Kurzbeschreibung
(Englisch)
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Epidemiological methods will be used in order to demonstrate an association between occupational exposure to diesel particulate and oxidative stress status, characterised by selected biomarkers (8OHdG and aldehydes).The validity and usefulness of such biomarkers will be assessed for such exposure type.
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Partner und Internationale Organisationen
(Englisch)
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A, B, CZ, DK, FIN, F, D, GR, H, I, LT, NL, N, PL, P, SI, E, CH, TR, GB
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Abstract
(Englisch)
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The aim of this research was to assess and characterize occupational exposure to fine/ultrafine particulates and to quantify in urine and serum several potential biomarkers for oxidative stress caused by exposure to these particulates. This research was done in real occupational situations, where exposure to diesel particulates was expected to be in a medium range: workers from bus depot and underground environments were surveyed. Each volunteer was its own control (sampling urine and blood before exposure). Several physical and chemical exposure parameters such as particulate number and mass, size distribution, elemental carbon, adsorbed organics (organic carbon and PAH), heavy metal contents (Fe, Cu, Mn) and surface functional groups were determined for each working environment. Potentially interfering compounds from the gas phase like aldehydes from diesel exhaust have also been measured. Surface properties of the sampled particulates have been probed with a new technique (Knudsen cell) in order to gain insight into their reactivity. A total of 5 different sites have been surveyed from march 2006 to february 2007 (4 maintenance yards and one underground metro construction workplace). Night activities have also been followed for two of these sites. Particulate exposure characterization indicated that PM4 mass was rather low (13-102 µg/m3) with multi-modal distribution (based on gravimetric determination) with modes at approximatively 1 and 5 µm. For some situations, a shoulder around 2-3 µm was also present. Particulate distribution in the sub-micron range was determined with a DMA/CPC equipment. A principal mode was observed around 80 nm, characteristic for primary diesel exhaust particulate. During this study, agglomeration phenomenon could also be observed and characterised. Particulate number concentrations (2'500-38'000 #/cm3) are indicative of a rather low contaminated working place. Diesel exposure determined by elemental carbon was low (1-17 µg/m3). Particulate heavy metal concentrations were: Fe: 253-6'025 ng/m3; Cu: <20-223 ng/m3; Mn: <10-470 ng/m3. Ozone was practically absent (1-16 ppb) but NOx levels could reach very high levels (116-996 ppb). Gaseous aldehydes (formaldehyde: 2-16 µg/m3, acetaldehyde: 3-10.5 µg/m3, glutaraldehyde: 0.2-1.1 µg/m3, hexanal: 0.2-19 µg/m3 and nonanal: 0.2-1.3 µg/m3) have been detected in all working conditions. Among all these aldehydes, formaldehyde had the highest concentration, but always smaller than 1/200 of the swiss OEL. The benzo[a]pyrene equivalent concentration on PM4 was determined to be always smaller than 9.5 ng/m3. Surface functional groups have been determined with a titration technique (Knudsen flow reactor). Results point to important differences in the reactivity of ambient particles, depending on the sampling site and the date. The particle surface appears multi-functional, with the simultaneous presence of antagonistic functional groups which do not undergo internal chemical reactions. Carbonyls were the most numerous encountered surface functions (on a #/mass basis), followed by Lewis base sites and finally Lewis acid sites. A total of 156 urine and 78 serum samples have been collected (corresponding to a total of 39 volunteers). Spot urine before and after shift have been collected during two consecutive days. Serum samples were collected before the first day shift and at the end of the second day shift. PM4 personal exposure was available for each worker as well as information from a questionaire related to their health and to their life style. Determination of 8-hydroxy-2'-deoxyguanosine (8OHdG, considered as a DNA oxidative stress biomarker) has been achieved on all urine samples with a validated LC-MS/MS based analytical method. Active smokers presented a higher urinary level of 8OHdG compared to non smokers. Moreover, a statistically significant (p<0.05) increase of 8OHdG levels in urine of non smokers was observed between the two days. Such an increase between both days was not observed for smokers. These differences are no more observed when the 8OHdG concentrations are not corrected for dilution with creatinine. These results suggest that non-smoker workers are subject to oxidative stress when working. Parallelly, we determined the total anti-oxidant level in the same matrix. The same trend as for 8OHdG has been observed: non smoker only presented an increased level of antioxidant (in their reduced form) in urine after two working days. This could indicate that the antioxidant pool has been activated by exposure to the oxidants present in the working place (PM ?, ...) in order to maintain the cellular redox homeostasis and decreasing the oxidative stress. Such a picture is in line with the proposed hierarchical cellular response paradigm explaining the role of oxidative stress in mediating biological effects of PM [Li et al., 2002]. Three aldehydes (hexanal, nonanal and 4-hydroxynonenal) considered as biomarkers of lipoperoxidation were determined in some of the serum samples. Hexanal and nonanal cannot be proposed as relevant biomarkers of effect due to the fact that they have been determined in the air. 4-hydroxynonenal has been detected in serum but at concentrations near to the detection level and didn't presented any significant change during the two sampling days. In this research we thus didn't observe any lipoperoxidation processes. Li N., Kim S., Wang M., Froines J., Sioutas C., Nel A. 2002. Use of a stratified oxidative stress model to study the biological effects of ambient concentrated and diesel exhaust particulate matter. Inhal Toxicol, 14:459-486
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