In 1925, the surgeon Frederick Pybus compared the lungs of people who had been living in smoke-polluted Newcastle with those of people from the Northumbrian countryside. One set was clean and pink; the other black and cancerous – no prizes for guessing which was which. The results led Pybus to conduct lifelong research into the links between air pollution and cancers.
The medical establishment at the time was dismissive of the smoke theory, but the scientific tide eventually turned and in 2013 the World Health Organisation finally accepted his hypothesis that the carcinogens found in soot and diesel fumes were a cause of some cancers.
Why did Pybus’s work take nearly 90 years to be accepted? Some would say there is still not enough scientific evidence to be certain; others that pressure from the fossil fuel, pharmaceutical and nuclear industries, which have funded much of the research into the causes of cancer, have suppressed or muddied knowledge. And others say that the medical establishment has always lagged behind what most people instinctively know: that how we live and what we breathe determines our health.
Now comes a paper in the journal Nature from researchers at the Stony Brook university in New York, which suggests that 70-90% of all cancers are caused by environmental factors such as lifestyle, the food we eat, the air we breathe and the chemicals we are exposed to. Using computer modelling, population data, and analysis of patterns in mutations, they make the overwhelming case for our way of life being the primary cause of the disease that can be expected to afflict one in two people born after 1960. By extension, say the authors, cancers are within our control once the underlying environmental causes are identified.
But this research contradicts an opposing theory, which proposes that the disease is out of our hands, because it comes down to random mutations in DNA replication. In January, a report in the journal Science tried to explain why some tissues were millions of times more vulnerable to developing cancer than others. The explanation came down to the number of times a cell divides, which is out of our control. The authors showed, statistically, that perhaps only one-third of all cancers were due to environmental factors and inherited genes. By this argument, cancer is caused by a variety of factors but is basically a disease most people are bound to get eventually. Your luck may hold out for a while, but one cancer or another will get you in the end. The timing is completely random.
Both theories are highly political and even philosophical. The “bad luck” theory drives a stake into the heart of the liberal consensus, which has long argued that how we live defines our health. It proposes that prevention is not much use – we may as well cut straight to surgery. It feeds into similar, fatalistic, arguments proposed by climate sceptics – that there is little anyone can do so we may as well adapt to climate change because it’s too expensive to try to mitigate. The other suggests that humans are the architects of their own downfall and have the power of self-determination. We therefore have the possibility and the public duty to minimise the risk, and try to find a cure for cancer, and not just to treat it.
Pybus probably got it right. He understood that while coal smoke was carcinogenic, inherited defective genes could trigger cancer too. Yet long after his time the debate rages on and is unlikely to be concluded soon. What we do now know is that cancer is caused by the body’s own stem cells “going rogue” and dividing out of control. But whether these cancers are actually caused by intrinsic or extrinsic factors may never be decided.
As the scientists continue to slog it out, we can only learn to live with the disease of our times.
