Bronchial responsiveness in children exposed to atmospheric pollution in Hong Kong

Investigation of respirable suspended particulate trend and relevant environmental factors in Hong Kong downtown areas

As the addressing of high demand of good air quality in urban area, a study on air pollutant dispersion and distribution resulting from vehicular exhaust emission is strongly required. In particular, vehicular exhaust emission has become a major air pollution source in metropolitan city like Hong Kong, which is characterized with the heavy, dense traffic flow and the limited land resources. Respirable suspended particulate (RSP) is one of main pollutants resulted from vehicular exhaust emission in urban area. Hence, in this study, we focus on analyzing the variation of RSP levels including diurnal, monthly and annual patterns at selected roadsides in Hong Kong during the period of 1998--2005. Furthermore, the relationships between RSP level and the relevant meteorological factors such as temperature, rainfall and wind conditions in Hong Kong territory have been discussed as well.

Declining asthma prevalence in Hong Kong Chinese schoolchildren

BACKGROUND

Many studies have reported an increase in the prevalence of asthma and related atopic disorders. The lack of standardized methodologies and 'objective' measurements make reliable comparison and monitoring of trends of asthma very difficult.

METHODS

In this study, a total of 3321 schoolchildren aged 13-14 years were recruited for study using the Phase III Protocol of the International Study of Asthma and Allergic disease in Childhood (ISAAC). The results were compared with those obtained in the Phase I ISAAC study (1994-95), which used the identical and validated core questionnaires.

RESULTS

The prevalence rates of physicians' diagnosis of asthma were similar in the two surveys (11.2% and 10.2%), but the prevalence rates of wheeze (written questionnaire) in the past year have decreased from 12.4% in 1994-95 to 8.7% in 2002 (P<0.001). For the video questionnaire, all asthmatic symptoms in the preceding 12 months were significantly lower in 2002 when compared with those in 1994-95. Among the subjects with diagnosed asthma, the prevalence rates of wheeze in the past 12 months (written questionnaire) has decreased from 39.1% to 27.6% (P<0.001). The prevalence rates of having wheezing attack at least once per month (video questionnaire) has decreased from 10.5% to 5.6% (P=0.013).

CONCLUSION

Using the same standardized and validated ISAAC questionnaire, the prevalence rates of asthma symptoms in Hong Kong Chinese schoolchildren have decreased since 1994. The exact reasons for such trend remain to be explored.

Adverse effects of low-level air pollution on the respiratory health of schoolchildren in Hong Kong

To evaluate the respiratory effects of long-term exposure to air pollution, schoolchildren (ages 8 to 12 years) from two districts in Hong Kong with contrasting air quality were studied. Parents of 1660 children completed questionnaires on respiratory symptoms, and 1294 children had their ventilatory function tested with a spirometer. After adjustment for relevant covariates, children living in the more polluted district had increased odds ratios for frequent cough (1.74), frequent sputum (1.87), chronic sputum (1.84), and doctor-diagnosed asthma (1.98). Children of both sexes in the more polluted district had significantly poorer lung function, and the differences among girls were more marked. The study provides additional evidence for the adverse effects of long-term exposure to relatively low-level air pollution.

Studies on common illnesses and medical care utilization patterns of adolescents in Hong Kong

PURPOSE

To estimate the prevalences of common illnesses in Hong Kong adolescents, the sociodemographic and selected risk factors associated with these illnesses, and their health care utilization behavior and attitudes.

METHODS

A cross-sectional questionnaire survey of 3355 participating secondary school students (response rate = 98%).

RESULTS

Self-reported 3-month prevalences were obtained for cough/cold/influenza (55.2%), digestive disorders (34.6%), accidental injuries (29.5%), headache/dizziness (23.6%), chronic anxiety/insomnia (20.1%), skin problems (9.5%), asthma (3.8%), liver disease (1.3%), and menstrual pain (13.8% of female students). Self-perceived poor health, smoking, and alcohol consumption were associated with many of these illnesses. Treatment choice depended on the illness suffered (e.g., most students with respiratory problems consulted medical practitioners, whereas most with chronic anxiety/insomnia did not). Many students lacked trust in their doctors, doctor-shopped, relied heavily on self-medication, did not comply with prescribed treatments, would not seek help about medical problems, felt they had insufficient access to health information, and wanted confidential health care.

CONCLUSIONS

This study examined for the first time the common illnesses and health care utilization patterns of Hong Kong adolescents. Students with chronic anxiety/insomnia were much less likely to seek care, indicating a need for better education on mental health. Efforts to prevent smoking and alcohol consumption among adolescents need to be strengthened. The students' attitudes, poor compliance and help-seeking behaviors suggest suboptimal use of the health care system. Our findings are useful for international comparisons by medical practitioners, health care managers, and researchers.

Ozone exposure and blood antioxidants: a study in a periurban area in Southern France

Major carotenoids in plasma--especially beta-carotene--are affected by oxidative stress (e.g., tobacco smoking). Environmental ozone induced oxidative stress in experimental in vitro and in vivo studies, and it also increased the incidence of lung cancer in mice. We proposed to measure, after controlling for other determinants, the impact of personal ozone exposure on carotenoids levels in plasma. During the summer, we recruited 58 volunteer subjects who worked in a periurban zone. We asked each subject to wear a passive sample, which measured ozone exposure for 5 consecutive d. At the end of this period, we assessed plasma antioxidants. We observed a negative significant regression coefficient between alpha- or beta-carotene and ozone exposure (r = -.39, p < .01, and r = -.45, p = .02, respectively). In a subsample of 45 nonsmoker subjects, among whom carotene intake was lower than the median intake value (i.e., 6.6 mg/d) of the overall group, we noted that a relatively low exposure to ozone (> or = 50 microg/m3 x h or > or = 23.8 ppb) induced a significant decrease in plasma beta-carotene levels (i.e., 0.7 micromol/l to 0.4 micromol/l). This significant decrease suggested that a high dietary intake of fruit or vegetables can have a beneficial influence on the levels of plasma antioxidants generated in response to ozone exposure.

Mast cell activation is not required for induction of airway hyperresponsiveness by ozone in mice

Exposure to ambient ozone (O3) is associated with increased exacerbations of asthma. We sought to determine whether mast cell degranulation is induced by in vivo exposure to O3 in mice and whether mast cells play an essential role in the development of pulmonary pathophysiological alterations induced by O3. For this we exposed mast cell-deficient WBB6F1-kitW/kitW-v (kitW/kitW-v) mice and the congenic normal WBB6F1 (+/+) mice to air or to 1 or 3 parts/million O3 for 4 h and studied them at different intervals from 4 to 72 h later. We found evidence of O3-induced cutaneous, as well as bronchial, mast cell degranulation. Polymorphonuclear cell influx into the pulmonary parenchyma was observed after exposure to 1 part/milllion O3 only in mice that possessed mast cells. Airway hyperresponsiveness to intravenous methacholine measured in vivo under pentobarbital anesthesia was observed in both kitW/kitW-v and +/+ mice after exposure to O3. Thus, although mast cells are activated in vivo by O3 and participate in O3-induced polymorphonuclear cell infiltration into the pulmonary parenchyma, they do not participate detectably in the development of O3-induced airway hyperresponsiveness in mice.

Comparison between two districts of the effects of an air pollution intervention on bronchial responsiveness in primary school children in Hong Kong

STUDY OBJECTIVE

This study examined the impact on children's respiratory health of a government air quality intervention that restricted the sulphur content of fuels to 0.5% from July 1990 onwards.

DESIGN/SETTING/PARTICIPANTS

This study examined the changes, one and two years after the introduction of the intervention, in airway hyperreactivity of non-asthmatic and non-wheezing, primary 4, 5, and 6, school children aged 9-12 years living in a polluted district compared with those in a less polluted district. Bronchial hyperreactivity (BHR)(a 20% decrease in FEV1 provoked by a cumulative dose of histamine less than 7.8 mumol) and bronchial reactivity slope (BR slope) (percentage change in logarithmic scale in FEV1 per unit dose of histamine) were used to estimate responses to a histamine challenge. The between districts differences after the intervention were studied to assess the effectiveness of the intervention.

MAIN RESULTS

In cohorts, comparing measurements made before the intervention and one year afterwards, both BHR and BR slope declined from 29% to 16% (p = 0.026) and from 48 to 39 (p = 0.075) respectively in the polluted district; and from 21% to 10% (p = 0.001) and 42 to 36 (p > 0.100) in the less polluted district. Comparing measurements made in 1991 (one year after intervention) with those in 1992 (two years after intervention), only the polluted district showed a significant decline from 28% to 12% (p = 0.016) and from 46 to 35 (p = 0.014), for BHR and BR slope respectively, with a greater decline in both responses (p = 0.018 and 0.073) than in the less polluted district.

CONCLUSION

Bronchial hyperresponsiveness tests can be used to support the evaluation of an air quality intervention. The demonstrated reduction in bronchial hyperresponsiveness is an indication of the effectiveness of the intervention.

Parental smoking, bronchial reactivity and peak flow variability in children

BACKGROUND

A systematic quantitative review was conducted of the evidence relating environmental tobacco smoke to bronchial hyperresponsiveness (BHR) during childhood.

METHODS

Twenty-nine relevant studies were identified after consideration of 1593 articles selected by electronic search of the Embase and Medline databases using keywords relevant to passive smoking in children. The search was completed in April 1997.

RESULTS

Of 19 studies using challenge tests in children of school age, 10 (5759 children) could be summarised as the odds ratio of being bronchial hyperreactive in children exposed to environmental tobacco smoke compared with those not exposed. The pooled odds ratio for maternal smoking was 1.29 (95% confidence limits 1.10 to 1.50) with no evidence of heterogeneity between studies. However, in five further studies of 3531 children providing some evidence, but not odds ratios, none were statistically significant. A further four studies on 5233 children have collected data but are not published. In contrast, all four studies of circadian variation in peak expiratory flow found increased variation in children exposed to environmental tobacco smoke.

CONCLUSIONS

A clear effect of exposure to environmental tobacco smoke on BHR in the general population has not been established. While the meta-analysis suggests a small but real increase in BHR in school aged children, it seems likely that this estimate is biased upwards due to publication bias. In contrast, limited evidence suggests greater variation in peak expiratory flow in children of smoking parents.