A while ago I was reflecting on the toxic effects of tea and tobacco. Eight years ago today, there was an obituary in the Grauniad for Sir Richard Doll, who probably did more than anyone else to expose the damage that smoking did to the lungs and other soft parts of the anatomy exposed to the complex volatiles of burning vegetation. Doll lived to the age of 92, not least because he paid attention to his own epidemiological results and gave up the fags in 1950. The chaps who record cause of death in London had noticed a recent spike in deaths from lung cancer and Doll set off to find the cause - expecting it to be known carcinogens like soot or tarmac. The data (and Doll's statistical analysis) showed that these were innocent but that cigarette smoking was strongly associated with lung cancer.
He later led a huge study investigating the longevity and causes of death among 40,000 (!) doctors. This was large enough to quantify the effect, summarised as the number of years you clip off your life for the pleasure of a few gaspers. Give up early (before 30) and you'll live as long as anyone else, smoke till you're 60 and your life-expectancy will on average be 7 years less. He also brought his statistical guns to bear on nickel, asbestos and radiation and showed that these also are carcinogenic. He was also keenly aware of the dilemma faced by governments in relation to tobacco - taxes on tobacco are huge revenue earners and cigarettes kill people early so you don't have to pay out so much for pensions. So much, so heroic. He was doctoring on the beaches at Dunkirk in 1940 too.
I wrote in January about William McBride another mathematically competent statistical epidemiologist. He revealed the connexion between the drug thalidomide and birth defects from a sample that was much smaller than Doll's doctor-death study. So props to him. Later, however, McBride was so sure that another drug Debendox was similarly dangerous that he doctored his data to prove his idea.
So I note that the Cancer Prevention Coalition has long essay dissing Doll for being a pawn of the Multinationals and obsessed about smoking and cancer to the exclusion of all other possible causes. Read that and make your own mind up - it will require more than a couple of tweets worth of reading and research. CPC's Board of Directors. A list of the publications. Their parting shot at Doll:
"Faced with growing evidence of the scientific
untenability of his virtual dismissal of causes of cancer other
revelations of conflicts of interest, Doll has suddenly retracted
his long-standing dismissal of environmental causes of cancer."
I interpret this as - confronted with new data, Doll has changed his mind. Not a lot of people are capable of changing their mind about things that matter under any circumstances. Being able to do so is a key attribute of intellectual honesty and scientific ability.