Gradient

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.

Ali Boroumand, Ph.D. 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"

Chase Butler, M.S. Full Bio

Chase Butler, M.S.

Senior Environmental Chemist

Expertise

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

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

Jiayang Chien, M.P.H. Full Bio

Jiayang Chien, M.P.H.

Senior Environmental Scientist

Expertise

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

Joel M. Cohen, Sc.D., DABT Full Bio

Joel M. Cohen, Sc.D., DABT

Senior Toxicologist

Expertise

  • Inhalation Toxicology
  • Human Health Risk Assessment
  • Product Safety
  • Alternative Assessment
  • Nanotechnology
  • Skin Sensitization

Amy L. Dale, Ph.D. 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

Anna M. Engel Full Bio

Anna M. Engel

Senior Research Associate

Expertise

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

Grace I. Greenberg, M.P.H. Full Bio

Grace I. Greenberg, M.P.H.

Senior Environmental Toxicologist

Expertise

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

Mary L. Hixon, Ph.D. Full Bio

Mary L. Hixon, Ph.D.

Senior Toxicologist

Expertise

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

Laura E. Kerper, Ph.D. Full Bio

Laura E. Kerper, Ph.D.

Managing Toxicologist

Expertise

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

Jessie M. Kneeland, Ph.D. Full Bio

Jessie M. Kneeland, Ph.D.

Senior Environmental Chemist

Expertise

  • Chemical Fingerprinting
  • Organic Geochemistry
  • Oceanography
  • Climate Change Science
  • Environmental Forensics
  • Fate and Transport
  • Product Stewardship

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

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

Senior Environmental Engineer

Expertise

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

Cynthia J. Langlois, M.S. Full Bio

Cynthia J. Langlois, M.S.

Senior Health Scientist

Expertise

  • Risk Communication
  • Exposure Assessment
  • Data Quality
  • Toxicology

Julie C. Lemay, M.P.H. 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

Charlotte Marsh, M.S. Full Bio

Charlotte Marsh, M.S.

Senior Toxicologist

Expertise

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

Rosemary Mattuck, M.S. Full Bio

Rosemary Mattuck, M.S.

Senior Environmental Engineer

Expertise

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

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

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

Isaac Mohar, Ph.D., DABT Full Bio

Isaac Mohar, Ph.D., DABT

Senior Toxicologist

Expertise

  • Risk Assessment
  • Toxicology
  • Immunology
  • Liver Pathology

Margaret C. Pollock, M.S. Full Bio

Margaret C. Pollock, M.S.

Managing Environmental Scientist

Expertise

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

Robyn Prueitt, Ph.D., DABT Full Bio

Robyn Prueitt, Ph.D., DABT

Senior Toxicologist

Expertise

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

Kathleen A. Radloff, Ph.D. 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

James W. Rice, Ph.D. 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

Jeffrey T. Rominger, Ph.D. Full Bio

Jeffrey T. Rominger, Ph.D.

Senior Environmental Engineer

Expertise

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

Naomi L. Slagowski, M.S. 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

Meghna H. Swamy, M.S. 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

Caroline B. Tuit, Ph.D. 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

Matthew P. Tymchak, M.S. 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

Jiaru Zhang, M.P.H. 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