SUMMARY Surveys were conducted in four areas in Wales with differing degrees of environmental lead. In two areas the source of the lead was traffic and in one it was spoil from lead mining in the past. The fourth area, which served as a control, was a village remote from heavy traffic, industry, and lead mining. Various environmental samples were taken, and children aged 1-3 years and their mothers were studied. Blood lead concentrations were raised in the lead mining area, and within the areas defined by traffic flow the blood lead concentrations of the mothers showed a gradient. Pica in the children, assessed by a questionnaire, showed no relation with blood lead, but the amount of lead removed from the children's hands with 'wet wipes' was an important contributor to blood lead concentrations.

SUMMARY Women resident in an area heavily contaminated by spoil from old lead mining have blood lead concentrations that are about 50% higher (p<0001) than those of women living in a "control" area some distance away. Blood lead concentrations were related to the consumption of home grown produce. Those with the highest consumptions had blood lead concentrations that were 28% higher (p<0001) than those of women who consumed no locally grown vegetables. Nevertheless, in the total population in the area this effect seemed likely to account for only about 5% of the population mean blood lead concentration. The data suggested that an increase in soil lead of 1000 ,ug/g is associated with an increase in blood lead of about 0-20 ,uM/1 (4.2 ,g/dl). The major limitation in the evidence is data relating food lead to body lead. To obtain direct evidence on this pathway a study was conducted in which vegetable consumption and blood lead concentrations were examined in an area with high soil lead concentrations.

Consensus principles from radiation biology were used to describe a generic set of nonlinear, first-order differential equations for modeling toxicity-induced compensatory

This is a very useful book. Over the last two decades, so many urban models have been proposed, so much has been written about urban modelling, with all this literature dispersed over so many books and journals, that it is difficult for someone who wants to get initiated to urban modelling, to know where to start. Moreover, many of these books and articles either present models based on highly simple, if not simplistic, assumptions, or use advanced mathematics, so that the average beginner may rightly wonder whether his efforts will lead him somewhere. By stressing the practical side of modelling, by explaining in a very clear and progressive way the mechanics of the different types of models, by applying them to real-world examples, by discussing their numerous applications, by making explicit their limitations and problems, the author succeeds in convincing the reader that urban models may indeed be a useful part of the analysis of urban systems and an important tool for assessing the consequences of urban planning decisions.The book begins with a brief discussion of the role of urban modelling within the planning process, and of some basic characteristics of urban models (Chapter I), followed by a chapter presenting the general procedure involved in developing a model for a study region (Chapter 2). The next two chapters are devoted to urban models based on the gravity principle. It is typical of the author's approach that, instead of first presenting a general overview of the whole family of spatial interaction gravity models, he starts with an example, using Reilly's law of retail gravitation (Chapter 3). The retail model is then reformulated to represent a model of spatial interaction and allocation (Chapter 4). The next step is to proceed to more general urban models, that is models which describe several parts of the urban system, and which simulate simultaneously the allocation and interaction between several landuse activities. General models obtained by coupling together partial gravity models are presented first: Chapter 5 describes the Garin-Lowry model and some of its applications. General models based on linear regression and econometric techniques are discussed in Chapter 6, and general optimizing models, particularly those using linear programming, are briefly presented in Chapter 7. A final chapter is devoted to hybrid models, along with a general consideration of the way operational urban models can be most usefully applied.As indicated in the title of the book, the author's purpose is to introduce the reader to urban modelling. This is indeed a text-book for undergraduate students and for practising planners and urban analysts. Only models which are operational, in the sense that they have been successfully developed and applied in actual planning studies, are discussed.The numerous examples and applications presented in the text refer to studies from many parts of the world. The level of mathematics required to follow the book is just a basic knowledge of algebra.This well-written book, with ...