Outdoor Particle Number Concentrations Research Articles

Effect of indoor and outdoor sources on indoor particle concentrations in South Korean residential buildings

The rising indoor air pollution from particles is a cause for concern especially in houses where children and the elderly reside. In South Korea, assessment of exposure to particle number (PN) in residential apartments, which account for 76% of all houses, is limited. In our study, the indoor and outdoor PN (sizes 0.3–10.0 µm) concentrations were measured in ten typical apartments for 24 h each. In addition, the occupants’ schedules were examined by conducting a survey.Results showed that the average outdoor PN concentrations were 0.30–4.37 × 109/m3 with very large deviations. Indoor peak events were mainly caused by cooking, and total emitted particles were 0.01–81.3 × 1013 particles. Indoor PN concentrations were sustained for a long time because of inefficient ventilation that led to lowered attenuation.Indoor particles are generated during various indoor activities. The daily-integrated particle exposures were 21.4% and 78.6% for indoor and outdoor sources, respectively. Thus, outdoor sources were the predominant sources of particle exposure compared with indoor sources. In conclusion, penetration from outdoor sources needs to be reduced by adding air filtration to improve the airtightness of buildings when introducing outdoor air to lower the indoor PN concentration.

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

Background: Trends of indoor-outdoor ratios (IOR) of particle number concentrations (PNC) by temporal and meteorological factors can enhance our understanding of this harmful exposure and its sources.Methods: PNC data was collected from a one-year field campaign where simultaneous meteorological parameters were measured continuously usind Dylos DC500 devices in five locations in Israel, which is one of the high PM area. Generalized linear models were used for estimating the association between the explanatory variables (outdoor PNC, hour of the day, weekend/workday, season, ambient temperature, ambient relative humidity, wind speed) and the IOR.Results: The median is 0.830 for fine IOR and is 0.702 for coarse IOR in general, and all IOR medians were ≤1 in entire locations. Lower IORs were experienced at night, with the daily peak in IOR around noon. The IORs shows a double-hump pattern with higher IOR in spring and autumn, and lower IOR in summer and winter.Conclusions: The outdoor PNC was found to be the most important predictor of indoor PNC at any meteorological conditions, especially for fine particles, but the residents’ preferences and activities may dominate the IOR when considerable indoor emissions prevail whereas smoking and cooking tend to elevate the fine PNC, house holding activities effect to a larger extent the coarse fraction.

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

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.

(Ultra) Fine particle concentrations and exposure in different indoor and outdoor microenvironments during physical exercising

ABSTRACTAlthough regular exercise improves overall well-being, increased physical activity results in enhanced breathing which consequently leads to elevated exposure to a variety of air pollutants producing adverse effects. It is well-known that one of these ambient air contaminants is ultrafine particles (UFP). Thus, this study aimed to (1) examine exposure to particle number concentrations (PNC) in size ranging from N20–1000 nm in different sport environments and (2) estimate the respective inhalation doses across varying activity scenarios based upon the World Health Organization recommendations for physical activity. PNC were continuously monitored (TSI P-Trak™ condensation particle counter) outdoors (Out1–Out2) and indoors (Ind1–Ind2; fitness clubs) over 4 weeks. Outdoor PNC (total median 12 563 # cm–3; means of 20 367 # cm–3 at Out1 and 7 122 # cm–3 at Out2) were approximately 1.6-fold higher than indoors (total median 7 653 # cm–3; means of 11 861 # cm–3 at Ind1 and 14 200 # cm–3 at Ind2). The lowest doses were inhaled during holistic group classes (7.91 × 107–1.87 × 108 # per kg body weight) whereas exercising with mixed cardio and strength training led to approximately 1.8-fold higher levels. In order to optimize the health benefit of exercises, environmental characteristics of the locations at which physical activities are conducted need to be considered.

Exposure to air particulate matter with a case study in Guangzhou: Is indoor environment a safe haven in China?

Urban residents spend the majority of time in indoor environments, which, however, may not be a safe haven for staying away from outdoor air pollution, especially in China. To examine this hypothesis, the particle mass concentrations (0.056–18 μm) and number concentrations (14–660 nm) were simultaneously measured in and outside of three typical urban indoor settings (n = 9), i.e., school, office and residence in Guangzhou, China from October–November 2014 (dry weather season) and June–August 2015 (wet weather season). The indoor and outdoor particle number concentrations were positively correlated with each other at all three sampling settings for both dry and wet weather seasons (r2 = 0.13–0.65, p < 0.001). The infiltration factors and indoor/outdoor ratios of particles (14–660 nm) were estimated at 0.30–0.75 and 0.85–1.5, respectively, which were comparable to or higher than those (0.12–0.76 and 0.03–1.1) found in cites of other countries under infiltration conditions. Furthermore, the average infiltration factor of fine particle numbers (50–660 nm) in an office was 0.61 during a severe haze episode, indicating that approximately 60% of outdoor particles penetrated indoors. All findings suggested an efficient transport of outdoor particle sources into indoor environment, confirming that exposure of the general public to indoor particles in China should not be overlooked due to effective infiltration of outdoor particles and frequent heavy haze episodes.

Aviation-Related Impacts on Ultrafine Particle Number Concentrations Outside and Inside Residences near an Airport.

Jet engine exhaust is a significant source of ultrafine particles and aviation-related emissions can adversely impact air quality over large areas surrounding airports. We investigated outdoor and indoor ultrafine particle number concentrations (PNC) from 16 residences located in two study areas in the greater Boston metropolitan area (MA, USA) for evidence of aviation-related impacts. During winds from the direction of Logan International Airport, that is, impact-sector winds, an increase in outdoor and indoor PNC was clearly evident at all seven residences in the Chelsea study area (∼4–5 km from the airport) and three out of nine residences in the Boston study area (∼5–6 km from the airport); the median increase during impact-sector winds compared to other winds was 1.7-fold for both outdoor and indoor PNC. Across all residences during impact-sector and other winds, median outdoor PNC were 19 000 and 10 000 particles/cm3, respectively, and median indoor PNC were 7000 and 4000 particles/cm3, respectively. Overall, our results indicate that aviation-related outdoor PNC infiltrate indoors and result in significantly higher indoor PNC. Our study provides compelling evidence for the impact of aviation-related emissions on residential exposures. Further investigation is warranted because these impacts are not expected to be unique to Logan airport.

Exploratory assessment of indoor and outdoor particle number concentrations in Hanoi households

No studies have been conducted in Vietnam to understand the levels of atmospheric ultrafine particles, despite having adverse health effects. Information about indoor air quality in Vietnam is also limited. Hence we aimed to conduct the first assessment of ultrafine particle concentrations in terms of particle number (PN) in Hanoi, by simultaneously measuring indoor and outdoor PN concentrations from six households at different locations across the city in January 2016. We also acquired PM2.5 data for this monitoring period from an air quality monitoring station located at the US Embassy in Hanoi, to compare the general trends between PN and PM2.5 concentrations. The mean daily indoor and outdoor PN concentrations for the monitoring period were 1.9×104p/cm3 and 3.3×104p/cm3, respectively, with an increase during rush hour traffic. It was concluded that traffic was the main contributor to outdoor PN concentrations, with agricultural burning having a small influence at one study location. The mean ratio of indoor to outdoor PN concentrations for all six sites was 0.66±0.26, which points to outdoor air as the main driver of indoor PN concentrations, rather than indoor sources. These PN concentrations and I/O ratios are similar to those reported for a number of cities in developed countries. However, in contrast to PN, ambient mean PM2.5 concentrations in Hanoi (60–70μg/m3) were significantly higher than those typically recorded in developed countries. These findings demonstrate that urban particle mass (PM2.5) concentrations are not indicative of the PN concentrations, which can be explained by different sources contributing to PN and PM, and that direct measurements of PN are necessary to provide information about population exposure to ultrafine particles and for management of air quality.

Ultrafine particle concentrations and exposures in four high-rise Beijing apartments

Abstract Ultrafine particle (UFP) exposures have the potential to elicit adverse health effects. People spend most of their time within their place of residence. Little information is available on UFP levels in homes in mainland China. To contribute new data to this important topic, we made time-series measurements of particle number (PN) concentrations and resident activities inside four apartments in high-rise buildings in Beijing during June to August 2009. Indoor PN concentrations at the four sites, averaged over the few-day duration of monitoring at each site, spanned an order of magnitude, from 2800 to 29,100 cm−3. This wide range resulted from differences among apartments in three main factors: (1) the frequency of indoor source events, including cooking activities and intrusion of cooking exhaust from neighboring apartments; (2) the extent of natural ventilation via open windows; and (3) the extent of active air filtration. Daily-integrated PN exposure of the thirteen residents, while in their apartments, ranged from 45,000 to 494,000 cm−3 h/d. For two sites at which outdoor PN concentrations were also measured, the percentage of daily-integrated residential exposure attributable to particles of outdoor origin was 58% for the residents of one site and 81% for residents of the other.

Long-Term Characterization of Indoor and Outdoor Ultrafine Particles at a Commercial Building

The particle number concentrations in the size range of 10-500 nm were measured inside and outside of a commercial building in Rochester, New York from 2005 to 2009. The indoor ventilation conditions were controlled by a heating, ventilation, and air-conditioning (HVAC) system. The overall average indoor and outdoor particle number concentrations were 2166 cm(-3) and 5214 cm(-3), respectively. Comparison of the indoor and outdoor ultrafine particles (UFP) distributions revealed that indoor sources contributed to the indoor UFP concentrations. The indoor/outdoor (I/O) ratio generally increased with particle size. The I/O ratios in the summer months were higher than those in the winter months. Indoor and outdoor correlations of particle concentrations were slightly weaker in warmer months. These results indicated that changes in the air exchange rates (AER) may have affected the correlation between indoor and outdoor UFP number concentrations. Moreover, indoor activities such as food preparation and cleaning may have contributed to the indoor UFP number concentrations.

Comparison of sources of submicron particle number concentrations measured at two sites in Rochester, NY

Sources contributing to the submicron particles (100–470 nm) measured between January 2002 and December 2007 at two different New York State Department of Environmental Conservation (NYS DEC) sites in Rochester, NY were identified and apportioned using a bilinear receptor model, positive matrix factorization (PMF). Measurements of aerosol size distributions and number concentrations for particles in the size range of 10–500 nm have been made since December 2001 to date in Rochester. The measurements are being made using a scanning mobility particle sizer (SMPS) consisting of a DMA and a CPC (TSI models 3071 and 3010, respectively). From December 2001 to March 2004, particle measurements were made at the NYS DEC site in downtown Rochester, but it was moved to the eastside of Rochester in May 2004. Each measurement period was divided into three seasons i.e., winter (December, January, and February), summer (June, July, and August), and the transitional periods (March, April, May, September, October, and November) so as to avoid experimental uncertainty resulting from too large season-to-season variability in ambient temperature and solar photon intensity that would lead to unstable/non-stationary size distributions. Therefore, the seasons were analyzed independently for possible sources. Ten sources were identified at both sites and these include traffic, nucleation, residential/commercial heating, industrial emissions, secondary nitrate, ozone- rich secondary aerosol, secondary sulfate, regionally transported aerosol, and a mixed source of nucleation and traffic. These results show that the measured total outdoor particle number concentrations in Rochester generally vary with similar temporal patterns, suggesting that the central monitoring site data can be used to estimate outdoor exposure in other parts of the city.

Impact of ventilation scenario on air exchange rates and on indoor particle number concentrations in an air-conditioned classroom

A 2-week intensive measurement campaign of indoor and outdoor air pollution was carried out in September 2006, in a primary school to investigate indoor–outdoor correlations of particle number (PN) concentrations, and the impact of air exchange rate (ACH) on the indoor PN concentration. The ACHs in the classroom for different conditions associated with window opening and the operational status of air conditioners (A/C) and fans were tested. As expected, the lowest ACH (0.12 h −1) was found when the windows were closed and A/C and fans were off. In contrast, the highest ACH (7.92 h −1) was observed when the windows were opened and A/C and fans were all on. The analysis of the PN I/ O ratios at different ACHs in the absence of indoor sources indicates that the mean I/ O ratio was 0.621±0.007 (mean±95% confidence interval) when the windows were closed, and A/C and fans were off; 0.524±0.023 when windows were closed, fans were off and A/C was on; and 0.502±0.029 when windows were closed, A/C was off and fans were on. To further understand the relationship between indoor and outdoor PN concentrations, the impact of outdoor PN concentration on I/ O ratios at different ACHs was investigated. It was found that the relationship between outdoor PN concentration and the I/ O ratio at different ACHs followed a power trendline with an equation of I/ O ratio= A PN out −b ( A and b are coefficients, PN out is outdoor PN concentration), suggesting that the penetration efficiency decreased with increasing outdoor PN concentration. It is the first time we found that when the outdoor PN concentration increased there was an associated increase in the concentration of nano-particles, which have been demonstrated to have higher deposition rates and lower penetration efficiencies. Based on the above equation, the study also showed a significant effect of ACH on indoor PN concentrations under stable outdoor PN concentrations. In general, the higher the ACH was, the lower the indoor PN concentration was.

Relative levels of indoor and outdoor particle number concentrations in a residential building in Xi'an

The time series of indoor and outdoor particle number concentrations in a naturally ventilated residential building in Xi'an were tested simultaneously for 7 days in summer. The relationships between indoor and outdoor concentrations were examined and discussed, and linear regression analysis was employed to correlate the indoor and outdoor concentrations. The diurnal cycles of indoor and outdoor particle concentrations of different particle size ranges all showed positive correlations between indoor and outdoor number concentrations. The I/O ratios of number concentrations varied with the increase of particle size in the range of 0.89 (±0.19) to 0.99 (±0.15).

Indoor and outdoor submicrometer particles: Exposure and epidemiologic relevance (“the 3 indoor Ls”)

Airborne particles represent a very important pollutant with respect to healthy housing conditions. The snag is that in lack of indoor data epidemiological studies focusing on submicron and ultrafine (<100 nm in diameter) particles are usually forced to use outdoor particle concentrations only. On the other hand it is known that people spend most of their time indoors. The aim of this paper is therefore to give a short comprehensive overview of the indoor/outdoor problem with regard to submicron and ultrafine particles, investigating how indoor particle size distributions correlate with outdoor concentrations in the absence of significant indoor sources. In the absence of a major indoor source, total indoor particle number concentrations were always lower than outdoor concentrations. The highest ratios between indoor and outdoor concentrations tend to correlate with lower rather than higher total outdoor particle number concentrations. Concentration ratios depend on particle size. Time lags of the correlation coefficients between the concentrations of indoor and outdoor particles of different diameters have been determined to assess the time the particles need to enter the indoor site through closed modern-type windows. Typical lag times of 0.5-3 h between somewhat smaller indoor particles and somewhat larger outdoor particles have been observed. To assess the resulting particle burden for humans, a suitably weighted average emphasizing indoor aerosol particles must be used. To classify the health effects of particles of different diameters, different decreases of particle number concentrations depending on the particle sizes must be taken into account if indoor concentrations cannot be measured and outdoor concentrations are used in place of indoor measurements. In urban areas, ultrafine particles originate primarily from rapidly increasing traffic, which is the dominating source at many urban sites. The influence of traffic on outdoor and indoor concentrations is therefore of special interest.

Particle Concentrations and Sizes with Normal and High Efficiency Air Filtration in a Sealed Air-Conditioned Office Building

During parts of 7 consecutive weeks, indoor and outdoor particle number concentrations and particle sizes were measured versus time in a large sealed air-conditioned office building without tobacco smoking. Building ventilation rates were also measured. During some periods, the normal filters in the building's air handling systems were replaced with high efficiency filters. A mass balance model was used to help interpret the study data. For all particle sizes, indoor number concentrations varied considerably between weeks and within a single work day. Even with the normal air filters, which have a low efficiency for submicron-size particles, indoor number concentrations of submicron particles were a factor of 3-6 smaller than outdoor particle number concentrations. For the range of particle sizes measured (> 0.3 μm), the indoor particle mass concentration was considerably less than outdoor particle mass concentration. The high efficiency filters dramatically reduced the indoor-outdoor particle concentration ratio for submicron particles (i.e., the decrease was 70% to 95%, depending on particle size). For larger particles, the decreases in indoor concentrations were substantially smaller. Comparisons of model predictions with measured data provide evidence of a large rate of removal of submicron indoor particles by some process other than ventilation or air filtration and also provide evidence of significant indoor generation or resuspension of particles larger than 1 μm.