Oxidative potential of particles in different occupational environments: a pilot study

The oxidative potential (OP) of particulate matter has been proposed as a toxicologically relevant metric. This concept is already frequently used for hazard characterization of ambient particles but it is still seldom applied in the occupational field. The objective of this study was to assess the OP in two different types of workplaces and to investigate the relationship between the OP and the physicochemical characteristics of the collected particles. At a toll station, at the entrance of a tunnel ('Tunnel' site), and at three different mechanical yards ('Depot' sites), we assessed particle mass (PM4 and PM2.5 and size distribution), number and surface area, organic and elemental carbon, polycyclic aromatic hydrocarbon (PAH), and four quinones as well as iron and copper concentration. The OP was determined directly on filters without extraction by using the dithiothreitol assay (DTT assay-OP(DTT)). The averaged mass concentration of respirable particles (PM4) at the Tunnel site was about twice the one at the Depot sites (173±103 and 90±36 µg m(-3), respectively), whereas the OP(DTT) was practically identical for all the sites (10.6±7.2 pmol DTT min(-1) μg(-1) at the Tunnel site; 10.4±4.6 pmol DTT min(-1) μg(-1) at the Depot sites). The OP(DTT) of PM4 was mostly present on the smallest PM2.5 fraction (OP(DTT) PM2.5: 10.2±8.1 pmol DTT min(-1) μg(-1); OP(DTT) PM4: 10.5±5.8 pmol DTT min(-1) μg(-1) for all sites), suggesting the presence of redox inactive components in the PM2.5-4 fraction. Although the reactivity was similar at the Tunnel and Depot sites irrespective of the metric chosen (OP(DTT) µg(-1) or OP(DTT) m(-3)), the chemicals associated with OP(DTT) were different between the two types of workplaces. The organic carbon, quinones, and/or metal content (Fe, Cu) were strongly associated with the DTT reactivity at the Tunnel site whereas only Fe and PAH were associated (positively and negatively, respectively) with this reactivity at the Depot sites. These results demonstrate the feasibility of measuring of the OP(DTT) in occupational environments and suggest that the particulate OP(DTT) is integrative of different physicochemical properties. This parameter could be a potentially useful exposure proxy for investigating particle exposure-related oxidative stress and its consequences. Further research is needed mostly to demonstrate the association of OP(DTT) with relevant oxidative endpoints in humans exposed to particles.

Le pas de l'échelle

A partir de la lecture d'un passage des Confessions qui raconte un voyage du jeune Jean-Jacques par le passage des Echelles, l'article montre comment Rousseau inscrit son corps et sa sensibilité dans l'espace et dans le temps. Rousseau témoigne d'une vision multiscalaire de l'homme et du monde, selon une triple échelle: celle de l'individu, celle de la société, et aussi celle de l'histoire de la Terre.

Sensitive photonic system to measure oxidative potential of airborne nanoparticles and ROS levels in exhaled air

A photonic system has been developed that enables sensitive quantitative determination of reactive oxygen species (ROS) - mainly hydrogen peroxide (H2O2) - in aerosol samples such as airborne nanoparticles and exhaled air from patients. The detection principle relies on the amplification of the absorbance under multiple scattering conditions due to optical path lengthening [1] and [2]. In this study, the presence of cellulose membrane that acts as random medium into the glass optical cell considerably improved the sensitivity of the detection based on colorimetric FOX assay (FeII/orange xylenol). Despite the loss of assay volume (cellulose occupies 75% of cell volume) the limit of detection is enhanced by one order of magnitude reaching the value of 9 nM (H2O2 equivalents). Spectral analysis is performed automatically with a periodicity of 5 to 15 s, giving rise to real-time ROS measurements. Moreover, the elution of air sample into the collection chamber via a micro-diffuser (impinger) enables quantitative determination of ROS contained in or generated from airborne samples. As proof-of-concept the photonic ROS detection system was used in the determination of both ROS generated from traffic pollution and ROS contained in the exhaled breath as lung inflammation biomarkers.

Qualité et DRG : mariage impossible ?

Les DRG, Diagnosis Related Groups, sont une classification permettant de regrouper les hospitalisations de soins aigus en fonction des affections traitées et des coûts engendrés. Ils ont été développes dans les années 70 à l'université de Yale aux Etats-Unis par le professeur Robert Fetter dans le but de standardiser les clientèles hospitalières dans un objectif de contrôle qualité. En Suisse, le financement en APDRG a commencé comme un projet pilote à Lausanne en 2002. Ce dernier a été repris du système déjà introduit aux Etat-Unis. Le 18 janvier 2008, la Suisse a décidé de passer à un financement en DRG au niveau national. La société anonyme SwissDRG a ainsi vu le jour en se basant sur Les G-DRG (=DRG allemand). Le coeur de ce mémoire consiste à déterminer si l'introduction des DRG ne causera pas une perte de qualité dans le système de soins. Afin de répondre à cette question, nous nous sommes basés sur l'expérience des autres pays notamment celle des Etats-Unis. L'étude réalisée par Kahn va être souvent prise en exemple. Les points forts qui en ressortent sont une augmentation de la sévérité des admissions, une baisse de la durée moyenne de séjour, une mortalité inchangée, ainsi que l'augmentation de l'état de santé instable à la sortie de l'hôpital. Ce qui ressort également dans l'ensemble des études documentées dans ce travail, c'est l'augmentation de l'efficience des hôpitaux et le risque qu'il y ait une sélection inverse des patients. [Auteur, p. 10]