Office Indoor PM and BC Level in Lithuania: The Role of a Long-Range Smoke Transport Event

Julija Pauraite,Jurgita Ovadnevaite,Inga Garbarienė,Steigvilė Byčenkienė,Kristina Plauškaitė,Agnė Minderytė,Simonas Kecorius,Gediminas Mainelis,Vadimas Dudoitis

doi:10.3390/atmos12081047

Abstract

While the impacts of climate change on wildfires and resulting air pollution levels have been observed, little is known about how indoor air filtering systems are performing under intensive smoke conditions. For this aim, particle number size distribution and concentration in a size range 0.5–18 µm and equivalent black carbon (eBC) mass concentration were measured in a modern office with a mechanical ventilation system. Measurements took place from 30 September to 6 October 2020 in the Center for Physical Sciences and Technology (FTMC) campus located in the urban background environment in Lithuania. During the measurement campaign, an intensive pollution episode, related to long-range transport wildfire smoke, was observed. The results indicated that the smoke event increased both indoor and outdoor eBC mass concentrations twice. Filters were non-selective for different eBC sources (biomass burning versus traffic) or chemical composition of carbonaceous aerosol particles (eBC versus brown carbon (BrC)). Air filtering efficiency was found to be highly dependent on particle size. During the smoke event the highest particle number concentration was observed at 2.1 µm and 1.0 µm size particles in outdoor and indoor air, respectively. Differences of indoor to outdoor ratio between event and non-event days were not significant. Because of lower removal rate for small particles, eBC had higher contribution to total PM2.5 mass concentration in indoor air than in outdoor air. The results gained are crucial for decision-making bodies in order to implement higher-quality air-filtering systems in office buildings and, as a result, minimize potential health impacts.

Highlights

Numerous studies found that climate change has greatly enhanced the probability of extreme wildfires [1,2,3]
These findings are important, because to date, environmental legislation is based on mass concentration of particulate matter, such as PM10 and PM2.5, rather than on other particle parameters that could be associated with human health effects
The present study focuses on the ratio of particle number concentration and mass concentration in office indoor air during days with long-range transport wildfire smoke present

Summary

Introduction

Numerous studies found that climate change has greatly enhanced the probability of extreme wildfires [1,2,3]. Fine particulate matter (PM2.5) is the main pollutant emitted by fires, and it has been linked to various respiratory and cardiovascular health effects, such as cardiopulmonary and lung cancer mortality [11,12]. While exposures to PM2.5 are typically estimated based on PM2.5 mass concentration, Manigrasso et al (2020) [13] showed that fine particle number concentration is a more adequate metric than the PM mass. These findings are important, because to date, environmental legislation is based on mass concentration of particulate matter, such as PM10 and PM2.5, rather than on other particle parameters that could be associated with human health effects (e.g., particle number, shape, and chemical composition). Reid et al (2009) [20] demonstrated consistent evidence linking exposure to eBC-rich wildfire smoke with respiratory health effects such as asthma and chronic obstructive pulmonary disease

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