Gradient

Senior Scientists

Mary L. Hixon, Ph.D.
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Education

Ph.D., Toxicology, University of North Carolina at Chapel Hill

M.S., Environmental Health, Case Western Reserve University

B.A., Biology, Hiram College

Expertise

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

    Mary L. Hixon, Ph.D.

    Senior Toxicologist

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    Dr. Hixon is experienced in reproductive and developmental toxicology.  Her primary responsibilities include environmental and chemical toxicology data analyses and the evaluation of specific environmental chemical exposures to assess potential human health risks.  Before coming to Gradient, Dr. Hixon was an Assistant Professor at Brown University, where she researched the reproductive health effects of endocrine-disrupting chemicals in the male and female reproductive systems.  Utilizing mouse models and toxicogenomic approaches, her research involved elucidating the signaling networks activated and gene expression signatures elicited by endocrine-disrupting chemicals.  She has authored original research articles, review articles, and book chapters on a wide variety of topics, including reproductive biology and toxicology. 

    Education

    Ph.D., Toxicology, University of North Carolina at Chapel Hill

    M.S., Environmental Health, Case Western Reserve University

    B.A., Biology, Hiram College

    Expertise

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

      Representative Projects

      Waiver Assessment for a US EPA-Required Pesticide: Provided technical expertise to successfully waive the Immunotoxicity Test Guideline (870.7800) requirement for an herbicide. Utilized a weight-of-evidence approach to evaluate the toxicity of the pesticide, including consideration of its chemical structure, toxicity profile, primary target organs(s), mode of action, and structural analog information.

      Product Safety Assessment: Provided technical expertise for a comprehensive literature search and review of the ingredients in an energy drink supplement. Prepared toxicity profiles for the ingredients in the energy drink supplement and determined the margin of safety for each constituent in the product under the recommended conditions of use.

      Medical Device Toxicological Risk Assessment: As part of a submission to FDA, managed and evaluated the toxicological hazard potential associated with leachable substances from a medical device.  Compiled toxicological profiles for leachable constituents (e.g., semi-volatile, volatile, and organic compounds and metals) from the device and determined the margin of safety for each under the conditions of product use.

      Alternatives Assessment:  Provided toxicology expertise on the analysis of several alternative flame retardant chemicals to replace the currently used ozone-depleting agent, Halon.  Compiled health and environmental data to characterize hazards for each of the chemical alternatives.  Performed an alternatives assessment to identify preferable alternatives for use in future aircraft fire prevention systems to support the selection of an environmentally preferable alternative compound for commercial aircraft.

      Industrial Hygiene: Managed and provided technical expertise in the evaluation of the degree of hazard to workers applying chemicals used in the coatings of optical fibers focusing, in particular, on dimethylacrylamide.  Conducted a toxicity review of each constituent in the coating as listed on suppliers' safety data sheets.  Evaluated whether under the conditions of use, additional safety measures were necessary to reduce exposure.

      Developmental and Reproductive Toxicology: Provided technical expertise in rapid reviews of the toxicology literature to determine whether chemicals of concern were developmental and reproductive toxicology (DART) agents.  Estimated worker doses and overall hazard indices.

      Selected Publications

      Goodman, JE; Peterson, MK; Hixon, ML; Pacheco Shubin, S.  2018. "Derivation of a Maximum Allowable Dose Level for Bisphenol A." Presented at the Society of Toxicology (SOT) 57th Annual Meeting, San Antonio, TX, March 11-15

      Beyer, LA; Hixon, ML.  2018. "Review of animal studies on the cardiovascular effects of caffeine." Food Chem. Toxicol. 118 : 566-571.

      Goodman, JE; Peterson, MK; Hixon, ML; Pacheco Shubin, S.  2017. "Derivation of an oral maximum allowable dose level for bisphenol A." Regul. Toxicol. Pharmacol. 86 : 312-318.

      Hixon, ML.  2015. "Toxic effects on reproduction." In Principles of Toxicology: Environmental and Industrial Applications (Third Edition). (Eds.: Roberts, SM; James, RC; Williams, PL), John Wiley & Sons, Inc., Hoboken, NJ., p211-221.

      Moyer, B; Hixon, ML.  2012. "Reproductive effects in F1 adult females exposed in utero to moderate to high doses of mono-2-ethylhexylphthalate (MEHP)." Reprod. Toxicol. 34 : 43-50.

      See All Mary Hixon Publications