The nation's largest tobacco companies recently released a closely guarded list of nearly 600 chemicals used as additives in processing and flavoring cigarettes. Release of the list gained widespread media attention, and a newly hatched debate on the harm these ingredients pose.
Ironically, with the disclosure of this information and the public's subsequent focus on it, the dangers of inherent, non-additive toxins in tobacco smoke are being overshadowed. Whatever health threat might be posed by these additives, the toxic "soup" in cigarette smoke already is well established.
Cigarette smoke contains potent carcinogenic environmental hazards, including benzene, formaldehyde, hydrazine, and vinyl chloride. The smoke inhaled contains many of these toxins at levels hundreds, even thousands of times what the government allows in workplace air.
I consulted Michael Trush, Ph.D., associate professor, Department and Center of Environmental Health Sciences, the Johns Hopkins School of Hygiene and Public Health, who is a biochemical toxicologist studying mechanisms of toxicity of environmental agents.
Q: Does this recent news detract from smoking's known dangers?
A: From a public health perspective, it's important to keep
focused on theestablished toxins in tobacco, which are still more toxic than any of the additives used. Two examples are benzene and lead. Benzene, which causes leukemia, now is recirculated in gas pumps, to keep it out of the air, yet it's breathed in anyway, via cigarettes. Lead was removed from gasoline and paint, but it's inhaled through smoking. As a nation, we spend billions to regulate these and other chemicals, but we're directly exposed to them through smoking.
Q: Is inhaling an important route of exposure for these chemicals?
A: From the environmental and occupational studies that have been conducted, inhalation has been found to be a major route of exposure for many of the identified toxins found in cigarette smoke. An unknown is whether some of the additives used in processing and flavoring cigarettes also would be toxic by the inhalation route of exposure.
Q: What about the long-term effects of inhaling these toxins in cigarette smoke?
A: The long-term health effects go beyond cancer. Carcinogens are also mutagens (gene-mutating agents). Cardiovascular damage, altered reproduction capabilities, and fetal abnormalities, to name just three examples, are all possibilities from long-term toxin exposure.
The long-term effects of many cigarette carcinogens still are being studied; the key is smokers are exposed to continuous low doses, over long periods of time.
Q: Does a toxin's potency differ with body weight; are women more at risk than men?
A: Body weight and hormonal status can be determinants of how chemicals persist and interact in the body. However, it seems that an individual's ability to process and metabolize these chemicals to reactive form is more important than a person's gender or body weight.
This metabolic activity varies widely between people and the sexes. Some cigarette smoke chemicals can actually induce the body's enzymes to metabolize toxins.
Other toxins are "direct acting," and don't need to be metabolized to cause damage. Lead, for example, directly alters iron metabolism in the body, and can be mobilized from bone stores in women during pregnancy and aging.
The emerging technologies of biomarkers and molecular epidemiology, which can be used to track evidence of exposure and changes in the body, will help determine an individual's susceptibilities to toxins.
Dr. Genevieve Matanoski is a physician and epidemiologist at the Johns Hopkins School of Hygiene and Public Health. She is a founding director of the school's Institute for Women's Health Research and Policy.