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New or the market Pepiices and proteins brief communications AS 'Urban benzene and population exposure motor traffic can cause leukaemia'”, with the risk being estimated at about four cases per million among people who | experience. lifelong exposure to benzene concentrations of 1 4gm”*in air”. But we show: here that personal exposure, and 1herefore risk estimates, cannot simply be estimated from environmental concentra- tions of benzene. Using a-new sampling device that monitors both of these param- eters, we have discovered that people living | in different European cities are exposed to concentrations of benzene that may be twice as high as the urban average. We have monitored benzene pollution in each of the European towns of Antwerp, Athens, Copenhagen, Murcia, Padua and Rouen at 100 sampling sites distributed over a multiscale grid drawn on the town map”. Every two months (from September 1997 to September 1998), these sites were tested from Monday morning to Friday afternoon by using a radial symmetry pas- sive sampler device (termed a radiello”). This device relies on the diffusion of gas molecules as a result of a concentration gradient across a diffusive barrier: diffusing molecules are captured by an adsorbing material that has a constant benzene- uptake rate of 80X 107" ug min” for each | ig m — present in air. Concentrations are calculated from the amount collected and ihe exposure time. Having tested ihe sampler reliability both ¡in a standard atmosphere chamber and at the- actual sampling sites, we found a maximum bias value of 4.45% and a coefficient of varia- tion of for 120. samplers exposed for 4.5 days to benzene concentra- | tons of 1.547 gm”. We monitored 50 volunteers and their homes in each town. These volunteers were non-smokers and were equally represented by people exposed to traffic fumes as part of their jobs (police, postal workers, street sweepers, stall-holders, and bus and taxi drivers) and by non-exposed people (stu- dents, teachers and clerks), who all wore the sampler from Monday morning to Friday afternoon. The results (Fig. 1) were derived from 6,205 measurements, of which 50.7, 25.1 and 24.2% represent environmental, per- sonal and home exposure records, respec- | enzene pollution emanating from ll tively. The urban pollution level, presented as the annual average, is seen to increase in European towns from north to south (Fig. 1a): this may be explained by a difference in prevailing meteorological conditions, such as local wind speeds (Fig. 1b). NATURE | VOL 404] 9 MARCH 2000 | www.nature.com: a However, personal exposure data and Imeasurements taken inside homes do not reflect this difference in urban pollution between northern and southern European towns: except in Athens, the population exposure exceeds the average urban concen- ¡on and is higher indoors than outdoors surprising finding may be explained by the hourly benzene concentra- tion oscillating. between very low values during the night and very high values dur- ing the middle of the day and the evening. 27:09 95109 0.13 Figure 1 Benzene personal exposure level cammot be calculated 'weiohted average ol outdoor and indoor mean concen railons org lo large: houriy nmban polluvon oscilations. a, Ben: uihem ene nt is lo increase hom noriher to s an pollution se :an towns. D, his observaron may be explained by ditter milalon. ciearing benzene Euro Iheretore 1085 n sind pee poltuiin al dilerent rates in norbhern and sowihern tos. n est lia the local population exposure, the reduction ín the pol alancad by an out hon ot noriherm compared ippesite end in indoor pollution, e, Popularion exposure depends on both outdoor and indoor pollutlon. Meastun ms is sents using the show Ihat pa exposure is mn Jevel. Annual va presented as averages for six monitoring. Sireex and home and: the Values esuling persona >xcentraons tn p1g algas, ln: te exposure e. Shov ae ayerage im vi 95% comience interval a Suyiler e, Wite, Ge Goldstcin, 3D Emiro. Heali Perspese 306 (1993). World cala Quai Gidines $ People aren't just at risk from carcinogenic benzene when they are out on city streets. As most people are about in the streets when the benzene concentration is higher than the daily average, then their actual exposure when out of doors is higher than the value calculated from the daily urban average benzene concentration and the time spent outdoors. But this outdoor exposure represents only a fraction of the total: as people spend on average 59.1% of their day at home, the contribution from indoor exposure is important. In the European towns studied here, the average pollution level at home turns out to be 1.51 times the outdoor street level, with the exception of Athens, where volunteers live far from the town centre. The value of the domestic-to-urban pol- lution ratio rises from southern to northern Europe. This tendency evens out the differ- ence in the level of personal exposure and the level of urban pollution: when no longer exposed out of doors, people are subject to indoor pollution, which is worse in Antwerp, Rouen and Copenhagen, com- parable in Padua and Murcia, and better in Athens. To explain these findings, we suggest that pollution indoors is caused by benzene entering from the streets outside, as shown by the good fit of respective seasonal trends (data not shown). The pollution indoors is generally higher than outdoors, possibly because of an imbalance between the flow of pollutant from outside and ¡ts removal from inside to outside. In other words, the house itself could be acting as a Mywheel created by adsorbent surfaces on walls, Moors and furnishings. This idea is support ed by the lower indoor pollution in south- ern European towns; in northern European houses, carpets, linoleum and wood sur- ha are favoured, whercas tiling, marble and bare walls are typically used in south- ern Europe. Vincenzo Cocheo*, Paolo Sacco*, Caterina Boaretto*, Emile De Saegert, Pascual Perez Ballesta, Henrik Skovj,. Eddy Goclen$, Norbert Gonzalezll, Antonia Baeza Caracena9 ndazione Salvatore Maugeri-IRCCS, 7 Padova, Italy fmpdotin.ie Joint Rescarch Centre, 21020 Ispra, Taly: ¿National Environmental Research Institute, Frederiksborgvej 399, 4000 Ro: Denmark 5 Vlaamse Instelling voor Technotogisch Onderzoek, Boeretang 200, 2400 Mol. Belgium Wlustitut National del Risques, 60550 Verneuil-en-Halatto, France $ Departamento de Ingenieria Quimica-Marcia, Universidad do Murcia 50071 Murcia, Spain sild wironmement Industriel et de d Koviston of the Air auion Upoai Europw Report no, EURIICH/ 141 Lol cal. Mutato Res, 268, 49-57 (19 ELAZ9JOS/MT 12 WHO Regional Oi for Europe, iglami, EC. Se Saito, GN. Emgl. Med. 271, 572-876 (1964 suse, 1996) sky Re Acetal, Am. J Jud. Med, 2, 19 Kumar, A. de Russel, AG Atrnos. Eva. 307, 1099-1116 (1996). Bond, 6.6, Mclaren, E. A.. Baldio, €. LS Cool RR. Clica, Yo, Bnarehto, € Se Sacco, Pe Am $97-901 11996; Br). Ind Med. 43.685-6 
