Cell phones, cigarette smoke, radiation, asbestos, artificial sweeteners. The list of carcinogens (things that cause cancer) found in popular media goes on and on. Sure, we like to joke within the cancer research community that everything causes cancer, but that’s not actually true. Many things, such as cigarette smoke and UV radiation, are well-documented causers of cancer; other things, such as cell phones and artificial sweeteners, are victims of misinformation and sensationalism.
Let’s go back to the basics before we tackle the myths and facts of commonly evoked carcinogens. In order to become cancerous, a normal cell must undergo several changes first. Cancer cells have to be able to grow all the time; they need to be able to survive with low levels of food and oxygen; they need to be immortal. They acquire these changes when the cell’s DNA is altered, or mutated. Only after acquiring several of these mutations will a normal cell become truly “cancerous.” Our cells are constantly acquiring mutations, but normally there are “repairmen” in the cell whose job it is to notice mutations and fix them; if the mutation can’t be fixed, the repairmen call in exterminators who force the cell to undergo cell death.
There’s a fixed number of these repairmen in the cell whose job it is to monitor the integrity of your DNA. So what happens if the number of mutations in a cell skyrockets? The repairmen can handle only a certain number of mutations at a time, meaning that some mutations are bound to slip under the radar if there are too many mutations. A house with a leaky faucet or a broken latch on the window won’t come crashing down around you; similarly, a mutation here or there probably won’t cause the cell to become cancerous. But as the house falls into disrepair it eventually becomes unlivable, and a cell that acquires too many mutations can become cancerous if it evades death.
So back to carcinogens. Carcinogens work by damaging DNA or metabolic processes in the cell, thus increasing the workload a cell’s repairmen have to handle – and consequently increasing the odds that a cell could become cancerous. Known carcinogens include radiation from sunlight, tanning beds, X-rays, and radioactive materials; cigarette smoke inhaled directly or second-hand; air pollution; and significant exposure to asbestos. High alcohol consumption clearly increases the risk for several types of cancer beyond the commonly associated liver cancer. Hormones can also influence cancer risk: hormone therapy prescribed at menopause has been shown to increase drastically the risk of breast cancer in women (fortunately, it’s not recommended treatment anymore). In all of these cases, there is clear evidence that cancer is directly caused by exposure to the carcinogen. No such clear evidence exists for other popular “cancer-causing” buzzwords. Several rigorous studies have concluded that cell phones do not cause brain cancer, even though they emit small levels of radiation near the ear. The same is true of artificial sweeteners, which have not been linked to any increased risk for developing cancer.
This list only covers a sliver of the long list of carcinogens, most of which are less commonly encountered than those listed above. If you’re interested in what the rest of them are, they’re covered extensively here. I chose the handful of carcinogens above based on a quick survey of friends and an internet search of carcinogens in the news, so feel free to comment and let me know if there are any other truths or myths about carcinogens floating around that I neglected to address.
A final aside about cancer risk: lifestyle also has important ramifications. Consumption of red meats, eating fruits and vegetables, level of exercise, obesity, working nightshifts/sleeping during the day, and the age at which a woman has her first child can all influence one’s cancer risk, but that’s another post’s worth of information and will have to wait for another week.