Duarte-Davidson R, Courage C, Rushton L, Levy L
National Centre for Risk Analysis and Opotions Appraisal, Steel House, 11 Tothill Street, London, UK.
Occup Environ Med. 2001 Jan;58(1):2-13. doi: 10.1136/oem.58.1.2.
Benzene has long been recognised as a carcinogen and recent concern has centred on the effects 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 effects, and uses this information to provide a risk evaluation for sections of the general United Kingdom population.
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 different exposure scenarios with time-activity 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.
Infants (<1 years old), the average child (11 years old), and non-occupationally exposed adults, receive average daily doses in the range of 15-26, 29-50, and 75-522 microg of benzene, respectively, which correspond to average ranges to benzene in air of 3.40-5.76 microg/m(3), 3.37-5.67 microg/m(3), and 3.7-41 microg/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 microg (equal to an estimated exposure of 41 microg/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 non-lymphocytic 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 effects 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.
Overall the evidence from human studies suggests that any risk of leukaemia at concentrations of exposure in the general population of 3.7-42 microg/m(3)-that is at concentrations three orders of magnitude less than the occupational lowest observed effect level-is likely to be exceedingly small and probably not detectable with current methods. This is also likely to be true for infants and children who may be exposed continuously to concentrations of 3.4-5.7 microg/m(3). As yet there is no evidence to suggest that continuous exposures to these environmental concentrations of benzene manifest as any other adverse health effect.
长期以来，苯一直被公认为致癌物，近期人们关注的焦点集中在职业和环境中持续接触低浓度苯的影响。本文基于最近公布的数据，概述了英国人群接触苯的现有知识，总结了已知的对人体健康的影响，并利用这些信息对英国普通人群的部分群体进行风险评估。
鉴于非吸入源对人体每日苯总摄入量的贡献较小，在估计普通人群每日苯接触量时，仅考虑吸入接触。结合一系列相关微环境中的实测苯浓度，利用时间 - 活动模式以及吸入和吸收率，针对不同接触场景估算了成年人、儿童和婴儿的苯接触量。加油和驾驶过程中的接触，以及主动和被动吸烟的影响，都被视为普通人群风险特征描述的一部分。
1岁以下婴儿、普通儿童（11岁）和非职业接触成年人，每日平均苯摄入量分别在15 - 26微克、29 - 50微克和75 - 522微克范围内，这分别对应婴儿、儿童和成年人空气中苯的平均浓度范围为3.40 - 5.76微克/立方米、3.37 - 5.67微克/立方米和3.7 - 41微克/立方米。接触环境烟草烟雾的婴儿和儿童的苯接触浓度与成年被动吸烟者相当。这是一个重要的接触源，因为1995年英国的一项调查显示，47%的2 - 15岁儿童生活在至少有一人吸烟的家庭中。由于婴儿体重较低，接触苯对其造成的后果比对儿童或成年人更为显著，导致婴儿的每日摄入量高于儿童或不吸烟的成年人。普通人群接触苯的最糟糕情况是城市吸烟者，例如一名维修工人，每天在繁忙道路旁工作8小时，其平均每日接触量约为820微克（相当于估计接触浓度为41微克/立方米）。低浓度接触苯相关的主要健康风险已被证明是白血病尤其急性非淋巴细胞白血病。职业接触工人中可靠检测到急性非淋巴细胞白血病发病率增加的最低接触浓度估计在32 - 80毫克/立方米范围内。尽管一些研究表明在较低浓度下可能会产生影响，但尚未确定明确的风险估计值，部分原因是接触数据不足且病例较少。
总体而言，人体研究的证据表明，普通人群接触浓度为3.7 - 42微克/立方米（即比职业最低观察效应水平低三个数量级的浓度）时患白血病的任何风险可能极小，用目前的方法可能无法检测到。对于可能持续接触浓度为3.4 - 5.7微克/立方米的婴儿和儿童来说可能也是如此。目前尚无证据表明持续接触这些环境浓度的苯会表现为任何其他不良健康影响。
