Gretchen Onstad, PhD

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 currently 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 -

Research Interests

  • Drinking water quality and treatment, analytical method development, oxidation kinetics, disinfection byproducts, harmful algal blooms, source apportionment of chemical contaminants (nitrates, fracking fluid) in household wells and removal by point-of-use water treatment.
  • KEYWORDS: Water treatment contamination; Cortisol, Disinfection byproducts and removal, Source apportionment; Chemical biomarkers

Teaching interests

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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