Environmental Factor, April 2008, National Institute of Environmental Health Sciences
Epidemiologist Calls for Revitalizing Toxicology
By Eddy Ball
For Devra Davis, Ph.D., the war on cancer is a prime example of the way economic and social forces can shape scientific inquiry and public health policy - and highlights the shortcomings of today's toxicology. An epidemiologist at the University of Pittsburgh, Davis outlined her argument in an NIEHS Frontiers of Environmental Sciences/Women's History Month Lecture March 3 in Rodbell Auditorium titled "The Need to Revitalize Toxicology: Lessons from the Secret History of the War on Cancer."
The host of Davis' talk, NIEHS Acting Director Sam Wilson, M.D., introduced the speaker, describing Davis as "an old friend of mine" and "one of the most influential and thoughtful leaders in field of environmental cancer research." Wilson praised Davis' contributions to environmental public health through raising public awareness and performing community outreach and through her steadfast commitment to uncovering the truth about environmental triggers of cancer.
Davis began her talk by acknowledging the 60th anniversary of the Killer Fog of Donora, where Davis grew up and where in one five-day period of time in 1948 a fog of industrial air pollution settled on the Monongahela River, killing 20 people. When she finally learned about it - "People didn't want to talk about it," she noted - the Killer Fog became the first of many emblematic events that would shape her career in environmental oncology.
The Killer Fog of Donora and cancers caused by environmental exposures led Davis to reassess the role of toxicology in preventive medicine and public health. "The motto of my work is that we have to learn from the past because we want the future to be different from the past," she explained. "And Donora is my past."
Davis traced the war on cancer back to the first x-ray of Bertha Roentgen in 1892, the death of Clarence Dally, Thomas Edison's assistant, in 1904 from radiation poisoning, and the death of Marie Curie from radiation-induced leukemia. By 1936, Davis said, scientists, such as pioneer cancer investigator Ángel Roffo, had presented convincing evidence linking cancer to newly synthesized hormones, x-ray and solar radiation, coal tars and soot, benzene, and cobalt and uranium mining.
"I think it's extraordinary to go back and realize how much was known," Davis continued, "and how much good scientific evidence the scientists had to back up their warnings. They actually had studies and very detailed studies," including in vitro and in vivo toxicology, clinical case reports and descriptive epidemiology.
According to Davis, industry funding influenced health research organizations and professional groups to ignore the growing body of evidence about environmental influences on cancer. The public's attention was effectively diverted from prevention to the search for the elusive "cure for cancer" and to development of such gimmicks as the "safe cigarette."
Davis has used what she learned to develop several proposals for revitalizing toxicology. One involves creating a Truth and Reconciliation Commission, much like the one established in South Africa, to clear up the quagmire in the field of toxicology. By offering protection from punitive damages, such a commission, she reasons, would encourage disclosure of the information industries already have on file about the dangers of their products.
Davis also proposes a fee on products suspected of causing harm to fund more research by government and greater use of high-throughput screening as other ways to help expand toxicology's knowledge base.
Yet another proposal calls for revision of what currently constitutes the burden of proof for deciding whether compounds may be harmful to humans. "Randomized control trials work for drugs, but they don't work for life because life is a mixture," she argued. "Missing data should not be confused with absence of proof of harm."
Davis also discussed cancer-related effects of CT scans (see text box), aspartame and Ritalin. She concluded the talk with a description of the way her university's Cancer Institute is helping with the greening of Pittsburgh by making more environmentally responsible choices about sanitation and energy.
Avoidable Cancer Risk of CT Scans
One of Davis' recent concerns is unnecessary exposure to radiation in computerized tomography (CT) scans. Her article on the topic appears in the winter 2008 issue of "Healthy Choices, Healthy Lives."
Davis and colleagues at the University of Pittsburgh Cancer Institute Center for Environmental Oncology have joined members of the radiological community in speaking out on the overuse of such scans, which can expose patients to radiation at levels great enough to eventually cause cancer as they age - especially children, who are far more vulnerable than adults.
A pediatric head CT scan, according Davis, can produce radiation equivalent to 400-6000 standard chest (PA/lateral) x-rays. Even the comparably "low-level" emissions from a screening mammogram expose patients to 20 to 300 times the radiation in a chest x-ray.
The American College of Radiology has called for national standards for training and certifying CT technicians and expanded educational programs for practitioners. Radiologists are warning the medical community of the possibility of a sharp increase in radiation-related cancers unless the number of CT scans is reduced in non-emergency situations.
Davis acknowledges the value of the CT scan as a tool for saving lives and avoiding exploratory surgery. However, physicians need to explore alternative diagnostic tools, such as MRI or ultrasound, before ordering procedures that involve the use of radiation.
"We have an opportunity here to take this technology, which we now understand can be used for good and has negative consequences as well," Davis reasons, "and marshal it in a much smarter way."