Ji Young Son

The Impact of Heat Waves on Mortality in Seven Major Cities in Korea

Background: Understanding the health impacts of heat waves is important, especially given anticipated increases in the frequency, duration, and intensity of heat waves due to climate change. Objectives: We examined mortality from heat waves in seven major Korean cities for 2000 through 2007 and investigated effect modification by individual characteristics and heat wave characteristics (intensity, duration, and timing in season). Methods: Heat waves were defined as ≥ 2 consecutive days with daily mean temperature at or above the 98th percentile for the warm season in each city. We compared mortality during heat-wave days and non-heat-wave days using city-specific generalized linear models. We used Bayesian hierarchical models to estimate overall effects within and across all cities. In addition, we estimated effects of heat wave characteristics and effects according to cause of death and examined effect modification by individual characteristics for Seoul. Results: Overall, total mortality increased 4.1% [95% confidence interval (CI): –6.1%, 15.4%] during heat waves compared with non-heat-wave days, with an 8.4% increase (95% CI: 0.1%, 17.3%) estimated for Seoul. Estimated mortality was higher for heat waves that were more intense, longer, or earlier in summer, although effects were not statistically significant. Estimated risks were higher for women versus men, older versus younger residents, those with no education versus some education, and deaths that occurred out of hospitals in Seoul, although differences among strata of individual characteristics were not statistically significant. Conclusions: Our findings support evidence of mortality impacts from heat waves and have implications for efforts to reduce the public health burden of heat waves.

Blood levels of lead, cadmium, and mercury in the Korean population: Results from the Second Korean National Human Exposure and Bio-monitoring Examination

In Korea, there have been a number of efforts to measure levels of exposure to environmental pollutants among the population. This paper focuses on investigating the distribution of, extent of, and factors influencing the blood levels of lead, cadmium, and mercury in the Korean population, working from data obtained from the Second Korean National Human Exposure and Bio-monitoring Examination. To that end, blood metal concentrations were analyzed from a total of 2369 participants who were 18 years of age and older. The geometric mean concentrations and their 95% confidence intervals of metals in blood were found to be lead, 1.72 microg/dL (95% CI, 1.68-1.76); cadmium, 1.02 microg/L (95% CI, 1.00-1.05); and mercury, 3.80 microg/L (95% CI, 3.66-3.93). Regression analyses indicate that the levels of metals in the blood are mainly influenced by gender, age, and the education levels of the participants. Current smoking status is also found to be a significant factor for increasing both lead and cadmium levels. Although our study, as the first nationwide survey of exposure to environmental pollutants in Korea, has value on its own, it should be expanded and extended in order to provide information on environmental exposure pathways and to watch for changes in the level of exposure to environmental pollutants among the population.

Characterization of Fine Particulate Matter and Associations between Particulate Chemical Constituents and Mortality in Seoul, Korea

Background: Numerous studies have linked fine particles [≤ 2.5 µm in aerodynamic diameter (PM2.5)] and health. Most studies focused on the total mass of the particles, although the chemical composition of the particles varies substantially. Which chemical components of fine particles that are the most harmful is not well understood, and research on the chemical composition of PM2.5 and the components that are the most harmful is particularly limited in Asia. Objectives: We characterized PM2.5 chemical composition and estimated the effects of cause-specific mortality of PM2.5 mass and constituents in Seoul, Korea. We compared the chemical composition of particles to those of the eastern and western United States. Methods: We examined temporal variability of PM2.5 mass and its composition using hourly data. We applied an overdispersed Poisson generalized linear model, adjusting for time, day of week, temperature, and relative humidity to investigate the association between risk of mortality and PM2.5 mass and its constituents in Seoul, Korea, for August 2008 through October 2009. Results: PM2.5 and chemical components exhibited temporal patterns by time of day and season. The chemical characteristics of Seoul’s PM2.5 were more similar to PM2.5 found in the western United States than in the eastern United States. Seoul’s PM2.5 had lower sulfate (SO4) contributions and higher nitrate (NO3) contributions than that of the eastern United States, although overall PM2.5 levels in Seoul were higher than in the United States. An interquartile range (IQR) increase in magnesium (Mg) (0.05 μg/m3) was associated with a 1.4% increase (95% confidence interval: 0.2%, 2.6%) in total mortality on the following day. Several components that were among the largest contributors to PM2.5 total mass—NO3, SO4, and ammonium (NH4)—were moderately associated with same-day cardiovascular mortality at the p < 0.10 level. Other components with smaller mass contributions [Mg and chlorine (Cl)] exhibited moderate associations with respiratory mortality on the following day (p < 0.10). Conclusions: Our findings link PM2.5 constituents with mortality and have implications for policy making on sources of PM2.5 and on the relevance of PM2.5 health studies from other areas to this region.

Individual exposure to air pollution and lung function in Korea: spatial analysis using multiple exposure approaches.

Interpolation methods can estimate individual-level exposures to air pollution from ambient monitors; however, few studies have evaluated how different approaches may affect health risk estimates. We applied multiple methods of estimating exposure for several air pollutants. We investigated how different methods of estimating exposure may influence health effect estimates in a case study of lung function data, forced expiratory volume in 1s (FEV1), and forced vital capacity (FVC), for 2102 cohort subjects in Ulsan, Korea, for 2003-2007. Measurements from 13 monitors for particulate matter <10 μm (PM(10)), ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide were used to estimate individual-level exposures by averaging across values from all monitors, selecting the value from the nearest monitor, inverse distance weighting, and kriging. We assessed associations between pollutants and lung function in linear regression models, controlling for age, sex, and body mass index. Cross-validation indicated that kriging provided the most accurate estimated exposures. FVC was associated with all air pollutants under all methods of estimating exposure. Only ozone was associated with FEV1. An 11 ppb increase in lag-0-2 8-h maximum ozone was associated with a 6.1% (95% confidence interval 5.0, 7.3%) decrease in FVC and a 0.50% (95% confidence interval 0.03, 0.96%) decrease in FEV1, based on kriged exposures. Central health effect estimates were generally higher using exposures based on averaging across all monitors or kriging. Results based on the nearest monitor approach had the lowest variance. Findings suggest that spatial interpolation methods may provide better estimates than monitoring values alone by reflecting the spatial variability of individual-level exposures and generating estimates for locations without monitors.

Effect of air pollution on asthma-related hospital admissions for children by socioeconomic status associated with area of residence.

The authors evaluated whether the effects of air pollution on asthma in children differed by the regional socioeconomic status (SES) associated with the area in which children resided. They analyzed data on air pollution, asthma-related hospitalization, weather conditions, and SES collected from 25 subregions in Seoul from January 1 to December 31, 2002. The National Health Insurance Cooperation provided data for children aged younger than 15 years who were living in Seoul and hospitalized for asthma-related health conditions (ICD-10 codes J45-J46). Exposure to interquartile range increase of airborne particles ≤ 10 μm in aerodynamic diameter, sulfur dioxide, and nitrogen dioxide in districts associated with a lower SES, the estimated percent increase of hospitalization for asthma among children was 31% (95% confidence interval [CI] = 14%-51%), 29% (95% CI = 8%-53%), and 29% (95% CI = 5%-58%), respectively. This suggests that not only biological sensitivity markers, but also the SES of subjects, should be considered as potentially confounding factors.

Benefits of Mitigated Ambient Air Quality Due to Transportation Control on Childhood Asthma Hospitalization during the 2002 Summer Asian Games in Busan, Korea

Abstract The objective of this study is to see whether there were any health benefits of mitigated air pollution concentration due to reduced traffic flow during a citywide intervention for the 2002 Summer Asian Games. Relative risks of hospitalization for childhood asthma during the post-Asian Game period compared with the baseline period were estimated using a time-series analysis of the generalized additive Poisson model. Fourteen consecutive days of traffic volume control in Busan during the Games reduced all regulated air pollutant levels by 1–25%. The estimated relative risk of hospitalization during the post-Games period over the baseline period was 0.73 (95% confidence interval [CI] = 0.49, 1.11). We observed that this reduced air pollution was unique in 2002 when the traffic volume reduction program was applied during the Games period. This empirical data provides epidemiologic evidence of the health benefits resulting from environmental interventions to reduce ambient air pollution.

Short-term effects of air pollution on hospital admissions in Korea.

Background: Numerous studies have identified short-term effects of air pollution on morbidity in North America and Europe. The effects of air pollution may differ by region of the world. Evidence on air pollution and morbidity in Asia is limited. Methods: We investigated associations between ambient air pollution and hospital admissions in eight Korean cities for 2003–2008. We applied a two-stage Bayesian hierarchical model to estimate city-specific effects and the overall effects across the cities. We considered lagged effects of pollutants by cause (allergic disease, asthma, selected respiratory disease, and cardiovascular disease), sex, and age (0–14, 15–64, 65–74, and ≥75 years). Results: We found evidence of associations between hospital admissions and short-term exposure to air pollution. An interquartile range (IQR) increase in PM10 (30.7µg/m3) was associated with an overall increase of 2.2% (95% posterior interval = 0.5%–3.9%), 2.8% (1.3%–4.4%), 1.7% (0.9%–2.6%), and 0.7% (0.0%–1.4%) in allergic, asthma, selected respiratory, and cardiovascular admissions, respectively. For NO2 (IQR 12.2 ppb), the corresponding figures were 2.3% (0.6%–4.0%), 2.2% (0.3%–4.1%), 2.2% (0.6%–3.7%), and 2.2% (1.1%–3.4%). For O3, we found positive associations for all the studied diagnoses except cardiovascular disease. SO2 was associated with hospital admissions for selected respiratory or cardiovascular causes, whereas O3 was negatively associated with cardiovascular admissions. We found suggestive evidence for stronger associations in younger and older age groups. Associations were similar for men and women. Conclusions: Ambient air pollution was associated with increased risk of hospital admissions in Korea. Results suggest increased susceptibility among the young or the elderly for pollution effects on specific diseases.

Survival Analysis of Long-Term Exposure to Different Sizes of Airborne Particulate Matter and Risk of Infant Mortality Using a Birth Cohort in Seoul, Korea

Background Several studies suggest that airborne particulate matter (PM) is associated with infant mortality; however, most focused on short-term exposure to larger particles. Objectives We evaluated associations between long-term exposure to different sizes of particles [total suspended particles (TSP), PM ≤ 10 μm in aerodynamic diameter (PM10), ≤ 10–2.5 μm (PM10–2.5), and ≤ 2.5 μm (PM2.5)] and infant mortality in a cohort in Seoul, Korea, 2004–2007. Methods The study includes 359,459 births with 225 deaths. We applied extended Cox proportional hazards modeling with time-dependent covariates to three mortality categories: all causes, respiratory, and sudden infant death syndrome (SIDS). We calculated exposures from birth to death (or end of eligibility for outcome at 1 year of age) and pregnancy (gestation and each trimester) and treated exposures as time-dependent variables for subjects’ exposure for each pollutant. We adjusted by sex, gestational length, season of birth, maternal age and educational level, and heat index. Each cause of death and exposure time frame was analyzed separately. Results We found a relationship between gestational exposures to PM and infant mortality from all causes or respiratory causes for normal-birth-weight infants. For total mortality (all causes), risks were 1.44 (95% confidence interval, 1.06–1.97), 1.65 (1.18–2.31), 1.53 (1.22–1.90), and 1.19 (0.83–1.70) per interquartile range increase in TSP, PM10, PM2.5, and PM10–2.5, respectively; for respiratory mortality, risks were 3.78 (1.18–12.13), 6.20 (1.50–25.66), 3.15 (1.26–7.85), and 2.86 (0.76–10.85). For SIDS, risks were 0.92 (0.33–2.58), 1.15 (0.38–3.48), 1.42 (0.71–2.87), and 0.57 (0.16–1.96), respectively. Conclusions Our findings provide supportive evidence of an association of long-term exposure to PM air pollution with infant mortality.

Vulnerability to temperature-related mortality in Seoul, Korea

Studies indicate that the mortality effects of temperature may vary by population and region, although little is known about the vulnerability of subgroups to these risks in Korea. This study examined the relationship between temperature and cause-specific mortality for Seoul, Korea, for the period 2000-7, including whether some subgroups are particularly vulnerable with respect to sex, age, education and place of death. The authors applied time-series models allowing nonlinear relationships for heat- and cold-related mortality, and generated exposure-response curves. Both high and low ambient temperatures were associated with increased risk for daily mortality. Mortality risk was 10.2% (95% confidence interval 7.43, 13.0%) higher at the 90th percentile of daily mean temperatures (25 °C) compared to the 50th percentile (15 °C). Mortality risk was 12.2% (3.69, 21.3%) comparing the 10th (-1 °C) and 50th percentiles of temperature. Cardiovascular deaths showed a higher risk to cold, whereas respiratory deaths showed a higher risk to heat effect, although the differences were not statistically significant. Susceptible populations were identified such as females, the elderly, those with no education, and deaths occurring outside of a hospital for heat- and cold-related total mortality. Our findings provide supportive evidence of a temperature-mortality relationship in Korea and indicate that some subpopulations are particularly vulnerable.

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 &mgr;g/m3, with sensitivity analysis considering 23, 28, and 37 &mgr;g/m3. 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 &mgr;g/m3) compared with matched non smoke wave days. We did not observe an association between smoke wave days with wildfire-specific PM2.5 ⩽ 37 &mgr;g/m3and 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.