Human Exposure and Atmospheric Sciences
Everyday activities – actions as simple as biting into an apple, or walking across a carpeted floor – may expose people to a host of chemicals through a variety of pathways. The air we breathe, the food and water we consume, and the surfaces we touch all are the homes of natural and synthetic chemicals, which enter our bodies through our skin, our digestive systems, and our lungs. This makes determining how (and how much of) certain chemicals enter our bodies challenging. In most cases, there is not one single source for any given chemical that may be found in our bodies.
EPA exposure scientists are developing laboratory and computer-based methods to estimate total exposures and risks from chemicals encountered in our daily lives. EPA scientists have developed a variety of predictive tools and databases to gather, store, and analyze chemical data and to understand how humans are exposed to chemicals. EPA scientists are also developing a suite of biomonitoring tools for assessing human exposures to environmental chemicals.
Investigating the Human Exposome
EPA scientists are evolving their research from a targeted "one exposure, one adverse effect" approach towards a broader "discovery" approach that incorporates the concept of the human "exposome" as the counterpart to the human genome. The human exposome is defined as all of the environmental chemicals, human metabolites, chemical metabolites, metabolic reaction products, as well as the byproducts and biochemistry of the symbiotic microorganisms in our gut. Unlike the human genome, which stays essentially unchanged from birth to death, the exposome changes constantly in response to the environment around you, your health state and activity, diet, and metabolic processes.
Stochastic Human Exposure and Dose Simulation Model (SHEDS)
EPA’s Stochastic Human Exposure and Dose Simulation model (known as SHEDS) allows scientists to estimate total exposures and risks people face from chemicals encountered in everyday activities. SHEDS can estimate the range of total chemical exposures in a population from different exposure pathways (inhalation, skin contact, dietary and non-dietary ingestion) over different time periods, given a set of demographic characteristics. The model enhances estimates of exposure in many different contexts, and has been used to inform EPA human health risk assessments and risk management decisions.
EPA’s ExpoCast Database
EPA’s ExpoCast database consolidates human exposure data from studies that have collected chemical measurements from homes and child care centers. Data include the amounts of chemicals found in food, drinking water, air, dust, indoor surfaces and urine. ExpoCast users can obtain summary statistics of exposure data and download datasets. EPA scientists are continuing to add internal and external chemical exposure data and advanced user interface features to ExpoCast. Users are able to link and compare the data in ExpoCast with EPA’s ToxCast database to gain greater understanding about chemical exposure and toxicity.
Biomonitoring: An exposure science tool
EPA scientists are developing a suite of biomonitoring tools for assessing human exposures to environmental chemicals and their likely health responses. Specifically, EPA scientists are working to identify the chemicals to which humans are most commonly exposed; exposure levels across various groups of people; and the likely biological responses of individuals following exposure. EPA scientists have developed a biomonitoring framework for integrating and interpreting existing data, and designing new studies to answer specific research questions.
Tools to access bioavailability and bioaccessibility of arsenic and lead in contaminated soils
EPA scientists are developing rapid, reliable, inexpensive methods for assessing the bioavailability of arsenic and lead in contaminated soils. One of these methods involves the use of mice to mimic how the human digestive system absorbs arsenic. EPA scientists are also working on a chemical extraction laboratory method that mimics the human gastrointestinal system. Scientists plan to use the mouse method to validate the new lab method. If successful, researchers will be able to determine the bioavailability of these contaminants without having to rely on animal testing at all.
Nanosilver and consumer products
EPA scientists are conducting research to determine whether consumer products containing nano-silver are releasing nanoparticles in unintended ways. EPA scientists are also conducting studies to examine chemical and physical changes that might occur in silver nanoparticles that are ingested with food or water by exposing the nanoparticles to synthetic human stomach fluid. To be protective of human health, EPA scientists and regulators must understand how nano-scale silver — used in a variety of consumer products — moves through the environment and transforms under different product use scenarios.
Consolidated Human Activity Database (CHAD)
EPA scientists have compiled detailed data on human behavior from 19 separate studies into EPA’s Consolidated Human Activity Database (CHAD). The database includes a total of more than 30,000 individual study days of detailed human behavior, with each day broken down into individual hours and activity types. The data also include demographic information which allows researchers to examine specific groups within the general population and how their unique behavior patterns influence their exposures to chemicals. Scientists at EPA, other government agencies, academia, and the private sector routinely use CHAD data in human exposure and health studies, and in models used for exposure and risk assessments that protect human health.
Computational atmospheric chemistry helps EPA scientists forecast future atmospheric conditions
EPA scientists have developed an innovative computational chemistry-based method called COMPCHEM that is used for predicting lifetimes and fates of atmospheric compounds. COMPCHEM consists of a set of well-established, state of the science, quantum chemistry and gas phase kinetic codes, all of which have been used in numerous studies reported in peer-reviewed literature. It is anticipated that COMPCHEM will be a cost effective tool for supplementing atmospheric chemistry data generated through laboratory studies.
Sophisticated test chambers used to simulate atmospheric conditions
EPA scientists are using experimental laboratory studies to gather and assess data on atmospheric gas phase and particulate phase chemistry in order to determine the effects that various source emissions have on humans and ecosystems. Researchers are also working on the construction and development of a new, mobile photochemical reaction chamber to be used to study the toxicity of combustion emission sources. Research results are anticipated improve understanding of how atmospheric reactions and transformations influence the toxicity of air pollutant mixtures.
Physiological and Anatomical Visual Analytics (PAVA)
In order to better address issues regarding chemical safety, EPA scientists have developed a new web-based modeling tool, known as PAVA (Physiological and Anatomical Visual Analytics), that lets users import and combine results from multiple computer models and transforms them into animated visualizations. The absorption, distribution, metabolism, and excretion results are automated and then rendered in a way that lets scientists see changes in chemical concentrations in specific tissues over time — from chemical to chemical, scenario to scenario, and model to model.
Air Pollution Exposure Model for Individuals (EMI)
Air pollution health studies help scientists understand potential health risks people face from air pollution exposure. However, because of the cost and participant burden associated with indoor and personal air monitoring, health studies often estimate exposures using outdoor ambient measurements from central site air monitors. Unfortunately, these ambient concentration levels do not necessarily reflect personal exposures since indoor air pollutant levels can differ from ambient levels. This potential exposure error can increase the uncertainty of air pollution health risks estimated in health studies. To reduce this potential error, EPA scientists have developed an exposure model for individuals (EMI) who are participating in air pollution health studies.
Systems Reality Modeling
EPA scientists are conducting the Systems Reality Modeling Project, which uses new and emerging technology to develop tools to help people understand chemicals in their environments and the risks they pose to health. This project uses smartphone barcode-scanning capabilities, computer game environments, and social media such as Facebook and Twitter to collect data on human activities and chemicals in the home. The data will be used to create detailed models of exposure. The scientists are developing custom-built smartphone apps to make data collection faster and more cost-effective. Ultimately, this research will provide scientists with a fast and inexpensive way to model chemical exposures and human behavior, and provide the general public with apps and other tools to find information about chemicals in their environments.
Probabilistic Reverse dOsimetry Estimating Exposure Distribution (PROcEED)
Probabilistic Reverse dOsimetry Estimating Exposure Distribution (PROcEED) is a web-based application used to conduct probabilistic reverse dosimetry calculations. The tool is used for estimating a distribution of exposure concentrations likely to have produced biomarker concentrations measured in a population.
EPA's Exposure Related Dose Estimating Model (ERDEM)
ERDEM is a physiologically-based pharmacokinetic (PBPK) and pharmacodynamic (PD) modeling system, developed by EPA scientists to predict how chemicals move through and concentrate in human tissues and body fluids. With ERDEM, scientists are able to examine how chemical exposures impact organs and tissues in the human body and determine how long they will take to be naturally processed or expressed. The ERDEM framework provides the flexibility for scientists to use either existing models or build new PBPK and PBPK/PD models to address specific science questions.
Understanding exposures in children’s environments
To protect children’s health, EPA scientists have conducted a series of studies to provide a better understanding of the chemical sources, pathways and routes of exposure, and other exposure factors that contribute most to children’s exposures to chemicals. EPA scientists are considering several factors in this research, including the influence of everyday environments, normal behaviors, and normal consumer product use in homes. Understanding these factors is necessary to inform key strategies for reducing children’s exposures to potentially harmful elements.
Chlordane Pesticide Dataset
EPA scientists have developed a dataset that compiles chlordane measurements from published literature in one place. The dataset provides researchers with a useful resource that taps into peer reviewed published results, summarizing and organizing the data into a user friendly tool. The dataset compiles about 2,400 enantiomer-specific measurements for five pairs of chlordane enantiomers. It consolidates information that may be useful for scientists interested in studying trends, estimating exposure and toxicity of mixtures, developing methods, and modeling enantiomers.
Consolidated Pesticide Information Dataset (CPI)
EPA scientists have developed a dataset of basic information on approximately 1,700 pesticides. The dataset was gathered from multiple sources and is in spreadsheet format. It contains a total of twenty fields, including chemical names, identification numbers, structures, and pesticide use class — such as insecticide, herbicide, and fungicide. The CPI dataset will serve as a valuable tool for those interested in pesticide mixtures, green or sustainable pesticides, development of methods and models, and other areas of pesticide research.
- EPA Exposure Research
- Fact Sheet: Chemical Safety for Sustainability research
- Chemical safety exposure research tools
- Fact Sheet: EPA Green Chemistry research
- Science Matters: Innovative tools help EPA scientists determine total chemical exposures
- Science Matters: Understanding exposures in children’s environments
- Science Matters: New testing methods for arsenic and lead in soil
- Substances and toxics information
- Exposure Science in the 21st Century
Personal Chemical Exposure Informatics Workshop Summary