Wildfire and African dust aerosol oxidative potential, exposure and dose in the human respiratory tract.

Exposure to wildfire smoke and dust can severely affect air quality and health. Although particulate matter (PM) levels and exposure are well-established metrics linking to health outcomes, they do not consider differences in particle toxicity or deposition location in the respiratory tract (RT). Usage of the oxidative potential (OP) exposure may further shape our understanding on how different pollution events impact health. Towards this goal, we estimate the aerosol deposition rates, OP and resulting OP deposition rates in the RT for a typical adult Caucasian male residing in Athens, Greece. We focus on a period when African dust (1-3 of August 2021) and severe wildfires at the northern part of the Attika peninsula and the Evia island, Greece (4-18 of August 2021) affected air quality in Athens. During these periods, the aerosol levels increased twofold leading to exceedances of the World Health Organization (WHO) [15(5) µg m-3] PM10 (PM2.5) air quality standard by almost 100 %. We show that the OP exposure is 1.5-times larger during the wildfire smoke events than during the dust intrusion, even if the latter was present in higher mass loads - because wildfire smoke has a higher specific OP than dust. This result carries two important implications: OP exposure should be synergistically used with other metrics - such as PM levels - to efficiently link aerosol exposure with the resulting health effects, and, certain sources of air pollution (in our case, exposure to biomass burning smoke) may need to be preferentially controlled, whenever possible, owing to their disproportionate contribution to OP exposure and ability to penetrate deeper into the human RT.

The Representativeness of Outdoor Particulate Matter Concentrations for Estimating Personal Dose and Health Risk Assessment of School Children in Lisbon.

This study investigated the suitability of outdoor particulate matter data obtained from a fixed monitoring station in estimating the personal deposited dose. Outdoor data were retrieved from a station located within the urban area of Lisbon and simulations were performed involving school children. Two scenarios were applied: one where only outdoor data were used assuming an outdoor exposure scenario, and a second one where an actual exposure scenario was adopted using the actual microenvironment during typical school days. Personal PM10 and PM2.5 dose (actual exposure scenario) was 23.4% and 20.2% higher than the ambient (outdoor exposure scenario) PM10 and PM2.5 doses, respectively. The incorporation of the hygroscopic growth in the calculations increased the ambient dose of PM10 and PM2.5 by 8.8% and 21.7%, respectively. Regression analysis between the ambient and personal dose showed no linearity with R2 at 0.07 for PM10 and 0.22 for PM2.5. On the other hand, linear regression between the ambient and school indoor dose showed no linearity (R2 = 0.01) for PM10 but moderate (R2 = 0.48) for PM2.5. These results demonstrate that ambient data must be used with caution for the representativeness of a realistic personal dose of PM2.5 while for PM10 the ambient data cannot be used as a surrogate of a realistic personal dose of school children.

Analysis of spatial factors, time-activity and infiltration on outdoor generated PM2.5 exposures of school children in five European cities.

Atmospheric particles are a major environmental health risk. Assessments of air pollution related health burden are often based on outdoor concentrations estimated at residential locations, ignoring spatial mobility, time-activity patterns, and indoor exposures. The aim of this work is to quantify impacts of these factors on outdoor-originated fine particle exposures of school children. We apply nested WRF-CAMx modelling of PM2.5 concentrations, gridded population, and school location data. Infiltration and enrichment factors were collected and applied to Athens, Kuopio, Lisbon, Porto, and Treviso. Exposures of school children were calculated for residential and school outdoor and indoor, other indoor, and traffic microenvironments. Combined with time-activity patterns six exposure models were created. Model complexity was increased incrementally starting from residential and school outdoor exposures. Even though levels in traffic and outdoors were considerably higher, 80-84% of the exposure to outdoor particles occurred in indoor environments. The simplest and also commonly used approach of using residential outdoor concentrations as population exposure descriptor (model 1), led on average to 26% higher estimates (15.7 µg/m3) compared with the most complex model (# 6) including home and school outdoor and indoor, other indoor and traffic microenvironments (12.5 µg/m3). These results emphasize the importance of including spatial mobility, time-activity and infiltration to reduce bias in exposure estimates.

Personal deposited dose and its influencing factors at several Greek sites: an analysis in respect to seasonal and diurnal variations.

The deposited dose in the human respiratory tract and its influencing factors were investigated for 8 urban/suburban locations within Greek cities. A dosimetry model (ExDoM2) was implemented assuming a 24-h exposure scenario to ambient PM10 whereby regional deposition rates were obtained. Simulations were performed considering three cases (Sahara dust, cold, and warm periods) with seasonal and diurnal variations examining the relative sources and other influencing factors in each case. Health risk indexes such as the relative risk and attributable fraction were also estimated. Overall, higher daily deposited dose was obtained for all urban compared with suburban locations (p < 0.05) and for cold compared with the warm periods (252-820 µg for cold period and 300-686 µg for warm period) for all locations. This finding was associated with increased deposition rate on cold period during evening/night hours, as a result of significant heating emissions. Besides that, most of the urban locations showed relative comparable deposition rates during the day, compared with the daily mean, for the two periods (cold and warm), indicating that urban-associated sources such as exhaust emissions and road dust resuspension contribute similarly to the deposited dose irrespectively of the season. Finally, the highest deposited dose was obtained during Sahara dust events ranged from 1881 to 4648 µg.

Development and application of a dosimetry model (ExDoM2) for calculating internal dose of specific particle-bound metals in the human body.

The objective of the current study was to develop a dosimetry model (ExDoM2) for calculating internal dose of specific particle-bound metals (As, Pb, Cd, Cr and Mn) in the human body. The ExDoM2 is a revised version of a respiratory tract model (ExDoM) incorporating a new particle clearance mechanism in the respiratory tract model and a Physiologically-Based PharmacoKinetic (PBPK) model. The revised respiratory tract model was used to calculate the deposition, clearance and retention of particles in the human respiratory tract and the mass transferred to the oesophagus (gastrointestinal tract) and blood. The PBPK module was used to analyze the distribution of metals (As, Pb, Cd, Cr and Mn) from the blood circulation system to other organs or tissues like liver, kidneys, heart, brain, muscle and bone. The model was applied to calculate the internal human dose for an adult Caucasian male exposed to particulate mass matter (PM), PMPb, PMCd, PMMn and PMCr in an urban area (Athens, Greece). The analysis showed that at the end of the exposure (one day exposure scenario) to PMPb, the major accumulation occurs in the bone, blood and muscle, whereas as regards PMCd the major accumulation occurs in the other tissues, like kidney and liver. In addition, for PMMn, the major accumulation occurs in the other tissues and lungs, whereas as regards PMCr the major accumulation occurs in the gastrointestinal (GI) tract and lungs. Therefore, ExDoM2 is an important feature in studying deposition of particles in the human body.

A methodology for the determination of fugitive dust emissions from landfill sites.

This study focuses on the development of a methodology for the determination of the contribution of fugitive dust emissions from landfill sites to ambient PM10 concentrations and the subsequent exposure to working personnel. Fugitive dust emissions in landfills mainly originate from resuspension due to truck traffic on paved and unpaved roads and from wind-blown dust from landfill cover soil. The results revealed that exposure to PM10, originating from fugitive dust emissions in the landfill site, was exceeding the health protection standards (50 µg m(-3)). The higher average daily PM10 concentration (average value) for weekdays was equal to 275 µg m(-3) and was computed for the areas nearby the unpaved road located inside the landfill facilities that lead to the landfill cell. The percentage contributions of road and wind-blown dust to the PM10 concentrations on weekdays were equal to 76 and 1%, respectively. The influence of the background concentration is estimated close to 23%.