What to believe? Try science. Instead of being caused by corporations, the overwhelmingly majority of cancerous mutations are caused by DNA. Most of the rest are caused by lifestyle choices, such as smoking or obesity. Only a small number can be traced to actual environmental factors, according to a numerical model based on DNA sequencing and epidemiological data from around the world.
This has long been known, but given the prevalence of "fake news" and "alternative facts" promoted by activists it has become confused. Instead, people who have no risk factors - they exercise, eat healthy and don't smoke - who have gotten cancer get lumped into whatever people are raising money for, everything from second-hand smoke (and even, strangely, third hand smoke) to BPA and epigenetics caused by something their grandparents ate.
In a 2015 study co-authored by two of the authors in Science, it was reported that DNA copying errors could explain why certain cancers in the U.S., such as those of the colon, occur more commonly than other cancers, such as brain cancer. This new model sought to estimate the fraction of mutations in cancer due to those DNA copying errors.
To answer this question, the scientists took a close look at the mutations that drive abnormal cell growth among 32 cancer types. They developed a new mathematical model using DNA sequencing data from The Cancer Genome Atlas and epidemiologic data from the Cancer Research UK database.
According to the researchers, it generally takes two or more critical gene mutations for cancer to occur. In a person, these mutations can be due to random DNA copying errors, the environment, or inherited genes. Knowing this, Tomasetti and Vogelstein used their mathematical model to show, for example, that when critical mutations in pancreatic cancers are added together, 77 percent of them are due to random DNA copying errors, 18 percent to environmental factors (such as smoking), and the remaining 5 percent to heredity.
In other cancer types, such as those of the prostate, brain, or bone, more than 95 percent of the mutations are due to random copying errors.
Lung cancer, they note, presents a different picture: 65 percent of all the mutations are due to environmental factors, mostly smoking, and 35 percent are due to DNA copying errors. Inherited factors are not known to play a role in lung cancers.
Looking across all 32 cancer types studied, the researchers estimate that 66 percent of cancer mutations result from copying errors, 29 percent can be attributed to lifestyle or environmental factors, and the remaining 5 percent are inherited.
The scientists say their approach is akin to attempts to sort out why "typos" occur when typing a 20-volume book: being tired while typing, which represents environmental exposures; a stuck or missing key in the keyboard, which represent inherited factors; and other typographical errors that randomly occur, which represent DNA copying errors.