Pediatric Environmental Health

Pediatric environmental health is the academic discipline that studies how environmental exposures in early life — biological, chemical, nutritional, physical, and social—influence health and development in childhood and across the lifespan. This discipline emerged in the mid-1980s after the discovery that secondhand smoke exposure was linked to increased rates of lower respiratory illness in children. Before that, most people did not realize that smoking cigarettes harmed anyone but the smoker. When the harmful effects of secondhand exposure to tobacco smoke were uncovered, researchers began asking questions about other pollutants—could it be that other biological, chemical, physical, and social agents to which children are routinely exposed also harm their health? Children have environmental exposures that are different from and often larger than those of adults. Children also have enormous susceptibilities in early development—unique “windows of vulnerability”—to toxic exposures that have no counterpart in adult life. It is well understood that timing of exposure is critically important in early human development. The tissues and organs of embryos, fetuses, infants, and children are rapidly growing and developing. Adolescence also is a period of rapid growth. These complex and delicate developmental processes are uniquely sensitive to disruption by environmental influences. Exposures sustained during windows of early vulnerability, even to extremely low levels of toxic materials, can cause lasting damage.

Food insecurity and the extremes of childhood weight: defining windows of vulnerability

Background Weight extremes and food insecurity (FIS) represent public-health challenges, yet their associations in childhood remain unclear. We aimed to investigate the longitudinal time-specific relationship between FIS and risk of overweight/obesity and underweight in kindergarten through 8th grade. Methods In the prospective Early Childhood Longitudinal Study–Kindergarten Cohort (1998–2007) of 6368 children, household FIS was assessed by the validated US Household Food Security Survey Module in kindergarten, 3rd, 5th and 8th grades. Multivariable linear-regression and Poisson-regression models were computed. Results Compared with children experiencing food security (FS), children exposed to FIS in 5th grade had 0.19 [95% confidence interval (CI): 0.07–0.30] and 0.17 (0.06–0.27) higher body mass index z-score (BMIZ) in the 5th and 8th grades, respectively, whereas FIS in the 8th grade was associated with a 0.29 (0.19–0.40) higher BMIZ at the same wave, after adjusting for covariates and FIS at earlier waves. Children with FIS vs FS had 27% (relative risk: 1.27, 95% CI: 1.07–1.51), 21% (1.21, 1.08–1.35) and 28% (1.28, 1.07–1.53) higher risk of overweight/obesity in the 3rd, 5th and 8th grades, respectively, adjusting for covariates and FIS at prior wave(s). Children with FIS vs FS in kindergarten had a 2.76-fold (1.22–6.25) higher risk of underweight in the 8th grade. Conclusions Proximal exposure to household FIS was associated with a higher risk of overweight/obesity in the 3rd, 5th and 8th grades. FIS in kindergarten was associated with a risk of underweight in the 8th grade. Thus, FIS coexists in weight extremes during vulnerable early-life windows in the USA, similarly to the global burden of FIS.

Stochastic models of just-in-time systems and windows of vulnerability in terms of the processes of birth and death

В работе предлагается метод построения моделей на основе анализа процессов размножения и гибели с линейным ростом в семимартингальных терминах. На основе этого метода рассматриваются стохастические модели простых систем точно-в-срок (анализируемые в теории продуктивных систем) и окна уязвимости (широко обсуждаемые в теории риска). Основные результаты, полученные в работе, представлены в терминах средних значений времени, за которое процессы достигают нулевых значений. При этом рассматриваются и используются при исследовании моделей оценки для локальных времен процессов. Здесь анализируются простые марковские процессы с линейным ростом интенсивностей (скорость которого, быть может, зависит от времени). При этом полученные и используемые оценки представляют теоретический интерес. Так, например, среднее значение момента, в который процесс достигает нулевого значения, зависит от таких функций параметров модели, как гармоническое число и остаточный член логарифмической функции в разложении Тейлора. В качестве основного результата предлагается метод математического моделирования систем точно-в-срок и окон уязвимости. Используемый здесь семимартингальный метод описания следует рассматривать как первый шаг такого моделирования, поскольку, являясь траекторным, он допускает диффузионные (в том числе немарковские) обобщения при построении стохастических моделей окон уязвимости и систем точно-в-срок. В настоящей работе получены утверждения для средних значений локального времени и моментов достижения процессами размножения и гибели заданного значения. Это позволило единообразно представить оценки для моделей системы точно-в-срок и для окон уязвимости (результат для которых представлен в форме предельной теоремы). Основные результаты сформулированы в виде теорем и лемм. Доказательства используют семимартингальные методы.