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Toxins in our Midst

Eunha Hoh searches for harmful pollutants that we never even knew existed.
By Michael Price, video by Jeneene Chatowsky

This story appears in the spring 2015 issue of 360:The Magazine of San Diego State University.

It’s not necessarily the pollutants we already know about that worry San Diego State University environmental scientist Eunha Hoh. Instead, she devotes her research to discovering harmful contaminants nobody knew even knew to look for.

Hoh didn’t begin her career as an environmental researcher. She studied chemistry in South Korea and took a job as a chemist for a major electronics manufacturer. Eventually, she grew concerned over the types of chemicals being used and disposed of during the production process.

“I never realized how many toxic chemicals went into manufacturing,” Hoh said. “That got me very interested in environmental health.”

Lake pollutants

Hoh moved to the United States to study environmental science at Indiana University, eventually earning her Ph.D. under the tutelage of one of the field’s luminaries, Ronald Hites. There she began researching pollutants in and around the Great Lakes.

The shores of the vast lakes are home to several cities with major manufacturing centers. In particular, manufacturing flame retardants can produce highly toxic products in the lakes. Environmental regulators struggle to keep up with manufacturer’s replacement of regulated retardants with unregulated ones.

In 2006, Hoh detected an airborne contaminant known as dechlorane plus—an old yet unregulated chemical—at very high concentrations in several places on the lakes. She was able to trace the pollutant to its likely source at a manufacturing facility in Niagara Falls, New York.

Chemical contaminants that stick around in the environment indefinitely are known as persistent organic pollutants (POPs). Little was known about dechlorane plus’s toxicity to animals and ecosystems, but the fact that it was right under people’s noses and nobody knew about it was troubling to Hoh.

“I thought that if I could find dechlorane plus, there must be lots of other POPs out there, too, that we don’t know about,” she said.

Smoke signals

Hoh spent the next three years as a postdoctoral scholar and research chemist in a U.S. Department of Agriculture chemical residue research group, then joined SDSU in 2009.

Here, she uses a combination of gas chromatography and mass spectrometry to look for previously unknown pollutants, even those that can only be found in low concentrations. Collaborating with fellow SDSU faculty Penelope J.E. Quintana and Georg Matt, Hoh has also begun to look into “thirdhand” smoke—the residual chemical leftovers of cigarette smoke.

“If you only look for the things you already know are present, then you might miss a lot of other things that could turn out to be extremely important, but you never knew they were there,” Hoh said.