Field measurements of indoor and community air quality in rural Beijing before, during, and after the COVID-19 lockdown.

The coronavirus (COVID-19) lockdown in China is thought to have reduced air pollution emissions due to reduced human mobility and economic activities. Few studies have assessed the impacts of COVID-19 on community and indoor air quality in environments with diverse socioeconomic and household energy use patterns. The main goal of this study was to evaluate whether indoor and community air pollution differed before, during, and after the COVID-19 lockdown in homes with different energy use patterns. Using calibrated real-time PM2.5 sensors, we measured indoor and community air quality in 147 homes from 30 villages in Beijing over 4 months including periods before, during, and after the COVID-19 lockdown. Community pollution was higher during the lockdown (61 ± 47 µg/m3 ) compared with before (45 ± 35 µg/m3 , p < 0.001) and after (47 ± 37 µg/m3 , p < 0.001) the lockdown. However, we did not observe significantly increased indoor PM2.5 during the COVID-19 lockdown. Indoor-generated PM2.5 in homes using clean energy for heating without smokers was the lowest compared with those using solid fuel with/without smokers, implying air pollutant emissions are reduced in homes using clean energy. Indoor air quality may not have been impacted by the COVID-19 lockdown in rural settings in China and appeared to be more impacted by the household energy choice and indoor smoking than the COVID-19 lockdown. As clean energy transitions occurred in rural households in northern China, our work highlights the importance of understanding multiple possible indoor sources to interpret the impacts of interventions, intended or otherwise.

Personal Exposure to PM2.5 Oxidative Potential in Association with Pulmonary Pathophysiologic Outcomes in Children with Asthma.

Fine particulate matter (PM2.5) with a higher oxidative potential has been thought to be more detrimental to pulmonary health. We aim to investigate the associations between personal exposure to PM2.5 oxidative potential and pulmonary outcomes in asthmatic children. We measured each of the 43 asthmatic children 4 times for airway mechanics, lung function, airway inflammation, and asthma symptom scores. Coupling measured indoor and outdoor concentrations of PM2.5 mass, constituents, and oxidative potential with individual time-activity data, we calculated 24 h average personal exposures 0-3 days prior to a health outcome measurement. We found that increases in daily personal exposure to PM2.5 oxidative potential were significantly associated with increased small, large, and total airway resistance, increased airway impedance, decreased lung function, and worsened scores of individual asthma symptoms and the total symptom score. Among the PM2.5 constituents, organic matters largely of indoor origin contributed the greatest to PM2.5 oxidative potential. Given that the variability in PM2.5 oxidative potential was a stronger driver than PM2.5 mass for the variability in the respiratory health outcomes, it is suggested to reduce PM2.5 oxidative potential, particularly by reducing the organic matter constituent of indoor PM2.5, as a targeted source control strategy in asthma management.

The impact of household air cleaners on the oxidative potential of PM2.5 and the role of metals and sources associated with indoor and outdoor exposure.

The health effects associated with human exposure to airborne fine particulate matter (PM2.5) have been linked to the ability of PM2.5 to facilitate the production of excess cellular reactive oxygen species (oxidative potential). Concern about the adverse human health impacts of PM2.5 has led to the increased use of indoor air cleaners to improve indoor air quality, which can be an important environment for PM2.5 exposure. However, the degree to which the oxidative potential of indoor and personal PM2.5 can be influenced by an indoor air cleaner remains unclear. In this study we enrolled 43 children with physician diagnosed asthma in suburban Shanghai, China and collected two paired-sets of 48-h indoor, outdoor, and personal PM2.5 exposure samples. One set of samples was collected under "real filtration" during which a functioning air cleaner was installed in the child's bedroom, and the other ("false filtration") with an air cleaner without internal filters. The PM2.5 samples were characterized by inductively coupled plasma mass spectroscopy for elements, and by an alveolar macrophage assay for oxidative potential. The sources of metals contributing to our samples were determined by the EPA Positive Matrix Factorization model. The oxidative potential was lower under real filtration compared to sham for indoor (median real/sham ratio: 0.260) and personal exposure (0.813) samples. Additionally, the sources of elements in PM2.5 that were reduced indoors and personal exposure samples by the air cleaner (e.g. regional aerosol and roadway emissions) were found by univariate multiple regression models to be among those contributing to the oxidative potential of the samples. An IQR increase in the regional aerosol and roadway emissions sources was associated with a 107% (95% CI: 80.1-138%) and 38.1% (17.6-62.1%) increase in measured oxidative potential respectively. Our results indicate that indoor air cleaners can reduce the oxidative potential of indoor and personal exposure to PM2.5, which may lead to improved human health.

The Oxidative Potential of Personal and Household PM2.5 in a Rural Setting in Southwestern China.

The chemical constituents of fine particulate matter (PM2.5) vary by source and capacity to participate in redox reactions in the body, which produce cytotoxic reactive oxygen species (ROS). Knowledge of the sources and components of PM2.5 may provide insight into the adverse health effects associated with the inhalation of PM2.5 mass. We collected 48 h household and personal PM2.5 exposure measurements in the summer months among 50 women/household pairs in a rural area of southwestern China where daily household biomass burning is common. PM2.5 mass was analyzed for ions, trace metals, black carbon, and water-soluble organic matter, as well as ROS-generating capability (oxidative potential) by one cellular and one acellular assay. Crustal enrichment factors and a principal component analysis identified the major sources of PM2.5 as dust, biomass burning, and secondary sulfate. Elements associated with the secondary sulfate source (As, Mo, Zn) had the strongest correlation with increased cellular oxidative potential (Spearman r: 0.74, 0.68, and 0.64). Chemical markers of biomass burning (water-soluble potassium and water-soluble organic matter) had negligible oxidative potential, suggesting that these assays may not be useful as health-relevant exposure metrics in populations that are exposed to high levels of smoke from household biomass burning.

The impact of household air cleaners on the chemical composition and children's exposure to PM2.5 metal sources in suburban Shanghai.

Increased public awareness of the health impacts of atmospheric fine particulate matter (PM2.5) has led to increased demand and deployment of indoor air cleaners. Yet, questions still remain about the effectiveness of indoor air cleaners on indoor PM2.5 concentrations and personal exposure to potentially hazardous components of PM2.5. Metals in PM2.5 have been associated with adverse health outcomes, so knowledge of their sources in urban indoor and outdoor areas and how exposures are influenced by indoor air cleaners would be beneficial for public health interventions. We collected 48-h indoor, outdoor, and personal PM2.5 exposure samples for 43 homes with asthmatic children in suburban Shanghai, China during the spring months. Two sets of samples were collected for each household, one set with a functioning air filter placed in the bedroom ("true filtration") and the other with a non-functioning ("sham") air cleaner. PM2.5 samples were analyzed for elements, elemental carbon, and organic carbon. The major sources of metals in PM2.5 were determined by Positive Matrix Factorization (PMF) to be regional aerosol, resuspended dust, residual oil combustion, roadway emissions, alloy steel abrasion, and a lanthanum (La) and cerium (Ce) source. Under true filtration, the median indoor to outdoor percent removal across all elements increased from 31% to 78% and from 46% to 88% across all sources. Our findings suggest that indoor air cleaners are an effective strategy for reducing indoor concentrations of PM2.5 metals from most sources, which could translate into improved health outcomes for some populations.