Association of a Housing Mobility Program With Childhood Asthma Symptoms and Exacerbations.

Importance: Structural racism has been implicated in the disproportionally high asthma morbidity experienced by children living in disadvantaged, urban neighborhoods. Current approaches designed to reduce asthma triggers have modest impact. Objective: To examine whether participation in a housing mobility program that provided housing vouchers and assistance moving to low-poverty neighborhoods was associated with reduced asthma morbidity among children and to explore potential mediating factors. Design, Setting, and Participants: Cohort study of 123 children aged 5 to 17 years with persistent asthma whose families participated in the Baltimore Regional Housing Partnership housing mobility program from 2016 to 2020. Children were matched to 115 children enrolled in the Urban Environment and Childhood Asthma (URECA) birth cohort using propensity scores. Exposure: Moving to a low-poverty neighborhood. Main Outcomes: Caregiver-reported asthma exacerbations and symptoms. Results: Among 123 children enrolled in the program, median age was 8.4 years, 58 (47.2%) were female, and 120 (97.6%) were Black. Prior to moving, 89 of 110 children (81%) lived in a high-poverty census tract (>20% of families below the poverty line); after moving, only 1 of 106 children with after-move data (0.9%) lived in a high-poverty tract. Among this cohort, 15.1% (SD, 35.8) had at least 1 exacerbation per 3-month period prior to moving vs 8.5% (SD, 28.0) after moving, an adjusted difference of -6.8 percentage points (95% CI, -11.9% to -1.7%; P = .009). Maximum symptom days in the past 2 weeks were 5.1 (SD, 5.0) before moving and 2.7 (SD, 3.8) after moving, an adjusted difference of -2.37 days (95% CI, -3.14 to -1.59; P < .001). Results remained significant in propensity score-matched analyses with URECA data. Measures of stress, including social cohesion, neighborhood safety, and urban stress, all improved with moving and were estimated to mediate between 29% and 35% of the association between moving and asthma exacerbations. Conclusions and Relevance: Children with asthma whose families participated in a program that helped them move into low-poverty neighborhoods experienced significant improvements in asthma symptom days and exacerbations. This study adds to the limited evidence suggesting that programs to counter housing discrimination can reduce childhood asthma morbidity.

Do temporal trends of associations between short-term exposure to fine particulate matter (PM2.5) and risk of hospitalizations differ by sub-populations and urbanicity-a study of 968 U.S. counties and the Medicare population.

While associations between short-term exposure to fine particulate matter (PM2.5) and risk of hospitalization are well documented and evidence suggests that such associations change over time, it is unclear whether these temporal changes exist in understudied less-urban areas or differ by sub-population. We analyzed daily time-series data of 968 continental U.S. counties for 2000-2016, with cause-specific hospitalization from Medicare claims and population-weighted PM2.5 concentrations originally estimated at 1km × 1 km from a hybrid model. Circulatory and respiratory hospitalizations were categorized based on primary diagnosis codes at discharge. Using modified Bayesian hierarchical modelling, we evaluated the temporal trend in association between PM2.5 and hospitalizations and whether disparities in this trend exist across individual-level characteristics (e.g., sex, age, race, and Medicaid eligibility as a proxy for socio-economic status) and urbanicity. Urbanicity was categorized into three levels by county-specific percentage of urban population based on urban rural delineation from the U.S. Census. In this cohort with understudied less-urban areas without regulatory monitors, we still found positive association between circulatory and respiratory hospitalization and short-term exposure to PM2.5, with higher effect estimates towards the end of study period. Consistent with current literature, we identified significant disparity in associations by race, socioeconomic status and urbanicity. We found that the percentage change in circulatory hospitalization rate per 10 µg/m3 increase in PM2.5 was higher in the 2008-2016 time period compared to the 2000-2007 period by 0.33% (95% posterior credible interval 0.22, 0.44%), 0.52% (0.33, 0.69%), and 0.67% (0.53, 0.83%) for low, medium and high tertiles of urban areas, respectively. We also observed significant differences in temporal trends of associations across socioeconomic status, sex, and age, indicating a possible widening in disparity of PM2.5-related health burden. This study raises the importance of considering environmental justice issues in PM2.5-related health impacts with respect to how associations may change over time.

Temporal variation in association between short-term exposure to fine particulate matter and hospitalisations in older adults in the USA: a long-term time-series analysis of the US Medicare dataset.

BACKGROUND: Short-term exposure to fine particulate matter (PM2·5) is associated with increased risk of hospital admissions and mortality, and health risks differ by the chemical composition of PM2·5. Policies to control PM2·5 could change its chemical composition and total mass concentration, leading to change in the subsequent health impact. However, there is little ence on whether associations between PM2·5 and health exhibit temporal variation. We investigated whether risks of hospitalisations from short-term exposure to PM2·5 varied over time in the USA. METHODS: We did a time-series analysis using a national dataset comprising daily circulatory and respiratory hospitalisation rates of Medicare beneficiaries (age ≥65 years) and PM2·5 in 173 US counties from 1999 to 2016. We fitted modified quasi-Poisson models to estimate temporal trends of associations within a county, and pooled county-level estimates using Bayesian hierarchical modelling to generate an overall estimate. FINDINGS: The study included 10 559 654 circulatory and 3 027 281 respiratory hospitalisations. We identified changes in the national average association between previous-day PM2·5 and respiratory hospitalisation over time, with a U-shape that is robust under stratification, linear, and non-linear models. The change in risk of respiratory hospitalisation per 10 µg/m3 increase in previous-day PM2·5 decreased from 0·75% (95% posterior credible interval 0·05 to 1·46) in 1999 to -0·28% (-0·79 to 0·23) in 2008, and then increased to 1·44% (0·00 to 2·91) in 2016. No statistically significant temporal change was observed for associations between same-day PM2·5 and circulatory hospitalisation. INTERPRETATION: Hospitalisation risk from PM2·5 changes over time and has increased over the past 7 years in study, especially in northeastern USA. The temporal trend differs by cause of hospitalisation. This study emphasises the necessity of evaluating temporal heterogeneity in health impacts of PM2·5 and suggests caution in applying association estimates to a different time period. FUNDING: US Environmental Protection Agency and Yale Institute for Biospheric Studies.

Tropical Cyclone Exposures and Risks of Emergency Medicare Hospital Admission for Cardiorespiratory Diseases in 175 Urban United States Counties, 1999-2010.

BACKGROUND: Although injuries experienced during hurricanes and other tropical cyclones have been relatively well-characterized through traditional surveillance, less is known about tropical cyclones' impacts on noninjury morbidity, which can be triggered through pathways that include psychosocial stress or interruption in medical treatment. METHODS: We investigated daily emergency Medicare hospitalizations (1999-2010) in 180 US counties, drawing on an existing cohort of high-population counties. We classified counties as exposed to tropical cyclones when storm-associated peak sustained winds were ≥21 m/s at the county center; secondary analyses considered other wind thresholds and hazards. We matched storm-exposed days to unexposed days by county and seasonality. We estimated change in tropical cyclone-associated hospitalizations over a storm period from 2 days before to 7 days after the storm's closest approach, compared to unexposed days, using generalized linear mixed-effect models. RESULTS: For 1999-2010, 175 study counties had at least one tropical cyclone exposure. Cardiovascular hospitalizations decreased on the storm day, then increased following the storm, while respiratory hospitalizations were elevated throughout the storm period. Over the 10-day storm period, cardiovascular hospitalizations increased 3% (95% confidence interval = 2%, 5%) and respiratory hospitalizations increased 16% (95% confidence interval = 13%, 20%) compared to matched unexposed periods. Relative risks varied across tropical cyclone exposures, with strongest association for the most restrictive wind-based exposure metric. CONCLUSIONS: In this study, tropical cyclone exposures were associated with a short-term increase in cardiorespiratory hospitalization risk among the elderly, based on a multi-year/multi-site investigation of US Medicare beneficiaries ≥65 years.

The Shape of the Concentration-Response Association between Fine Particulate Matter Pollution and Human Mortality in Beijing, China, and Its Implications for Health Impact Assessment.

BACKGROUND: Studies found approximately linear short-term associations between particulate matter (PM) and mortality in Western communities. However, in China, where the urban PM levels are typically considerably higher than in Western communities, some studies suggest nonlinearity in this association. Health impact assessments (HIA) of PM in China have generally not incorporated nonlinearity in the concentration-response (C-R) association, which could result in large discrepancies in estimates of excess deaths if the true association is nonlinear. OBJECTIVES: We investigated nonlinearity in the C-R associations between with PM with aerodynamic diameter [Formula: see text] ([Formula: see text]) and mortality in Beijing, China, and the sensitivity of HIA to linearity assumptions. METHODS: We modeled the C-R association between [Formula: see text] and cause-specific mortality in Beijing, China (2009-2012), using generalized linear models (GLM). [Formula: see text] was included through either linear, piecewise-linear, or spline functions to investigate evidence of nonlinearity. To determine the sensitivity of HIA to linearity assumptions, we estimated [Formula: see text]-attributable deaths using both linear- and nonlinear-based C-R associations between [Formula: see text] and mortality. RESULTS: We found some evidence that, for nonaccidental and circulatory mortality, the shape of the C-R association was relatively flat at lower concentrations of [Formula: see text], but then had a positive slope at higher concentrations, indicating nonlinearity. Conversely, the shape for respiratory mortality was positive and linear at lower concentrations of [Formula: see text], but then leveled off at the higher concentrations. Estimates of excess deaths attributable to short-term [Formula: see text] exposure were, in some cases, very sensitive to the linearity assumption in the association, but in other cases robust to this assumption. CONCLUSIONS: Our results demonstrate some evidence of nonlinearity in [Formula: see text]-mortality associations and that an assumption of linearity in this association can influence HIAs, highlighting the importance of understanding potential nonlinearity in the [Formula: see text]-mortality association at the high concentrations of [Formula: see text] in developing megacities like Beijing. https://doi.org/10.1289/EHP4464.

Rural Residence and Poverty Are Independent Risk Factors for Chronic Obstructive Pulmonary Disease in the United States.

RATIONALE: In developing countries, poor and rural areas have a high burden of chronic obstructive pulmonary disease (COPD), and environmental pollutants and indoor burning of biomass have been implicated as potential causal exposures. Less is known about the prevalence of COPD in the United States with respect to urban-rural distribution, poverty, and factors that uniquely contribute to COPD among never-smokers. OBJECTIVES: To understand the impact of urban-rural status, poverty, and other community factors on COPD prevalence nationwide and among never-smokers. METHODS: We studied a nationally representative sample of adults in the National Health Interview Survey 2012-2015, with data linkage between neighborhood data from the U.S. Census's American Community Survey and the National Center for Health Statistics Urban-Rural Classification Scheme. The main outcome was COPD prevalence. MEASUREMENTS AND MAIN RESULTS: The prevalence of COPD in poor, rural areas was almost twice that in the overall population (15.4% vs. 8.4%). In adjusted models, rural residence (odds ratio [OR], 1.23; P < 0.001) and census-level poverty (OR, 1.12; P = 0.012) were both associated with COPD prevalence, as were indicators of household wealth. Among never-smokers, rural residence was also associated with COPD (OR, 1.34; P < 0.001), as was neighborhood use of coal for heating (OR, 1.09; P < 0.001). CONCLUSIONS: In a nationally representative sample, rural residence and poverty were risk factors for COPD, even among never-smokers. The use of coal for heating was also a risk factor for COPD among never-smokers. Future disparities research to elucidate contributors to COPD development in poor and rural areas, including assessments of heating sources and environmental pollutants, is needed.

Long-Term Coarse Particulate Matter Exposure Is Associated with Asthma among Children in Medicaid.

RATIONALE: Short- and long-term fine particulate matter (particulate matter ≤2.5 µm in aerodynamic diameter [PM2.5]) pollution is associated with asthma development and morbidity, but there are few data on the effects of long-term exposure to coarse PM (PM10-2.5) on respiratory health. OBJECTIVES: To understand the relationship between long-term fine and coarse PM exposure and asthma prevalence and morbidity among children. METHODS: A semiparametric regression model that incorporated PM2.5 and PM10 monitor data and geographic characteristics was developed to predict 2-year average PM2.5 and PM10-2.5 exposure during the period 2009 to 2010 at the zip-code tabulation area level. Data from 7,810,025 children aged 5 to 20 years enrolled in Medicaid from 2009 to 2010 were used in a log-linear regression model with predicted PM levels to estimate the association between PM exposure and asthma prevalence and morbidity, adjusting for race/ethnicity, sex, age, area-level urbanicity, poverty, education, and unmeasured spatial confounding. MEASUREMENTS AND MAIN RESULTS: Exposure to coarse PM was associated with increased asthma diagnosis prevalence (rate ratio [RR] for 1-µg/m3 increase in coarse PM level, 1.006; 95% confidence interval [CI], 1.001-1.011), hospitalizations (RR, 1.023; 95% CI, 1.003-1.042), and emergency department visits (RR, 1.017; 95% CI, 1.001-1.033) when adjusting for fine PM. Fine PM exposure was more strongly associated with increased asthma prevalence and morbidity than coarse PM. The estimates remained elevated across different levels of spatial confounding adjustment. CONCLUSIONS: Among children enrolled in Medicaid, exposure to higher average coarse PM levels is associated with increased asthma prevalence and morbidity. These results suggest the need for direct monitoring of coarse PM and reconsideration of limits on long-term average coarse PM pollution levels.

Urban residence, neighborhood poverty, race/ethnicity, and asthma morbidity among children on Medicaid.

BACKGROUND: Although poor-urban (inner-city) areas are thought to have high asthma prevalence and morbidity, we recently found that inner cities do not have higher prevalent pediatric asthma. Whether asthma morbidity is higher in inner-city areas across the United States is not known. OBJECTIVE: This study sought to examine relationships between residence in poor and urban areas, race/ethnicity, and asthma morbidity among children with asthma who are enrolled in Medicaid. METHODS: Children aged 5 to 19 enrolled in Medicaid in 2009 to 2010 were included. Asthma was defined by at least 1 outpatient or emergency department (ED) visit with a primary diagnosis code of asthma over the 2-year period. Urbanization status was defined at the county level and neighborhood poverty at the zip-code level. Among children with asthma, logistic models were created to examine the effects of urbanization, neighborhood poverty, and race/ethnicity on rates of asthma outpatient visits, ED visits, and hospitalizations. RESULTS: This study included 16,860,716 children (1,534,820 with asthma). Among children enrolled in Medicaid, residence in inner-city areas did not confer increased risk of prevalent asthma in either crude or adjusted analyses, but it was associated with significantly more asthma-related ED visits and hospitalizations among those with asthma in crude analyses (risk ratio, 1.48; 95% CI, 1.24-1.36; and 1.97; 95% CI, 1.50-1.72, respectively) and when adjusted for race/ethnicity, age, and sex (adjusted risk ratio, 1.23; 95% CI, 1.08-1.15; and 1.62; 95% CI, 1.26-1.43). Residence in urban or poor areas and non-Hispanic black race/ethnicity were all independently associated with increased risk of asthma-related ED visits and hospitalizations. CONCLUSIONS: Residence in poor and urban areas is an important risk factor for asthma morbidity, but not for prevalence, among low-income US children.

Wildfire-specific Fine Particulate Matter and Risk of Hospital Admissions in Urban and Rural Counties.

BACKGROUND: The health impacts of wildfire smoke, including fine particles (PM2.5), are not well understood and may differ from those of PM2.5 from other sources due to differences in concentrations and chemical composition. METHODS: First, for the entire Western United States (561 counties) for 2004-2009, we estimated daily PM2.5 concentrations directly attributable to wildfires (wildfires-specific PM2.5), using a global chemical transport model. Second, we defined smoke wave as ≥2 consecutive days with daily wildfire-specific PM2.5 > 20 µg/m, with sensitivity analysis considering 23, 28, and 37 µg/m. Third, we estimated the risk of cardiovascular and respiratory hospital admissions associated with smoke waves for Medicare enrollees. We used a generalized linear mixed model to estimate the relative risk of hospital admissions on smoke wave days compared with matched comparison days without wildfire smoke. RESULTS: We estimated that about 46 million people of all ages were exposed to at least one smoke wave during 2004 to 2009 in the Western United States. Of these, 5 million are Medicare enrollees (≥65 years). We found a 7.2% (95% confidence interval: 0.25%, 15%) increase in risk of respiratory admissions during smoke wave days with high wildfire-specific PM2.5 (>37 µg/m) compared with matched non smoke wave days. We did not observe an association between smoke wave days with wildfire-specific PM2.5 ≤ 37 µg/mand respiratory or cardiovascular admissions. Respiratory effects of wildfire-specific PM2.5 may be stronger than that of PM2.5 from other sources. CONCLUSION: Short-term exposure to wildfire-specific PM2.5was associated with risk of respiratory diseases in the elderly population in the Western United States during severe smoke days. See video abstract at, http://links.lww.com/EDE/B137.

Ambient Coarse Particulate Matter and Hospital Admissions in the Medicare Cohort Air Pollution Study, 1999-2010.

BACKGROUND: In recent years a number of studies have examined the short-term association between coarse particulate matter (PM(10-2.5)) and mortality and morbidity outcomes. These studies, however, have produced inconsistent conclusions. OBJECTIVES: We estimated both the national- and regional-level associations between PM(10-2.5) and emergency hospitalizations for both cardiovascular and respiratory disease among Medicare enrollees ≥ 65 years of age during the 12-year period 1999 through 2010. METHODS: Using air pollution data obtained from the U.S. Environmental Protection Agency air quality monitoring network and daily emergency hospitalizations for 110 large urban U.S. counties assembled from the Medicare Cohort Air Pollution Study (MCAPS), we estimated the association between short-term exposure to PM(10-2.5) and hospitalizations using a two-stage Bayesian hierarchical model and Poisson log-linear regression models. RESULTS: A 10-µg/m3 increase in PM(10-2.5) was associated with a significant increase in same-day cardiovascular hospitalizations [0.69%; 95% posterior interval (PI): 0.45, 0.92]. After adjusting for PM2.5, this association remained significant (0.63%; 95% PI: 0.38, 0.88). A 10-µg/m3 increase in PM(10-2.5) was not associated with a significant increase in respiratory-related hospitalizations. CONCLUSIONS: We found statistically significant evidence that daily variation in PM(10-2.5) is associated with emergency hospitalizations for cardiovascular diseases among Medicare enrollees ≥ 65 years of age. This association was robust to adjustment for concentrations of PM2.5. CITATION: Powell H, Krall JR, Wang Y, Bell ML, Peng RD. 2015. Ambient coarse particulate matter and hospital admissions in the Medicare Cohort Air Pollution Study, 1999-2010. Environ Health Perspect 123:1152-1158; http://dx.doi.org/10.1289/ehp.1408720.

Ambient PM2.5 and Risk of Hospital Admissions: Do Risks Differ for Men and Women?

BACKGROUND: While strong evidence exists for associations between fine particles (PM2.5) and health, less is known about whether associations differ by sex. METHODS: We used Bayesian hierarchical modeling to estimate associations between PM2.5, based on ambient monitors, and risk of cause-specific cardiovascular and respiratory hospitalizations for about 12.6 million Medicare beneficiaries (>65 years) residing in 213 US counties for 1999-2010. RESULTS: Point estimates were higher for women than men for almost all causes of hospitalization. PM2.5 risks were higher for women than men for respiratory tract infection, cardiovascular, and heart rhythm disturbance admissions. A 10 µg/m(3) increase in same-day PM2.5 was associated with a 1.13% increased risk of heart rhythm disturbance admissions for women (95% posterior interval [PI]: 0.63%, 1.63%), and 0.03% for men (95% PI: -0.48%, 0.55%). Differences remained after stratification by age and season. CONCLUSIONS: Women may be more susceptible to PM2.5-related hospitalizations for some respiratory and cardiovascular causes.

Neighborhood poverty, urban residence, race/ethnicity, and asthma: Rethinking the inner-city asthma epidemic.

BACKGROUND: Although it is thought that inner-city areas have a high burden of asthma, the prevalence of asthma in inner cities across the United States is not known. OBJECTIVE: We sought to estimate the prevalence of current asthma in US children living in inner-city and non-inner-city areas and to examine whether urban residence, poverty, or race/ethnicity are the main drivers of asthma disparities. METHODS: The National Health Interview Survey 2009-2011 was linked by census tract to data from the US Census and the National Center for Health Statistics. Multivariate logistic regression models adjusted for sex; age; race/ethnicity; residence in an urban, suburban, medium metro, or small metro/rural area; poverty; and birth outside the United States, with current asthma and asthma morbidity as outcome variables. Inner-city areas were defined as urban areas with 20% or more of households at below the poverty line. RESULTS: We included 23,065 children living in 5,853 census tracts. The prevalence of current asthma was 12.9% in inner-city and 10.6% in non-inner-city areas, but this difference was not significant after adjusting for race/ethnicity, region, age, and sex. In fully adjusted models black race, Puerto Rican ethnicity, and lower household income but not residence in poor or urban areas were independent risk factors for current asthma. Household poverty increased the risk of asthma among non-Hispanics and Puerto Ricans but not among other Hispanics. Associations with asthma morbidity were very similar to those with prevalent asthma. CONCLUSIONS: Although the prevalence of asthma is high in some inner-city areas, this is largely explained by demographic factors and not by living in an urban neighborhood.

Inference for environmental intervention studies using principal stratification.

Previous research has found evidence of an association between indoor air pollution and asthma morbidity in children. Environmental intervention studies have been performed to examine the role of household environmental interventions in altering indoor air pollution concentrations and improving health. Previous environmental intervention studies have found only modest effects on health outcomes and it is unclear if the health benefits provided by environmental modification are comparable with those provided by medication. Traditionally, the statistical analysis of environmental intervention studies has involved performing two intention-to-treat analyses that separately estimate the effect of the environmental intervention on health and the effect of the environmental intervention on indoor air pollution concentrations. We propose a principal stratification approach to examine the extent to which an environmental intervention's effect on health outcomes coincides with its effect on indoor air pollution. We apply this approach to data from a randomized air cleaner intervention trial conducted in a population of asthmatic children living in Baltimore, Maryland, USA. We find that among children for whom the air cleaner reduced indoor particulate matter concentrations, the intervention resulted in a meaningful improvement of asthma symptoms with an effect generally larger than previous studies have shown. A key benefit of using principal stratification in environmental intervention studies is that it allows investigators to estimate causal effects of the intervention for sub-groups defined by changes in the indoor air pollution concentration.

Temporal trends and racial/ethnic disparity in self-reported pediatric food allergy in the United States.

BACKGROUND: The prevalence of food allergy is thought to be increasing, but data from the United States have not been systematically synthesized. OBJECTIVE: To summarize the data on prevalence of food allergy in the US pediatric population and to estimate the effects of time, race/ethnicity, and method of assessing food allergy on the estimated prevalence. METHODS: Embase, MEDLINE, bibliographies of identified reports, and data from publically available data sets were searched. Studies were limited to those in English with data from the general pediatric US population. Study synthesis was performed by meta-analysis and meta-regression to estimate the effect of study- and participant-level covariates. Meta-regression was limited to nationally representative surveys conducted by the Centers for Disease Control and Prevention. RESULTS: A total of 10,090 publications were identified, from which 27 different survey administrations, representing 452,237 children, were identified, covering the period of 1988 to 2011. Because of heterogeneity among surveys in the estimated food allergy prevalence, a summary estimate of food allergy prevalence was not possible. Meta-regression was performed using 20 of these surveys. Temporal trends were pronounced, with an estimated increased prevalence of self-reported food allergy of 1.2 percentage points per decade (95% confidence interval [CI], 0.7-1.6). The increase per decade varied by race/ethnicity: 2.1% among non-Hispanic blacks (95% CI, 1.5%-2.7%), 1.2% among Hispanics (95% CI, 0.7%-1.7%), and 1.0% among non-Hispanic whites (95% CI, 0.4%-1.6%). CONCLUSION: Self-report of food allergy among US children has sharply increased in the past 2 decades. The increase has been greatest among non-Hispanic black children, a disparity that needs to be investigated.

Heat-related emergency hospitalizations for respiratory diseases in the Medicare population.

RATIONALE: The heat-related risk of hospitalization for respiratory diseases among the elderly has not been quantified in the United States on a national scale. With climate change predictions of more frequent and more intense heat waves, it is of paramount importance to quantify the health risks related to heat, especially for the most vulnerable. OBJECTIVES: To estimate the risk of hospitalization for respiratory diseases associated with outdoor heat in the U.S. elderly. METHODS: An observational study of approximately 12.5 million Medicare beneficiaries in 213 United States counties, January 1, 1999 to December 31, 2008. We estimate a national average relative risk of hospitalization for each 10°F (5.6°C) increase in daily outdoor temperature using Bayesian hierarchical models. MEASUREMENTS AND MAIN RESULTS: We obtained daily county-level rates of Medicare emergency respiratory hospitalizations (International Classification of Diseases, Ninth Revision, 464-466, 480-487, 490-492) in 213 U.S. counties from 1999 through 2008. Overall, each 10°F increase in daily temperature was associated with a 4.3% increase in same-day emergency hospitalizations for respiratory diseases (95% posterior interval, 3.8, 4.8%). Counties' relative risks were significantly higher in counties with cooler average summer temperatures. CONCLUSIONS: We found strong evidence of an association between outdoor heat and respiratory hospitalizations in the largest population of elderly studied to date. Given projections of increasing temperatures from climate change and the increasing global prevalence of chronic pulmonary disease, the relationship between heat and respiratory morbidity is a growing concern.

Assessment of heterogeneity of metal composition of fine particulate matter collected from eight U.S. counties using principal component analysis.

The main objectives of this study are to (1) characterize chemical constituents of particulate matter (PM) and (2) compare overall differences in PM collected from eight US. counties. This project was undertaken as a part of a larger research program conducted by the Johns Hopkins Particulate Matter Research Center (JHPMRC). The goal of the JHPMRC is to explore the relationship between health effects and exposure to ambient PM of differing composition. The JHPMRC collected weekly filter-based ambient fine particle samples from eight US. counties between January 2008 and January 2010. Each sampling effort consisted of a 5-6-week sampling period. Filters were analyzed for 25 metals using inductively coupled plasma mass spectrometry (ICP-MS). Overall compositional differences were ranked by principal component analysis (PCA). The results showed that weekly concentrations of each element varied 3-40 times between the eight counties. PCA showed that the first five principal components explained 85% of the total variance. The authors found significant overall compositional differences in PM as the average of standardized principal component scores differed between the counties. These findings demonstrate PCA is a useful tool to identify the differences in PM compositional mixtures by county. These differences will be helpful for epidemiological and toxicological studies to help explain why health risks associated with PM exposure are different in locations with similar mass concentrations of PM.

Emergency hospital admissions for cardiovascular diseases and ambient levels of carbon monoxide: results for 126 United States urban counties, 1999-2005.

BACKGROUND: Evidence on risk of cardiovascular disease (CVD) hospitalization associated with short-term exposure to outdoor carbon monoxide (CO), an air pollutant primarily generated by traffic, is inconsistent across studies. Uncertainties remain on the degree to which associations are attributable to other traffic pollutants and whether effects persist at low levels. METHODS AND RESULTS: We conducted a multisite time-series study to estimate risk of CVD hospitalization associated with short-term CO exposure in 126 US urban counties during 1999-2005 for >9.3 million Medicare enrollees aged > or =65 years. We considered models with adjustment by other traffic-related pollutants: NO2, fine particulate matter (with aerodynamic diameter < or =2.5 microm), and elemental carbon. We found a positive and statistically significant association between same-day CO and increased risk of hospitalization for multiple CVD outcomes (ischemic heart disease, heart rhythm disturbances, heart failure, cerebrovascular disease, total CVD). The association remained positive and statistically significant but was attenuated with copollutant adjustment, especially NO2. A 1-ppm increase in same-day daily 1-hour maximum CO was associated with a 0.96% (95% posterior interval, 0.79%, 1.12%) increase in risk of CVD admissions. With same-day NO(2) adjustment, this estimate was 0.55% (0.36%, 0.74%). The risk persisted at low CO levels <1 ppm. CONCLUSIONS: We found evidence of an association between short-term exposure to ambient CO and risk of CVD hospitalizations, even at levels well below current US health-based regulatory standards. This evidence indicates that exposure to current CO levels may still pose a public health threat, particularly for persons with CVD.

Seasonal and regional short-term effects of fine particles on hospital admissions in 202 US counties, 1999-2005.

The authors investigated whether short-term effects of fine particulate matter with an aerodynamic diameter < or =2.5 microm (PM(2.5)) on risk of cardiovascular and respiratory hospitalizations among the elderly varied by region and season in 202 US counties for 1999-2005. They fit 3 types of time-series models to provide evidence for 1) consistent particulate matter effects across the year, 2) different particulate matter effects by season, and 3) smoothly varying particulate matter effects throughout the year. The authors found statistically significant evidence of seasonal and regional variation in estimates of particulate matter effect. Respiratory disease effect estimates were highest in winter, with a 1.05% (95% posterior interval: 0.29, 1.82) increase in hospitalizations per 10-microg/m(3) increase in same-day PM(2.5). Cardiovascular diseases estimates were also highest in winter, with a 1.49% (95% confidence interval: 1.09, 1.89) increase in hospitalizations per 10-microg/m(3) increase in same-day PM(2.5), with associations also observed in other seasons. The strongest evidence of a relation between PM(2.5) and hospitalizations was in the Northeast for both respiratory and cardiovascular diseases. Heterogeneity of PM(2.5) effects on hospitalizations may reflect seasonal and regional differences in emissions and in particles' chemical constituents. Results can help guide development of hypotheses and further epidemiologic studies on potential heterogeneity in the toxicity of constituents of the particulate matter mixture.