LIVING DOWNSTREAM

This remarkable book about cancer and the environment extends Rachel Carson's earlier work that culminated in her epoch-making Silent Spring. Carson herself died of breast cancer in 1964, with two further books on the stocks - an inestimable loss to the field. In a submission before a US Senate subcommittee during the last year of her life, Carson asserted that the problems addressed in her book were one piece of a larger story, 'the threat to human health created by reckless pollution of the living world'. It is this issue that is taken up by Steingraber in relation to cancer incidence. She herself is a poet and professor of biology, who was diagnosed with bladder cancer at the age of 20, while her mother first suffered from breast cancer at 44? Inherited? Probably not, as the book explains at great length.

Carson contended in 1962 that 'we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons, without their consent and often without their knowledge'. In the last 40 years, thousands of new chemicals have been invented. The best estimate is that some 75,000 chemicals are in common commercial use, of which only 1,500 (3%) have been tested for carcinogenicity, while it is likely that 5-10% are carcinogenic. This leaves a huge gap of ignorance and therefore risk.

After an initial chapter on silence, partly taking its cue from Carson, the book runs through the dimensions of cancer incidence and expression in relation to the environment: time and space distribution, the effects of war on chemical development, the use of animals for testing and the incidence of cancer in wild animals, poisoning of the earth in agriculture (pesticides and herbicides), of air and of water. Then the effect of waste incinerators (fire), the toxic accumulation in our bodies, and, finally, tracing the ecological roots of cancer. The book is at once poetic and scientific, passionate and objective. The narrative moves along briskly, even in the more technical sections.

The first significantly alarming fact is that the incidence of all types of cancer rose by nearly 50% in the US between 1950 and 1991. This translates into an increase from 25% then to 40% in the early 1990s (38% for women and 48% for men). Women born between 1947 and 1958 are three times more likely than their great-grandmothers to contract cancer at the same age. Something larger is going on. A WHO study of cancer mortality in 70 countries concluded that a staggering 80% of all cancer is attributable to environmental influences. The part of the jigsaw linking specifically to breast cancers may be that it is one of the organs with high fat content capable of absorbing fat-soluble, synthetic chemicals, many of which are classified as known, probable or possible carcinogens. Can we be sure of the correlation? No, because such research has not been funded, which means that nothing has been done in terms of policy. And people, especially in certain toxic areas or professions, continue to die in larger numbers.

In all the years that the author has been under medical scrutiny, no one has ever asked her about the environmental conditions in which she grew up, even though bladder cancer in young women is highly unusual. Hence her quest in this book. We all carry a chemical 'body burden', so that 177 different organochloride residues can be found in the body of an average middle-aged American man; and such chemicals easily pass into human breast milk, which is then ingested by highly susceptible infants. Cancer is an incredibly complex field, but we have tended to concentrate our efforts in certain areas, ignoring the wider environmental background.

A vast amount of work is dedicated to genes and heredity. Yet 'fewer than 10% of malignancies are thought to involve inherited mutations'. Moreover, 'genetic risks are not exclusive of environmental risks', in that damaging mutations may make some people even more susceptible to environmental carcinogens. Furthermore, it is much harder to do anything about hereditary than environmental factors. This leads the author on to a very important distinction between environmental and lifestyle factors. Brochures tend to stress the latter (behaviour), textbooks the former - exposure. So a narrow focus on lifestyle can obscure cancer's environmental roots. Early detection is all very well, but prevention would be better.

Steingraber advocates a powerful and rational approach to this problem, but it is one that is bound to upset a few chemical apple carts. Our current approach regulates the use of known and suspected carcinogens instead of preventing their generation in the first place. We are all being subjected to an uncontrolled chemical experiment that is not even being properly researched! So Steingraber puts forward a human rights approach that recognises that we do not all bear equal risks when carcinogens circulate in the environment. The most conservative estimate of annual US deaths directly from environmental carcinogens is 2% or 11,000 people, more than the number who die from hereditary breast cancer. The author makes a persuasive case for use of the precautionary principle whereby indication of harm is a trigger for action. Next, the principle of reverse onus shifts the burden onto the chemical companies to prove that their product is almost certainly not going to harm people. And finally, the principle of the least toxic alternative. All of these proposals have important research and policy implications that require serious consideration at the highest level and a redirection of research funding towards the role of environmental carcinogens. The book is a powerful wake-up call and a fitting continuation of Rachel Carson's pioneering work.