Cancer World

DEVRA DAVIS* | Friday April 25, 2008 00:00

 

True, cancer deaths have dropped chiefly because of long-delayed - and still poorly supported - efforts to curb smoking. Successes with screening and treatment of breast, colo-rectal, and cervical cancer have also helped.

But blacks and other minorities in the United States - and elsewhere in the world - do not share in these successes, and environmental factors appear to explain the disparity. For example, while one in eight Americans is black, one in three is employed in sanitation or other blue-collar jobs. Moreover, they have half the level of cancer-protective vitamin D as whites, and they are much more likely to live in polluted neighborhoods.

Indeed, cases of cancer that are not tied to smoking or aging are increasing. Cancer is the leading cause of death in middle-aged persons and children (after accidents), and we can't explain why, for most forms of cancer, death rates are higher for blacks than they are for whites. 

What we can say is that the disease itself is the wrong enemy. Instead, we should be attacking known environmental carcinogens - not just tobacco, but also radiation, sunlight, benzene, solvents, and some drugs and hormones. Modern cancer-causing agents like diesel exhaust, pesticides, and other air pollutants are not systematically studied. When they are considered at all, they are deemed to be the inevitable price of progress. 

But most cancers are made, not born, arising from damage to our genes that occurs throughout our lives. Despite having remarkably similar genes at birth, identical twins do not develop the same cancers. By age 50, their chromosomal bands are profoundly different from one another.

America's Centers for Disease Control and Prevention confirm that children's blood today contains dozens of chemicals that did not exist two decades earlier, including many gene-damaging compounds known to cause cancer and a host of other diseases. Men and women of child-bearing age now carry enough hormone-disturbing compounds in their bodies to impair their fertility.

Women exposed to higher levels of the pesticide DDT before the age of fourteen have a five times higher chances of developing breast cancer when they reach middle age. Could such compounds play a role in unexplained and growing rates of childhood cancer, testicular cancer, and non-Hodgkin's Lymphoma throughout the industrial world? Should we wait to find out?

While we are phenomenally successful at keeping young people from dying of cancer today, that success comes as a Faustian bargain. One of three young women treated with radiation to the chest to arrest Hodgkin's disease will develop breast cancer by age 32. Of course, many cancers might not have developed in the first place had these patients not been exposed to other cancer-causing agents in the environment. Our dependence on many modern conveniences makes us the subject of vast uncontrolled experiments to which none of us is asked to consent.

For example, the long-term safety of mobile phones remains unproven. Widely publicized studies in the early 1990's touting their safety excluded business users. Recent reports from France and Sweden find that those who have used mobile phones for ten or more years have double the risk of brain cancer. Also troubling is the fact that the limit for microwave emission from mobile phones is 500 times lower in Switzerland and China than in the US. 

A way of looking is a way of not looking, runs a Chinese proverb. The limited nature of evidence on some environmental cancer hazards should not be confused with proof that no harm has occurred: the research is hard to do, and, in the US, very little of it is now funded by the government and private sector. Moreover, confusion about environmental cancer risks also results from longstanding, carefully cultivated, and well-financed disinformation campaigns inspired by the machinations of the tobacco industry.

We cannot afford to ignore the signs of the importance of the environment for our health. To address the scourge of cancer, we must complement efforts to detect and treat cancer with new ways to keep people from developing the disease in the first place.

*Derva Davis is Director of the Center for Environmental Oncology University of Pittsburgh Cancer Institute and Professor of Epidemiology University of Pittsburgh School of Public Health.
Copyright: Project Syndicate, 2008.