Bing-Fang Hwang

Home dampness and molds, parental atopy, and asthma in childhood: a six-year population-based cohort study

Previous studies of how parental atopy and exposure to dampness and molds contribute to the risk of asthma have been mainly cross-sectional or prevalent case–control studies, where selection and information bias and temporality constitute problems. We assessed longitudinally the independent and joint effects of parental atopy and exposure to molds in dwellings on the development of asthma in childhood. We conducted a population-based, 6-year prospective cohort study of 1,984 children 1–7 years of age at the baseline in 1991 (follow-up rate, 77%). The study population included 1,916 children without asthma at baseline and complete outcome information. The data collection included a baseline and follow-up survey. The outcome of interest was development of asthma during the study period. The studied determinants were parental allergic diseases and four indicators of exposure at baseline: histories of water damage, presence of moisture and visible molds, and perceived mold odor in the home. A total of 138 (7.2%) children developed asthma during the study period, resulting in an incidence rate of 125 cases per 10,000 person-years [95% confidence interval (CI), 104–146]. In Poisson regression adjusting for confounding, parental atopy [adjusted incidence rate ratio (IRR) 1.52; 95% CI, 1.08–2.13] and the presence of mold odor in the home reported at baseline (adjusted IRR 2.44; 95% CI, 1.07–5.60) were independent determinants of asthma incidence, but no apparent interaction was observed. The results of this cohort study with assessment of exposure before the onset of asthma strengthen the evidence on the independent effects of parental atopy and exposure to molds on the development of asthma.

Household environmental tobacco smoke and risks of asthma, wheeze and bronchitic symptoms among children in Taiwan

BackgroundAlthough studies show that maternal smoking during pregnancy increases the risks of respiratory outcomes in childhood, evidence concerning the effects of household environmental tobacco smoke (ETS) exposure remains inconsistent.MethodsWe conducted a population-based study comprised of 5,019 seventh and eighth-grade children in 14 Taiwanese communities. Questionnaire responses by parents were used to ascertain childrens exposure and disease status. Logistic regression models were fitted to estimate the effects of ETS exposures on the prevalence of asthma, wheeze, and bronchitic symptoms.ResultsThe lifetime prevalence of wheeze was 11.6% and physician-diagnosed asthma was 7.5% in our population. After adjustment for potential confounders, in utero exposure showed the strongest effect on all respiratory outcomes. Current household ETS exposure was significantly associated with increased prevalence of active asthma, ever wheeze, wheeze with nighttime awakening, and bronchitis. Maternal smoking was associated with the increased prevalence of a wide range of wheeze subcategories, serious asthma, and chronic cough, but paternal smoking had no significant effects. Although maternal smoking alone and paternal smoking alone were not independently associated with respiratory outcomes, joint exposure appeared to increase the effects. Furthermore, joint exposure to parental smoking showed a significant effect on early-onset asthma (OR, 2.01; 95% CI, 1.00-4.02), but did not show a significant effect on late-onset asthma (OR, 1.17; 95% CI, 0.36-3.87).ConclusionWe concluded that prenatal and household ETS exposure had significant adverse effects on respiratory health in Taiwanese children.

Traffic related air pollution as a determinant of asthma among Taiwanese school children

Background: There is evidence that long term exposure to ambient air pollution increases the risk of childhood asthma, but the role of different sources and components needs further elaboration. To assess the effect of air pollutants on the risk of asthma among school children, a nationwide cross sectional study of 32 672 Taiwanese school children was conducted in 2001. Methods: Routine air pollution monitoring data for sulphur dioxide (SO2), nitrogen oxides (NOx), ozone (O3), carbon monoxide (CO), and particles with an aerodynamic diameter of 10 μm or less (PM10) were used. Information on individual characteristics and indoor environments was from a parent administered questionnaire (response rate 93%). The exposure parameters were calculated using the mean of the 2000 monthly averages. The effect estimates were presented as odds ratios (ORs) per 10 ppb changes for SO2, NOx, and O3, 100 ppb changes for CO, and 10 μg/m3 changes for PM10. Results: In a two stage hierarchical model adjusting for confounding, the risk of childhood asthma was positively associated with O3 (adjusted OR 1.138, 95% confidence interval (CI) 1.001 to 1.293), CO (adjusted OR 1.045, 95% CI 1.017 to 1.074), and NOx (adjusted OR 1.005, 95% CI 0.954 to 1.117). Against our prior hypothesis, the risk of childhood asthma was weakly or not related to SO2 (adjusted OR 0.874, 95% CI 0.729 to 1.054) and PM10 (adjusted OR 0.934, 95% CI 0.909 to 0.960). Conclusions: The results are consistent with the hypothesis that long term exposure to traffic related outdoor air pollutants such as NOx, CO, and O3 increases the risk of asthma in children.

Ozone and Other Air Pollutants and the Risk of Oral Clefts

Background Air pollution influences the development of oral clefts in animals. There are few epidemiologic data on the relation of prenatal air pollution exposure and the risk of oral clefts. Objectives Our goal in this study was to assess the relations between exposure to ambient air pollution and the risk of cleft lip with or without cleft palate (CL/P). Methods We conducted a population-based case–control study of all 653 cases of CL/P and a random sample of 6,530 control subjects from 721,289 Taiwanese newborns in 2001–2003. We used geographic information systems to form exposure parameters for sulfur dioxide, nitrogen oxides, ozone, carbon monoxide, and particulate matter with an aerodynamic diameter ≤ 10 μm (PM10) during the first 3 months of pregnancy using inverse distance weighting method. We present the effect estimates as odds ratios (ORs) per 10-ppb change for SO2, NOx, and O3, 100-ppb change for CO, and 10-μg/m3 change for PM10. Results The risk of CL/P was increased in relation to O3 levels in the first gestational month [adjusted OR = 1.20; 95% confidence interval (CI), 1.02–1.39] and second gestational month (adjusted OR = 1.25; 95% CI, 1.03–1.52) in the range from 16.7 ppb to 45.1 ppb, but was not related to CO, NOx, SO2, or PM10. Conclusions The study provides new evidence that exposure to outdoor air O3 during the first and second month of pregnancy may increase the risk of CL/P. Similar levels of O3 are encountered globally by large numbers of pregnant women.

Water chlorination and birth defects: a systematic review and meta-analysis.

The authors used the Medline data retrieval system for 1966-2001 to identify and synthesize the epidemiological evidence for adverse effects of prenatal exposure to chlorination byproducts on birth defects. For 5 studies that provided estimates of the effect of exposure on 1 or several birth defects, the authors calculated summary odds ratios and 95% confidence intervals using the Mantel-Haenszel method for a fixed-effects model, and the DerSimonian-Laird method for a random-effects model. The results of this meta-analysis provide evidence for an effect of exposure to chlorination byproducts on the risk of any birth defect, and of neural tube and urinary system defects. The results for respiratory system, major cardiac, and oral cleft defects were heterogeneous and inconclusive. Differences in the susceptibility of populations, and different approaches in exposure assessment, may explain the heterogeneity of the results.

Air Pollution and Newly Diagnostic Autism Spectrum Disorders: A Population-Based Cohort Study in Taiwan

There is limited evidence that long-term exposure to ambient air pollution increases the risk of childhood autism spectrum disorder (ASD). The objective of the study was to investigate the associations between long-term exposure to air pollution and newly diagnostic ASD in Taiwan. We conducted a population-based cohort of 49,073 children age less than 3 years in 2000 that were retrieved from Taiwan National Insurance Research Database and followed up from 2000 through 2010. Inverse distance weighting method was used to form exposure parameter for ozone (O3), carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and particles with aerodynamic diameter less than 10 µm (PM10). Time-dependent Cox proportional hazards (PH) model was performed to evaluate the relationship between yearly average exposure air pollutants of preceding years and newly diagnostic ASD. The risk of newly diagnostic ASD increased according to increasing O3, CO, NO2, and SO2 levels. The effect estimate indicating an approximately 59% risk increase per 10 ppb increase in O3 level (95% CI 1.42–1.79), 37% risk increase per 10 ppb in CO (95% CI 1.31–1.44), 340% risk increase per 10 ppb increase in NO2 level (95% CI 3.31–5.85), and 17% risk increase per 1 ppb in SO2 level (95% CI 1.09–1.27) was stable with different combinations of air pollutants in the multi-pollutant models. Our results provide evident that children exposure to O3, CO, NO2, and SO2 in the preceding 1 year to 4 years may increase the risk of ASD diagnosis.

Water disinfection by-products and the risk of specific birth defects: a population-based cross-sectional study in Taiwan

BackgroundRecent findings suggest that exposure to disinfection by-products may increase the risk of birth defects. Previous studies have focused mainly on birth defects in general or groups of defects. The objective of the present study was to assess the effect of water disinfection by-products on the risk of most common specific birth defects.MethodsWe conducted a population-based cross-sectional study of 396,049 Taiwanese births in 2001–2003 using information from the Birth Registry and Waterworks Registry. We compared the risk of eleven most common specific defects in four disinfection by-product exposure categories based on the levels of total trihalomethanes (TTHMs) representing high (TTHMs 20+ μg/L), medium (TTHMs 10–19 μg/L), low exposure (TTHMs 5–9 μg/L), and 0–4 μg/L as the reference category. In addition, we conducted a meta-analysis of the results from the present and previous studies focusing on the same birth defects.ResultsIn multivariate logistic regression analysis the risk of ventricular septal defects (adjusted odds ratio 1.81, 95% confidence interval: 0.98 3.35), cleft palate (1.56. 95% CI: 1.00, 2.41), and anencephalus (1.96, 95% CI: 0.94, 4.07) were elevated in the high exposure compared to the reference category. In the meta-analysis, the summary odds ratio for ventricular septal defects (1.59, 95% CI: 1.21, 2.07) was consistently elevated.ConclusionThe present study suggests that prenatal exposure to disinfection by-products increases the risk of ventricular septal defects, cleft palate, and anencephalus. The evidence on ventricular septal defects is consistent in the three available studies.

Home Dampness and Molds as Determinants of Allergic Rhinitis in Childhood: A 6-Year, Population-based Cohort Study

The authors assessed the relation between exposure to dampness and molds in dwellings and the development of allergic rhinitis in childhood in a 6-year, population-based prospective cohort study of 1,863 children aged 1-7 years at baseline in 1991 (follow-up rate, 77%) from Espoo, Finland. The studied exposures were history of water damage, presence of moisture and visible mold, and perceived mold odor in the home, based on parent-administered questionnaire. A total of 246 (13.2%) children developed physician-diagnosed allergic rhinitis during the study period, resulting in an incidence rate of 440 cases per 10,000 person-years (95% confidence interval (CI): 387, 499). In logistic regression adjusting for confounding, any mold or dampness exposure indicator at baseline (adjusted odds ratio = 1.55, 95% CI: 1.10, 2.18), at follow-up (adjusted odds ratio = 1.62, 95% CI: 1.21, 2.18), or both (adjusted odds ratio = 1.96, 95% CI: 1.29, 2.98) was an important independent determinant of the risk of allergic rhinitis. Of the individual indicators, water damage and moisture on the surfaces were consistent determinants of allergic rhinitis. The results of this cohort study, which assessed exposure before the onset of allergic rhinitis, strengthen considerably the evidence of the role of indoor dampness problems as determinants of allergic rhinitis in children.

Foetal growth and duration of gestation relative to water chlorination

OBJECTIVE To assess the effect of exposure to chlorination byproducts during pregnancy on foetal growth and duration of pregnancy. METHODS A population based study was conducted of 137 145 Norwegian children born alive in 1993–5. Information was obtained from the Norwegian medical birth registry, waterwork registry, and social science data service. The outcomes of interest were birth weight, low birth weight (<2500 g), small for gestational age, and preterm delivery (gestational age <37 weeks). The exposure assessment was based on quality of drinking water in the municipality where the mother lived during pregnancy. Municipal exposure was calculated with information on chlorination and the amount of natural organic matter in raw water measured as colour in mg precipitate/l. The main exposure category was high colour and chlorination, which was contrasted with the reference category of low colour and no chlorination. RESULTS In logistic regression analysis adjusting for confounding, the risks of low birth weight (odds ratio (OR) 0.97, 95% confidence interval (95% CI) 0.89 to 1.06) and small for gestational age (OR 1.00, 95% CI 0.91 to 1.10) were not related to exposure. Contrary to the hypothesis, the risk of preterm delivery was slightly lower among the exposed than the reference category (OR 0.91, 95% CI 0.84 to 0.99). The risks of the studied outcomes were similar in newborn infants exposed to high colour drinking water without chlorination and chlorinated drinking water with low colour compared with the reference category. CONCLUSIONS The present study did not provide evidence that prenatal exposure to chlorination byproducts at the relatively low concentrations encountered in Norwegian drinking water increases the risk of the studied outcomes.

Time trend of asthma prevalence among school children in Taiwan: ISAAC phase I and III surveys

The standardized International Study of Asthma and Allergies in Childhood (ISAAC) is a valid tool in assessing prevalence of asthma indices. In order to determine the time trends of childhood asthma in Taiwan, we compared data from nationwide ISAAC surveys from a very large sample of Taiwanese 12‐ to 15‐year‐old school children, using ISAAC core written and video questionnaires. The number of participants was 44,104 in 1995–96 (phase I) and 11,048 in 2001 (phase III). We found a general tendency towards an increase in lifetime prevalence of physician‐diagnosed asthma and asthma symptoms between two surveys, more marked for girls than for boys. Most of the 12‐month prevalence of asthma symptoms decreased among boys but stabilized among girls. When comparing different severity levels, we also noted that the decreasing trends of current symptoms were more marked with regard to severe symptoms than mild symptoms in both sexes. A combination of both improved awareness and management of asthma might in part explain this circumstance. Over the past decade in Taiwan, the lifetime prevalence of childhood asthma was increasing, more marked among girls; however, the 12‐month prevalence of asthma symptoms was decreasing, mostly among boys. The exact reasons for such trends remain to be explored.