Predictors of the Indoor-to-Outdoor Ratio of Particle Number Concentrations in Israel

Siyu Zhang,Raanan Raz,Yuval Yuval,David M Broday

doi:10.3390/atmos11101074

Abstract

Exposure to airborne particles is a risk factor of many short- and long-term health effects. Most epidemiological studies include estimates of exposure to ambient particles, however, people living in developed countries spend most of their time indoors. This work presents an analysis of a field campaign of simultaneous measurements of indoor-to-outdoor particle number concentrations (PNCs) in Israel. Fine and coarse PNCs were continuously measured using Dylos DC1700 devices from October 2016 to October 2017. The median outdoor PNC was always higher than the indoor PNC in all the five sampling locations. Outdoor fine PNCs peak during the night and experience a trough in the afternoon. The median of the fine indoor-to-outdoor PNC ratio (IOR) was 0.83, with an inter quartile range (IQR) of 0.59. The median of the coarse IOR was 0.70, with an IQR of 0.77. Lower IORs were experienced at night than during the day, with a daily peak (IOR > 1) around noon. Information about the IOR in different regions and seasons may help epidemiologists and policy makers understand the true health effects of particulate air pollution, and correct their exposure estimations such that they account for indoor exposure as well.

Highlights

Exposure to particulate matter (PM) is a risk factor of many short- and long-term health effects, especially for respiratory and cardiovascular diseases [1]
PM is consisted of a mixture of solid and liquid particles, with actual components that vary according to its source, season, geographic region, and meteorological conditions [2,3]
The observed hourly particle number concentrations (PNCs) distribution may reflect a larger impact of indoor human activities on PNC of the coarse fraction than on PNC of the fine fraction, since suspended dust is commonly found in the coarse size fraction

Summary

Introduction

Exposure to particulate matter (PM) is a risk factor of many short- and long-term health effects, especially for respiratory and cardiovascular diseases [1]. Numerous epidemiological studies already found associations between PM and adverse health effects, most studies accounted only for ambient PM. Indoor particles can originate from both outdoor and indoor sources, with the prominent anthropogenic indoor sources being cooking, smoking, heating, and domestic activities that can be impacted by many factors [7,8]. Penetration of outdoor particles to indoor environments occurs by three main mechanisms: mechanical (forced) ventilation, natural ventilation and infiltration [9]. Other factors that affect the penetration of ambient particles into built environments are the geographic location, meteorology and the particle composition [10], as well as the occupants personal preferences regarding open windows and heating, ventilation and air conditioning (HEVAC)

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Results

Discussion

Conclusion