Thus, some research groups have developed methodologies to measure personal exposure to multiple airborne pollutants ( Demokritou et al. In recent years, some research was conducted collecting personal exposure with a multiparametric approach, as air pollution is composed of a mixture of different substances with potential impact on human health, whose effects can sometimes be combined in a synergistic way. It is also unfeasible when it is necessary to determine concentrations of several co-pollutants as it can be very difficult to perform sampling in the breathing zone while wearing a lot of instruments without interfering with normal daily activities. Studies using this type of approach, however, have the disadvantage of being very time consuming and expensive. In some rare cases (Finuncane 1998) the breathing zone definition was restricted to an hemisphere having a radius from 15 to 23 cm (6 to 9 inches). In general, such a direct exposure measurement approach strictly refers to sampling within a hemisphere of 30 cm (12 inches) radius extending in front of a person's face ( Grammer et al. In the field of direct measurements, personal sampling is preferable for assessing human exposure, as it is representative of the contaminant concentration in the breathing zone ( Esmen and Hall 2000 Zartarian et al. Human exposure to air pollutants can be assessed using direct measurements, biological monitoring, or estimated using indirect methods, such as models predicting exposure from fixed sampling locations (indoor, outdoor, or ambient). Individual exposures measured by the MMU could be of importance in toxicological and epidemiological studies on PM, with the advantage of accounting for exposure to several gaseous co-pollutants. Nevertheless, the capability of the MMU to detect the variations of personal exposures to O 3 and CO was better than that normally observed using fixed measurements, likely due to the placement of the MMU in the different microenvironments where subjects spent their time. The concentrations of gaseous pollutants measured by MMU were less correlated with those collected in the breathing zone (R 2 = 0.34–0.65). Short-time number concentrations of ultrafine, fine, and coarse particles collected by MMU were characterized by a high predictivity of personal exposures (R 2 ≥ 0.89 slope 0.94–1.17 for PM 0.99). The obtained concentrations were compared with those simultaneously collected in the breathing zone, considered as the gold standard for estimating human exposure to air pollutants. Individual exposure was measured using a mobile monitoring unit (MMU), developed to sample simultaneously some urban pollutants of interest for public health purposes. Individual exposure was defined as the exposure constantly measured in proximity to the subject, even during transfers. This study tested the reliability of a novel method developed for assessing the individual exposure to size-fractionated particulate matter (PM) and gaseous urban pollutants.
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