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Environmental Factor, October 2012

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Former Superfund trainee honored for mass spec research

By Eddy Ball

Nils Schebb, Ph.D.

Schebb is a prolific scholar who has co-authored 24 PubMed indexed publications. (Photo courtesy of Nils Schebb)

Bruce Hammock, Ph.D.

Hammock’s research interests range across omics platform development, pest control, and drug development. He has been honored for his teaching and mentoring, as well as for his groundbreaking scientific research. (Photo courtesy of Bruce Hammock)

Food chemist and toxicologist Nils Schebb, Ph.D., was honored Sept. 18 for research he conducted as an NIEHS-supported postdoc at the University of California (UC), Davis. The award-winning study, “Investigation of human exposure to triclocarban after showering and preliminary evaluation of its biological effects,” was published in 2011 in Environmental Science and Technology.

The section of liquid chromatography mass spectrometry (LC/MS) of the German Society for Mass Spectrometry presented Schebb with the 2012 AB SCIEX LC/MS Award for this work, during its annual workshop at the historic town hall in Wuppertal, Germany. The award included a prize of 3,000 euro, funded by the company AB SCIEX, a major producer of MS systems for a host of applications, including drug discovery, clinical research, food production, and toxicology.

From 2009 to 2011, Schebb was a member of the UC Davis Laboratory of Pesticide Biotechnology, headed by veteran NIEHS grantee Bruce Hammock, Ph.D., prior to forming his own group in the Institute for Food Toxicology and Chemical Analysis at the University of Veterinary Medicine Hannover in Hannover, Germany. Schebb’s award-winning study was one of 15 toxicological and laboratory methods papers he has co-authored on work with the Hammock group.

Improved sensitivity and analytical throughput

To assess human exposure to the persistent and widely used antibacterial soap additive triclocarban (TCC), Schebb and his co-authors developed and validated a sensitive online solid-phase extraction (SPE) LC/MS. Unlike earlier approaches, the new method is capable of rapidly analyzing the compound and its major metabolites in urine and other complex biological samples.

The study referenced recent findings indicating that TCC is persistent in the aquatic environment and has significant off-target biological activity. In order to assess potential biological effects arising from TCC exposure, the researchers screened the compound for effects on human enzymes in vitro.

One result of special interest to the group was evidence that TCC strongly inhibits the enzyme soluble epoxide hydroxylase (sEH), suggesting that exposure could impact human health. Hammock and his group have published a series of studies on the efficacy of sEH suppression in the regulation of blood pressure, inflammation, and pain. A preliminary followup study with rats failed to replicate the in vitro results systemically in vivo, although the team could not rule out local dermal effects that might be significant.

In their experiments, Schebb and his co-authors identified urinary glucuronides as a sensitive marker of TCC, and found sufficient evidence of biological activity to justify follow-up studies. “Long-term exposure studies in humans, that include biomonitoring of TCC in blood, should be carried out to evaluate if exposure after using personal care products, containing up to 1.5 percent TCC, provides a sufficient margin of safety,” they concluded. “With the online-SPE-LC/MS method described herein, we provide an excellent analytical tool to answer these questions.”

Since the publication of the 2011 study, Schebb has been involved in five follow-up studies on TCC, as part of his research on bioactivity and pharmacokinetics of food ingredients and environmental contaminants.

Citation: Schebb, NH, Inceoglu B, Ahn KC, Morisseau C, Gee SJ, Hammock BD. 2011. Investigation of human exposure to triclocarban after showering and preliminary evaluation of its biological effects. Environ Sci Technol 45(7):3109-3115.

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