Senior Scientists

Gradient is proud to have a diverse, skilled, and well-trained technical staff who work collaboratively to manage our projects, perform research, and deliver innovative solutions with superior quality.

Full Bio

Steven R. Boomhower, Ph.D.

Senior Toxicologist

Expertise

• Metals Toxicology
• Developmental Toxicology
• Neurotoxicology
• Psychopharmaceuticals
• Cannabis
• Animal Testing and Extrapolation
• Statistical Modeling

Full Bio

Ali Boroumand, Ph.D.

Senior Environmental Engineer

Expertise

• Contaminant Fate & Transport
• Groundwater Hydrology
• Remedial Investigation & Design
• Groundwater Modeling
• Multiphase Flow and Reactive Transport
• "Green and Sustainable Remediation"

Full Bio

Chase Butler, M.S.

Senior Environmental Chemist

Expertise

• Environmental Chemistry
• Read-Across Assessment
• Materials Science and Degradation Pathways
• Analytical Testing Methods

Full Bio

Jonathan C. Callura, Ph.D., E.I.T.

Senior Environmental Engineer

Expertise

• Contaminant Fate and Transport
• Environmental Chemistry
• Numerical Modeling
• Sorption Processes
• Metal Chemistry

Full Bio

Jiayang Chien, M.P.H.

Senior Environmental Scientist

Expertise

• Human Health Risk Assessment
• Vapor Intrusion
• Database Construction and Management
• Epidemiology

Full Bio

Amy L. Dale, Ph.D.

Senior Environmental Engineer

Expertise

• Contaminant Fate & Transport
• Risk Assessment
• Numerical Modeling
• Computational Fluid Dynamics
• Quantitative Policy Analysis
• Climate Impact Assessment
• Nanomaterials

Full Bio

Anna M. Engel

Senior Research Associate

Expertise

• Epidemiology
• Exposure Science
• Specific Causation Analysis
• Historical State-of-Knowledge
• Site History Assessment

Full Bio

Grace I. Greenberg, M.P.H., BCES

Senior Environmental Toxicologist

Expertise

• Exposure Modeling
• Human Health Risk Assessment
• Ecological Risk Assessment
• Database Construction and Management
• Data Analysis and Interpretation

Full Bio

Mary L. Hixon, Ph.D.

Senior Toxicologist

Expertise

• Reproductive and Developmental Toxicology
• Toxicogenomics
• Mode of Action Analyses
• Human Exposure

Full Bio

Laura E. Kerper, Ph.D.

Managing Toxicologist

Expertise

• Risk Assessment
• General and Molecular Biology
• Heavy Metals Toxicity
• Solvent Toxicity
• Toxicology
• Perfluorinated Chemicals

Full Bio

John M. Kondziolka, M.S., E.I.T.

Senior Environmental Engineer

Expertise

• Contaminant Fate and Transport
• Risk Assessment
• Fluid Dynamics
• Numerical Modeling

Full Bio

Cynthia J. Langlois, M.S.

Senior Health Scientist

Expertise

• Risk Communication
• Exposure Assessment
• Data Quality
• Toxicology

Full Bio

Julie C. Lemay, M.P.H.

Senior Environmental Health Scientist

Expertise

• Risk Communication
• Human Health Risk Assessment
• Exposure Assessment
• Epidemiology
• Public Health
• Data Analysis and Interpretation

Full Bio

Charlotte Marsh, M.S.

Senior Toxicologist

Expertise

• Human Health Risk Assessment
• Toxicology
• Product Safety Evaluation
• Product Stewardship
• GHS Hazard Assessment

Full Bio

Rosemary Mattuck, M.S.

Senior Environmental Engineer

Expertise

• Exposure Assessment
• Blood Lead Modeling
• Product Safety
• Risk Assessment
• Proposition 65

Full Bio

David B. Mayfield, M.S., DABT, BCES

Senior Toxicologist

Expertise

• Metals Toxicology
• Human Health Risk Assessment
• Exposure Analysis
• Toxicology
• Ecological Risk Assessment
• Dose-Response Analysis
• Environmental Site Investigation

Full Bio

Matthew J. Mayo, M.S., GISP, CPG, PG

Senior GIS/Environmental Scientist

Expertise

• Hydrogeology
• GIS Management
• 2D and 3D Geospatial Modeling
• Remote Sensing and Aerial Imagery Analysis
• Database Construction and Management
• Geospatial Data Acquisition and Visualization

Full Bio

Isaac Mohar, Ph.D., DABT

Senior Toxicologist

Expertise

• Risk Assessment
• Toxicology
• Immunology
• Liver Pathology

Full Bio

Margaret C. Pollock, M.S.

Managing Environmental Scientist

Expertise

• Statistical Methods
• Exposure Assessment
• Database Development
• Cost Estimation and Allocation

Full Bio

Robyn Prueitt, Ph.D., DABT

Senior Toxicologist

Expertise

• Molecular Biology & Toxicology
• Carcinogenesis
• Mode-of-action Analyses
• Human Genetics
• Molecular Epidemiology

Full Bio

Kathleen A. Radloff, Ph.D.

Senior Environmental Engineer

Expertise

• Contaminant Fate & Transport
• Aqueous Geochemistry
• Lead, Arsenic, and Metals
• Groundwater Hydrology
• Risk-based Remediation

Full Bio

James W. Rice, Ph.D.

Senior Environmental Scientist

Expertise

• Contaminant Fate & Transport
• Polycyclic Aromatic Hydrocarbons (PAH)
• Read-Across Assessment
• Environmental Sampling and Data Interpretation

Full Bio

Jeffrey T. Rominger, Ph.D.

Senior Environmental Engineer

Expertise

• Contaminant Fate & Transport
• Environmental Forensics
• Fluid Dynamics
• Numerical Modeling
• PCBs

Full Bio

Naomi L. Slagowski, M.S.

Senior GIS/Environmental Engineer

Expertise

• Remedial Investigation/Design
• Database Development
• GIS and Spatial Analysis
• Data/Document Validation
• Historical Information Review

Full Bio

Meghna H. Swamy, M.S.

Managing Environmental Engineer

Expertise

• Contaminant Fate & Transport
• NAPL Transport
• Remedial Investigation & Design
• Risk-based Remediation
• Environmental Cost Analysis
• Manufactured Gas Plants
• Site Characterization and Remedial Strategy

Full Bio

Rebecca C. Ticknor, M.S.

Senior Toxicologist

Expertise

• Inhalation Toxicology
• Risk Communication
• Occupational Health
• Product Safety
• Risk Assessment
• Toxicology

Full Bio

Caroline B. Tuit, Ph.D.

Senior Environmental Chemist

Expertise

• Chemical Fate/Transport
• Rare Earth and Minor Metals
• Sediment Management
• Cost Allocation
• Chemistry/Forensics

Full Bio

Matthew P. Tymchak, M.S.

Senior Hydrologist

Expertise

• Remedial Investigation & Design
• Hydraulic Fracturing
• NAPL
• Contaminant Fate and Transport
• Environmental Cost Analysis
• Groundwater-Surface Water Hydrology

Full Bio

Jiaru Zhang, M.P.H.

Senior Toxicologist

Expertise

• Product Safety Evaluation
• Product Stewardship
• Medical Device and Pharmaceutical Safety Assessments
• GHS hazard assessment, SDS, and Label