Gretchen Onstad, PhD

Acting Assistant Professor, Env. and Occ. Health Sciences (Primary department)
Gretchen Onstad is an environmental chemist who utilizes analytical chemistry to characterize sources of pollution, to study human exposure to environmental pollution and to examine control measures for preventing exposure. She is specifically interested in preventing exposure to groundwater contaminants in rural populations that rely on household wells for drinking water. Her expertise is in analysis of drinking water disinfection by-products and disinfection chemistry, and markers of human exposure to air pollution (pesticides, woodsmoke, diesel exhaust).

Contact Information

University of Washington
Office: HSB F226B
Box: 357234
Environmental and Occupational Health Sciences
Seattle, WA 98195-7234
Tel: 206-616-9870
Fax: 206-616-2687

Research Interests

  • Research is focused on characterizing sources of pollution and preventing human exposure to environmental pollutants, in air and water: Nitrate contamination of household wells and point-of-use water treatment in rural populations; Cortisol as a biomarker of stress in children or shift-work in adults; Differential spectroscopy as predictive measure of disinfection byproduct potential; Iodinated disinfection byproduct potential of point-of-use drinking water disinfectants; Woodsmoke source apportionment of ambient fine particulate matter (PM2.5); Measurement of chemical markers of exposure to woodsmoke and diesel exhaust in environmental and occupational settings; Oxidative removal of algal toxins during drinking water disinfection Formation and removal of disinfection byproducts during drinking water treatment
  • KEYWORDS: Water treatment contamination; Cortisol, Disinfection byproducts and removal, Source apportionment; Chemical biomarkers

In the News

Teaching interests

ENVH 432: Environmental and Occupational Sampling and Analysis II

ENVH 205: Environmental Health in Media

ENVH 111: Exploring Environment and Health Connections


PhD, Environmental Sciences and Engineering, University of North Carolina (Chapel Hill), 2003
BS, Chemistry, University of Washington, 1997
Selected Publications

Onstad G.D., Canfield D., Quay P., and Hedges J.I. (2000) Sources of particulate organic matter in rivers from the continental USA: Lignin phenol and stable carbon isotope compositions. Geochimica et Cosmochimica Acta. 64:20:3539-3546.

Onstad G.D. and Weinberg H.S. (2005) Evaluation of the stability and analysis of halogenated furanones in disinfected drinking waters. Analytica Chimica Acta. 534:2:281-292.

Ho L., Onstad G., von Gunten U., Rinck-Pfeiffer S., Craig K., Newcombe G. (2006) Differences in the chlorine reactivity of four microcystin analogues. Water Research. 40:6:1200-1209.

Krasner S.W., Weinberg H.S., Richardson S.D., Pastor S.J., Chinn R., Sclimenti M.J., Onstad G.D., Thruston, Jr., A.D. (2006) Occurrence of a new generation of disinfection byproducts. Environmental Science and Technology. 40:7175-7185.

Onstad G.D., Strauch S., Meriluoto J., Codd G., von Gunten U. (2007) Selective oxidation of key functional groups in cyanotoxins during drinking water ozonation. Environmental Science and Technology. 41:12:4397-4404.

Rodriguez E., Onstad G.D., Kull T.P.J., Metcalf J.S., Acero J.L., von Gunten U. (2007) Oxidative elimination of cyanotoxins: Comparison of ozone, chlorine, permanganate and chlorine dioxide. Water Research. 41:15:3381-3393. (shared first-authorship)

Onstad G.D., Weinberg H.S., Krasner S.W. (2008) Occurrence of Halogenated Furanones in U.S. Drinking Waters. Environmental Science and Technology. 42:9:3341-3348. Featured by Chemical & Engineering News ("Minimizing Halogenated Mutagens in Water: Water-treatment process affects formation of toxic compounds" March 31, 2008, 86:13:26)

Sullivan A.P., Frank N., Onstad G., Simpson C.D., Collett Jr. J.L. (2011) Application of High-Performance Anion-Exchange Chromatography – Pulsed Amperometric Detection for Measuring Carbohydrates in Routine Daily Filter Samples Collected by a National Network: 1. Determination of the Impact of Biomass Burning in the Upper Midwest. Journal of Geophysical Research-Atmospheres. 116:D08302.

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