Christopher Stevens

Project Scientist

Christopher Stevens Project Scientist

Mr. Christopher Stevens has 13 years of professional work experience in exposure modeling and assessment, ecological and human health risk assessment, and data management and analysis. He has developed exposure models for a wide range of consumer product applications, in particular for large-scale screening assessments. He has also completed computational and graphical analysis of collected and modeled data. Mr. Stevens has extensive experience in the creation and management of databases and database tools for a wide range of projects and exposure applications. He has also supported multiple litigation projects and projects focusing on emerging contaminants. Mr. Stevens is experienced wit...

Christopher Stevens

Project Scientist

Product Stewardship

TSCA Emissions Testing Support for o-Dichlorobenzene (o-DCB), Confidential Client Conducted modeling runs of EPA’s Consumer Exposure Model to evaluate model sensitivity to user-defined empirically derived emission rates. Supported the calculation of emission rate metrics from data derived through emissions chamber testing.

Comments on EPA’s Draft Risk Evaluation for Formaldehyde, Confidential Client Evaluated the exposure assumptions and modeling in EPA’s Draft Risk Evaluation for Formaldehyde. Developed extensive comments to support client advocacy and stakeholder needs. Conducted multiple review cycles with client input and feedback.

Cleaning Product Ingredient Environmental Safety Development, Confidential Client Developed an exposure and risk screening tool in R to support the client’s characterization of ingredients in cleaning products. The model uses conservative and scientifically rigorous assumptions to screen chemicals using a risk-based framework evaluating exposure to surface water from hypothetical down-the-drain releases. Results are used to prioritize client’s review and evaluation of cleaning product ingredients.

High-Throughput Environmental Risk Assessment of Fragrance Materials, Confidential Client Assisted in the design and development of an updated screening framework to support the environmental evaluation of fragrance materials. Incorporated high-throughput screening methodologies and adapted client’s previous framework using updated methods and best-practices. Included the development of a R-Shiny webtool to facilitate easy execution and reporting of the model.

Consumer Product Risk Tool Development, Confidential Personal Care Product Manufacturer Developed an exposure and risk screening tool built using a Microsoft^® Access framework. The tool allows the extraction and storage of chemical data and associated exposure, fate, and toxicology data, along with the development of screening values and data reports.

Consumer Exposure Model (CEM), EPA Office of Pollution Prevention and Toxics Developed a Microsoft Access based modeling tool, including the addition and coding of new exposure models and scenario options in response to comments and peer review. Developed a module that interfaces with a compiled Python executable for complex mathematical analysis. CEM assesses exposure to semivolatile and volatile organic compounds in residential/commercial products and articles.

Data Management

Database Development and Analysis, Multiple Confidential Locations, West Coast, United States Developed databases of sediment and biota data compiled by another consulting firm. Developed queries and conducted quality assurance on the compiled data. Conducted spatial and numerical analyses of the data in support of the development of multiple expert reports.

TSCA-Reform Data Collection, Problem Formulation, and Scoping Support, EPA Office of Pollution Prevention and Toxics Managed and organized data of a screening process for more than 72,000 studies. Developed Microsoft Access and Excel based reports of study data and screening results.

Air Toxics Health Effects Database, EPA Office of Air Quality and Planning Standards Reorganized, restructured, and managed relational data tables as well as redesigned the front-end for a database consisting of inhalation benchmarks used to support exposure and risk assessment for EPA’s Office of Air Quality Planning and Standards Residual Risk Program.

Dose Response Analytical Generator and Organization Network (DRAGON) Conducted maintenance, development, and support of DRAGON for multiple chemical assessments. DRAGON consists of a suite of Microsoft Access based tools designed to improve transparency and objectivity in literature searches, hazard identification, and dose-response assessment.

Sampling

Pulp Mill, Maine Conducted effluent and water sampling of mill outflow and intake, respectively, for the purpose of conducting aquatic bioassays to inform the development of site-specific water effects ratios.

Berry’s Creek Superfund Site, Meadowlands, New Jersey Completed multiple field surveys of Berry’s Creek and surrounding tributaries of the Hackensack River, including aquatic fauna surveys, marsh invertebrate surveys, and air quality monitoring. Efforts included extensive coordination with colleagues and teaming partners, as well as refinement to standard operating procedures.

Bear Brook Mountain Watershed, Maine Assisted in collection of mid-canopy foliage for use in a study on the impacts of long-term nitrogen addition on tree phenology.

Sampling Regimes for Damselfly Diversity, Maine Coordinated and conducted extensive field collection of both larval and adult damselflies at more than 25 ponds in the state of Maine. Performed substantial species-level identification in the laboratory.

Environmental Impact Assessment

Critical Review and Conceptual Site Model of Sediment Data Fate and Transport, New York Reviewed and critiqued multiple peer-reviewed articles regarding sediment contaminant fingerprinting analysis. Acquired and analyzed contaminated sediment data to improve understanding of sediment fate and transport in an estuarial system in a heavily industrialized setting.

Air Quality Exposure Assessment, Confidential Location, Gulf Coast, United States Conducted a frequency, intensity, duration, and onset analysis of hydrogen sulfide emissions from a landfill for multiple receptors using modeled concentration data. Evaluated multiple receptor exposures for various locations and exposure scenarios. Supported an ongoing litigation effort.

Ecological Baseline Pre-Design Investigations, CERCLA Site, Rhode Island Conducted various multimedia analyses in support of a pre-design investigation. Developed statistical and graphical analyses of current and historical data in support of multiple report sections submitted to the U.S. Environmental Protection Agency. Created multiple data outputs for report appendices.

Conceptual Site Model, New Jersey, United States Assisted in the development of a conceptual site model for a CERCLA site in New Jersey. Focused on both human and ecological exposure pathways and development of exposure factors across media and receptor groups.

Historical Site Review, Confidential Location, East Coast, United States Assisted in the development of an expert report detailing the history of contamination and possible discharges at a historical manufacturing facility. Effort required reviewing documents as old as 130 years as well as current data and reports, assisting with development of an expert report, and generating figures and statistical analyses representing contamination in sediments spatially through time.

Fate, Transport, and Loading Evaluation, Former Manufacturing Facility and RCRA Landfill, Ohio Assisted in an evaluation of former groundwater contamination fate and transport and loading to a nearby creek. Managed collected data and data analyses. Conducted graphical and statistical analyses of groundwater well data and modeling of associated stream flow and contaminant concentrations.

Fish Tissue Analysis, Confidential Location, United States Conducted an analysis of fish tissue data from multiple sources in support of expert report development.

Mining Site, Confidential Location Assisted in the development and quality assurance of hazard calculations for multiple human receptor scenarios. Developed code to conduct a sensitivity analysis for the outdoor worker exposure scenario.

Berry’s Creek Superfund Site, Meadowlands, New Jersey Co-authored a report appendix submitted to EPA. Assisted in revisions and updates to reports, work plans, and sampling procedures. Performed extensive statistical and graphical analysis of collected data. Efforts included database creation and management and coordination with field and office staff.

Escambia Bay, Florida Assisted in preliminary evaluation and human health risk assessment of possible contamination in the Pensacola Bay system.

S&W Sawmill Facility, Montana Assisted with data entry and quality assurance for a baseline risk assessment.

San Jacinto River Waste Pits Superfund Site, Texas Assisted with multiple data efforts and calculations in conjunction with a risk assessment. Performed quality assurance of multiple work products, including risk calculations, and efforts involving raw data.

Bonafide Landfill, Maine Reviewed benthic invertebrate data to determine whether any adverse effects were present using Maine Department of Environmental Protection’s “Methods for Biological Sampling and Analysis of Maine’s Rivers and Streams.”

Bear Brook Mountain Watershed, Maine Conducted laboratory studies on forest soils, including exchangeable and total acidity, analysis for cations and anions, and carbon nitrogen analysis. In addition, participated in sample processing, data entry, and quality assurance and handled hazardous materials.

Human Health Risk Assessment

Risk Assessment Services in Support of Deconstruction at a Former Power Facility, New York Calculated risk-based action levels in consideration of potential receptors and deconstruction activities. Developed background-level air concentrations based on pre- and post-deconstruction monitoring data.

Development of a Database of Liver Toxicity Case Report and Pharmacokinetic Data, National Toxicology Program Office of Health Assessment and Translation Developed a Microsoft^® Access database complete with data extraction forms, user interface, and reports to collate human exposure data in support of high-throughput transcriptomic analysis.

Systematic Review of the Developmental Effects of PCBs, Nationwide Reviewed more than 100 studies on the developmental effects of PCBs in multiple human media with multiple effects. Performed quality assurance of study summary tables.

Environmental Modeling

Probabilistic Human Exposure Model, Confidential Location, United States Collaborated on the initial stages of development of a probabilistic exposure model for fish tissue consumption that tracks receptors for each day throughout their period of exposure.

Exposure Factors Interactive Resource and Scenarios Tool (ExpoFIRST), EPA Office of Research and Development Revised the ExpoFIRST tool based on responses to beta testing and peer review. Developed an export-to-Excel module that dynamically creates the formulas generated in the tool and exports them in a report format.

Integrated Indoor–Outdoor Air Calculator, EPA Office of Pollution Prevention and Toxics Developed a Microsoft Excel based tool intended to quickly process new and existing chemicals for release and exposure potential in support of TSCA reform efforts. The tool estimates outdoor and indoor air concentrations, as well as wet and dry particle deposition from chemical releases to air through facility (stack, incinerator, and fugitive), area soil, and area water sources.

Assessment of Livestock Carcass Disposal Options, EPA National Homeland Security Research Center Conducted multiple exposure assessments of various carcass disposal options for simulated chemical exposures using previously developed modeling tools.

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