Assessing indoor exposures to particulate matter and radon
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CitationCarrion-Matta, Aleshka. 2021. Assessing indoor exposures to particulate matter and radon. Doctoral dissertation, Harvard University Graduate School of Arts and Sciences.
AbstractIndoor air pollutants are ranked in the top five environmental risks to public health. As the time spent indoors is large enough and increasing over time, we were interested in understanding sources, transport, physicochemical characteristics, influential factors, and trends to enhance our understanding of exposures in the indoor environment.
In Chapter 2, we analyzed PM2.5 and its components to determine indoor and outdoor possible sources affecting indoor PM2.5 in classrooms. PM2.5 mass and its components were collected from 32 inner-city schools in the Northeastern U.S. from 2009-2013. We applied the USEPA PMF to the PM2.5 components to estimate the source apportionment both indoors and outdoors. Classroom indoor concentrations of PM2.5 (an average of 5.2 μg/m3) were lower than outdoors (an average of 6.5 μg/m3). The major sources (contributions) of indoor PM2.5 were secondary pollution (41%) and motor vehicles (17%), followed by Calcium (Ca)-rich particles (12%), biomass burning (15%), soil dust (6%), and marine aerosols (4%). Likewise, the major sources of outdoor PM2.5 were secondary pollution (41%) and motor vehicles (26%), followed by biomass burning (17%), soil dust (7%), road dust (3%), and marine aerosols (1%).
In Chapter 3, we were interested to find influential factors of radon levels in residential environments from different geographical areas. We analyzed factors from the soil, geology, topography, atmospheric variables, radiation, urbanization, community economic well-being, and monthly and year variations using random forest. We analyzed 802 zip codes from Massachusetts, Michigan, and Minnesota during 2005-2018. Factors that predict radon varied across the states, due possibly to a different soil composition in the states. Cross-validated R2 between predictions and measurements was 0.68 (RMSE = 47.81 Bq/m3) in Minnesota, 0.67, (RMSE = 52.61 Bq/m3) in Michigan, and 0.41 (RMSE = 52.57 Bq/m3) in Massachusetts.
In Chapter 4, we assessed whether proximity to shale gas development areas affect indoor radon levels. We analyzed 35,442 monthly indoor radon observations from Pennsylvania between 2001-2015 using linear mixed effects model, with a random intercept for zip code. We found that shale gas development via hydraulic fracturing was associated with an increase in downwind indoor radon levels [slope = 1.93 (± 0.94); p-value 0.0393]. In addition, our analysis revealed that the contribution of having 100 wells in 1 km will increase indoor radon levels by 185 Bq/m3 (5 pCi/L).
Citable link to this pagehttps://nrs.harvard.edu/URN-3:HUL.INSTREPOS:37369482
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