Seasonal Variability of Airborne Particulate Matter and Bacterial Concentrations in Colorado Homes

Abstract

Aerosol measurements were collected at fifteen homes over the course of one year in Colorado (USA) to understand the temporal variability of indoor air particulate matter and bacterial concentrations and their relationship with home characteristics, inhabitant activities, and outdoor air particulate matter (PM). Indoor and outdoor PM 2.5 concentrations averaged (±st. dev.) 8.1 ± 8.1 µg/m 3 and 6.8 ± 4.5 µg/m 3 , respectively. Indoor PM 2.5 was statistically significantly higher during summer compared to spring and winter; outdoor PM 2.5 was significantly higher for summer compared to spring and fall. The PM 2.5 I/O ratio was 1.6 ± 2.4 averaged across all homes and seasons and was not statistically significantly different across the seasons. Average indoor PM 10 was 15.4 ± 18.3 µg/m 3 and was significantly higher during summer compared to all other seasons. Total suspended particulate bacterial biomass, as determined by qPCR, revealed very little seasonal differences across and within the homes. The qPCR I/O ratio was statistically different across seasons, with the highest I/O ratio in the spring and lowest in the summer. Using one-minute indoor PM 10 data and activity logs, it was observed that elevated particulate concentrations commonly occurred when inhabitants were cooking and during periods with elevated outdoor concentrations.

Impact of Outdoor Air Pollution on Indoor Air Quality in Low-Income Homes during Wildfire Seasons

“…The highest levels of outdoor air pollution in the Denver metro area of Colorado can be expected during the summer season (the months of June through October of every year) [6]. During this time of the year, outdoor particulate matter levels are elevated due to the usual background level of traffic-related emissions superimposed with atmospheric chemistry processes [7,8,9] and aerosols produced by both short- and long-range wildfires, which are increasing in number over the decades as a result of climate change [10,11].…”

The Abundance and Diversity of Antibiotic Resistance Genes in the Atmospheric Environment of Biology Laboratories and Surroundings

“…This led to decreasing 16S rRNA concentrations from SL2 to SC2, then to SC1 and SL1 which physically comprised one entire oor of the building (Figure. Overall, all the indoor samples were higher in atmospheric bacterial loadings than family residences [58,59], vacant classrooms, but comparable to occupied classrooms [57,60]. The outdoor samples were also higher than urban air of Seoul, Colorado, Ji'nan, and Nanjing investigated in several previous studies [36,59,[61][62][63], but quite comparable to Beijing, Milan and Berkeley urban air [64][65][66]. The atmospheric bacterial loading represented by 16S rRNA measured by qPCR showed a totally different pattern from the one exhibited by cultivable airborne bacteria concentration.…”

Implications of indoor microbial ecology and evolution on antibiotic resistance

“…However, many more studies are needed to understand microbial exposure effects on humans and which microbial taxa humans preferentially transfer to the built environment. We have not yet fully quantified these exchanges, established their directionality or been able to design effective and appropriate interventions [101][102][103]. Efforts to ensure public health within the built environment should continue to impose limitations on microbial growth, but more importantly to regulate and control exposure to specific microbes.…”

“…The challenge of heterogeneity calls for more studies of the built environment microbiome through multiple spatial scales from entire buildings, to individual rooms, to surfaces within rooms. Thus far, many studies have been performed at a large scale, comparing, e.g., the microbiomes of several houses located in different geographical areas [103][104][105][106] in order to determine geographical patterns. However, few studies tackle the question of how representative a given sample is of a particular building's microbial community composition or structure.…”