the prenatal period and childhood through adolescence.…”

Statistical Approaches for Assessing Health Effects of Environmental Chemical Mixtures in Epidemiology: Lessons from an Innovative Workshop

“…As shown in biomonitoring studies, children and adults are exposed to a large number of environmental chemicals across the life span (Aylward et al 2013; CDC 2012; Exley et al 2015; Frederiksen et al 2014). Many are potentially toxic, but little is known about health effects from exposure to complex mixtures (Carlin et al 2013; Claus Henn et al 2014; Goodson et al 2015; Grandjean and Landrigan 2014; Johns et al 2012). By examining chemical mixtures, instead of one chemical at a time, it may be possible to more accurately identify risk factors for diseases with environmental origins and develop more targeted public health interventions.…”