Monday, October 31, 2005

A little honesty in secondhand smoke statistics . . . please

Posted by Craig Westover | 12:19 PM |  

One of the statistics I've asked Bob Moffitt of the American Lung Association to defend, a challenge he has consistently avoided, is "3,000 annual deaths from lung cancer due to secondhand smoke." Bob has not produced a study supporting that number, nor has he stated how this number is arrived at. I got tied of waiting, so I did the research myself -- in the interest of accuracy, somebody has to understand what Bob himself can't articulate.

The first fact, which Bob should have known off the top of his head, is that there is a standard formula used in assumption of risk calculations. Unfortunately for Bob, it is based on the concept of "relative risk," which Bob has referred to a "scientific minutia." For stat freaks the equation is

R(dE) = (1 + Z * ßdN)/(1 + ßdN)

where R(dE) is the relative risk for the group of never-smokers identified as “exposed” to spousal ETS (plus background ETS) compared with the group identified as “unexposed” (but actually exposed to background ETS). Z is the ratio between the operative mean dose level in the exposed group, dE, and the mean dose level in the unexposed group, dN. ß is the amount of increased risk per unit dose.

Now I frankly admit I’m not 100 percent sure I understand all that -- Bob is the professional and this is his business, so I’m sure he can explain it -- but I understand enough to know that in simple terms, the equation says you apply the relative risk factor to the affected population to determine what percent of the affected population is the result of exposure to the factor you are testing.

Now, here comes the interesting part. Remember, Bob and other smoking ban proponents have always state the statistic as "3,000 deaths" without any reference to the affected population referenced, which leaves the impression that the statistic refers to a random group that puts everybody or anybody at risk. This is not the case.

The 3,000 figure comes from a study (quoted here, Chapter 7) of lung cancer rates in non-smoking spouses of smoking spouses. In other words, assuming the study methodology is valid, what the 3,000 number indicates is that lung cancer deaths for 3,000 non-smoking spouses might be correlated to secondhand smoke.

I use the words “might be” because the “odds ratio” determined by the study is 1.25. Statistically, a calculation greater than 1 indicates correlation, but that calculation must be in the 3-4 range before definite causality can be assumed.

Nonetheless, for sake of argument let’s assume causality at 1.25. The spousal study findings have no relevance to the policy question of a smoking ban in bars and restaurants. The study might support government going into private homes and preventing smoking, but the limits of extrapolation of this data is to non-smoking spouses of smokers. It has virtually no impact on the health of restaurant patrons or employees.

If Bob were doing his job, he’d be spending is time educating smokers about the danger they pose to their spouse, not trying to borrow the power of government to impose smoking bans in bars and restaurants. But I digress.

At this point, what Bob might say if he were inclined to actually debate his case rather than simply state it, is that if secondhand smoke is dangerous to non-smoking spouses, then it must also be dangerous to bar employees as well. Fair question. So let's go back to the study data. (I’m only using data in the report itself, no outside information to show the internal inconsistencies in Bob’s positions.)

Using data from the same study, applying the same statistical risk ratio analysis that is used to arrive at the 3,000 death number (which Bob agrees with), the data shows no statistical correlation between secondhand smoke and lung cancer in non-smoking spouses until 31 years of exposure. And then the risk is as low as a 1 percent increase in risk, a 51 percent increase in risk on the high side of the confidence interval.

In other words, a study that supports Bob's contention that exposure to secondhand smoke over time can increase the risk of lung cancer also invalidates his claim that there is no safe level of exposure to secondhand smoke. The study data supports the unquestioned, except by Bob, scientific notion of “threshold dosage” -- that most any chemical is not harmful at some level (every person has trace amounts of arsenic in their systems) and deadly at some threshold level.

Although certainly not healthy for a person, secondhand smoke, in the extreme case where a non-smoker is living with a smoker, requires 31 years of exposure to create a very modest increase in risk for lung cancer.

How does this analysis apply to the workplace -- the area where Bob wants government to step in and trump property rights, individual choice and if some entrepreneurial small business goes down, so be it?

According to the California EPA Study: "Proposed Identification of Environmental Tobacco Smoke as a Toxic Air Contaminant," a study done by “big government,” not “big tobacco,” there is no statistically significant risk of lung cancer from secondhand smoke exposure in the work place until the duration of exposure reaches 21 years. For exposure less than eight years, there is no statistical correlation between secondhand smoke and lung cancer.

Of course, the report does not make that statement, but that is what the data compiled in Table 7.2A illustrates.

This is where the government policy, criteria for public health regulation comes into play -- the context for smoking ban imposition that Bob also refuses to discuss. Bob and his ilk want government to impose smoking bans to protect bar employees that are, as shown by the California EPA study, at no statistical risk for lung cancer until they have been exposed to secondhand smoke for 21 years. And then, similar to the statistics for spousal exposure, the risk is only 3 to 51 percent greater than the unexposed population.

Might one not assume that a person that elects to work in the hospitality industry for 21 yeas has made the choice to accept that risk? One might ask here what the turnover rate is in the bar business. Smoking ban proponents use college students working in bars as examples of the people they want to protect. Data from this study shows that they are not at risk.

Might one not also assume that if Bob were doing his job educating people about the true dangers of secondhand smoke, not using exaggerated scare tactics to influence government policy, a person working in the hospitality industry might have regular medical check-ups to further mitigate the risk? But I digress again.

I’ve focused this discussion on lung cancer because of all health problems associated with secondhand smoke, this is the methodologically cleanest and also best supports Bob’s position. For example, looking at the same data analysis for “all cancers,” the study shows that one must be exposed to secondhand smoke for more than 39 years to reach a level of statistically significant risk from secondhand smoke.

Again, the California EPA study supports Bob's primary contention that exposure to secondhand smoke can, over time, increase the likelihood of health problems. However, from a government policy perspective, the data simply does not support a smoking ban as the best policy solution. The data does not support elevating secondhand smoke in bars and restaurants to a public health issue that requires government intervention.

The California EPA study is a wealth of information and a microcosm of tobacco research. The raw data of the study is not much different than that found in any study done by independent researches or researchers associated with tobacco companies (aside from a few statistical tricks by the EPA that really don't alter the findings significantly, but certainly reveal the bias). But when it comes to analysis (assuming a risk factor of 1.25 equates to causality, for example) and drawing subjective conclusions, the EPA study drifts off into Moffittland and makes policy recommendations that are simply not supported by the data.

The California EPA study is one Bob ought to be able to support, explain, defend and whatever. It's done by "his people." A professional communicator would latch onto it, and be prepared to summarize it and defend it and hopefully at least read it -- although it is long, the carcinogenic section alone is 226 pages and has math. I truly regret that Bob is unable or won’t comment on this or any other study in any meaningful way. I readily admit there is “minutia” in it I don’t understand. It would be nice if just one professional communicator from a health organization would take the time to explain data rather than just spit misleading and meaningless statistics.

Category: Public Health, Smoking Ban