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Faculty Focus

Joshua Hamilton, Ph.D.: A certain kind of scientist

By Laura Stephenson Carter

Early in his career, Joshua Hamilton was chastised for calling himself an eclectic scientist. Young researchers were expected to develop expertise in a specific area so they could attract funding, publish their work, get promoted, be granted tenure, and develop an international reputation.

Things have changed. In today's interdisciplinary environment, being well versed in other fields is an asset. By defying that long-ago advice, Hamilton has become a tenured full professor in DMS's Department of Pharmacology and Toxicology; the director of two important interdisciplinary programs at Dartmouth— the Superfund Basic Research Program Project on Toxic Metals and the Center for Environmental Health Sciences (CEHS); and a collaborator on several other major research projects. He is well funded and has developed an international reputation.

"The cartoon image in science," says Hamilton, is "of the blind men feeling the elephant, where one feels the tail and says, 'It's a rat,' and the other one feels the trunk and says, 'No, it's a snake,' and the other one feels a leg and says, 'No, it's a hippopotamus.'" But, he continues, "it's when you put all the pieces together that you realize what the actual structure is of the thing that you're looking at."

Putting the pieces together has been key to CEHS research on the arsenic that occurs naturally in many of New Hampshire's private wells. Researchers from different departments are studying arsenic's relationship to the incidence of cancer; investigating the movement of toxic metals through aquatic food webs; exploring how toxic metals interact with cellular proteins; determining arsenic's effect on DNA repair; looking at arsenic

He may have ended up as a toxic metals expert rather than a marine biologist, but Hamilton still loves to gaze into the fish tank at the local Montshire Museum of Science.

as an endocrine disrupter; trying to understand the geology related to arsenic in groundwater systems; and finding out where old arsenic mines are located.

"I think our biggest contributions scientifically have been the discovery of arsenic as an endocrine disrupter," says Hamilton, whose latest study on the topic was published late in 2007 in Environmental Health Perspectives. By disrupting important hormones, arsenic is believed to contribute to cancer, cardiovascular disease, and diabetes.

The CEHS also engages in public outreach and helps shape public policy at both the state and federal level. "We were one of the principal groups whose new research findings led to the U.S. EPA [Environmental Protection Agency] lowering the U.S. drinking water standard for arsenic," says Hamilton. He rattles off the names of some Dartmouth

colleagues, saying that the EPA "cited Margaret Karagas's epidemiological studies, my work on arsenic as an endocrine disrupter, and Aaron Barchowsky's work on arsenic and cell signaling as new information that compelled them to consider the maximum contaminant level in drinking water." The new guidelines—which were adopted in 2001 and took effect in 2006—dropped the maximum acceptable level of arsenic in drinking water from 50 parts per billion to 10 parts per billion. Even that, Hamilton argues, is still too high.

When he was young, Hamilton dreamed of being a marine biologist, but by the time he got to college marine biology was feeling a funding pinch. "People in the field [suggested] that Imight look at other career paths," he says. So in graduate school at Cornell, he pursued an interest in genetics, figuring he could always apply what he learned to marine biology later on. But then he got hooked on genetic toxicology, "looking at how chemicals and radiation damage DNA, which can lead to birth defects and cancer." After getting his Ph.D., he did a postdoctoral fellowship in Dartmouth's chemistry department with an inspiring scientist—toxic metals researcher Karen Wetterhahn. "She was really an amazing person, probably the smartest person I've ever met," says Hamilton, "and in science, that's saying a lot."

When he joined the DMS faculty in 1990, he continued to work closely with Wetterhahn. In 1994, Wetterhahn was at a conference where an administrator from the National Institute of Environmental Health Sciences suggested that she apply for a Superfund Basic Research Program grant, because of Dartmouth's expertise in metals toxicology. Over the next few weeks, Wetterhahn, Hamilton, and others scrambled to put a grant proposal together and, in 1995, Dartmouth's

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Laura Carter is Dartmouth Medicine magazine's associate editor.

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