A section of the Mississippi River from New Orleans to Baton Rouge, which is crowded with chemical plants, is called the "Canal Alley" because of the health problems there.
Giles Clark / Getty Images
Giles Clarke / Getty Images
We already know how to stop many cancers before they start, scientists say. But there is still a lot of work to be done
"About half of the cancer can be prevented," Christopher Wilde said at the opening of an international scientific meeting on environmental causes of cancer in June. Wild is the former director of the International Agency for the Study of Cancer of the World Health Organization. "The biology and cancer treatment is where most money goes," he said, but prevention requires more attention. "I'm not saying we should not work to improve the treatment, but we did not balance it properly."
Perhaps there is no question of cancer that is more controversial than the reasons. People wonder and scientists are discussing if most malignancies result from random DNA mutations and other occasional events or from exposure to carcinogens or avoidable behavior.
At a conference in Charlotte, New York, scientists insisted on reassessing the role of environmental exposures by applying modern molecular techniques in toxicology. They called for a more aggressive collection of examples of human pathology and environmental samples, including water and air, so as to be able to elucidate the cellular reactions of chemicals.
The hope is that by identifying specific traces of exposures in human cancer specimens, scientists can identify the causes of the disease that can be prevented. "Over 80,000 chemicals are used in the United States, but only a few have been tested for carcinogenic activity," said Margaret Kripke, an immunologist and professor at the MD Anderson Cancer Center, in an interview during the meeting. "This is a very neglected area of cancer research over the last few decades," said Krypke, the driving force of the conference, which was launched by the American Cancer Research Association. "Ecological toxicology is very popular in the 1
950s and 1960s," she said, but genetics began to overshadow the research into the environmental causes of cancer. "Toxicology has fallen off the road."
While smoking-related cancers are declining, non-smoking malignancies are on the rise, says Krypke. Recent data suggest that the lung cancer rate in non-smokers is increasing. This trend is related to other environmental factors. This year, 18 million people will be diagnosed with some form of cancer and over 9 million will die from it.
Infections – very preventable, such as human papillomavirus – account for 15% of new cases.
Another growing cause is obesity along with urbanization. People generally get less physical activity and feed differently in cities, and pollution is also heavier. "As people move to cities, this will lead to an increase in cancer," said Wild.
One of the biggest obstacles to preventing cancer is that many people just do not think it's possible. Progress "requires long-term vision and commitment," said Wild. "Financing is limited and there is little investment in the private sector."
Changing the way the benefits of cancer prevention are being used can help. "When I was in the IARC, one thing that struck me was the strength of the economic arguments for health arguments to prevent cancer," said Wild.
The cost of treating cancer can be too high. Productivity lost by premature deaths in Brazil, Russia, India, China and South Africa is only $ 46.3 billion a year. "Developing countries are not ready to cope with the growing burden of cancer."
The exact percentage of cancers arising from exposure to carcinogens in the environment and occupations is uncertain. In 2009, a report by the Chair of Cancer Councils called ex ante estimates of about 6% "obsolete" and low. A 2015 document from over a hundred interested scientists cites "reliable" estimates from 7% to 19%. by investigating interactions of environmental and genetic risks and by examining cells after mixing exposures. "Most toxic exposures do not occur individually," says Rick Wojchik, Deputy Director of the National Institute of Environmental Health Sciences.
Until recently, many toxicological tests have been conducted in rodents, as it would be unethical to purposefully assess possible carcinogens in humans. But these experiments with animals are laborious and slow, he said.
New alternatives are now being tested. "We have learned from pharmacy that with robot technology and high-performance technology you can question many biology quickly and at a lower cost," he said.
Epidemiological studies on human exposure are hampered by the difficulty of proving the cause and effect – that a substance actually causes cancer – and the shortcomings of the survey data.
At the conference, scientists proposed new technologies that help fill in information gaps.
Bogdan Fedeles of MIT explained how DNA serves as a lifelong learning device. He and others use a duplex sequence to examine human samples for genetic "fingerprints of exposure".
Allan Balmein, a geneticist from the University of California, San Francisco, talks about mutational signatures for malignancies. For liver cancer, for example, these signatures can offer causal evidence – such as smoking, alcohol or aflatoxin, a mold product that grows on some foods. Many chemicals that cause or stimulate the growth of cancer are produced inside our bodies. "It's not just about the environment," Balmein said.
Others highlighted the conceptual change in the way scientists determine the carcinogens. Key features may include the ability of a substance to stimulate the growth of malignant cells or to induce inflammation – without necessarily causing DNA damage – long considered necessary.
"The answer to" What is a carcinogen? "is changing," said Rutland Rudel, a toxicologist at the Silent Spring Institute, which has extensively published breast carcinogens. It details new techniques for tracking breast cancer cells for changes in response to specific chemical exposures.
Public health bets in the field are high. Professor Polly Hoppin of the University of Massachusetts, Lowell, discussed industrial pollution of drinking water causing cancer in Camp Lawn, North Carolina, air pollution in St. and planned plastic production in Pennsylvania.
Hopkins affect US experience with tobacco cessation. Scientists knew that smoking caused cancer in the 1950s, she said. Applying this knowledge required policies and incentives – such as high taxes on cigarettes and smoking bans in society – and it takes decades. "Science was not enough," said Hoppin. How many lives could be saved if we had acted earlier? Elaine Shatner is a New York doctor who writes a book on cancer treatment to be published by Columbia University Press