2015 Progress Report: Assessing the Potential Impact of Global Warming on Indoor Air Quality and Human Health in Two US Cities: Boston, MA and Atlanta, GAEPA Grant Number: R835755
Title: Assessing the Potential Impact of Global Warming on Indoor Air Quality and Human Health in Two US Cities: Boston, MA and Atlanta, GA
Investigators: Koutrakis, Petros , Mickley, Loretta J. , Sarnat, Stefanie Ebelt , Sarnat, Jeremy , Zanobetti, Antonella
Institution: Harvard T.H. Chan School of Public Health , Harvard University
EPA Project Officer: Ilacqua, Vito
Project Period: November 1, 2014 through October 31, 2017 (Extended to October 31, 2018)
Project Period Covered by this Report: November 1, 2014 through October 31,2015
Project Amount: $999,948
RFA: Indoor Air and Climate Change (2014) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Climate Change , Air
Rising temperatures associated with climate change are expected to impact future home air exchange rates, decreasing air exchange during the summer and increasing these rates during the spring and fall relative to the present. These changes in turn will alter the contributions of both indoor and outdoor PM2.5 sources to indoor air quality, and subsequently lead to differential effects of PM2.5 exposures on human health. To investigate this, we propose to use the indoor/outdoor sulfur ratio to link concentrations of indoor particles of outdoor and indoor origin to ambient temperature. We will estimate the effects of outdoor PM2.5 on total and cause-specific mortality in each city, and ultimately examine the impact of climate change-related differences in indoor particle exposures on PM2.5-related mortality.
Overall, the study is on schedule. The Year 1 progress on each of the specific aims of the study is summarized below.
Specific Aim 1: Assemble a large database on indoor and outdoor levels of PM2.5 mass and sulfur in two U.S. cities with very different climatic conditions: Boston, MA, and Atlanta, GA. The Boston, MA, data assembly has been completed. Retrospective data from Atlanta also are available.
In January 2016, we began prospective field sampling in Atlanta. In total, we will collect 840, 24 h integrated samples from 60 single-family residences throughout the city. Sampling in each household is scheduled for two sessions during both cool and warms months, and lasting 7 consecutive days. In addition, questionnaires are administered to participants for information regarding home type, age, and size, as well as indoor sources that may impact PM2.5 levels. Questions regarding parameters that influence home air exchange rates also are asked, including the use of AC, the number and time of open windows. To date, we have completed initial sampling sessions for 22 homes (154 samples).
Prior to field sampling (Oct – Nov, 2015), we conducted QAQC analyses including side-by-side collocated measurements (4 samplers per session) in three households. A total of 42 samples were collected and analyzed. The mean sulfur mass concentration for this period across three households was 0.17 ± 0.11 ug/m3. Despite the low concentrations typical during this season in Atlanta, the colocation pairs were strongly correlated with each, with a relative precision of ± 13.1% and an absolute precision of ± 0.02 ug/m3. During the upcoming project period, we will continue to conduct field sampling in Atlanta and anticipate completion by summer 2017.
Specific Aim 2: Using data collected in SA 1, establish relationships between the impact of outdoor and indoor sources on indoor PM2.5 concentrations, Ro and Ri, respectively, and ambient T. This analysis will be accomplished in two steps: first, we will express Ro, Ri, and air exchange rate α as a function of the indoor/outdoor sulfur ratio Sr, and; second, we will establish a quantitative relationship between Sr and T.
We have worked on SA 2 with retrospective data collected in the Boston Area and have used the indoor-outdoor sulfur ratio (Sr) as a surrogate of the particle infiltration factor (Finf) for PM2.5. Using linear mixed effects models, we examined the Sr-temperature relationship for both the whole population of homes studied and a subpopulation of naturally ventilated homes. Data collection in Atlanta is in progress, so future work on SA 2 will include the analysis of Atlanta data using the techniques developed with Boston data, and comparison with Boston results.
Specific Aim 3: Forecast climatic conditions in Boston and Atlanta for two 20-year periods: 1994 to 2014 (present) and 2044 to 2064 (future), using data from the Coupled Model Inter-comparison Project Phase 5 (Intergovernmental Panel on Climate Change, AR5). We will use present and future temperatures, TP and TF, to predict present and future Sr, α, Ro, and Ri values.
Projected meteorology for Boston, MA, has been modeled for both the 20 year future and 20 year past periods. We have used these forecasts to predict Sr for these past and future 20 year periods. We found that in Boston, the predicted future summer-winter difference in Sr was as high as 54% for naturally ventilated homes and 30% for the whole population, using winter as the baseline. In contrast, the long-term difference was small with a maximum of 7% and 2% increase in Sr in summer for the populations, respectively. Although the influence of monthly temperature variation outweighed the long-term climate changes effects on Sr, the predicted changes in Sr can be used in future studies to modify exposure and assess climate change impact on PM2.5 associated health endpoints. A manuscript on the results of the Boston analysis (SA 2 and SA 3) has been prepared for submission to a peer review journal. Projected meteorology for Atlanta, GA, is in progress. Analysis of Atlanta data will be conducted after prospective sampling is complete. Future work on SA 3 will also include comparison with Boston results.
Specific Aim 4: Estimate the effects of outdoor PM2.5 on total and cause-specific mortality in each city, and examine the impact of climate change-related differences in particle exposures on PM2.5-related mortality.
Data for Boston cause-specific and total mortality for the 20 year past period has been gathered, and the analysis of Boston data is scheduled to begin as soon as the SA 2/SA 3 modeling paper is finalized. Data for Atlanta cause-specific and total mortality for the 20 year past/current period is in progress, and will be completed along with the prospective sampling that is ongoing. Analysis of the Atlanta data, using methods developed with Boston data, will occur when prospective sampling is complete. Future work on SA 4 also will include comparison with Boston results.
No significant study delays are reported. It took slightly longer than anticipated to get everything in place to begin prospective sampling in homes. Additional delays are unlikely, sampling is underway and going well, and is currently on schedule to be completed by mid-Y3. Since this delay has already been resolved, and much of the modeling in the study has been or will be developed using the retrospective Boston data, overall study completion is not expected to be significantly impacted.
Expenditures. Current expenditures are comparable to the budget plan at the date of report. The delay in beginning prospective sampling in homes has moved some Y1 expenditures into Y2. No significant changes in the size or scope of the project or in the originally-negotiated total estimated costs are reported for the Y1 reporting period or anticipated for the remainder of the Y2 project period.
Quality Assurance. A Quality Assurance Project Plan (QAPP) was submitted in November 2015. The plan was based on the Quality Assurance Statement in our proposal. Revisions to the plan were requested by the EPA project officer in December of 2015. A supplemental QAPP that addresses the points requested by the EPA Project Officer will be submitted concurrently with this report.
Human Subjects. We have submitted our original IRB Approval for this project on 4/7/2015. The annual review was approved on March 21, 2016. We are including the approval letter in this report.
Research conduct. All research effort in this study has been performed to the highest standard of conduct.
Future activities are discussed above for each specific aim.