An email correspondent became interested in the question of whether there is any clinical proof that tobacco smoke causes lung cancer in animals. He sent an inquiry to the American Cancer Society and received this response:

"Thank you for contacting your American Cancer Society. My name is [name deleted to protect the guilty], and I will be assisting you.

In response to your inquiry, the following information was provided by a nurse in our e-mail center. Hopefully, the information will be helpful in addressing your questions.

In answer to your question on studies that have produced lung tumors in rats exposed to tobacco smoke, the following citations may be helpful to you. It can take many years for cancer to develop in response to exposure to carcinogens. Most research studies are time limited. In reviewing the scientific literature, we found that some studies lasted for only a few weeks while others extended to two years. You may access abstracts for these studies from a Medline search at Pub Med (www.ncbi.nlm.nih.gov/PubMed) by doing a Citation Matcher search."

There followed about a dozen citations to old papers, but I've snipped them because, except for one, which I will discuss, they are all old studies, already discussed in my book, which failed to produce any lung cancers. Note well, however, that the Cancer Society anticipated these failures. In their opening caveat, they suggested that while all of the studies may have failed, they would have surely succeeded if the experiments had just kept up the good work a little longer. They didn't even mention Auerbach's study of the Beagles; he has been discredited as a fraud, a charlatan and a sadist, long ago.

There was, however, a reference to a paper by H. Witschi, published at Experimental Lung Research 1998 July-Aug; 24(4): 385-94 and entitled "Tobacco Smoke as a mouse lung carcinogen". I pulled the abstract from Med Line [it is *never* possible to get the entire article; they apparently don't want you to know too many details, lest they become the subject of ridicule].

According to the abstract, "Male and female strain A/J mice were exposed to environmental tobacco smoke that was generated by burning Kentucky 1R4F reference cigarettes. Exposures lasted 6 hours per day, 5 days per week, for a total of 5 months, followed by a 4-month recovery period in air. Chamber concentrations of total suspended particulate matter (TSP) ranged from 50 to 90 mg/m3. Under these conditions, the average lung tumor multiplicity was 1.2 to 1.4 tumors per lung, significantly higher (p<0.05) than in concomitant controls..."

I have often written that fame and fortune and a Nobel Prize await the first person to induce lung cancer in an experimental animal from exposure to tobacco smoke. Yet, we have heard nothing about Witschi in the popular press, and his paper appeared only in a relatively obscure Journal, and has so far been ignored by the JAMA and the New England Journal of Medicine. Why?

Well, because of those words "strain A/J mice". A/J mice, you see, are mice similar to the F344 rats, i.e.; they are mice especially bred to develop lung cancer. Unless it has the misfortune to be prematurely terminated by some researcher's scalpel, every A/J mouse will eventually die either with, or from lung cancer. Witschi, a researcher at the University of California (Davis) is reported in the abstract as concluding that "The strain A/J lung tumor model is...suitable to study questions associated with tobacco smoke toxicity and carcinogenicity". Actually, nothing could be further from the truth!

Studies done on specially bred rats and mice who always develop lung cancer are as worthless as the old studies on "nude mice" who develop skin cancer when painted with tobacco tars but also develop skin cancers when painted with all sorts of substances, ranging from mustard to tomato juice.

In this month's issue of Life Extension magazine, there's article about DHEA, a hormone which people can take to improve muscle mass and libido. In the article, we are told that in healthy people, DHEA appears to prevent prostate cancer. In people who already have prostate cancer, however, DHEA can be deadly; it can promote rapid growth of the cancer and rapid death of the victim.

The same is true of the supplemental testosterone, used by many older men. The manufacturer's warnings that accompany testosterone patches explain that, on the basis of animal studies, it is perfectly safe for healthy people to use them; that they won't cause any sort of cancer. In people who already have prostate cancer, however, they have the effect of promoting rapid growth of the cancer.

Thus, we have a paradox: substances, which are perfectly safe and beneficial in normal, healthy animals and people, may be deadly when administered to cancer victims. For this reason, standing alone, experiments on animals that already have cancer yield no useful information concerning the etiology of cancer in normal, healthy animals.

But that's not all that's wrong with Witschi's experiment. His controls, apparently, breathed ordinary air. That's like comparing a nude mouse whose skin has not been painted with a nude mouse that has been painted with some substance. It's comparing apples with oranges. Here, you have a group of mice living in a normal environment compared with mice living in closed cabinets, subject to noisy fans spewing out a perpetual haze of smoke.

For the experiment to have any meaning at all, the controls also need to be living in noisy, closed cabinets, in an atmosphere laced with particulates. To do that, you could grind up pumice or talc or some other similar substance to the same particle size as the particles in tobacco smoke, and lace the air with these particles. But there is no evidence that this was done.

So, Witschi's experiment doesn't change anything. Nobody has yet been able to induce lung cancer in an experimental animal by exposing the animal to tobacco smoke (or, for that matter, to any other substance). At best, the experiment demonstrates that in animals who already have lung cancer, exposure to particulates may result in an increase in the number of tumors that develop. But even if that is conceded, there's no reason to think that the same result wouldn't occur if the animals were exposed to particulates, which had no relationship to tobacco smoke.

Lauren Colby

(Reprinted with permission from the author)