Environmental and Occupational Causes of Cancer

A new report by the Cancer Working Group of the Collaborative on Health and Environment reviews the state of our knowledge about the causes of cancer.

First, a bit of history: Sir Richard Doll was a famous British epidemiologist. In 1954 he was one of the first scientists to warn of the link between asbestos and cancer. Through the 1950s and 1960s, he continued to warn about the link between various exposures and cancer, but then in the 1970s and beyond, he seemed to back away from making such connections. By the 1980s, he was publishing oft-cited scientific papers suggesting that over 90% of all cancers were linked to lifestyle, and that fewer than 4% had any environmental or occupational connection. His numbers were widely used to justify a status-quo approach to cancer research, and to support the pursuit of new treatment options rather than implementing prevention strategies.

Doll passed away in 2005. His papers were donated to the Wellcome Library, a British medical library. Researchers reviewing the collection discovered that Doll had been on the dole: he received regular payments as a "consultant" from Monsanto, DOW Chemical, Turner & Newell (an asbestos company) and the Chemical Manufacturers Association, beginning by 1979 and continuing almost to his death. He never disclosed his relationship with these special interests, even when testifying before government entities around the world about the safety of the chemical products they made.

Blame smoking. Blame bad eating habits. But don't blame the chemicals we're exposed to. Hmmm. You can read more on the Doll story, here, at Our Stolen Future.

Over the years, people in environmental health questioned Doll's numbers, yet he was considered the pillar of respectability, and his results and opinion were bandied about with great authority by anyone wanting to downplay environmental links to our health. Three environmental health researchers decided to do some digging to see if Doll's numbers stood up to scrutiny. Richard Clapp, Molly Jacobs, and Genevieve Howe plunged into a literature survey, reading all the published studies and reports they could find. Their 2005 conclusion: "Environmental and occupational contributions to cancer in the U.S. are substantial and justify continued efforts to prevent these types of exposures."

This year, Clapp, Jacobs, and researcher Edward Loechler, revisited the earlier report, Environmental and Occupational Causes of Cancer, A Review of Recent Scientific Literature, studying over one hundred papers and reports that have seen print since their first review. What did they find? Unfortunately, nothing unexpected: The evidence is stronger than ever for a link between many exposures we face with some regularity and cancer, such as:

breast cancer to DDT exposure, particularly before puberty;

brain cancer from nonionizing radiation, particularly from radiofrequency fields emitted by mobile telephones;

non-Hodgkin's lymphoma from exposure to pesticides and solvents;

lung cancer from bad air days (pollution);

and, prostate cancer from exposure to pesticides, polyaromatic hydrocarbons (PAHs), and metal working fluids or mineral oils.

In this year's report, the authors come out forcefully. Perhaps, surprisingly so. Remember, scientists are trained to avoid opinionated conclusions, to remain comfortable in the sanctuary in their numbers and their peer-reviewed publications. Yet Clapp, Jacobs, and Loechler concluded this year's report with this:

We consider the scientific literature linking environmental and occupational exposures to cancer to be substantial and getting stronger as time goes on. One of us (R.Clapp) has been reviewing this literature for over thirty years. In the 1970s there were approximately a dozen substances or exposures that were considered “established” human carcinogens by international agencies. That number now approaches 100, with many more considered “likely” to cause cancer in humans. As we noted in our previous review, incidence rates for many types of cancer in the U.S. continue to rise, although we welcome the apparent decline in lung cancer in males and soon in females. The cancer burden, defined as the number of people living with cancer, with the attendant economic and human costs, will inevitably continue to grow.

This justifies urgent action to limit exposures to avoidable environmental and occupational carcinogens and to find safer alternatives to present chemical and physical risks. To repeat the call of ecologist Sandra Steingraber, “From the right to know and the duty to inquire flows the obligation to act.”1

The report can be downloaded here.