The breast cancer threat is overstated. Even if we are correct that inhaling secondhand tobacco smoke leads to higher breast cancer rates in women, we should still take this into account: The risk of getting cancer generally increases with age. This shouldn’t surprise anyone who knows anything about cancer risk. Between the ages of 20 and 25, there is a 76 percent greater risk for women, and between the ages of 50 and 60, there is a 74 percent greater risk for women. So, while it’s very true that smoking can raise the risk of breast cancer, it is not true that smoking causes breast cancer.

Theoretically, only three things can cause cancer: smoking, radiation from the sun and birth defects. All three occur more often in women than in men, and in pregnant women, radiation from the sun is the overwhelming cause of cancer. From 1975 to 1977, for instance, yearly averages of the sun’s harmful rays varied from 10 to 25 percent. Smoking produces nicotine, which is a vasoconstrictor, meaning that it prevents blood vessels from growing in an acidic way, making them less vulnerable to water buildup, damage, and so on. But the chemical components of nicotine are a bit ambiguous. In fact, in a recent meta-analysis, these chemical components were identified as having a less-than-1 percent to 6 percent risk of breast cancer, depending on the formulation. While nicotine is certainly a vasoconstrictor, it does not confound it to the same degree as other vasoconstrictors.

In this context, the pronouncement that nicotine alone causes breast cancer is meaningless. If the term “smoking” seems to carry much weight, the view that the most important ingredient in it causes cancer, then we may have got something else wrong.