Identifying critical windows of exposure for children's health.

Abstract

Several authors have considered the importance of exposure timing and how this affects the outcomes observed, but no one has systematically compiled preconceptional, prenatal, and postnatal developmental exposures and subsequent outcomes. Efforts were undertaken to examine the information available and to evaluate implications for risk assessment for several areas: a) respiratory and immune systems, b) reproductive system, c) nervous system, d) cardiovascular system, endocrine system, and general growth, and e) cancer. Major conclusions from a workshop on "Critical Windows of Exposure for Children's Health" included a) broad windows of sensitivity can be identified for many systems but detailed information is limited; b) cross-species comparisons of dose to target tissue and better data on the exposure-dose-outcome continuum are needed; c) increased interaction among scientific disciplines can further understanding by using laboratory animal results in designing epidemiological studies and human data to suggest specific laboratory studies on mechanisms and agent-target interactions; and d) thus far, only limited attention has been given to peripubertal/adolescent exposures, adult consequences of developmental exposures, and genome-environment interactions. More specific information on developmental windows will improve risk assessment by identifying the most sensitive window(s) for evaluation of dose-response relationships and exposure, evaluation of biological plausibility of research findings in humans, and comparison of data across species. In public health and risk management, information on critical windows may help identify especially susceptible subgroups for specific interventions.

Early-life adversity and brain development: Is the microbiome a missing piece of the puzzle?

“…The enduring influence of an insult depends on the maturational stage of the brain and to what extent the normal developmental trajectory is disrupted (Andersen, 2003). Epidemiological data supports the concept that the time of exposure may be essential to some types of stressors, as similar adverse events occurring at early or late stages have been associated with differing outcomes (Selevan et al, 2000, Meyer et al, 2011. Stress and infection occurring during gestation or in early life can differentially increase the risk of several distinct disorders (Glynn et al, 2001, Bale et al, 2010, Brown, 2012, Howerton and Bale, 2012.…”

Maternal blood metal levels and fetal markers of metabolic function

“…Early pregnancy is a critical window of fetal development and exposure to environmental contaminants during this time period may adversely impact the pregnancy as well as neonatal, early childhood, and later life outcomes (Gluckman et al, 2008;Selevan et al, 2000). Previous studies have suggested that prenatal exposure to metals, such as lead, mercury, cadmium, and arsenic, may adversely affect fetal growth (Drouillet-Pinard et al, 2010;Gundacker et al, 2010;Kippler et al, 2012;Lin et al, 2011;Menai et al, 2012;Schell et al, 2009;Xie et al, 2013;Zhu et al, 2010).…”

Multi-jurisdictional expert opinion for improving children's environmental health protection

“…For example, elevated gastric absorption of inorganic elements is observed in infants and preschool-aged children compared to adults (Makri et al 2004). Dermal absorption and inhalation uptake of environmental chemicals may be enhanced in infants due to thinner skin as well as greater skin and lung surface area, and increased ventilation rates (Silvaggio and Mattison 1993;Selevan et al 2000;Scheuplein et al 2002;Makri et al 2004).…”