We need to find out the facts of marijuana’s dangers

The greatest public-health disaster our species ever brought upon itself began in Europe 400 years ago — the introduction and use of tobacco.

In the 20th century alone, 100 million people died from cigarette smoking worldwide. And while the incidence rate has fallen in western countries, it remains high in Third World nations. Six million tobacco users still die each year.

The cause of smoking deaths is not, primarily, the active ingredient in tobacco — nicotine. Rather it is the chemicals that comprise tobacco smoke — among them various tars, ammonia, hydrogen cyanide and formaldehyde.

Collectively, these chemicals cause a host of fatal maladies, including cancer, heart disease and emphysema. In short, a perfect horror show.

Now at this point, you’re probably saying: Tell me something I didn’t know. Well, here it is: Many of those same chemicals form marijuana smoke, and we are about to legalize the consumption of this drug.

It’s not clear yet which forms of use might be authorized. If smoking is not among them, we might yet avoid another public-health calamity.

True, there are worrisome effects that come with consuming marijuana by other means, among them elevated pulse rates and memory loss. But these are minor matters, by comparison. However, if smoking marijuana is blessed for general use, we might have an entirely different situation on our hands. For here is what is currently known with medical certainty about the health impacts of lighting up a joint: Nothing.

Since marijuana is currently illegal in all but physician-approved circumstances, there have been no properly constructed clinical trials of smoking this drug.

For the same reason, there have been no robust after-market research projects, in which users are tracked down years later, and their health status compared with that of non-users. Yet this is an essential process in revealing whether drugs that appear safe at first blush turn out to have serious side-effects downstream.

There have been suggestions that marijuana might act as a gateway drug to such potent narcotics as heroin and fentanyl. But whether these are anecdotal or fact-based, no one really knows. There is also the matter of what is called the dose effect. Cigarettes have a high dose effect, meaning the risk of illness increases exponentially the more you consume. Hence the toxicology maxim: “The dose is the poison.”

So what is the dose effect of smoking marijuana? Again, we simply do not know and this is no small concern.

Generally speaking, it seems fair to assume that making an addictive substance more readily available will increase consumption rates. So what happens if people begin smoking 20 marijuana joints a day?

What happens if manufacturers find ways to strengthen the active ingredient — THC — while making their product less harsh? That’s what cigarette companies did.

In short, we are on the brink of approving a form of drug use, the medical consequences of which remain uncertain, but which might involve inhaling carcinogens.

You would think the history of tobacco might have taught us something about fooling with addictive substances before we know the facts. In particular, you might think we would have learned how difficult, if not impossible, it is to close a Pandora’s box like this after it has been opened.

Once a government-sanctioned infrastructure of production, marketing and distribution is erected around marijuana, and millions of additional users are recruited, there will be no going back, regardless of whatever medical verdict is finally rendered. That’s principally why we continue to license tobacco production, despite its many ills.

I recognize we already turn a blind eye to occasional or “recreational” use of marijuana. But between turning a blind eye and conferring on this drug an official stamp of approval lies a world of unknown harm.