Observations and impacts of bleach washing on indoor chlorine chemistry.

Ambient levels of chlorinated gases and aerosol components were measured by online chemical ionization and aerosol mass spectrometers after an indoor floor were repeatedly washed with a commercial bleach solution. Gaseous chlorine (Cl2 , 10's of ppbv) and hypochlorous acid (HOCl, 100's of ppbv) arise after floor washing, along with nitryl chloride (ClNO2 ), dichlorine monoxide (Cl2 O), and chloramines (NHCl2 , NCl3 ). Much higher mixing ratios would prevail in a room with lower and more commonly encountered air exchange rates than that observed in the study (12.7 h-1 ). Coincident with the formation of gas-phase species, particulate chlorine levels also rise. Cl2 , ClNO2 , NHCl2 , and NCl3 exist in the headspace of the bleach solution, whereas HOCl was only observed after floor washing. HOCl decays away 1.4 times faster than the air exchange rate, indicative of uptake onto room surfaces, and consistent with the well-known chlorinating ability of HOCl. Photochemical box modeling captures the temporal profiles of Cl2 and HOCl very well and indicates that the OH, Cl, and ClO gas-phase radical concentrations in the indoor environment could be greatly enhanced (>106 and 105  cm-3 for OH and Cl, respectively) in such washing conditions, dependent on the amount of indoor illumination.

Overweight, obesity, weight-related concerns and behaviours in Hong Kong Chinese children and adolescents.

AIM: To study the prevalence of overweight and obesity, and weight-related concerns and behaviours among overweight, obese and non-overweight children and adolescents. METHODS: We carried out a cross-sectional survey of all Chinese students in primary schools in the Central and Western District of Hong Kong in March 2002. Thirty-one of 32 schools participated, and 5402 boys and 5371 girls aged 8 to 15 y who completed a standardized questionnaire were included. We used the International Obesity Task Force definition (IOTF reference) to define overweight and obesity. RESULTS: The prevalence (95% CI) of overweight was 16.4% (15.7-17.1%) (19.9% in boys, 12.9% in girls), and that of obesity was 7.7% (7.2-8.2%) (10.3% in boys and 5.1% in girls). The combined prevalence of overweight and obesity was similar to that based on the local reference. Overweight children had more concerns about their weight than obese children. They were more likely than obese children to feel fat, wish to be lighter, diet and exercise to lose weight. Although obese children were heavier, they did not make more effort to lose weight than overweight children. CONCLUSIONS: The differences in weight-related concerns and behaviours among overweight, obese and non-overweight children suggested good validity of the IOTF reference and the self-reported data. The differences between overweight and obese children suggested that the two groups had different psychological states and that they needed different weight management programmes and other intervention strategies.