Christopher Williams has written a potentially important book filled with striking insights about a growing and largely unsuspected problem. He makes a strong case that we are damaging our brains by our own activities - not just in a few obvious instances, such as mercury poisoning at Miyamata in Japan and the release of toxins by Union Carbide in Bhopal, India, but in more general and subtle ways often virtually impossible to detect.

There is no organ in our bodies more susceptible to damage from lack of oxygen, or from trace elements and other chemicals, than our brains. And the brains of children are even more easily affected than those of adults. Williams surveys a commendably wide range of evidence from many parts of the developed and developing world to show that the cost of this damage has been very high. Lead and mercury are two of the worst villains, and have received much attention. But Williams casts his net much wider, citing many studies of the effect of malnutrition on the intellect. He also investigates the spread of disease and its effects.

The cost of brain damage to society is enormous. Williams refers only glancingly to studies that show a remarkably clear connection between head injury and aggressive and criminal behaviour. For example, in one study wife abusers were ten times as likely as the general population to have suffered severe head injury. What is the cost, in terms of crime, of the increase in sports and vehicle injuries taking place in societies worldwide? And what is the effect of brain damage on the health of societies? How much smarter would we be if we had not breathed lead fumes for so many years? Would we have chosen better leaders, and wiser social policies?

In various parts of the book, Williams lays out the social and legal responses to these problems. He recounts how, because it is based on precedent rather than logic, the legal system has acted in its usual capricious fashion, bestowing millions on a few and leaving the majority of slightly brain-damaged victims without compensation. And he is occasionally, and commendably, waspish about the role of multinational corporations in all this.

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Unfortunately, Williams's book is damaged in three ways. The cover and title can most charitably be described as loathsome, and are sure to keep readers away in droves. There are long sections of the book in which the argument is lost. The author's confusion is made manifest by flow charts and diagrams that are supposed to make things clearer, but that only obfuscate. And finally, whenever the author wrestles with the long-term consequences of all this brain damage, he tends to lose his way in a thicket of arguments that sometimes smack of Lamarckism.

Williams falls foul of biology when he suggests that we might be heading into a kind of downward intellectual spiral in the future. He never really makes it clear that brain damage is not the same as gene damage. An evolutionist would predict, not a downward spiral, but rather the survival and success of people who are best able to withstand extreme environmental insults.

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There is no doubt that the problems detailed in this earnest but flawed book are real ones. I hope and expect that this will not be the last word on the subject.

Christopher Wills is professor of biology, University of California, San Diego.