Final Report: Climate Change Mitigation in Low-Income Communities in Colorado: Home Weatherization Impacts on Respiratory Health and Indoor Air Quality during Wildfires

EPA Grant Number: R835752
Title: Climate Change Mitigation in Low-Income Communities in Colorado: Home Weatherization Impacts on Respiratory Health and Indoor Air Quality during Wildfires
Investigators: Miller, Shelly , Adgate, John L. , Carlton, Elizabeth , Root, Elisabeth
Institution: University of Colorado at Boulder , Colorado School of Public Health , University of Colorado at Denver
EPA Project Officer: Chung, Serena
Project Period: November 1, 2014 through October 31, 2017 (Extended to June 30, 2018)
Project Amount: $999,899
RFA: Indoor Air and Climate Change (2014) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Climate Change , Air


As societies adopt green building practices in efforts to reduce energy expenditures and emissions that contribute to climate change, it is important to consider how such building design changes influence health. These practices include efforts to reduce air exchange rates between the building interior and the outdoor environment to minimize energy loss, the health effects of which are not well characterized. The effectiveness of the methods used to improve home energy efficiency by tightening the building shell are also not well known. This study aims to evaluate the relationship between air exchange rates and respiratory health in a multi-ethnic population living in low-income, urban homes. Additionally, it explores the impact of retrofit methods on air exchange rates, and how wildfires can degrade indoor air quality in homes, which are becoming increasingly more common in the western US as the climate changes, and how urban neighborhood profiles can be associated to respiratory health.

Summary/Accomplishments (Outputs/Outcomes):

The Colorado Home Energy Efficiency and Respiratory Health (CHEER) study was a cross-sectional study of 303 participants who live in 216 homes with a range of ventilation rates across the Northern Front Range of Colorado. CHEER participants were recruited from low-income, non-smoking households from the cities of Denver, Aurora, Boulder, Loveland, and Fort Collins over 18 months, from October 15, 2015 to April 15, 2017. Households were recruited through partnerships with agencies that provide housing or work to improve energy efficiency in low-income homes. Income eligibility was different across the partner agencies, but all used thresholds well below the HUD definition of low income.1 Eligible households were those that: 1) met the low-income criteria defined by the participating agency, 2) all residents in the home were reported non-smokers, 3) residents must have lived in the home for at least 6 months, and 4) the residence was a single family home or duplex or townhome with no direct air exchange vents in between each unit.

Upon enrollment, a 3-person study team conducted a 2-hour home visit to assess energy efficiency, household characteristics, individual socio-demographics, subjective measures of respiratory health, and pulmonary function tests. walk-through inspections were used to record observations of air-sealing retrofits in building envelopes and indirect indicators of poor IAQ in the homes like visible mold or stains, vapor condensation on windows, dampness, and perceived indoor air quality (IAQ). Participants were asked about the frequency and severity of chronic respiratory symptoms using questions from the American Thoracic Society DLD-78. Pulmonary function tests were administered to eligible participants using an EasyOne Plus peak flow portable spirometer. A blower door test was conducted at each home and the annual average air exchange rate (AAER) was estimated using a model for each home.

As part of the Colorado Home Energy Efficiency and Respiratory Health (CHEER) study, we evaluated the infiltration of outdoor air pollution in 28 low-income homes during the 2016 and 2017 wildfire seasons (June through October). Simultaneous indoor and outdoor measurements of fine particulate matter (PM2.5), black carbon (BC), ozone (O3), carbon monoxide (CO), and nitrogen dioxide (NO2) were collected continuously for two to seven days in each home to capture the concentrations of pollutants that are markers for traffic and wildfire-related emissions.

An additional latent profile analysis (LPA) was conducted to explore how social and environmental neighborhood characteristics cluster together to create distinct typologies and examine whether those typologies are associated with lung function. Neighborhoods were 625 census tracts in the Denver Metro and Front Range area of Colorado where the 303 participants in the Colorado Home Energy Efficiency and Respiratory Health study resided between 2015-2017. LPA was used to identify distinct neighborhood typologies, and generalized estimating equations were used to examine the association between neighborhood typology and lung function as measured by spirometry.

All participants provided assent and/or written informed consent. The study protocol was approved by the University of Colorado Boulder Institutional Review Board.


Air exchange rates in many homes were relatively high (median 0.54 air changes per hour, range 0.10, 2.17). The majority of participants were female (69.6%), older (mean age 53 years), never smokers (60.5%), non-Hispanic white (39.9%) or Hispanic (36.0%), had not completed a 4-year college education (66.8%), and spent an average of 16.8 hours per day inside their home. Results from the walk-through inspections of 226 households showed that building characteristics like age and volume affected AAER more significantly than air-sealing energy efficiency retrofits (EERs). Among the air-sealing EERs, homes with the air-handler ductwork sealed and windows weather-stripped were found to have significantly lower AAER compared to the homes without these features. Although median AAER of homes with EERs were 17% lower than non-EER homes, some homes with EERs had higher AAERs than conventional homes due to the poor quality of the EER work. Mold growth, wall stains, notably higher level of dust, and unacceptable odor levels were more frequently reported in homes with higher AAER, showing that leakier homes do not necessarily have better IAQ.

We estimated the association between AAER and respiratory symptoms for 302 individuals as determined by questionnaires and respiratory health from the spirometry tests, adjusting for relevant confounders. Residents in homes with higher AAER were more likely to report chronic cough, asthma and asthma-like symptoms, including taking medication for wheeze, wheeze that limited activities and dry cough at night. A one-unit change in AAER was associated with a 5.03-fold increase in the odds of taking medication for wheezing in the past year (95% confidence interval: 1.83, 13.87) and a 5.44-fold increase in the odds of having a current asthma diagnosis (95% CI: 1.58, 18.76). Allergic symptoms were not associated with AAER in any models. The association between AAER and asthma-like symptoms were stronger for households located in areas with high potential exposure to traffic related pollutants, but this was not consistent across all health outcomes.

Acceptable pulmonary function tests were completed by 253 CHEER participants in 187 homes. Residents in homes with higher AAER were more likely to have better lung function. AAER was positively associated with increased FEV1/FVC z-scores in adjusted models, such that a 1-unit change in AAER was related to a half of a standard deviation increase in lung function (β=0.51, CI: 0.02-1.00, p=0.04). Models that included AAER as a quartile indicated a positive, linear relationship between AAER and FEV1/FVC. The results of this analyses are different from those using the questionnaire data summarized above. This is possibly due to different sample sizes and different subject populations. Additionally, questionnaire data is a subjective assessment, whereas spirometry is an objective measurement. The population that completed spirometry were generally healthier since not all individuals could complete the test or were disqualified due to pre-existing conditions.

Results for the wildfire study showed that during high-density wildfire smoke plume episodes indoor PM2.5 concentrations were 3.6 times, and BC 1.5 times, higher than on days with no wildfire smoke. In the absence of cooking, all outdoor pollutant concentrations were higher compared to indoors except for CO, which had an elevated indoor/outdoor ratio (I/O) of 4, indicating the presence of additional indoor sources of CO other than cooking. BC, CO, and NO2 were higher indoors in homes closer to roadways compared to those further away. Mechanical ventilation systems were observed in five study homes and these homes had increased I/O ratios of PM2.5 and BC compared to homes without mechanical ventilation. Most homes had windows open during the study and homes with windows that were open for more than 12 hours had indoor BC 2.4 times higher than homes with windows closed.

From the LPA we found that census-tract level greenspace, traffic-related air pollution, violent and property crime, racial/ethnic composition, and socioeconomic status clustered into four distinct neighborhood profiles across the Northern Front Range of Colorado. Our findings revealed that the health enhancing or health threatening aspects of the social and physical neighborhood environment accumulate within typologies, and suggest that these empirically identified neighborhoods may be capturing a larger process - related to both environmental exposures and socioeconomic inequalities - which impacts lung function.

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Other project views: All 6 publications 1 publications in selected types All 1 journal articles
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Journal Article Carlton EJ, Barton K, Shrestha PM, Humphrey J, Newman LS, Adgate JL, Root E, Miller S. Relationships between home ventilation rates and respiratory health in the Colorado Home Energy Efficiency and Respiratory Health (CHEER) study. Environmental Research 2018;169:297-307. R835752 (Final)
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