Particulate matter is an air pollutant emitted from both natural and anthropogenic sources, and its adverse health effects have been well documented in time-series analyses and cohort studies. The effect size of particulate matter exposure—a roughly 0.5% increase in mortality for each 10 µg/m³ increment of short-term exposure to particulate matter with aerodynamic diameter ≤10 µm and approximately a 10% increase for each 10 µg/m³ increment of long-term exposure to particulate matter with aerodynamic diameter ≤2.5 µm—is small compared to other risk factors, but the exposure is involuntary and affects the entire population, which makes particulate matter pollution an important public health issue. The World Health Organization and Korean government have both established guidelines for particulate matter concentrations, but the Korean guideline is less stringent than that of the World Health Organization. The annual mean concentration of particulate matter in Korea is decreasing, but the trend seems to be slowing. In addition to policy efforts to reduce particulate matter emission, personal approaches such as the use of face masks and air purifiers have been recommended. Personal approaches may not solve the fundamental problem, but can provide temporary mitigation until efforts to reduce emission make progress.
Air Filters ; Cohort Studies ; Environmental Medicine ; Epidemiology ; Humans ; Korea ; Masks ; Mortality ; Particulate Matter ; Public Health ; Risk Factors ; World Health Organization

PURPOSE: The effects of air pollution on health can vary regionally. Our goal was to comprehensively review previous epidemiological studies on air pollution and health conducted in Korea to identify future areas of potential study. MATERIALS AND METHODS: We systematically searched all published epidemiologic studies examining the association between air pollution and occurrence of death, diseases, or symptoms in Korea. After classifying health outcomes into mortality, morbidity, and health impact, we summarized the relationship between individual air pollutants and health outcomes. RESULTS: We analyzed a total of 27 studies that provided 104 estimates of the quantitative association between risk of mortality and exposure to air pollutants, including particulate matter with aerodynamic diameter less than 10 µm, particulate matter with aerodynamic diameter less than 2.5 µm, sulfur dioxide, nitrogen dioxide, ozone, and carbon monoxide in Korea between January 1999 and July 2018. Regarding the association with morbidity, there were 38 studies, with 98 estimates, conducted during the same period. Most studies examined the short-term effects of air pollution using a time series or case-crossover study design; only three cohort studies that examined long-term effects were found. There were four health impact studies that calculated the attributable number of deaths or disability-adjusted life years due to air pollution. CONCLUSION: There have been many epidemiologic studies in Korea regarding air pollution and health. However, the present review shows that additional studies, especially cohort and experimental studies, are needed to provide more robust and accurate evidence that can be used to promote evidence-based policymaking.
Air Pollutants ; Air Pollution ; Carbon Monoxide ; Cohort Studies ; Environmental Medicine ; Epidemiologic Studies ; Korea ; Mortality ; Nitrogen Dioxide ; Ozone ; Particulate Matter ; Sulfur Dioxide

Particulate matter is an air pollutant emitted from both natural and anthropogenic sources, and its adverse health effects have been well documented in time-series analyses and cohort studies. The effect size of particulate matter exposure—a roughly 0.5% increase in mortality for each 10 µg/m³ increment of short-term exposure to particulate matter with aerodynamic diameter ≤10 µm and approximately a 10% increase for each 10 µg/m³ increment of long-term exposure to particulate matter with aerodynamic diameter ≤2.5 µm—is small compared to other risk factors, but the exposure is involuntary and affects the entire population, which makes particulate matter pollution an important public health issue. The World Health Organization and Korean government have both established guidelines for particulate matter concentrations, but the Korean guideline is less stringent than that of the World Health Organization. The annual mean concentration of particulate matter in Korea is decreasing, but the trend seems to be slowing. In addition to policy efforts to reduce particulate matter emission, personal approaches such as the use of face masks and air purifiers have been recommended. Personal approaches may not solve the fundamental problem, but can provide temporary mitigation until efforts to reduce emission make progress.

OBJECTIVES: Osteoarthritis is the most common joint disease, with a higher prevalence among women than men. The present study aimed to examine the associations of breastfeeding duration and the total number of children breastfed with osteoarthritis in Korean women aged 50 years and older. METHODS: In this cross-sectional study, we used representative data from the Korea National Health and Nutrition Examination Survey, phases 5 through 7 (2010-2018). Our analysis included 10,102 women aged ≥50 years. Osteoarthritis experience was defined as whether a physician had ever diagnosed osteoarthritis. Breastfeeding duration was categorized as 1-6 months, 7-24 months, and ≥25 months. The total number of children breastfed was categorized as 1-2, 3-4, and ≥5. The covariates were health behavior characteristics and risks of diseases (smoking, drinking, physical activity, body mass index, diabetes, hypertension, oral contraceptive use, and menopause) as well as socioeconomic characteristics (income, educational level, and occupation). A multiple logistic regression model was used to investigate associations between osteoarthritis and aspects of breastfeeding experience. RESULTS: Compared to the non-breastfeeding group, the breastfeeding group had an odds ratio (OR) of 1.55 (95% confidence interval [CI], 1.18 to 2.03) for osteoarthritis. Those who reported breastfeeding for >25 months had an OR of 1.56 (95% CI, 1.19 to 2.06). CONCLUSIONS The advantages of breastfeeding are already well known, but the present study suggests that women who breastfeed children for a longer time may have a higher risk of osteoarthritis after middle age.

OBJECTIVES: We investigated the association between particulate matter less than 10 microm in aerodynamic diameter (PM10) exposure and non-accidental mortality in Asian populations by meta-analysis, using both time-series and case-crossover analysis. METHODS: Among the 819 published studies searched from PubMed and EMBASE using key words related to PM10 exposure and non-accidental mortality in Asian countries, 8 time-series and 4 case-crossover studies were selected for meta-analysis after exclusion by selection criteria. We obtained the relative risk (RR) and 95% confidence intervals (CI) of non-accidental mortality per 10 microg/m3 increase of daily PM10 from each study. We used Q statistics to test the heterogeneity of the results among the different studies and evaluated for publication bias using Begg funnel plot and Egger test. RESULTS: Testing for heterogeneity showed significance (p<0.001); thus, we applied a random-effects model. RR (95% CI) per 10 microg/m3 increase of daily PM10 for both the time-series and case-crossover studies combined, time-series studies relative risk only, and case-crossover studies only, were 1.0047 (1.0033 to 1.0062), 1.0057 (1.0029 to 1.0086), and 1.0027 (1.0010 to 1.0043), respectively. The non-significant Egger test suggested that this analysis was not likely to have a publication bias. CONCLUSIONS: We found a significant positive association between PM10 exposure and non-accidental mortality among Asian populations. Continued investigations are encouraged to contribute to the health impact assessment and public health management of air pollution in Asian countries.
Air Pollutants/*chemistry ; Asian Continental Ancestry Group ; Cross-Over Studies ; Databases, Factual ; *Environmental Exposure ; Humans ; Models, Theoretical ; *Mortality ; Particulate Matter/*chemistry ; Time Factors

OBJECTIVES: Although the entire process extending from food production to dietary consumption makes a large contribution to total greenhouse gas (GHG) emissions, little and inconsistent evidence exists on the epidemiological associations of daily diet-related GHG emissions with chronic disease risk or all-cause mortality. This systematic review and meta-analysis explored the observational epidemiological relationship between daily diet-related GHG emissions and health outcomes, including the risk of chronic diseases and all-cause mortality. METHODS: Original articles published in English until May 2022 were identified by searching PubMed, Ovid-Embase, Web of Science, CINAHL, and Google Scholar. The extracted data were pooled using both fixed-effects and random-effects meta-analyses and presented as hazard and risk ratios (RRs) with 95% confidence intervals (CIs). RESULTS: In total, 7 cohort studies (21 study arms) were included for qualitative synthesis and meta-analysis. The GHG emissions of dietary consumption showed a significant positive association with the risk of chronic disease incidence and mortality in both fixed-effects and random-effects models (fixed: RR, 1.04; 95% CI, 1.03 to 1.05; random: RR, 1.04; 95% CI, 1.02 to 1.06). This positive association was robust regardless of how daily diet-related GHG emissions were grouped. More strongly animal- based diets showed higher GHG emissions. However, there were only a few studies on specific chronic diseases, and the subgroup analysis showed insignificant results. There was no evidence of publication bias among the studies (Egger test: p=0.79). CONCLUSIONS A higher GHG-emission diet was found to be associated with a greater risk of all-cause mortality.

OBJECTIVES: To test the hypothesis that tobacco exposure is associated with elevated blood pressure (EBP) in Korean adolescents, and that the association is dose dependent. METHODS: This cross-sectional study used data from the 2011-2020 Korea National Health and Nutrition Survey (KNHANES). Subjects were eligible if they were 13-18 years at the time of participation in KNHANES. Tobacco exposure was defined by urine cotinine level. The main outcomes were EBP and hypertension. Statistical analyses were conducted using SAS version 9.4 with appropriate sampling weights to account for the complex survey design, stratification, and cluster variable. RESULTS: A total of 2,518 adolescents was included in the analysis, representing 2.5 million Korean adolescents. The mean± standard deviation participant age was 15.3±1.7 years, and 55.3% were male. The number of participants with active tobacco smoke exposure was 283 (11.2%), passive tobacco smoke exposure was 145 (5.8%), and no smoke exposure was 2,090 (83.0%). Analysis of the 2,518 urine-cotinine-verified participants showed that tobacco smoke exposure had a significant effect on EBP: with an odds of elevated blood pressure of 3.00 (95% confidence interval [CI], 1.14 to 7.89). The odds of hypertension were 3.61 (95% CI, 1.13 to 11.49) in the active smoking group compared with the no tobacco exposure group after adjustment for potential confounders. CONCLUSIONS It is necessary to present a range of public health plans to reduce tobacco exposure that affects adolescents’ blood pressure, and further research with a larger number of participants using urine cotinine as a biomarker is needed.

OBJECTIVES: We evaluated the reliability of the possible covariates of the baseline survey data collected for the Epidemiological Investigation on Cancer Risk Among Residents Who Reside Near the Nuclear Power Plants in Korea. METHODS: Follow-up surveys were conducted for 477 participants of the cohort at less than 1 year after the initial survey. The mean interval between the initial and follow-up surveys was 282.5 days. Possible covariates were identified by analyzing the correlations with the exposure variable and associations with the outcome variables for all the variables. Logistic regression analysis with stepwise selection was further conducted among the possible covariates to select variables that have covariance with other variables. We considered that these variables can be representing other variables. Seven variables for the males and 3 variables for the females, which had covariance with other possible covariates, were selected as representative variables. The Kappa index of each variable was calculated. RESULTS: For the males, the Kappa indexes were as follow; family history of cancer was 0.64, family history of liver diseases in parents and siblings was 0.56, family history of hypertension in parents and siblings was 0.51, family history of liver diseases was 0.50, family history of hypertension was 0.44, a history of chronic liver diseases was 0.53 and history of pulmonary tuberculosis was 0.36. For females, the Kappa indexes were as follow; family history of cancer was 0.58, family history of hypertension in parents and siblings was 0.56 and family history of hypertension was 0.47. CONCLUSIONS: Most of the possible covariates showed good to moderate agreement.
Aged ; Cohort Studies ; Confounding Factors (Epidemiology) ; Environmental Exposure/adverse effects ; Female ; Health Behavior ; Health Surveys ; Humans ; Logistic Models ; Male ; Middle Aged ; Neoplasms/*epidemiology/etiology ; *Nuclear Power Plants ; Republic of Korea/epidemiology ; Sex Factors

OBJECTIVES: Although mercury (Hg) exposure is known to be neurotoxic in humans, its effects on liver function have been less often reported. The aim of this study was to investigate whether total Hg exposure in Korean adults was associated with elevated serum levels of the liver enzymes aspartate aminotransferase (AST), alanine transaminase (ALT), and gamma-glutamyltransferase (GGT). METHODS: We repeatedly examined the levels of total Hg and liver enzymes in the blood of 508 adults during 2010-2011 and 2014-2015. Cross-sectional associations between levels of blood Hg and liver enzymes were analyzed using a generalized linear model, and nonlinear relationships were analyzed using a generalized additive mixed model. Generalized estimating equations were applied to examine longitudinal associations, considering the correlations of individuals measured repeatedly. RESULTS: GGT increased by 11.0% (95% confidence interval [CI], 4.5 to 18.0%) in women and 8.1% (95% CI, -0.5 to 17.4%) in men per doubling of Hg levels, but AST and ALT were not significantly associated with Hg in either men or women. In women who drank more than 2 or 3 times per week, AST, ALT, and GGT levels increased by 10.6% (95% CI, 4.2 to 17.5%), 7.7% (95% CI, 1.1 to 14.7%), and 37.5% (95% CI,15.2 to 64.3%) per doubling of Hg levels, respectively, showing an interaction between blood Hg levels and drinking. CONCLUSIONS: Hg exposure was associated with an elevated serum concentration of GGT. Especially in women who were frequent drinkers, AST, ALT, and GGT showed a significant increase, with a significant synergistic effect of Hg and alcohol consumption.
Adult* ; Alanine Transaminase ; Alcohol Drinking ; Aspartate Aminotransferases ; Drinking ; Female ; gamma-Glutamyltransferase ; Humans ; Linear Models ; Liver* ; Longitudinal Studies* ; Male

Inferring causality is necessary to achieve the goal of epidemiology, which is to elucidate the cause of disease. Causal inference is conducted in three steps: evaluation of validity of the study, inference of general causality, and inference of individual causality. To evaluate validity of the study, we propose a checklist that focuses on biases and generalizability. For general causal inference, we recommend utilizing Hill’s 9 viewpoints. Lastly, individual causality can be inferred based on the general causality and evidence of exposure. Additional considerations may be needed for social or legal purposes; however, these additional considerations should be based on the scientific truth elucidated by the causal inference described in the present article.
Bias (Epidemiology) ; Checklist ; Environmental Exposure ; Epidemiology