Lies, damn lies, and category 1 carcinogens

The World Health Organization recently placed processed meat in category 1 of carcinogens, along with radioactive elements and asbestos. That’s the list of agents “carcinogenic to humans.” They also placed red meat in 2A which includes Glyphosate (Roundup) and lead compounds which are merely “probably carcinogenic to humans.”

bacon

Is eating bacon more likely to cause cancer than exposure to an herbicide? No. Agents aren’t listed according to risk. The criterion used is: do they or do they not cause cancer. The categories are grouped by experts according to certainty from the most evident all the way down to category 4, “Probably not carcinogenic to humans” of which there is one item, Caprolactam (used to make nylon).

Risk is determined by how much you are exposed to the carcinogen. André Picard, public health reporter for the Globe and Mail explains:

“The expert group does hazard identification, not risk assessment. Practically, that means they determine, yes or no, whether something may cause cancer, but not how potent it is at a causing cancer,” and adds, “It’s important to remember, however, that not every exposure to a potential carcinogen will cause cancer: Frequency, intensity and potency matter.”

All agents in a category don’t carry the same risk. If they did, people would be dropping like flies from eating meat. Compared to other items, they are not.

Eating processed meat and smoking tobacco, both in category 1, don’t have the same mortality rate. Processed meats result in 34,000 deaths worldwide annually whereas smoking causes about one million cancer deaths. Also in category 1, asbestos kills more than 100,000 and alcohol causes 600,000 cancer deaths a year.

Also misleading is the way percentages are used to translate statistics. For example, two slices of bacon are reported to increase your risk of colorectal cancer by 18 per cent. Eating a 4 ounce steak will result in a similar increase. But when risks of colorectal cancer are low to begin with, a small percentage increase of a small risk is still a small risk. The actual numbers expose this fallacy, explains Pickard:

“Based on these estimates, about 66 in every 1,000 people who eat a lot of red meat or processed meat will develop colorectal cancer in their lifetime; by comparison, 56 of every 1,000 who eat very little meat, processed or otherwise, will develop colorectal cancer.”

In other words, the increased risk is 10 out of 1,000. If you are one of those 10 persons who acquire cancer from eating meat, it’s tragic but as a risk assessment it’s not that bad.

Risk assessment is complicated by the toxicity of the agent, the amount of the agent you are exposed to, the length of time exposed to it, the way you are exposed (inhaled, ingested, topically applied), and your genetics.

The categories are useful in determining what to avoid, if possible. But some things are almost unavoidable. Like living: walking in the sun (ultraviolet rays), working (painter, hairdressers and shift-workers), eating (barbequing at high temperatures), camping (wood smoke), and travelling (cosmic rays from flying in a plane, breathing vehicle exhaust).

Unavoidable, like being alive: the naturally produced hormone estrogen has been linked with cancer, especially when combined with the artificial hormone progestin.

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