The Rise and Fall of Modern Medicine (48 page)

Nonetheless, this notion that most cancers, not just those of the lung, might be ‘preventable' had enormous appeal, especially for policy-makers and legislators apprehensive at the escalating costs of health care. In the late 1970s, they approached Sir Richard to produce a much more detailed review, duly published in 1981 as
The Causes of Cancer
, in which he makes the claim that, excluding tobacco, food causes 70 per cent of cases of cancer.
³⁵

The Causes of Cancer
is an impressive document, with an abundance of graphs and statistics, hundreds of references and no less than five appendices. The crucial argument centres on a comparison between the rates of specific cancers as recorded in the Connecticut Cancer Registry and the lowest recorded incidence of the same cancers elsewhere in the world. There are 60.2 cases per million of cancer of the pancreas in Connecticut, compared to 21 per million in India; presumably ‘something' explains the difference. What could it be other than the fact that the citizens of Connecticut eat different sorts of food from the inhabitants of the Indian subcontinent? And that, astonishingly, is all there is to it.

The Causes of Cancer
may look impressive, but appearances can be deceptive. The intellectual rigour required by Sir Richard Doll's mentor, Sir Austin Bradford Hill, for assessing the coherence of any hypothesised relationship between an environmental factor and disease – such as food and cancer – is conspicuous only by its absence. Thus the distinguishing feature between the Western diet, as eaten in Connecticut, and that of other countries, such as India, is the relatively high consumption of
meat and dairy products. Hence cancers common in the West, such as those of the breast, colon and pancreas, are attributed to a ‘high-fat' diet. True or false? The Mormons and Seventh-Day Adventists are identical in virtually every way: they lead sober lives, don't smoke or drink and go to church on Sundays. The only difference is that the Mormons eat meat and the Seventh-Day Adventists on the whole are vegetarians. If the ‘high-fat' diet explanation for cancer was valid, then the meat-eating Mormons must
by definition
have a higher incidence of these cancers than the Seventh-Day Adventists. But they do not. Such an important observation in the context of a report in which diet is strongly incriminated in cancer requires serious consideration. There is none.
³⁶

But this omission fades into insignificance when compared to the manner in which Sir Richard Doll deals with the relationship between cancer and ageing. As pointed out, the likelihood of cancer is strongly age-determined, with an eighty-year-old having a thousand times greater risk compared to when he was a teenager. This is
fifty times greater
than the twenty-fold increased risk of lung cancer in the smoker compared to the non-smoker.
³⁷

Ageing must therefore be right at the top of the list of ‘causes of cancer', but Sir Richard dismisses it in the following manner: ‘It is sometimes argued that because cancer is ten or a hundred times more likely to occur in the old rather than the young then ageing per se might be thought of as an important determinant of cancer. We rather doubt whether this viewpoint is a scientifically fruitful one . . . ' On the contrary it is scientifically very fruitful, for recognising the primacy of ageing as a powerful determinant of cancer is essential if one is not to fall into the trap of generating false notions about what else might be the cause.

Sir Richard Doll subsequently conceded the weaknesses of
The Causes of Cancer
but never publicly retracted his conclusions, and his claim that he had ‘proved that food caused more than a third of cancers' was repeatedly cited by all those who had an interest – nutritionists, health educationists, food fanatics and others – in incriminating the Western diet as a major cause of death and disease. And so it was that without the slightest hint of irony the Chief Medical Officer in 1998 advised that the recommended ‘safe' level of meat consumption for those wishing to avoid cancer should be raised from two lamb chops (or its equivalent) per day to three. Medical advice had become indistinguishable from quackery.

Those who may find it difficult to take seriously the proposition that the number of lamb chops they eat a day might influence the risk of getting cancer or heart disease must look elsewhere for ‘causes'. The obvious other culprits are ‘environmental' – the minuscule quantities of chemicals present in the air and water. At the beginning of the 1980s there was something of a turf war between these two contending theories, with the dietary protagonists such as Sir Richard Doll accusing (a bit richly perhaps) the environmentalists of ‘bias, exaggeration and lack of balance'.
³⁸
From the environmentalist camp Professor Samuel Epstein of the University of Illinois responded with the ‘
tu quoque
' argument: ‘The scant scientific evidence for the dietary theory is contradicted by a substantial body of published evidence.'
³⁹
There turned out to be room for both explanations and, over the next fifteen years, the public were exposed to a double whammy of health fears, with those of Sir Richard Doll's camp warning that bacon and eggs for breakfast were the culprits in heart attack, strokes and cancer, and those of Professor Epstein's persuasion arguing that chemicals and radiation were responsible for everything else: electricity pylons were implicated in leukaemia, hormonal chemicals in falling sperm counts and testicular cancer, and pesticides, mobile phones and even sewing machines in many other types.

The concern that environmental pollution might pose a threat to health started in 1962 with the publication of Rachel Carson's
Silent Spring
. The children of future generations, Carson argued, would never again hear the sound of birdsong
in spring because pesticides thinned the shells of their eggs, resulting in a precipitous fall in their numbers. Carson's claims were at least partially vindicated, and following instructions on pesticide use the threat of a ‘silent spring' was averted. This episode was so powerful a pointer to the possible harm of man-made chemicals that, inevitably, the question arose as to the dangers they might pose to human health. It certainly seems plausible enough that pesticides might be responsible for several diseases for which there is as yet no satisfactory explanation, including falling sperm counts which, if true, would mean that not just birds, but the human species, could soon be facing extinction.
⁴⁰

It is, of course, only sensible that the amounts of chemicals in the environment should be kept to the irreducible minimum, but the issue to be examined here is quite specific. Environmental pollution certainly posed a significant threat to health in the nineteenth century, when the all too readily detectable pollution of our great industrial cities, with their stinking canals and rat-infested tenements, limited the average lifespan to little more than forty years. It certainly can matter in situations of high exposure, as experienced by workers in the asbestos industry or following major catastrophes such as the Bhopal accident in India that killed 2,000 people. The question rather is whether, at the concentrations of these chemicals to which the general public is exposed – measured in parts per billion – they are injurious to health.

Many believe they are, including leading academics in Britain and America. Thus in a discussion on the effects of water pollution, Professor Howard Hu of Harvard University observes: ‘The threat to health from water contamination remains high,' and goes on to cite examples – traces of arsenic could cause cancer ‘in significant numbers'; nitrate residues from fertilisers
have been linked to stomach cancer; pesticides have been linked with breast cancer; halogenated solvents ‘with childhood leukaemia'; and so on. It certainly sounds scary enough, and this is just water pollution. Parallel litanies of hidden dangers apply to air pollution, food contamination and radiation.
⁴¹

It should not be supposed that any of these allegations is scientifically proven for, as can be imagined, it is simply not possible to conduct the required experiments of exposing large numbers of people for long enough to any pollutant in the minuscule quantities that are present in air and water to detect whether it is indeed harmful. Rather, the argument rests almost entirely on extrapolation from the consequences of high levels of exposure or toxicology tests in rodents. Certainly these chemicals in high doses can have adverse effects in rats, and so, the argument goes, even at a millionth of the dose they might, theoretically, adversely affect one in a million people.

The central assumption here, crucial to the environmental case, is that there is no ‘threshold' of exposure below which even a scarcely measurable pollutant in the air or water can still be harmful to health. This ‘no threshold' concept is best understood by analogy for, if it were correct, it would mean that not only the person drinking a bottle of whisky a day for five years is likely to damage his liver but also someone eating an alcohol-flavoured Christmas cake once a year for thirty years. This would seem unlikely and is contrary to the fundamental axiom expressed by the great French scientist Claude Bernard in the mid-nineteenth century: ‘
Tout est poison, rien n'est poison, tout est une question de dose
' – everything is poisonous, nothing is poisonous, it is all a matter of dose.
⁴²

It is clearly impossible to evaluate each and every alleged environmental threat to health. Some, such as global warming and the threat to the ozone layer from CFCs, are theoretical, in
that the putative harmful consequences have not yet occurred. Clearly no definitive verdict, one way or another, can be given on such predictions, and they will not be considered further. The focus rather is on the claims of those like Professor Hu who maintain that pollutants are responsible for contemporary health problems in the Western world.

It is customary to test the safety of chemicals such as synthetic pesticides, minuscule doses of which may be present in fruit and vegetables, by exposing experimental animals (such as rats) to the Maximum Tolerated Dose (MTD), and if a substantial number develop cancer, the chemical could possibly be carcinogenic in humans. Now, vegetables and fruit – such as bananas – produce their own ‘natural' pesticides to discourage bugs and weevils and other small creatures who might wish to eat them. In the mid-1980s an eminent toxicologist, Dr Bruce Ames of the University of California, decided to test these ‘natural' pesticides in precisely the same way as synthetic pesticides by giving the Maximum Tolerated Dose to rats. He discovered, to his surprise, that half of these naturally occurring ‘pesticides' were similarly carcinogenic:

Dr Ames then calculated the average amount of these allegedly ‘carcinogenic' natural pesticides people consume in fruit and vegetables to be 1,500mg a day, compared to only 0.09mg per day of synthetic chemical pesticides. Hence 99.9 per cent of the ‘carcinogenic pesticides' to which we are exposed come from annis, apple, apricot, banana, etc., so presumably the 0.01 per cent from man-made pesticides is unlikely to do much harm. Dr Ames's calculation points to the crucial weakness of the environmentalist argument. Every mouthful of food we eat contains thousands of different ‘natural' chemicals in amounts greater by orders of magnitude than any man-made chemicals we might be exposed to; thus, when evaluating the potential of any such chemical to be harmful, its effects have to be viewed against the background of this much greater quantity of ‘natural' chemicals that have similar biological effects.

The point is well illustrated by the claim, already alluded to, that the human species faces extinction from falling sperm counts. When in 1995 it appeared that sperm counts were falling in Western Europe, environmentalists claimed the culprit to be chemical residues of PCBs (used in the manufacture of plastics) in the water supply, on the grounds that they have biological properties similar to the female hormone oestrogen and are thus likely to depress sperm development. Now there are around forty types of vegetables that also contain small amounts of ‘natural' oestrogens, including garlic, pineapple, cabbage, coffee, carrots, fennel, olive oil, rice, potatoes and corn. Predictably the average daily consumption of these ‘natural' oestrogens is enormously greater than the amount of oestrogenic PCB residues in drinking water which constitute an infinitesimal 0.00000025 percent
of the total. Hence ‘the suggestion that they contribute to male reproductive problems, such as low sperm counts, is not plausible'. The sensationalist claim that ‘feminising chemicals' were threatening the survival of the human race simply cannot be true. Some other explanation must be found for the decline in sperm counts, if indeed they are declining.
⁴⁴

Precisely the same type of calculation applies to
all
the allegedly harmful chemicals on which Professor Hu based his claim that ‘the threat to health from water contamination remains high'. Similar arguments apply to allegations about the dangers of radiation. Thus, in the early 1980s, the link was easily made between the cluster of leukaemia cases in west Cumbria and the nearby nuclear reprocessing plant in Sellafield. But the levels of radiation exposure from the plant are only a small fraction of the ‘natural' background radiation (from, for example, granite) to which everyone is exposed, which is itself only a minute fraction of the level of radiation exposure necessary to cause leukaemia. Indeed, radiation discharges from Sellafield would have to have been 400 times greater than those recorded by the National Radiological Protection Board to have caused leukaemia in children in the vicinity. Clearly, Sellafield cannot be the culprit and there must be (as will be seen in the next chapter) some other explanation.
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