International audiencePeople aren't just at risk from carcinogenic benzene when they are out on city streets. Benzene pollution emanating from 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 micro g m-3 in air. But we show here that personal exposure, and therefore risk estimates, cannot simply be estimated from environmental concentrations of benzene. Using a new sampling device that monitors both of these parameters, 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 averag

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The performance of two types of radiello diffusive samplers, filled with a thermally desorbable adsorbent (graphitised carbon Carbograph 4) and with a solvent desorbable adsorbent (activated charcoal), respectively, have been evaluated for the monitoring of BTEX in ambient air, by comparison with active (pumped) samplers. A two year survey was carried out in Padua, a medium-sized town, in a traffic site, close to a busy crossroad. The concentrations of BTEX were measured for 15 campaigns, during which four series of radial diffusive samplers were exposed for 2 day, 7 day, 10 day and 14 day time periods, respectively. Every series of chemical desorption samplers included three replicates; thermal desorption samplers included six replicates, three of them filled with freshly conditioned cartridges and three filled with regenerated cartridges. No significant difference in the levels measured either by new or by regenerated cartridges has been found. During three campaigns (summer 2004, winter and spring 2005) two active (pumped) samplers were added for each sampling period. The diffusive uptake rates have been calculated and modelled under various conditions of concentration, temperature and exposure time. The effects of the environmental factors on the performances of both solvent and thermally desorbable samplers have been evaluated. The repeatability of the whole measurement process (sampling and analysis) was calculated for every sampling duration. The comparison of concentration levels measured by diffusive and active sampling methods shows correlation coefficients R >or= 0.98 (p<0.01) for all the compounds. The uncertainty of the diffusive sampling method under field conditions, using active sampling as the reference method, has been assessed according to the ISO 13752 requirements. On field relative expanded uncertainty for benzene has been found below 20%.

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A simple and inexpensive cryofocusing device was developed ad hoc in order to analyse at sub-ppb levels airborne organics, sampled by Tenax tubes and recovered by thermal desorption. By means of this device and of gas chromatography-mass spectrometry, the odorous compounds in the air around a polyester resin factory were identified as 2-ethyl-4-methyl-I ,3-dioxolane (EMD), 5,5-dimethyl-l,3-dioxane (DMD), 2,5,5trimethyl-l,3-dioxane (TMD), 2-ethyl-5,5-dimethyl-1,3-dioxane (EDMD) and 2-isopropyl-5,5-dimethyl-1,3-dioxane (IDMD). These compounds are produced during the synthesis of polyester resins by cyclic acetalization of vicinal diols under acid catalysis. Their structures were confirmed by laboratory syntheses. The Odour Index of these organics was evaluated by means of dynamic olfactometry, and the results were 22 100 for IDMD, 27 200 for DMD, 98 100 for EMD, 1 003 000 for TMD and 2 094000 for EDMD. Their odour changes dramatically from a pleasant mint scent at higher concentrations to a very unpleasant smell at ppb level con cent rat ions.