Exposure Assessment in the National Children’s Study: Introduction

The science of exposure assessment is relatively new and evolving rapidly with the advancement of sophisticated methods for specific measurements at the picogram per gram level or lower in a variety of environmental and biologic matrices. Without this measurement capability, environmental health studies rely on questionnaires or other indirect means as the primary method to assess individual exposures. Although we use indirect methods, they are seldom used as stand-alone tools. Analyses of environmental and biologic samples have allowed us to get more precise data on exposure pathways, from sources to concentrations, to routes, to exposure, to doses. They also often allow a better estimation of the absorbed dose and its relation to potential adverse health outcomes in individuals and in populations. Here, we make note of various environmental agents and how best to assess exposure to them in the National Children’s Study—a longitudinal epidemiologic study of children’s health. Criteria for the analytical method of choice are discussed with particular emphasis on the need for long-term quality control and quality assurance measures

Contributions of a Child's Built, Natural, and Social Environments to Their General Cognitive Ability: A Systematic Scoping Review.

The etiology of a child's cognitive ability is complex, with research suggesting that it is not attributed to a single determinant or even a defined period of exposure. Rather, cognitive development is the product of cumulative interactions with the environment, both negative and positive, over the life course. The aim of this systematic scoping review was to collate evidence associated with children's cognitive health, including inherent factors as well as chemical and non-chemical stressors from the built, natural, and social environments. Three databases were used to identify recent epidemiological studies (2003-2013) that examined exposure factors associated with general cognitive ability in children. Over 100 factors were evaluated from 258 eligible studies. We found that recent literature mainly assessed the hypothesized negative effects of either inherent factors or chemical exposures present in the physical environment. Prenatal growth, sleep health, lead and water pollutants showed consistent negative effects. Of the few studies that examined social stressors, results consistently showed cognitive development to be influenced by both positive and negative social interactions at home, in school or the community. Among behavioral factors related to diet and lifestyle choices of the mother, breastfeeding was the most studied, showing consistent positive associations with cognitive ability. There were mostly inconsistent results for both chemical and non-chemical stressors. The majority of studies utilized traditional exposure assessments, evaluating chemical and non-chemical stressors separately. Collective evidence from a limited number of studies revealed that cumulative exposure assessment that incorporates multiple chemical and non-chemical stressors over the life course may unravel the variability in effect on cognitive development and help explain the inconsistencies across studies. Future research examining the interactions of multiple stressors within a child's total environment, depicting a more real-world exposure, will aid in understanding the cumulative effects associated with a child's ability to learn

Factors Associated With General Cognitive Ability Further Divided Into Sub-categories.

<p>The color of the circles corresponds to the larger categories in which these sub-categories are grouped (inherent: blue; behavioral: orange; social environment: yellow and physical environment: green). The size of the circles is in proportion to the total number of publications included in the review (n = 258). The colored section in each circle represents the proportion of publications within each category that found a statistically significant association with general cognitive score (solid color–<i>P</i><0.05; pattern – 0.05<<i>P</i><0.10). This graphic is adapted from Strina et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147741#pone.0147741.ref282" target="_blank">282</a>].</p

Flowchart of selection process for review.

<p>Flowchart of selection process for review.</p

Covariates Used Across Publications Included in the Review.

<p>Covariates Used Across Publications Included in the Review.</p

Factors Examined in Multiple Studies as EOI or IP of General Cognitive Ability.

<p>Factors Examined in Multiple Studies as EOI or IP of General Cognitive Ability.</p

Summary of Characteristics of the Included Studies.

<p>Summary of Characteristics of the Included Studies.</p