BRiC 2019 ID.12

 

Integrated study of workers' exposure to atmospheric particulate matter in indoor environments: numerical-experimental simulation of fluid dynamics and concentration fields, in real and laboratory scale; chemical, morphological and toxicological characterization of fine and ultrafine particles

Financed by: INAIL Period: November 2020 - November 2022

Introduction

It is widely demonstrated that much of the exposure to atmospheric particulate matter (PM) occurs indoors and it is therefore essential to characterize the PM present in these environments and quantify its effects on the health of exposed people. Most of the studies aimed at estimating the PM concentration in indoor environments assume that the PM concentrations are homogeneous and stationary and do not properly consider the influence on air quality by both the fluid dynamic field in the environment itself and the outdoor micrometeorological conditions near the building. This makes it necessary to quantify the relationship between indoor and outdoor concentrations in points adjacent to the considered environment and highlight the role of the presence and movement of people in indoor emissions, in addition to any other internal sources and infiltration of PM from the outside.

Description

The activities foreseen by the project will take place in working environments and include: - the micrometeorological characterization of the study domain using meteorological sensors capable of acquiring, at high frequency, air speed and temperature in different points of the area of ​​interest, both inside and outside the building; - the numerical simulation of air circulation in indoor environments using both modeled and acquired fluid dynamic data; - the evaluation of the concentrations inside the building using dispersion models suitable for the turbulent characteristics of the indoor environments, to be compared with experimental data acquired in the field; - the analysis of indoor levels of fine and ultrafine PM, with instruments with low sampling flows and with high time resolution measurements, for the evaluation of the size distributions, the concentration in number, the surface and the volume of the particles; - analysis of the chemical composition of fine powders, with particular reference to the main non-refractory components of PM, both organic (black carbon and brown carbon) and inorganic (nitrate, sulphate, ammonium, chloride); - the characterization of indoor and outdoor sources of ultra-fine particles and of the organic fraction of indoor fine PM, with particular interest in the contribution from transport systems; - the realization of an exposure system for in vitro toxicological tests based on cellular systems characteristic of the human lung epithelium and representative of a real exposure; - PM sampling on filter membranes, in multiple sites and in different seasons, simultaneously indoors and outdoors, carried out using silent instrumentation and over a period of time suitable for the work activities of the chosen site (working / night hours, working days / weekends ); - the measurement of the concentration of PM and its chemical composition through the determination of the macro-elements, micro-elements and trace elements in the bioaccessible and residual fractions, ions, elemental and organic carbon; - morphological analysis of the PM by scanning electron microscopy and quantitative determination of the bioaerosol by optical microscopy analysis; - the measurement of the oxidative potential of PM to estimate its ability to induce oxidative stress, to be compared with the results obtained from in vitro tests.

Aims

The general objective of the project is to provide an integrated physical, chemical, morphological and toxicological description of air pollution from particulate matter in indoor work environments, with particular reference to the ultrafine fraction and the effects due to the presence of individuals. The methodological approach in fact provides for the integration of data on the fluid dynamic characteristics of the environments with the measurement of the chemical, morphological and dimensional properties of the particulate material. Furthermore, the variations of PM in space and at different time scales (minutes, working day and weekends, seasons) and the toxicological properties will be evaluated by means of chemical tests and direct exposure of cellular systems. PM concentration maps will be created which will allow to identify the dynamics at the origin of the spatial distribution of particles in confined work environments and to evaluate the exposure of workers by estimating the fluctuations in the concentrations to which they may be exposed. Therefore, useful elements will be provided for the drafting of guidelines to identify the optimal positioning of the PM concentration control devices and workstations. We will also compare the different metrics currently under discussion for the measurement of worker exposure to PM (concentration in number, mass, surface area of ​​the particles) on the basis of real toxicity measures, identifying the most appropriate for the estimation of the risk to which they are exhibited indoors. The study of the chemical composition, morphology and microphysics of PM will make it possible to separate the contribution deriving from typically indoor sources from that due to the infiltration of particles from outdoor sources, evaluating the toxicity associated with each of them. We will apply for the first time, also for indoor environments, methods that foresee the in-vitro exposure of human lung cell lines for the evaluation of oxidative stress in conditions of real exposure. The CNR-IIA working group will realize the specific objectives of the project which include the indoor and outdoor sampling of the PM₁₀ on filter membranes, the sampling of the dimensionally segregated PM on 10 dimensional stages, the subsequent analysis of the chemical composition of the sampled powders, the morphological characteristics, the percentage of bioaerosol and the oxidative potential and the evaluation of the strength of the PM macro-sources. PM sampling₁₀ it will be performed simultaneously indoors and outdoors on Teflon, quartz and polycarbonate filter membranes, with different temporal resolution (sampling performed during working hours, at night and at weekends) and during the summer and winter seasons. Each measurement campaign will be conducted using silent instrumentation suitable for use also in indoor environments. For the chemical characterization of the sampled material, the analytical protocol provides, for all the PM samples collected on Teflon membranes, the determination of the total macro-elements by XRF, of the micro-elements and trace elements divided between bioavailable and residual fraction. by ICP, of ionic species by ion chromatography, and on the quartz membranes of elemental and organic carbon by thermo-optical analysis. The polycarbonate membranes will be used for the analysis of the content of the organic fraction attributable to the bioaerosol by selective coloring of the sampled material and observation under an optical microscope. The study of the morphology of the sampled particles will be carried out using a scanning electron microscope (SEM). Finally, the evaluation of the redox properties of PM and of the ability to induce oxidative stress will be evaluated using three different chemical methods (based on the use of ascorbic acid, dichlorofluorescein and dithiothriethol), which will allow to compare the results obtained with the tests performed in vitro.

Participants

- University of Rome "La Sapienza" - Department of Civil, Building and Environmental Engineering (DICEA) - University of Cagliari - Department of Civil, Environmental and Architecture Engineering (DICAAR) - National Research Council - Institute of Atmospheric and Climate Sciences ( CNR-ISAC) - National Agency for New Technologies, Energy and Sustainable Economic Development - Sustainability Department of Productive and Territorial Systems (ENEA-SSPT)

Working group