5 research outputs found
SHEDS-HT: An Integrated Probabilistic Exposure Model for Prioritizing Exposures to Chemicals with Near-Field and Dietary Sources
United
States Environmental Protection Agency (USEPA) researchers
are developing a strategy for high-throughput (HT) exposure-based
prioritization of chemicals under the ExpoCast program. These novel
modeling approaches for evaluating chemicals based on their potential
for biologically relevant human exposures will inform toxicity testing
and prioritization for chemical risk assessment. Based on probabilistic
methods and algorithms developed for The Stochastic Human Exposure
and Dose Simulation Model for Multimedia, Multipathway Chemicals (SHEDS-MM),
a new mechanistic modeling approach has been developed to accommodate
high-throughput (HT) assessment of exposure potential. In this SHEDS-HT
model, the residential and dietary modules of SHEDS-MM have been operationally
modified to reduce the user burden, input data demands, and run times
of the higher-tier model, while maintaining critical features and
inputs that influence exposure. The model has been implemented in
R; the modeling framework links chemicals to consumer product categories
or food groups (and thus exposure scenarios) to predict HT exposures
and intake doses. Initially, SHEDS-HT has been applied to 2507 organic
chemicals associated with consumer products and agricultural pesticides.
These evaluations employ data from recent USEPA efforts to characterize
usage (prevalence, frequency, and magnitude), chemical composition,
and exposure scenarios for a wide range of consumer products. In modeling
indirect exposures from near-field sources, SHEDS-HT employs a fugacity-based
module to estimate concentrations in indoor environmental media. The
concentration estimates, along with relevant exposure factors and
human activity data, are then used by the model to rapidly generate
probabilistic population distributions of near-field indirect exposures
via dermal, nondietary ingestion, and inhalation pathways. Pathway-specific
estimates of near-field direct exposures from consumer products are
also modeled. Population dietary exposures for a variety of chemicals
found in foods are combined with the corresponding chemical-specific
near-field exposure predictions to produce aggregate population exposure
estimates. The estimated intake dose rates (mg/kg/day) for the 2507
chemical case-study spanned 13 orders of magnitude. SHEDS-HT successfully
reproduced the pathway-specific exposure results of the higher-tier
SHEDS-MM for a case-study pesticide and produced median intake doses
significantly correlated (<i>p</i> < 0.0001, <i>R</i><sup>2</sup> = 0.39) with medians inferred using biomonitoring
data for 39 chemicals from the National Health and Nutrition Examination
Survey (NHANES). Based on the favorable performance of SHEDS-HT with
respect to these initial evaluations, we believe this new tool will
be useful for HT prediction of chemical exposure potential
Suspect Screening Analysis of Chemicals in Consumer Products
A two-dimensional gas chromatography-time-of-flight/mass
spectrometry
(GC×GC-TOF/MS) suspect screening analysis method was used to
rapidly characterize chemicals in 100 consumer productsî—¸which
included formulations (e.g., shampoos, paints), articles (e.g., upholsteries,
shower curtains), and foods (cereals)î—¸and therefore supports
broader efforts to prioritize chemicals based on potential human health
risks. Analyses yielded 4270 unique chemical signatures across the
products, with 1602 signatures tentatively identified using the National
Institute of Standards and Technology 2008 spectral database. Chemical
standards confirmed the presence of 119 compounds. Of the 1602 tentatively
identified chemicals, 1404 were not present in a public database of
known consumer product chemicals. Reported data and model predictions
of chemical functional use were applied to evaluate the tentative
chemical identifications. Estimated chemical concentrations were compared
to manufacturer-reported values and other measured data. Chemical
presence and concentration data can now be used to improve estimates
of chemical exposure, and refine estimates of risk posed to human
health and the environment
Suspect Screening Analysis of Chemicals in Consumer Products
A two-dimensional gas chromatography-time-of-flight/mass
spectrometry
(GC×GC-TOF/MS) suspect screening analysis method was used to
rapidly characterize chemicals in 100 consumer productsî—¸which
included formulations (e.g., shampoos, paints), articles (e.g., upholsteries,
shower curtains), and foods (cereals)î—¸and therefore supports
broader efforts to prioritize chemicals based on potential human health
risks. Analyses yielded 4270 unique chemical signatures across the
products, with 1602 signatures tentatively identified using the National
Institute of Standards and Technology 2008 spectral database. Chemical
standards confirmed the presence of 119 compounds. Of the 1602 tentatively
identified chemicals, 1404 were not present in a public database of
known consumer product chemicals. Reported data and model predictions
of chemical functional use were applied to evaluate the tentative
chemical identifications. Estimated chemical concentrations were compared
to manufacturer-reported values and other measured data. Chemical
presence and concentration data can now be used to improve estimates
of chemical exposure, and refine estimates of risk posed to human
health and the environment
Conceptual Framework To Extend Life Cycle Assessment Using Near-Field Human Exposure Modeling and High-Throughput Tools for Chemicals
Life
Cycle Assessment (LCA) is a decision-making tool that accounts
for multiple impacts across the life cycle of a product or service.
This paper presents a conceptual framework to integrate human health
impact assessment with risk screening approaches to extend LCA to
include near-field chemical sources (e.g., those originating from
consumer products and building materials) that have traditionally
been excluded from LCA. A new generation of rapid human exposure modeling
and high-throughput toxicity testing is transforming chemical risk
prioritization and provides an opportunity for integration of screening-level
risk assessment (RA) with LCA. The combined LCA and RA approach considers
environmental impacts of products alongside risks to human health,
which is consistent with regulatory frameworks addressing RA within
a sustainability mindset. A case study is presented to juxtapose LCA
and risk screening approaches for a chemical used in a consumer product.
The case study demonstrates how these new risk screening tools can
be used to inform toxicity impact estimates in LCA and highlights
needs for future research. The framework provides a basis for developing
tools and methods to support decision making on the use of chemicals
in products
Measuring Physicochemical Properties to Inform the Scope of Existing QSAR/QSPR Models
Presented at the Annual Society of Toxicology meetin