March mailbag: Physically fit adults and carcinogens in marijuana

It's time once again for a peek into the PolitiFact Rhode Island's mailbag to look at some of the reactions we've gotten from readers to recent fact checks.

After we gave a True to the statement by author Bing West that 75% of young adults in the United States are not mentally or physically fit to serve in the military, we heard from Gary Brownell, of North Kingstown, who said we were missing important context.

"PolitiFact should have looked back at the times we have used the draft (for example, World War II and Vietnam) to determine what percentage of young people would have been fit for duty back then, using today's standards. Then they could have followed that up to see what percentage of people called up for the draft were rejected," he wrote.

"Having come of draft age during Vietnam, I can tell you that it certainly didn't seem to us at the time that you had a 75 percent chance of being rejected," said Brownell. "In fact, when I took my draft physical, I was totally inebriated for the mental test portion, and still I passed. The real question should be, 'What percentage of people would qualify for being drafted,' not what percentage of people are qualified to be soldiers without having gone through any training, etc."

Justin Strong of Berlin, Germany, wanted to know if women were included in the statistic. "It would be useful to know if a progressive gender-neutral draft is implied, or a male only draft, since this may impact the percentage a great deal," he wrote.

The analysis included all young adults, not just men.

After we gave a Mostly False to the assertion that "marijuana contains 50 to 70 percent more carcinogenic hydrocarbons than tobacco," Kathy Melvin, a member of the Portsmouth Coalition Against Drugs took us to task.

"I read your article carefully, and don't believe you made the case that marijuana isn't more of a carcinogen problem than tobacco, so your ruling came across as a tip of the hat toward passage of legalizing marijuana," she wrote. "Shame on you."

We were looking at the percentage of carcinogens, noting that there was no good evidence that marijuana smoking increased lung cancer risk, for whatever reason.

But another reader said we should have looked at a study, published in 2013, that tracked people in Sweden. It found that heavy marijuana smokers appeared to double their risk of lung cancer, even after statistically adjusting for whether the marijuana smokers also smoked tobacco. It followed more than 49,000 men conscripted into the Swedish military from 1969 to 1970.

The chief author, Russ Callaghan, an associate professor at the University of Northern British Columbia, said the study suggests that marijuana might pose a lung cancer problem, but doesn't prove it. The best answer will come from tracking people who just smoke marijuana.

"But those kinds of studies are so difficult to do because many marijuana users are also tobacco users," Callaghan said. "That's the biggest limitation of the current literature. Most of the long-term studies have major problems, including my own."

It's the same problem scientists faced in the 1950s and 1960s when they were trying to assess the cancer risk from tobacco smoking, he said.

Keep the feedback coming. And we're always interested in hearing suggestions from readers on interesting facts to check.