Personal, Indoor, and Outdoor Concentrations of Fine and Ultrafine Particles Using Continuous Monitors in Multiple Residences

Abstract

Concentrations of airborne continuous fine particulate matter or (PM 2.5 ), black carbon (BC), and ultrafine particles (UFP) were continuously measured over 5 days in winter and summer both indoors and outdoors at residences for forty-eight adults in 2005 and forty-seven asthmatic children in 2006. During 2006, personal concentrations of PM 2.5 were also measured continuously. All 4 continuous instruments employed performed well both in laboratory and field conditions. Mean outdoor concentrations of PM 2.5 , BC, and UFP were significantly higher than either indoor or personal concentrations. Air exchange rates were low (median value only 0.2/h), there was widespread use of central forced air and high-quality furnace filters. Outdoor concentrations of all particle-related pollutants showed overnight decreases followed by increases during the morning rush hours. Afternoon concentrations increased for UFP and decreased for BC, with PM 2.5 staying about the same. Between 5:00 pm and 7:00 pm, indoor UFP and PM 2.5 concentrations exceeded their mean daily values by 160% and 60%, respectively, suggesting that cooking is an extremely important source for these two pollutants. However, BC values did not increase at these hours. The highest indoor-outdoor ratios were observed for UFP suggesting that indoor sources were relatively more important for UFP than for other particle components. BC measurements in Windsor agreed moderately well (R 2 = 41%) with an independent measure of elemental carbon (EC) in Detroit. This large residential air pollution study has provided data making it possible to identify short-term variations and possible sources that can influence the relationships between pollutants and environments.

Assessment of Indoor-Outdoor Particulate Matter Air Pollution: A Review

“…Diapouli et al [68] report higher UFP mean concentrations outdoors (32,000 ± 14,200 particles/cm 3 ) rather than indoors (24,000 ± 17,900 particles/cm 3 ), with a maximum indoor mean value found in a library with a carpet-covered floor and a smoking office (both ≈52,000 particles/cm 3 ). Similar results are also found in other studies [53,60,61]. In particular, Zauli Sajani et al [61] investigate I-O concentrations in the front and back of a building along a high traffic street: the highest UFP 1 h-mean value is found for the outdoor front sampling (≈25,500 particles/cm 3 ) and the lowest in the indoor located in the back of the building (≈3500 particles/cm 3 ).…”

“…A similar temporal variation between occupancy and non-occupancy is also found in a previous study by Branis et al [56] which, however, developed the study using different sampling strategies and time references as discussed later in this review. High variability of PM 2.5 I-O concentrations is also described by other analysed studies [40,50,[57][58][59][60][61]. In particular, the findings of Liu et al [58] through different residential and commercial buildings in Beijing, clearly show the wide variability within indoor PM 10 and PM 2.5 concentrations which are, resultantly, higher in restaurants, dormitories, and classrooms, rather than in supermarkets, computer rooms, offices, and libraries (PM 10 and PM 2.5 ranging, respectively, from 373.8 µg/m 3 and 136.6 µg/m 3 in restaurants to 33.8 µg/m 3 and 5.6 µg/m 3 in libraries).…”

“…Moreover, a former study by Branis et al [56] adopted a custom 12 h time interval in order to collect mass concentrations on filters describing different periods of use of a university hall (lecture hours vs. nighttime). Among long-term measurement campaigns, semi-continuous approaches are also reported [60]. Such methodologies do not permit the collection of representative data over the time series, but merely to have a general picture of the phenomena over the sampling period.…”

“…Comparable values are found indoors at the front and outdoors at the back (7635 particles/cm 3 and 7444 particles/cm 3 , respectively) leading the authors to suggest similarities between the gradients of front-back (I-O) and of high-low traffic areas (I-O). Seasonal variability investigated by Wheeler et al [60] show both indoor and outdoor 24 h-averaged values are higher during winter rather than summer. Furthermore, the difference between indoor and outdoor concentrations is narrow during one of the sampled periods (the second summer campaign) due to a significantly lower outdoor averaged value compared to an another considered period with the same awaited meteorological conditions (first summer campaign).…”

“…In the reviewed articles, a heterogeneity in the use of multiple indicators is observed: the joint use of two indicators is found in different studies with PM 10 and PM 2.5 or PM 2.5 and UFP, while studies considering more than two indicators employed PM 10 and PM 2.5 with UFP or TSP [38,60,61]. The recurrence of the use non-typical PM classes (i.e., PM 5 , PM 4 , PM 1 ) is also found in many studies, frequently joint with the most-used indicators [49,50,54,57,62,71].…”