CE34 - Contaminants, écosystèmes et santé

GET OP STAND OP : crossing Geochemistry, Exposure, healTh: Oxidative Potential, a first STANDardization before OPerativeness. – GET_OP_STAND_OP

At the intersection of geochemistry, exposure, and HEALTH: Oxidative potential, towards a demonstration of operationality.

Determination of the reliability of the oxidative potential as a relevant indicator of fine-particle-related health effects, a necessary step before its evaluation as a new metric for air quality regulation.

Issues for future air quality measurement

Poor air quality is the 4th leading cause of premature death worldwide. Epidemiological studies agree on the importance of airborne particles (PM) in the health conditions linked to the air we breathe. However, it is also well established that a large fraction of PM is of low toxicity, and that only a few chemical species that contribute little to the total mass may play a major role in the inflammatory mechanisms that underlie known diseases. Thus, the mass concentration of PM, currently used as a regulatory metric, is probably not the most comprehensive.<br /><br />Aerosol oxidative potential (OP) is an integrative measure of the reaction capacities of PM, which mimics the contact of particles with the pulmonary environment and assesses the capacity of particles to induce a redox imbalance at the base of the inflammatory cascade. Different cell-free measurements of the OP of PM are proposed in the literature, depending on the antioxidant considered (DTT, AA, RTLF, DCFH, etc.), without however establishing a consensus as to the «right test« to use. Indeed, measurements are still scattered and the links between OP and toxicology, or between OP and epidemiology, require numerous observations and in-depth studies.<br />This ANR proposes both an extensive measurement of the PO on numerous measurement sites covering at least one complete year of sampling, the evaluation of exposure with this metric, as well as a cross study with an epidemiological cohort. This set of studies could lead to definite progress in testing the predictive character of the OP as a relevant metric of health exposure to air pollution.

WP1: Contribution of sources to the oxidative potential of aerosols :
The contribution of the different sources of particulate matter emissions (whether natural or anthropogenic) is estimated from field samples allowing an in-depth analysis of their composition. An inverse model (e.g. PMF) is then used to determine which sources have contributed how many µg/m³ per day to the PM mass concentration. A second inverse model allows the attribution of an intrinsic OP to each of these sources by multivariate linear regression. The contribution of each source to the PM OP is thus estimated for a set of 15 French urban sites.
In parallel, a deterministic air quality prediction model (similar to a meteorological model) is confronted with field measurements, and the spatial and temporal prediction of the OP thanks to this model is considered.

WP2: Exposure/health
This work package is based on the SEPAGES cohort which follows more than 450 families in Grenoble to study the health impacts of air pollution.
Personal exposure is measured using miniature particle samplers worn during pregnancy and early childhood. These samplers allow for a measurement of exposure (mass concentration and personal OP) as close as possible to real conditions, and are then compared with health observations of the child's development.
In addition, measurements were carried out on 40 volunteer participants in indoor and outdoor air, which will also allow the estimation of OP sources in indoor air and a first very local mapping of OP.

The wide spatial stability of the intrinsic PM source OP allows a robust estimation of the contribution of the different PM sources to the OP. In doing so, an important redistribution of the contribution of the sources is observed according to the observation metric (mass or OP). In particular, road traffic is the first source contributing to the OP, far ahead of the other sources, which was not the case for the contribution to PM mass. The difference between the different OP tests underlines the importance of epidemiological studies to determine which of these OP measures is most relevant.

The large and fine scale documentation of the OP of such a magnitude constitutes a scientific first and will allow the investigation of the relationship between OP and health within this ANR (SEPAGES cohort), but also through the reuse of other European cohorts thanks to the spatialized prediction of the OP by deterministic modeling.

In the end, the demonstration of the more predictive character of the OP in relation to the mass for the health affections, in connection with the public policies, will allow a more effective prevention of the air quality and the installation of regulation of the emissions all the more relevant.

Plusieurs articles concernant la contribution des sources de PM au OP ont d’ors et déjà été publiés, à propos de la variabilité fine échelle du OP au sein d’un bassin métropolitain, mais également sur les généralités observables à l’échelle de la France et de l’Europe.
1. “Source apportionment of atmospheric PM10 Oxidative Potential: synthesis of 15 year-round urban datasets in France”. Atmospheric Chemistry and Physics. 2021. doi.org/10.5194/acp-2021-77
2. “Disparities in particulate matter (PM10) origins and oxidative potential at a city-scale (Grenoble, France) – Part II: Sources of PM10 oxidative potential using multiple linear regression analysis and the predictive applicability of multilayer perceptron neural network analysis”. Atmospheric Chemistry and Physics. 2021. doi.org/10.5194/acp-21-5415-2021
3. “Disparities in particulate matter (PM10) origins and oxidative potential at a city-scale (Grenoble, France) – Part I: Source apportionment at three neighbouring sites”. Atmospheric Chemistry and Physics. 2020. doi.org/10.5194/acp-2021-57
4. “Sources of particulate-matter air pollution and its oxidative potential in Europe”. KR Daellenbach, G Uzu, J Jiang, LE Cassagnes… - Nature, 2020 doi.org/10.1038/s41586-020-2902-8

Poor air quality has become one of the main controllable public health problems in many areas, both in developing countries and industrial societies. Epidemiological studies suggest that the larger parts of air pollution chronic effects are likely to stem from Particulate Matter (PM). Most of these studies use PM mass concentration as the exposure metric and current regulation actions are also based on PM mass. However, much of the ambient particle mass consists of low toxicity components, whereas reactive trace species can be major contributors to PM toxicity. Mass may thus not be the best marker of the health impact of PM. However, there is currently no consensus regarding a possible alternative metric that would provide relevant information for health, and could be standardized and used in routine measurements.

One key parameter that drives the PM toxicity is their carrying or inducing reactive oxygen species (ROS) in the lung, at the origin of biological effects by disrupting the lung natural redox balance. This new health metric is defined as the Oxidative Potential (OP) of PM. Since OP integrates processes related to particles size and surface properties together with their chemical composition, it is believed to give a “simple” integrative metric more representative of PM potential interactions with specific targets in the human body.

GET OP, STAND OP overarching aim is to make significant progresses to validate or invalidate oxidative potential of PM as a relevant indicator of health impacts of PM exposure, as a step towards proposing it as metric for air quality regulation. To achieve this overall objective, the following program is being implemented.

WP1: Towards a CTM-based source apportionment of OP over Europe. WP1 methodology relies first on extended time series of OP measurements including three complementary assays. PM10/2.5 samples will come from contrasted environments from many past and ongoing programs that include extensive chemical characterization (~ 4 500 samples). We will apply an OP apportionment method for all sites, combining positive matrix factorization and multi-dimensional analysis of OP. Then, we perform the implementation of OP as a prognostic variable in chemical transport model LOTOS-EUROS with the overall goal to get daily OP maps over Europe. WP1 will lead to a comprehensive “climatology” of OP for various environments, assessing quantitative links with PM chemistry and sources. Ranking sources of PM emissions as OP contributors is a key parameter for policy initiatives, as is the demonstration of the capability of a large scale chemical-transport model to predict OP.

WP2: OP exposure in a medium-size town. WP2 will rely on a field campaign with both indoor and outdoor sampling for about 40 sites in the Grenoble area, in cold and warm seasons. We aim at recalculating a realistic average OP exposure for the whole population derived from personal OP and outdoor/indoor OP and to assess further spatial and temporal variations of OP in Grenoble. It is based on the Land-Use-Regression interpretation of OP measurements from indoor/outdoor campaigns and from the extended time-series of OP measurements from one background outdoor site of Grenoble.

WP3: OP relevance for cohort’s health. OP is usually assessed on filters from ambient samples which are not representative of personal exposure. In the context of the SEPAGES mother-child cohort in Grenoble, women and their newborns have carried for 8 days in several occasions a personal active PM sampler to monitor their exposure. We will characterize the association between personal OP (from cohort’s filter) and the health of pregnant women adjusting for the relevant confounders using regression models. WP3 will give a proper evaluation of the hypothesis that OP’s could be better predictor than the mass for each of the health endpoint.

Project coordinator

Madame Gaelle UZU (Institut des Géosciences de l'Environnement)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IGE Institut des Géosciences de l'Environnement

Help of the ANR 311,843 euros
Beginning and duration of the scientific project: December 2019 - 36 Months

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