Tze Wai Wong

Publications (240) View all

• Article: Cool and dry weather enhances the effects of air pollution on emergency IHD hospital admissions.

  Hong Qiu, Ignatius Tak-Sun Yu, Xiaorong Wang, Linwei Tian, Lap Ah Tse, Tze Wai Wong
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  ABSTRACT: BACKGROUND: Associations between ambient pollution and cardiovascular morbidity including ischemic heart disease (IHD) have been confirmed. Weather factors such as temperature, season and relative humidity (RH) may modify the effects of pollution. We conducted this study to examine the effects of air pollution on emergency IHD hospital admissions varied across seasons and RH levels, and to explore the possible joint modification of weather factors on pollution effects. METHODS: Daily time series of air pollution concentrations, mean temperature and RH were collected from IHD hospital admissions from 1998 to 2007 in Hong Kong. We used generalized additive Poisson models with interaction term to estimate the pollution effects varied across seasons and RH levels, after adjusting for time trends, weather conditions, and influenza outbreaks. RESULTS: An increase in the detrimental effects of air pollution in cool season and on low humidity days was observed. In the cool and dry season, a 10μg/m(3) increment of lag(03) exposure was associated with an increase of emergency IHD admissions by 1.82% (95% CI: 1.24-2.40%), 3.89% (95% CI: 3.08-4.70%), and 2.19% (95% CI: 1.33-3.06%) for particles with an aerodynamic diameter less than 10μm (PM(10)), nitrogen dioxide (NO(2)), and ozone (O(3)), respectively. The effects of pollutants decreased greatly and lost statistical significance in the warm and humid season. CONCLUSIONS: We found season and RH jointly modified the associations between ambient pollution and IHD admissions, resulting in increased IHD admissions in the cool and dry season and reduced admissions in the warm and humid season.
  International journal of cardiology 10/2012; · 7.08 Impact Factor
• Article: Levels of PCDDs, PCDFs, and dioxin-like PCBs in human milk among Hong Kong mothers.

  Tze Wai Wong, Andromeda H S Wong, E Anthony S Nelson, Hong Qiu, Susanna Y K Ku
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  ABSTRACT: Dioxins are a family of persistent organic pollutants (POPs) listed under the Stockholm Convention, and include PCDDs, PCDFs, and dioxin-like PCBs. These toxic chemicals are carcinogenic, widely dispersed, and have long half-lives. They have contaminated the food web and, being fat-soluble, accumulate in adipose tissues and milk in the human body. To assess human exposure, we collected breast milk samples from 137 first-time mothers recruited from around Hong Kong. Samples were analysed by HRGC-HRMS in four pools, according to the subject's age and length of residency. Exposure was related to age, duration of stay, and possibly diet. Generally, older mothers, and mothers with a longer stay in Hong Kong, had higher levels of dioxins in their milk. This pattern was clearest for the PCBs, although deviations were observed for some of the PCDD/Fs. Mean concentrations, measured per gram of lipid weight in terms of WHO toxic equivalents (WHO-TEQs), were 7.48pg/g for PCDD/Fs and 3.79pg/g for PCBs, giving a total of 11.27pg/g for PCDD/Fs and PCBs combined. Compared to an earlier Hong Kong study we conducted in 2002, the mean WHO-TEQ values in our latest findings were about 9% lower overall for PCDD/Fs and 19% lower for PCBs, with the mean total WHO-TEQ for PCDD/Fs and PCBs being around 13% lower in this study. This indicates a general declining trend in the levels of POPs in Hong Kong. However, our levels were still high when compared to those in some other Asian-Pacific countries. More stringent policies on reducing and eliminating POPs should help to lower these. Continued surveillance for POPs in human milk, as well as in common foodstuffs, will provide us with important information on human exposures that will be necessary for tracking our progress, and making future health risk assessments.
  Science of The Total Environment 08/2012; · 3.29 Impact Factor
• Article: Effect of dust storm events on daily emergency admissions for cardiovascular diseases.

  Wilson W S Tam, Tze Wai Wong, Andromeda H S Wong
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  ABSTRACT: Dust storm is a meteorological phenomenon and dust particles have been suspected as harmful to heart and lungs. The aim of this study was to investigate the association between coarse particles and emergency hospital admissions for cardiovascular diseases (CVD) in Hong Kong. Data on mean daily emergency admissions for CVD to major hospitals in Hong Kong, concentrations of air pollutants and meteorological variables from January 1998 to December 2002 were obtained from several government departments. We identified 5 dust storm days during the study period. Independent t-tests were used to compare the mean daily number of admissions on dust storm and non-dust storm days. Case-crossover analysis, using the Poisson regression, was used to examine the effects of coarse particles' concentration on emergency hospital admissions for CVD. A marginally significant increase in emergency hospital admissions for ischemic heart disease (IHD) was found with RR=1.04 (95% confidence interval: 1.00, 1.08) per 10 µg/m(3) increase in the concentration of coarse particles. This study demonstrated a marginally significant increase in emergency hospital admissions for IHD on the day of dust storm events in Hong Kong, when the levels of coarse particles were very high. Further studies are required to assess the role of coarse particles on cardiac health.
  Circulation Journal 02/2012; 76(3):655-60. · 3.77 Impact Factor
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  Article: Effects of coarse particulate matter on emergency hospital admissions for respiratory diseases: a time-series analysis in Hong Kong.

  Hong Qiu, Ignatius Tak-Sun Yu, Linwei Tian, Xiaorong Wang, Lap Ah Tse, Wilson Tam, Tze Wai Wong
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  ABSTRACT: Many epidemiological studies have linked daily counts of hospital admissions to particulate matter (PM) with an aerodynamic diameter ≤ 10 μm (PM10) and ≤ 2.5 μm (PM2.5), but relatively few have investigated the relationship of hospital admissions with coarse PM (PMc; 2.5-10 μm aerodynamic diameter). We conducted this study to estimate the health effects of PMc on emergency hospital admissions for respiratory diseases in Hong Kong after controlling for PM2.5 and gaseous pollutants. We conducted a time-series analysis of associations between daily emergency hospital admissions for respiratory diseases in Hong Kong from January 2000 to December 2005 and daily PM2.5 and PMc concentrations. We estimated PMc concentrations by subtracting PM2.5 from PM10 measurements. We used generalized additive models to examine the relationship between PMc (single- and multiday lagged exposures) and hospital admissions adjusted for time trends, weather conditions, influenza outbreaks, PM2.5, and gaseous pollutants (nitrogen dioxide, sulfur dioxide, and ozone). A 10.9-μg/m(3) (interquartile range) increase in the 4-day moving average concentration of PMc was associated with a 1.94% (95% confidence interval: 1.24%, 2.64%) increase in emergency hospital admissions for respiratory diseases that was attenuated but still significant after controlling for PM2.5. Adjusting for gaseous pollutants and altering models assumptions had little influence on PMc effect estimates. PMc was associated with emergency hospital admissions for respiratory diseases in Hong Kong independent of PM2.5 and gaseous pollutants. Further research is needed to evaluate health effects of different components of PMc.
  Environmental Health Perspectives 01/2012; 120(4):572-6. · 7.04 Impact Factor
• Article: Environmental tobacco smoke exposure and Chinese schoolchildren's respiratory health: a prospective cohort study.

  Qi-Qiang He, Tze-Wai Wong, Lin Du, Zhuo-Qin Jiang, Tak-sun Ignatius Yu, Hong Qiu, Yang Gao, Andromeda H S Wong, Wei-Jia Liu, Jia-Gang Wu
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  ABSTRACT: Although China is the most coveted cigarette market worldwide, few studies have examined the longitudinal effects of environmental tobacco smoke (ETS) on health. To examine the relationship between exposure to ETS and respiratory health in Chinese schoolchildren. The study subjects included 1718 children, who were never-smokers, aged 10.05±0.86 years and asthma-free at baseline. The children performed spirometric tests in 2006 and 18 months later. Parents reported the children's respiratory symptoms and illnesses, ETS exposure, and other related information by self-administered survey at both assessment points. The data were analyzed in 2010. Significant exposure-response relationships were found between ETS exposure and coughing at night (p for trend<0.001); sneezing (p for trend=0.031); and sneezing with itchy, watery eyes (p for trend=0.006) in the first survey, and coughing at night (p for trend=0.019); phlegm without a cold (p for trend<0.001); and sneezing (p for trend=0.036) in the second survey. Compared with those who reported no ETS exposure in either survey, children who had a high ETS exposure level (>5 cigarettes/day) in either survey had lower growth rates in forced expiratory flow between 25% and 75% of forced vital capacity (FEF(25-75); β= -0.104, p=0.020) and forced expiratory flow at 25% of forced vital capacity (FEF(25); β= -0.077, p=0.027). A monotonic exposure-response effect was observed between ETS exposure and the deficits in the growth rate of FEF(25) and FEF(25-75.) Exposure to ETS increased the risks of respiratory symptoms in Chinese school-aged children and was associated with impaired lung function growth. A dose-response relationship was observed for the latter effect.
  American journal of preventive medicine 11/2011; 41(5):487-93. · 4.24 Impact Factor