Chi Sing Chan

Ambient Carbon Monoxide and the Risk of Hospitalization Due to Chronic Obstructive Pulmonary Disease

Data from recent experimental and clinical studies have indicated that lower concentrations of inhaled carbon monoxide might have beneficial antiinflammatory effects. Inhaled carbon monoxide has the potential to be a therapeutic agent for chronic obstructive pulmonary diseases (COPD). However, population-based epidemiologic studies of environmentally relevant carbon monoxide exposure have generated mixed findings. We conducted a time-series study in Hong Kong to estimate the association of short-term exposure to ambient carbon monoxide with emergency hospitalizations for COPD. We collected daily emergency hospital admission data and air pollution data from January 2001 to December 2007. We used log-linear Poisson models to estimate the associations between daily hospital admissions for COPD and the average daily concentrations of carbon monoxide while controlling for the traffic-related co-pollutants nitrogen dioxide and particulate matter with an aerodynamic diameter less than 2.5 μm. Results showed that ambient carbon monoxide was negatively associated with the risk of hospitalizations for COPD. After adjustment for levels nitrogen dioxide or particulate matter with an aerodynamic diameter less than 2.5 μm, the negative associations of carbon monoxide with COPD hospitalizations became stronger. The risk estimates were similar for female and male subjects. In conclusion, short-term exposure to ambient carbon monoxide was associated with a decreased risk of hospitalization for COPD, which suggests that carbon monoxide exposure provides some acute protection of against exacerbation of COPD.

Carbon monoxide and stroke: A time series study of ambient air pollution and emergency hospitalizations

BACKGROUND Recent experimental and clinical studies suggested that exogenous carbon monoxide (CO) at low concentrations may have beneficial neuroprotective effects under certain circumstances. However, population-based epidemiological studies of environmentally relevant CO exposure generated mixed findings. The present study aimed to examine the short-term association of ambient CO with emergency stroke hospitalizations. METHODS A time series study was conducted. Daily air pollution concentrations and emergency hospital admission data from January 2004 to December 2011 in Hong Kong were collected. Generalized additive Poisson models were used to estimate the associations between daily 24-hour mean concentrations of CO and emergency hospital admissions for stroke, while controlling for other traffic related co-pollutants: NO₂ and PM₂.₅. Sensitivity analyses were performed using daily 1-hour maximum concentration of CO as exposure indicator. RESULTS Negative associations were observed between ambient CO concentrations and emergency hospital admissions for stroke. The previous 1-3 day cumulative exposure to CO was associated with a -2.0% (95%CI, -3.3% to -0.7%) decrease in stroke admissions per interquartile range (IQR) increment in CO concentration (0.3 ppm). Similar results were obtained when using 1-hour maximum concentration of CO as exposure indicator. The negative association was robust to the co-pollutant adjustment for either NO₂ or PM₂.₅. Females and elders appeared to be more sensitive to ambient CO exposure. The negative association tended to be larger in cool season. CONCLUSION Short-term exposure to ambient CO was associated with decreased risk of emergency hospitalizations for stroke, suggesting some acute protective effects of CO exposure against stroke onsets.

Characterisation of Volatile Organic Compounds at Hotels in Southern China

In the recent years, there has been a dramatic growth in the development of hotels in Southern China to meet the rapid demand of business and tourism industry. The indoor air quality of the hotels has become an important consideration due to a large workforce that is engaged in this industry. The objective of this study was to characterise the volatile organic compounds (VOCs) found in the indoor air in 13 new hotels in Southern China and assess their possible health impact. A 2-day non-simultaneous sampling was carried out in each of the hotels. Decorating materials, cleansing agents and even local regional pollutants outside the hotels could have a contribution and worsen indoor air quality. Toluene level was as high as 498 μg m—3 in a hotel fitted with lots of plywood products. The highest concentrations of methylene chloride (34 μg m—3) and total carbonyls (517 μg m—3) were detected in a hotel where high VOCs cleansing agents were used in guest rooms. In a hotel located in an industrial centre, acetone concentration of 102 μg m —3 was found. The second highest total VOCs concentration (445 μg m—3) was observed in a newly renovated hotel. Wooden interior fixtures and wall panels were identified as the major sources of VOCs and carbonyls found inside the guest rooms.

Hazardous airborne carbonyls emissions in industrial workplaces in China

A pilot hazardous airborne carbonyls study was carried out in Hong Kong and the Mainland of China. Workplace air samples in 14 factories of various types of manufacturing and industrial operations were collected and analyzed for a panel of 21 carbonyl compounds. The factories can be classified into five general categories, including food processing, electroplating, textile dyeing, chemical manufacturer, and petroleum refinery. Formaldehyde was invariably the most abundant carbonyl compound among all the workplace air samples, accounting for 22.0–44.0% of the total measured amount of carbonyls on a molar basis. Acetone was also found to be an abundant carbonyl in workplace settings; among the selected industrial sectors, chemical manufacturers’ workplaces had the highest percentage (an average of 42.6%) of acetone in the total amount of carbonyls measured in air. Benzaldehyde accounted for an average of 20.5% of the total amount of detected carbonyls in electroplating factories, but its contribution was minor in other industrial workplaces. Long-chain aliphatic carbonyls (C6–C10) accounted for a large portion (37.2%) of the total carbonyls in food-processing factories. Glyoxal and methylglyoxal existed at variable levels in the selected workplaces, ranging from 0.2% to 5.5%. The mixing ratio of formaldehyde ranged from 8.6 to 101.2 ppbv in the sampled workplaces. The observed amount of formaldehyde in two paint and wax manufacturers and food-processing factories exceeded the World Health Organization (WHO) air quality guideline of 81.8 ppbv. Carcinogenic risks of chronic exposure to formaldehyde and acetaldehyde by the workers were evaluated. The lifetime cancer hazard risks associated with formaldehyde exposure to male and female workers ranged from 2.01 × 10−5 to 2.37 × 10−4 and 2.68 × 10−5 to 3.16 × 10−4, respectively. Such elevated risk values suggest that the negative health impact of formaldehyde exposure represents a valid concern, and proper actions should be taken to protect workers from such risks. Implications: Many carbonyl species (e.g., formaldehyde, acetaldehyde, and acrolein) are air toxins and they pose public health risks. The scope of this investigation covers 21 types of carbonyls based on samples collected from 14 different workplaces. Findings of the study will not only provide a comprehensive assessment of indoor air quality with regard to workers’ healthy and safety, but also establish a theoretical foundation for future formulation of intervention strategies to reduce occupational carbonyl exposures. No similar study has been carried out either in Hong Kong or the Mainland of China.

Effects of polycyclic aromatic compounds in fine particulate matter generated from household coal combustion on response to EGFR mutations in vitro

Induction of PM2.5-associated lung cancer in response to EGFR-tyrosine kinase inhibitors (EGFR-TKI) remains unclear. Polycyclic aromatic hydrocarbons (PAHs) and their polar derivatives (oxygenated PAHs: OPAHs and azaarenes: AZAs) were characterized in fine particulates (PM2.5) emitted from indoor coal combustion. Samples were collected in Xuanwei (Yunnan Province), a region in China with a high rate of lung cancer. Human lung adenocarcinoma cells A549 (with wild-type EGFR) and HCC827 (with EGFR mutation) were exposed to the PM2.5, followed by treatment with EGFR-TKI. Two samples showed significant and dose-dependent reduction in the cell viability in A549. EGFR-TKI further demonstrated significantly decreased in cell viability in A549 after exposure to the coal emissions. Chrysene and triphenylene, dibenzo[a,h]anthracene, benzo[ghi]perylene, azaarenes and oxygenated polycyclic aromatic hydrocarbons (carbonyl-OPAHs) were all associated with EGFR-TKI-dependent reduced cell viability after 72-h exposure to the PM2.5. The findings suggest the coal emissions could influence the response of EGFR-TKI in lung cancer cells in Xuanwei.

Evaluation of hazardous airborne carbonyls on a university campus in southern China.

A comprehensive assessment of indoor carbonyl compounds for the academic staff, workers, and students was conducted on a university campus in Xiamen, China. A total of 15 representative environment categories, including 12 indoor workplaces and three residential units, were selected. The potential indoor pollution sources were identified based on the variability in the molar compositions and correlation analyses for the target carbonyls. Furnishing materials, cooking emissions, and electronic equipment, such as photocopiers, can generate various carbonyls in the workplace. Comparison studies were conducted in the clerical offices, demonstrating that off-gases from wooden furniture and lacquer coatings, environmental tobacco smoke (ETS), and the use of cleaning reagents elevated the indoor carbonyl levels. The measured concentrations of formaldehyde and acetaldehyde in most locations surpassed the exposure limit levels. The lifetime cancer hazard risk (R) associated with formaldehyde was above the concern risk level (1 × 10−6) in all of the workplaces. The results indicate that formaldehyde exposure is a valid occupational health and safety concern. Wooden furniture and refurbishing materials can pose serious health threats to occupants. The information in this study could act as a basis for future indoor air quality monitoring in Mainland China. Implications: A university campus represents a microscale city environment consisting of all the working, living, and commercial needs of staff and students. The scope of this investigation covers 21 hazardous carbonyl species based on samples collected from 15 categories of workplaces and residential building in a university campus in southern China. Findings of the study provide a comprehensive assessment of indoor air quality with regards to workers’ health and safety. No similar study has been carried out in China.

Exploratory study of the indoor and outdoor relationships and chemical compositions of particulate matter in urban households in Colombo

Air pollution associated with emissions of fine particulates (PM10 and PM2.5) is becoming acute, especially in the urban environments of Sri Lanka during the last decade. Recent air quality data obtained from the monitoring stations located in Colombo Fort revealed that the average annual ambient PM10 concentrations in Colombo ranged between 72 and 82 µg/m3, exceeding the national ambient air quality PM10 standard of 50 µg/m3 and WHO air quality guideline of 20 µg/m3. This paper presents the chemical compositions of indoor and outdoor PM10 at selected locations in Colombo, Sri Lanka. Twelve-hour indoor/outdoor PM10 were collected simultaneously from six naturally ventilated roadside households from 13 March to 27 April 2010. Chemical compositions were obtained by using thermal optical reflectance method for carbonaceous compounds and ion chromatography method for water-soluble ions. The results show that indoor micro-environments were significantly affected by the infiltration of outdoor air in Sri Lanka, revealing that outdoor emission sources have significant effects on the indoor air quality. This study provides valuable information on chemical profile of particulates in Colombo which will definitely contribute to the formulation of environmental policy, especially on air pollution control in the future.

Hong Kong Vehicle Emission Changes from 2003 to 2015 in the Shing Mun Tunnel

ABSTRACT This study characterized motor vehicle emission rates and compositions in Hong Kongs Shing Mun tunnel (SMT) during 2015 and compared them to similar measurements from the same tunnel in 2003. Average PM2.5 concentrations in the SMT decreased by ∼70% from 229.1 ± 22.1 µg/m3 in 2003 to 74.2 ± 2.1 µg/m3 in 2015. Both PM2.5 and sulfur dioxide (SO2) emission factors (EFD) were reduced by ∼80% and total non-methane (NMHC) hydrocarbons EFD were reduced by 44%. These reductions are consistent with long-term trends of roadside ambient concentrations and emission inventory estimates, indicating the effectiveness of emission control measures. EFD changes between 2003 and 2015 were not statistically significant for carbon monoxide (CO), ammonia (NH3), and nitrogen oxides (NOx). Tunnel nitrogen dioxide (NO2) concentrations and NO2/NOx volume ratios increased, indicating an increased NO2 fraction in the primary vehicle exhaust emissions. Elemental carbon (EC) and organic matter (OM) were the most abundant PM2.5 constituents, with EC and OM, respectively, contributing to 51 and 31% of PM2.5 in 2003, and 35 and 28% of PM2.5 in 2015. Average EC and OM EFD decreased by ∼80% from 2003 to 2015. The sulfate EFD decreased to a lesser degree (55%) and its contribution to PM2.5 increased from 10% in 2003 to 18% in 2015, due to influences from ambient background sulfate concentrations. The contribution of geological materials to PM2.5 increased from 2% in 2003 to 5% in 2015, signifying the importance of non-tailpipe emissions.