CLEARING THE SMOKE: WHAT WE KNOW AND SUSPECT ABOUT CANCER AND THE ENVIRONMENT

by: Devra L. Davis, PhD, MPH, Director, CEO-UPCI and Professor of Epidemiology, Graduate School of Public Health, University of Pittsburgh
and Ronald B. Herberman, MD, Director, UPCI and UPMC Cancer Centers

Smoke doesn't only get in your eyes, like the popular Platters song harmonizes. Cancer-causing agents in cigarette smoke also can find their way throughout the body. Tobacco smoke can cause lung, breast, and many other cancers and chronic diseases. This newsletter conveys an important message: some of the same toxic chemicals found in tobacco smoke also are in numerous products we encounter on a daily basis in modern life. Formaldehyde, benzene, cadmium, and butadiene, for example, have all been shown to have carcinogenic activity and can be found at hazardous levels in gasoline, pesticides, cleaning chemicals, building materials, or paint supplies. We need to be informed consumers and reduce our exposures to such hazards through healthy choices to lead healthy lives.

People often ask staff of the Center for Environmental Oncology: "What exactly do you work on?" With this newsletter, we are starting a public educational campaign on some well-known cancer-causing hazards— namely tobacco smoking, radon, alcohol, and inactivity. We begin with what everybody knows. Smoking tobacco increases your risk of cancer and many other chronic diseases. Exposure to invisible amounts of radon gas, a natural form of ionizing radiation, can increase the risk of lung cancer and possibly other forms of cancer as well, and this exposure is particularly hazardous to people who smoke tobacco. Drinking excessive amounts of alcohol and being physically inactive also increase the risk of cancer and other diseases. While some scientists warned about these hazards more than a century ago, it has taken nearly that long to achieve a broad consensus on these issues.

Let's look at the science of tobacco today as a model for how we can identify other important, avoidable environmental hazards. Tobacco smoke contains several thousand chemicals, including more than 70 known to cause cancer.¹

Both mainstream and sidestream smoke, also known as second-hand or environmental tobacco smoke (ETS), consist of gases and tiny particles 50 times smaller than a human hair, and can remain suspended in the air for weeks. The smallest of these particles can attract to their surface some of the gases of smoke, and bring them deeply into the lung, where they can enter the blood. The lungs of smokers are usually tighter and less able to get rid of bacteria, viruses, and pollution because they have lost their natural resilience. Smokers' lungs also contain a number of chemicals that have been shown to increase cancer in experimental animals and in some highly exposed workers including painters, pesticide applicators, and beauticians.

The list of cancer-causing ingredients in cigarette smoke includes: butane, a form of lighter fuel; beta-naphthyl methylether, found in mothballs; heavy metals, arsenic, cadmium, and lead, which can be found in smokestacks from power plants; and volatile agents, such as benzene, tars and butadiene, which can be released through car and truck exhausts. Smokers also can inhale additional toxins including pesticides and methanol.

The National Cancer Institute reminds us that all cancer comes about when our healthy genes stop doing their jobs of keeping things under control. Only one in 10 cases occurs in people who have inherited some defects in genes from their families. Changes in rates of cancer that have taken place over the past few decades in many countries cannot be tied with sudden alterations in the distribution of genes with which we were born.

There have been remarkable advances at the University of Pittsburgh Cancer Institute in our ability to break the cancer process down to finer levels—that of the sub-micron and nanoparticle. With dazzlingly precise modern electron microscopes and scales, we can see 5 million times smaller than a human hair and measure a billionth of a gram in weight. Is some of the increase in cancer just due to the fact that we are getting better at finding it? Of course…but that does not tell the full story.

Some of the chemicals found in cigarette smoke have been shown in laboratory studies to cause breast, prostate, or lung cancer cells to grow much more rapidly. Studies have compared patterns of breast cancer in women with exposures to these agents to those without such exposures. Many of these same agents that cause cancer cells to grow in the laboratory are known or suspected of increasing the risk of this common cancer in women.

While the levels of exposure to any single cancer-causing agent found in smoke may be relatively low, their combined effect over a lifetime is believed to contribute to the long-term increase in cancer risk associated with smoking.

“Clearing the Smoke” launches our campaign to achieve three important goals:

• Working with state and local officials throughout Pennsylvania, we are spearheading efforts to secure legal protections from second hand exposure to cigarette smoke for children and nonsmokers, especially those who work in restaurants and other smoky workplaces.
• Working with local and regional groups, we are developing educational materials for health professionals that clarify information about some of the cancer-causing chemicals that can be found at hazardous levels in consumer products as well as in cigarette smoke.
• Working with our partners at the Center for Minority Health at the Graduate School of Public Health, with the Collaborative on Health and the Environment, and with nonprofit groups throughout the nation, we are creating public educational materials to extend knowledge about these hazards and the simple things that can be done to reduce the risks that we and our families bear.

We understand that all cancer cannot be prevented. We also know that most cancer is not directly inherited from our parents. The Center for Environmental Oncology of University of Pittsburgh Cancer Institute is committed to educating the public and health professionals about ways to lower their risks of cancer by controlling exposure to tobacco smoke and other known and suspected cancer-causing agents in the environment.