Are your beans clean and green?

These two books shed light on two topics of interest to environmentalists and discerning food consumers. There are potential and real benefits from advancing technologies, beyond salary slips and share prices. It is these that motivate the authors of both volumes.

Multi-authored books such as these can provide a spectrum of diverse scientific attitudes as well as factual information. In Pesticide Chemistry and Bioscience , the proceedings of the ninth International Congress on Pesticide Chemistry, Colin Berry stresses the need to examine benefits as well as risks. But "it is irrational to expect the non-trained population to undertake rational analysis of risk; this is not meant to be a patronising comment but is intended to emphasise the fact that most of us have had to be trained in rational thought." I found this patronising, nevertheless, perhaps wrongly supposing that the "science" of rational risk analysis is fraught with hidden dangers, the risk being that it will be used to manipulate public opinion. Berry is correct, however, that benefits to global food production from chemically efficient agriculture are often overlooked.

Colin Spedding does his best to expatiate on benefits. "Clearly however, a benefit with no disbenefits is more worthwhileI than one with consequent costs." He adds: "The sensible use of pesticides will be an essential tool in producing enough food."

One of the four authors of a paper on the impact of biotechnology on pesticide delivery wisely writes: "In most countries, the public-sector component has been reduced dramatically, possibly caused by a reduction in the perceived value of agriculture with the voting publicI Thus in a revolutionary period of rapidly evolving technologies in agriculture there are few scientists who will be viewed as unbiased by the public."

A concern is the level of sampling from which conclusions are drawn and the way in which the questions are framed. In a frighteningly informative chapter on pesticides in food, Ian Shaw from the Lancaster Centre for Toxicology tabulates the 1996 level of sampling for pesticide residues in fruit and vegetables in all European Union countries. The United Kingdom took the fewest samples - J15 per million of population, about one-ninth of the rate in Italy and one-seventh of that in Greece. The UK survey found that 34 per cent of the samples were contaminated by pesticides, but less than 1 per cent were above the officially approved maximum residue level (MRL).

Alasdair Robertson of Safeway stores recalled that "over the last two years we have seen the discovery of residues of organophosphate compounds in individual carrot roots in excess of the MRL. This was surprising as these compounds had been applied in accordance with label recommendations and good agricultural practice."

Identifying and possibly enhancing the natural ways in which food crop plants resist pests and pathogens is an attractive goal for research. Many of the natural protective substances, however, are distinctly consumer-unfriendly. Farmers and plant breeders have been selecting for lower levels of anti-nutritional as well as more overtly toxic compounds. Is it clever now to try to enhance their expression?

Rudiger Hain's paper on the modification of secondary plant metabolism by foreign phytoalexin genes brings us to Paul Reynolds's book. Reynolds offers a timely reminder that cataloguing complete genomes is akin to writing dictionaries rather than literature. It is the way in which DNA, through transcription and translation, orchestrates orderly development that will lead to an understanding of how organisms work and possibly to new creative possibilities.

It is not enough to transfer the chosen genes of interest into a cell. Suitable promoter sequences must be present or must be transferred along with the genes. This book is about promoters that can be regulated and manipulated to provide external physical or chemical control over particular genes at the level of the whole intact organism.

Reynolds is optimistic about genetic engineering. "The boundaries to the development of different methods of control over expression of the introduced genes are limited only by the scope of human ingenuity and its ability to trap and utilise the masterful and intricate systems that control the growth, development and survival of all organisms on the planet." In subsequent chapters ten different facets of the present scope of such human ingenuity are explored in depth.

Colin Leakey is an applied biologist and a plant breeder.