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Objectives-Benzene has long been recognised as a carcinogen and recent concern has centred on the eVects of continuous exposure to low concentrations of benzene both occupationally and environmentally. This paper presents an overview of the current knowledge about human exposure to benzene in the United Kingdom population based on recently published data, summarises the known human health eVects, and uses this information to provide a risk evaluation for sections of the general United Kingdom population. Method-Given the minor contribution that non-inhalation sources make to the overall daily intake of benzene to humans, only exposure from inhalation has been considered when estimating the daily exposure of the general population to benzene. Exposure of adults, children, and infants to benzene has been estimated for diVerent exposure scenarios with timeactivity patterns and inhalation and absorption rates in conjunction with measured benzene concentrations for a range of relevant microenvironments. Exposures during refuelling and driving, as well as the contribution of active and passive tobacco smoke, have been considered as part of the characterisation of risk of the general population. Results-Infants (<1 years old), the average child (11 years old), and nonoccupationally exposed adults, receive average daily doses in the range of 15-26, 29-50, and 75-522 µg of benzene, respectively, which correspond to average ranges to benzene in air of 3.40-5.76 µg/m 3 , 3.37-5.67 µg/m 3 , and 3.7-41 µg/m 3 for infants, children, and adults, respectively. Infants and children exposed to environmental tobacco smoke have concentrations of exposure to benzene comparable with those of an adult passive smoker. This is a significant source of exposure as a 1995 United Kingdom survey has shown that 47% of children aged 2-15 years live in households where at least one person smokes. The consequence of exposure to benzene in infants is more significant than for children or adults owing to their lower body weight, resulting in a higher daily intake for infants compared with children or non-smoking adults. A worst case scenario for exposure to benzene in the general population is that of an urban smoker who works adjacent to a busy road for 8 hours/day-for example, a maintenance worker-who can receive a mean daily exposure of about 820 µg (equal to an estimated exposure of 41 µg/m 3 ). The major health risk associated with low concentrations of exposure to benzene has been shown to be leukaemia, in particular acute non-lymphocytic leukaemia. The lowest concentration of exposure at which an increased incidence of acute nonlymphocytic leukaemia among occupationally exposed workers has been reliably detected, has been estimated to be in the range of 32-80 mg/m 3 . Although some studies have suggested that eVects may occur at lower concentrations, clear estimates of risk have not been determined, partly because of the inadequacy of exposure data and the few cases. Conclusions-Overall the evidence from human studies suggests that ...

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The United Kingdom is used as a study area in which to examine (i) the relationship between primary and potential secondary emissions of PCDD/Fs; (ii) the balance between atmospheric emissions and deposition; and (iii) the contemporary environmental burden of PCDD/Fs and possible historical input profiles. This critical review exercise is seen as an important aid to identifying gaps in knowledge and research needs and directing a scientifically sound strategy for PCDD/F risk reduction. The paper focuses on two key compartments, air and soil, as these play an important role in the movement and storage of PCDD/Fs. The terrestrial agricultural food chain supplies the majority of human exposure to PCDD/Fs via the pathway air−deposition−crop/pasture/soil−grazing animals−meat/dairy products−human diet. Primary emissions of PCDD/Fs to the atmosphere are expected to decline in the future following the implementation of new legislative controls. This should be reflected by a further decline in ambient air concentrations, as our calculations indicate that primary emissions are currently the main PCDD/F sources to air. The soil burden will take much longer to decline, due to the extreme persistence of these compounds in this environmental matrix. The paper highlights uncertainties and future research needs concerning the environmental sources, fate, and behavior of this group of compounds.

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