Exposure Reconstruction for the TCDD-Exposed NIOSH Cohort Using a Concentration- and Age-Dependent Model of Elimination

Recent studies demonstrating a concentration dependence of elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suggest that previous estimates of exposure for occupationally exposed cohorts may have underestimated actual exposure, resulting in a potential overestimate of the carcinogenic potency of TCDD in humans based on the mortality data for these cohorts. Using a database on U.S. chemical manufacturing workers potentially exposed to TCDD compiled by the National Institute for Occupational Safety and Health (NIOSH), we evaluated the impact of using a concentration- and age-dependent elimination model (CADM) (Aylward et al., 2005) on estimates of serum lipid area under the curve (AUC) for the NIOSH cohort. These data were used previously by Steenland et al. (2001) in combination with a first-order elimination model with an 8.7-year half-life to estimate cumulative serum lipid concentration (equivalent to AUC) for these workers for use in cancer dose-response assessment. Serum lipid TCDD measurements taken in 1988 for a subset of the cohort were combined with the NIOSH job exposure matrix and work histories to estimate dose rates per unit of exposure score. We evaluated the effect of choices in regression model (regression on untransformed vs. ln-transformed data and inclusion of a nonzero regression intercept) as well as the impact of choices of elimination models and parameters on estimated AUCs for the cohort. Central estimates for dose rate parameters derived from the serum-sampled subcohort were applied with the elimination models to time-specific exposure scores for the entire cohort to generate AUC estimates for all cohort members. Use of the CADM resulted in improved model fits to the serum sampling data compared to the first-order models. Dose rates varied by a factor of 50 among different combinations of elimination model, parameter sets, and regression models. Use of a CADM results in increases of up to five-fold in AUC estimates for the more highly exposed members of the cohort compared to estimates obtained using the first-order model with 8.7-year half-life. This degree of variation in the AUC estimates for this cohort would affect substantially the cancer potency estimates derived from the mortality data from this cohort. Such variability and uncertainty in the reconstructed serum lipid AUC estimates for this cohort, depending on elimination model, parameter set, and regression model, have not been described previously and are critical components in evaluating the dose-response data from the occupationally exposed populations.     

Introduction to the Special Section Value Development from Middle Childhood to Early Adulthood—New Insights from Longitudinal and Genetically Informed Research

Research into values at an early age has only started recently, although it has expanded quickly and dynamically in the past years. The purpose of this article is twofold: First, it provides an introduction to a special section that aims to help fill the gap in value development research. The special section brings together four new longitudinal and genetically informed studies of value development from the beginning of middle childhood through early adulthood. Second, this article reviews recent research from this special section and beyond, aiming to provide new directions to the field. With new methods for assessing children's values and an increased awareness of the role of values in children's and adolescents' development, the field now seems ripe for an in‐depth investigation. Our review of empirical evidence shows that, as is the case with adults, children's values are organized based on compatibilities and conflicts in their underlying motivations. Values show some consistency across situations, as well as stability across time. This longitudinal stability tends to increase with age, although mean changes are also observed. These patterns of change seem to be compatible with Schwartz's (1992) theory of values (e.g., if the importance of openness to change values increases, the importance of conservation values decreases). The contributions of culture, family, peers, significant life events, and individual characteristics to values are discussed, as well as the development of values as guides for behavior.     

No reliable evidence for immediate noise-induced song flexibility in a suboscine

Urban Ecosystems - Vermilion flycatchers, a suboscine, sing songs with more elements in territories with higher urban noise levels. We tested the hypothesis that this pattern is achieved through...     

Low‐Income Mothers’ Private Safety Nets and Children’s Socioemotional Well‐Being

Using longitudinal data from the Fragile Families and Child Well‐being Study (N = 1,162) and the National Evaluation of Welfare‐to‐Work Strategies (N = 1,308), we estimate associations between material and instrumental support available to low‐income mothers and young children’s socioemotional well‐being. In multivariate OLS models, we find mothers’ available support is negatively associated with children’s behavior problems and positively associated with prosocial behavior in both data sets; associations between available support and children’s internalizing and prosocial behaviors attenuate but remain robust in residualized change models. Overall, results support the hypothesis that the availability of a private safety net is positively associated with children’s socioemotional adjustment.     

Economic Strain and Children's Behavior in the Aftermath of the Great Recession

Families across the income spectrum experienced subjective feelings of economic strain during the Great Recession. Existing evidence suggests that much of that economic strain did not arise from individual‐specific economic shocks, such as unemployment or income loss, as much as it did from worry and uncertainty about the future. The authors tested a model in which a measure of subjective perceptions of economic strain was the key predictor of children's behavior problems and objective indicators of economic experiences were treated as control variables. To do so, they used new data from a population‐based sample of children ages 4–17 (N = 303) living in southeast Michigan during the period 2009–2012. They found that economic strain exhibited a qualitatively large independent association with internalizing behavior problems for White—but not Black—children. This association was statistically significant over and above objective indicators of economic experiences and the family psychosocial context.