Layman's pollution primer

They say you should not judge a book by its cover. Understanding Environmental Pollution, however, is a book whose cover sums up the contents rather well. It shows a picture of Los Angeles so immersed in smog that it has a rather woolly appearance.

The back cover contains an interesting blurb that rather usefully introduces the book. I could not help noticing that the same blurb appears in the preliminary pages with one subtle difference. The cover proclaims the book to be "an excellent text for introducing students to pollution problems and to earth science"; the wording inside describes it as "a perfect textI". Much stimulated by this promise of perfection, I searched the contents to see if they matched up to the billing.

The book proclaims itself to be "a lucidly written and thorough approach to comprehending pollution issuesI". I would certainly agree with the former statement - it is lucidly written - but as to thoroughness, I would beg to differ. This is perhaps because of my standpoint as a physical scientist, for this is a book that addresses pollution issues at a level suitable for a mixture of science and non-science undergraduate students. This is a difficult task. Almost inevitably, the book has to trivialise the science to satisfy the needs of non-scientists and simplify the policy issues to a level below that which non-scientists might be used to in their own disciplines. The book is genuinely accessible to educated non-scientists, which sets it apart from the vast majority of books in this field. For them, it probably provides a lucid and broad introduction to environmental issues, but an inevitable consequence of its breadth is that it is also shallow.

As to the contents, the book goes through general introductions to pollution, pollution prevention, toxicology and environmental risk before delving into specific areas such as local and global air pollution, water pollution, solid waste, and then chapters on specific pollutant groups (metals, pesticides and environmental oestrogens). Final chapters deal with energy production and use, and pollution at home. This is a vast remit to cover when even the most basic scientific terms have to be explained. In the areas with which I am familiar, the text is remarkably up to date, showing, for example, a good appreciation of current air pollution concerns relating to particulate matter.

I looked for the kind of silly errors that authors so often make in covering a very broad field, but these are few and some could be considered a matter of opinion. One relates to the contribution of petrol lead emissions to population blood lead levels - a measure of the concentration of lead in blood in a representative sample. During the phase-out of lead in petrol, a naive and common interpretation of the data (repeated in this book) leads to the conclusion that the phase-out was largely responsible for the dramatic reduction in blood lead levels in the United States between about 1975 and 1995. A more comprehensive examination of the US data shows that control of other sources such as lead in food cans was far more influential. If data from other countries is included, it becomes clear that cutting lead in petrol has been a minor contributor to the reduction in population blood lead levels.

The one aspect of this book that is extremely irritating was that it is almost unbelievably parochial. There is scarcely a page that does not mention some US government agency, US scientist or piece of US legislation. This no doubt makes the book very valuable for the US market, but makes it very difficult to use in a European context. Although many of the general principles of the regulatory laws are similar, the details are very different, and it is rather painful to go through all of this US-oriented material when it gives little insight into what happens in other countries.

One particularly unfortunate error in the chapter on environmental risk, having gone through the linear response non-threshold assumptions on genotoxic carcinogens, is the statement that "England, Denmark and the Netherlands take a different approach to carcinogens than the United States. They believe that carcinogens do have safe doses (thresholds)". This is a serious mis-statement of the truth and probably a consequence of the parochial nature of the treatment and the over-simplifications introduced so widely. The fact is that the US differs from much of the world in having placed far greater confidence in the quantitative risk approach to evaluating "safe" exposures to environmental carcinogens. In the United Kingdom it is appreciated that the estimates of risk derived from quantitative risk assessment methods are very sensitive to the models used; consequently quantitative risk assessment can be no more than a crude guide to risk levels and is only one aid to setting standards for protection. To interpret this view as implying a belief that carcinogens have thresholds, and therefore that there are totally safe doses, is a travesty.

Some of the over-simplifications become seriously misleading, and one questions whether the author has any deep appreciation of the subject. An example is that carbon monoxide is described as being of concern because "all by itself carbon monoxide accounts for more than 50 per cent of air pollution nationwide and worldwide". Other air pollutants are also described in terms of the percentage of pollution which they account for. Such statements are almost meaningless and extremely misleading. Is the percentage based on a mass or volume basis? Is it based on emissions or airborne concentrations? These points are not answered. Why is carbon dioxide not included in the calculation? If it were, carbon monoxide's percentage would look tiny. The degree of concern attached to a pollutant relates not to its total abundance, but to the ratio of its environmental concentrations to effects-based standards, a concept that does not come through.

This book is a useful introduction to policy on environmental protection for non-scientists. It is certainly not a "perfect" text for introducing students to pollution problems, and certainly is not an adequate introduction to earth science. I am not sure what the author understands earth science to be. The book is basically one about pollution, and the space devoted to describing the fundamental properties of earth systems, which is what I understand by earth science, is negligible. However, for those for whom the orientation to the United States is not a disadvantage, this could prove a useful introductory text.

Roy M. Harrison is professor of environmental health, University of Birmingham.