Higher health effects of ambient particles during the warm season: The role of infiltration factors

Abstract

A large number of studies have shown much higher health effects of particulate matter (PM) during the warm compared to the cold season. In this paper we present the results of an experimental study carried out in an unoccupied test apartment with the aim of understanding the reasons behind the seasonal variations of the health effects due to ambient PM exposure. Measurements included indoor and outdoor PM mass and chemical composition as well as particle size distribution of ultrafine particles. Monitoring campaigns were carried out during summer and winter following a ventilation protocol developed to replicate typical occupant behaviour according to a questionnaire-based survey. Our findings showed that seasonal variation of the relationship between ambient and indoor mass concentrations cannot entirely explain the apparent difference in PM toxicity between seasons and size distribution and chemical composition of particles were identified as other possible causes of changes in the apparent PM toxicity. A marked decrease of ultrafine particles (<100 nm) passing from outdoors to indoors was observed during winter; this resulted in higher indoor exposure to nanoparticles (<50 nm) during summer. With regards to the chemical composition, a pooled analysis showed infiltration factors of chemical species similar to that obtained for PM mass with values increasing from 0.73 during winter to 0.90 during summer and few deviations from the pooled estimates. In particular, significantly lower infiltration factors and sink effect were found for nitrates and ammonium during winter. In addition, a marked increase in the contribution of indoor and outdoor sulfates to the total mass was observed during summer.

Estimations of infiltration factors of diurnal PM 2.5 and heavy metals in children’s bedrooms

“…Thus, estimating the PM 2.5 F inf is crucial in epidemiological studies of the effects of PM 2.5 exposure on children’s health. Our results are consistent with PM 2.5 F inf in residences in the previous studies (0.5–0.7) 11,18,19 . However, the PM 2.5 F inf from the present study was higher than MacNeill’s study in residence homes (average: 0.33, min to max: 0.24–0.36) 17 .…”

“…Previous studies have suggested that particle size is negatively associated with deposition rate. 18,56 In the present study, the median aerodynamic diameter (reported in related studies) was used (Table S2). Cr registered the largest median aerodynamic diameter, followed by V, Zn, Pb, and Mn.…”

“…The particle F inf can represent the equilibrium fraction of outdoor particles that penetrate indoors and remains suspended, 16 which is useful in calculating the fraction of outdoor particles ingress into buildings. Two methods can be used to calculate the PM 2.5 F inf (1) collecting the indoor and outdoor PM 2.5 concentrations, ventilation rate, particle penetration factor, and deposition rate to calculate the F inf 11‐13 and (2) estimating the PM 2.5 F inf from a predictive model 17‐19 . Researchers have reported seasonal and spatial variations in PM 2.5 F inf 19,20 due to variations in climates or regions.…”

Outdoor and indoor fine particulate matter at skilled nursing facilities in the western United States during wildfire and non‐wildfire seasons

“…The source of variability in infiltration could be due to external factors, built environment factors, or behavioral factors. There are seasonal trends in particulate infiltration with more outdoor particulate reaching the indoor space in the summer rather than winter; these trends also yield more ultrafine and nanoparticle infiltration in the summer than in the winter 37 . Here, we only captured a modest amount of data related to building characteristics.…”

Seasonal Variation in the Biological Effects of PM2.5 from Greater Cairo

“…In recent years, many developing countries, like Egypt, have experienced rapid urbanization, industrial development, construction activities and an increase in traffic flow, all of which seriously threaten the environment with the huge amounts of pollutants emitted. One of the major air pollutants is particulate matter (PM), which contributes to acidification of precipitation and climatic change, and affects Earth’s radiation balance, agriculture, material and cultural heritages and ecosystems [4,5,6]—but is also one of the most deleterious pollutants for human health.…”