by Ashley Mooney
The similarities between chromium workers and whales are greater than one might think.
Environmental toxicology researcher John Wise has been studying the connection between exposure to pollutants and the onset of cancer in humans. To understand the link, he said one must take into account all species, especially whales. Wise spoke at Duke Oct. 25 at the Inaugural Duke Distinguished Lecture in Cancer and the Environment.
Chromium crystals. Courtesy of Wikimedia Commons.
“For environmental health for me, [the Earth] is the big picture,” Wise said. “This is home and we only have one, so we have to think pretty hard about environmental health.”
Wise studies the effect of pollutants—specifically forms of chromium—on genetic material in humans, marine mammals, and birds and other marine species. While the standard approach to environmental toxicology research is to conduct epidemiology studies on highly exposed populations and then expose animals to high doses of the toxin, Wise has adopted a new method of study.
“We don’t really know what high-dose exposures mean on a day-to-day basis,” he said.
To understand the relationship between chromium exposure and the onset of cancer, Wise looks at the personal factors that affect one’s health, such as an individual’s body and genome, lifestyle, daily exposures and what kind of environment one lives in.
“We need to know mechanism: how does a normal cell become a tumor cell?” he said. “For a long time that is where the field has been hung up, trying to identify the ultimate carcinogen.”
Most forms of naturally occurring chromium are not toxic. Man-made hexavalent chromium, however, has been shown to cause lung cancer in those who are regularly or heavily exposed to it. Prolonged exposure induces an altered chromosome number and structure, as well as DNA double strand breaks.
Chronic exposure to chromium also causes a shift from more a protective form of DNA repair called homologous recombination to a less stable and error-prone pathway called non-homologous end joining. This means that cells will have permanently deficient repair mechanisms.
Wise applies his research in the context of ocean health, namely how chromium exposure might harm whale DNA.
Most ocean pollutants, including the toxic form of chromium, are in the ocean sediment. As the ocean becomes increasingly more acidic, the sediment breaks off and poses a growing threat to marine species.
Wise measured chromium levels in baleen whale skin, and found that Atlantic seaboard species—the northern right whale, fin whale and humpback whale—have 16- to 41-fold higher levels than other baleen whales. Toothed whales living in the Gulf of Mexico exhibited levels that resembled those found in chromium workers who died of lung cancer.
A humpback whale surfacing for air. Courtesy of: Protected Resouces Division, Southwest Fisheries Science Center, La Jolla, California. swfsc.nmfs.noaa.gov/PRD/.
In whales, chromium can lead to DNA damage and reproductive suppression.
“There’s only 400 [northern right whales] left in existence,” Wise said. “If you only have 400 animals, you need every single one of them [to be able to reproduce].”
Wise said he hopes his research will encourage people to think more about habitat degradation and climate change, and how they affect all species.
Wise (back right) photographed with his lab and Conor Kennedy (back left). Courtesy of popdust.com.
His lab, however, has recently gained publicity not for its research, but for the public figures that have worked with it. Conor Kennedy, a member of the influential Kennedy family, worked with Wise’s team and Ocean Alliance last year. At the time he was dating pop-star Taylor Swift.
“[He was], like any other high school student, constantly texting on his phone and I would do what I did with my kids and the other students, and say ‘put the girl down, we have to go to work,’ not knowing the girl was Taylor Swift,” Wise said. “It really hit home that we were traveling in very different circles.”