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NATURE|Vol 437|20 October 2005 BOOKS & ARTS

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standing, and more accurate use, of poisons. Unwanted side effects of scientific and tech-

nological progress are evident throughouthuman history. The industrial age has pro-duced one of the most obvious: the contami-nation of the environment by potentiallyharmful, synthetic products. More recently,with the mass production of foods, widespreaddietary contamination has become a problem.Finally, while a better understanding of diseaseprocesses has fostered the development ofeffective and powerful drugs, these can alsocause unexpected, adverse reactions.

Better education and information have alsoincreased the general awareness of the risksposed by chemicals and drugs, raising concernamong the public, media and governments. Inthe past three decades, there has been pressureto reduce environmental contamination, andthe safety requirements for foods and drugshave become more stringent. Nevertheless, thepublic perception of risk from chemicals hassince grown disproportionately. It may be pos-sible in many cases to provide safe productswithout adverse effects, but it is not universallyachievable. Hence, the margins for developingsafe yet effective medicines have been consis-tently reduced by the increasing pressure to

develop drugs that are devoid of side effects.For example, aspirin would probably not passthe regulatory process today because of itsmany side effects, despite its therapeutic value.Chemicals are intrinsically hazardous and allpose some degree of risk, which is perhaps not entirely appreciated by the public. Virtuallyall human endeavours are potentially harmful,and all agents are potentially toxic. However,the dose or level of exposure and an indi-vidual’s susceptibility will play a major role indetermining the risk posed by a compound.

In The Poison Paradox, John Timbrelladdresses the problem of the risks posed bychemicals, and considers how, when and whythey can be toxic. The book is pervaded by the reminder that it is the dose that makes achemical toxic. Using easily understandable examples, Timbrell guides the reader throughthe basic principles of toxicology (such as theinteraction between chemicals and biologicalorganisms). Often using an anecdotal style, heclearly explains the dangers and risks linked tonatural and synthetic products, including med-icines, food and environmental contaminants.Finally, he summarizes the criteria required toassess chemical hazard and risk.

This is not a book for the specialist, butrather is aimed at a general reader who wants tounderstand the principles that have guided tox-icology and the difference between hazards,risks and their assessment. The conclusionsare well balanced and illustrate the difficulty ofpredicting and determining the risk of expo-sure to agents that we perceive as toxic. Onerevealing example is given in the chapter onendocrine disruptors — chemicals that causeadverse health effects as a result of changes in hormone function, such as dioxins andoestrogens. Timbrell describes the experimen-tal evidence for their toxicity, the problem withdifferent species’ susceptibility to these chem-icals, and the lack of convincing evidence fortheir toxicity in man. He concludes that furtherevidence is needed to assess their potentialadverse health effects in humans.

The chapters on risk assessment and the per-ception of risk by the public further highlightthe need for a better understanding of risk, andshow how some risk is unavoidable. Throughthe analysis of known and yet unresolved problems linked to chemical toxicity, the bookalso suggests that we need more and diverseresearch in toxicology. Science, rather thanprecaution or concern, should drive the assess-ment of risk and decisions on public health, asTimbrell states: “When the public perception ofrisk is greater than it really is, politicians needto take steps (which are really unnecessary) toreduce the risk, with the result that huge sumsof money may be spent for no real benefit.”

The Poison Paradox provides the reader withthe information to form an educated perceptionof risk and its implications in toxicology. ■

Pierluigi Nicotera is at the Toxicology Unit,University of Leicester, Hodgkin Building,Lancaster Road, Leicester LE1 9HN, UK.

Mixed reactionsThe Poison Paradox: Chemicals as Friendsand Foesby John TimbrellOxford University Press: 2005. 360 pp.£19.99, $29.95

Pierluigi NicoteraIt is remarkable that historical periods charac-terized by a surge of intellectual growth havealso been remembered for violence and mis-chief. As Harry Lime (played by Orson Welles)famously remarked in the film The Third Man:“In Italy for 30 years under the Borgias theyhad warfare, terror, murder and bloodshed,but they produced Michelangelo, Leonardo daVinci and the Renaissance. In Switzerland theyhad brotherly love — they had 500 years ofdemocracy and peace, and what did that pro-duce? The cuckoo clock.”

Although we may not entirely sympathizewith this quote, it is clear that cultural devel-opment and scientific and economic progressalmost inevitably have side effects. During the Renaissance in France and Italy, the firstsystematic studies of anatomy and physiology,and the empirical experimentation of thedose–effect relationship (often in humans who did not volunteer), led to a better under-

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Shelf conscious? Many people have no idea that it is the dose that makes a chemical toxic.

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