On this blog, I’ve pretty consistently made the point that small doses of second-hand smoke are basically harmless. The studies that claim otherwise — particularly of the “city bans public smoking, sees death drop precipitously in six months” variety — have been pretty ridiculous.

However, I’d always had the impression that the research said something. The logical deduction was that people who lived with smokers probably really did increase their risks.

I still believe that’s the case (more on why later), but one expert thinks there’s no evidence it is, according to this Washington Post op-ed.

First off, the author’s bio, lest readers think he’s some hack:

“Gio Batta Gori, an epidemiologist and toxicologist, is a fellow of the Health Policy Center in Bethesda. He is a former deputy director of the National Cancer Institute’s Division of Cancer Cause and Prevention, and he received the U.S. Public Health Service Superior Service Award in 1976 for his efforts to define less hazardous cigarettes.”

Here’s how he says anti-second-hand smoke studies work:

“Typically, the studies asked 60-70 year-old self-declared nonsmokers to recall how many cigarettes, cigars or pipes might have been smoked in their presence during their lifetimes, how thick the smoke might have been in the rooms, whether the windows were open, and similar vagaries. Obtained mostly during brief phone interviews, answers were then recorded as precise measures of lifetime individual exposures.”

He points out the obvious problem: Non-smokers with cancer will be prone to report higher levels of second-hand smoke, whether or not they experienced it. The power of suggestion is strong in survey research.

Nonetheless — and most surprising:

“[R]esults are not consistently reproducible. The majority of studies do not report a statistically significant change in risk from secondhand smoke exposure, some studies show an increase in risk, and astoundingly, some show a reduction of risk.”

In other words, these second-hand smoke studies are garbage, and some even suggest the impossibility that inhaling toxins is good for you.

But — a major but — there’s an easy way to get around the problems mentioned: Look only at non-smokers who live with smokers. This won’t speak to very minor second-hand smoke (say, oh, in bars and restaurants), but it will show whether massive amounts can hurt.

According to the National Institutes of Health:

“Nonsmokers who live or work with smokers experience a 30 to 50 percent elevated risk for lung cancer.”

Still, I think the op-ed demolishes the notion that minor smoke inhalation is a significant cancer cause. I wonder if Nancy Pelosi will change her policy.

Robert VerBruggen blogs at http://www.therationale.com.