Environmental Statistics Projects
National Human Exposure Assessment Survey (NHEXAS) Phase I Field Study
We developed the design for NHEXAS, the objective of which was to evaluate comprehensive human exposure to multiple chemicals on a community and regional scale. The information gained from NHEXAS helps individuals, communities, states, the EPA, and other organizations understand the greatest health risks from various chemicals and decide whether steps to reduce those risks are needed.
Sampling Designs for Surface Water Monitoring
In a post-registration study for a major nationally distributed pesticide, we identified the best surface water sampling designs for the estimation of proposed regulatory quantities. Estimation approaches were evaluated using simulation and time-series methods.
Estimation of Extreme Values in Historical Surface Water Monitoring Data
Effective use of historical monitoring data can reduce the need for more extensive monitoring efforts. In this project, survey sampling techniques were applied to find confidence intervals for upper percentiles of surface water pesticide concentration using large historical datasets.
Temporal Trends in Herbicide Surface Water Concentrations 1990–2010
Mixed-effect models were used to study the long-term trend in annual pesticide concentrations using data from a monitoring network. The analysis allowed an understanding of the effect of interventions such as pesticide use pattern changes, increasing environmental stewardship efforts, and implementation of best management practices.
EPA/OAQPS/SPPD Pulp and Paper Multi-Pollutant Sector Strategies Project
We developed a geostatistical model of the impact of sulfur dioxide (SO2) emissions from individual pulp and paper mills on ambient PM2.5 levels and visibility (regional haze). The model allowed the EPA to identify those pulp and paper mills that have the most significant contributions to PM2.5 levels in or near PM2.5 nonattainment areas and Class I areas (national parks).
EMAP Southeast Isolated Wetlands Assessment
Working with GIS and wetland scientists, we developed a population frame using multiple geodatabases and selected a probability sample of sites that were used to assess population frame accuracy and to estimate the number, extent, and value of isolated wetlands in four counties each in North and South Carolina.
Technical Support for Evaluating PBPK/PD Models for Interpreting Biomarkers of Exposure to Assess Cumulative Risk
We conducted exploratory research to evaluate the potential techniques for interpreting biomarkers of exposure using physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) models. Our statistical analysis evaluated the utility of selected biomarkers of exposure in understanding potential pathways of exposure and dose.
Endocrine Disruptor Screening and Testing Standardization and Validation Technical Support Services (EDSP)
We applied mixed models to validate results obtained from several laboratories performing assays to detect endocrine-active chemicals by measuring body and organ weight changes, organ microscopic changes, and nine circulating hormones according to a standard protocol and in compliance with regulatory agency guidelines and GLP and laboratory standard operating procedures.
Developmental Toxicity Testing and Research for the National Toxicology Program of NIEHS
Our statisticians developed, documented, and implemented optimal methods of analysis for a variety of developmental toxicology studies. We developed methods of analysis for dose-interaction studies involving multiple compounds and cluster-correlated data, with continuous and binary outcomes. We wrote the statistical analysis plans for three dose-interaction studies with incomplete factorial designs, and we reviewed all project protocols and final reports for accuracy of interpretation of statistical methods and results.
The Non-Occupational Pesticide Exposure Study
We studied human, non-occupational exposures to 32 pesticides and their degradation products in two U.S. cities during three seasons. Environmental monitoring consisted of 24-hour indoor, personal, and outdoor air samples.