Recently, portable monitors have been increasingly used to quantify air pollutant concentrations at high spatiotemporal resolution. A sampling campaign was conducted to measure the fine particulate matter (PM2.5) and carbon monoxide (CO) exposure concentrations in transport microenvironments (TMEs) in Hong Kong in January and June 2015 using TSI DustTrak and Q-Trak portable monitors. The objectives were to: (1) calibrate DustTrak and Q-Trak; (2) evaluate variability between seasons and microenvironments; (3) estimate indoor/outdoor relationships; and (4) determine minimum sample size. Calibration equations, obtained through side-by-side measurement against stationary reference methods in winter and summer, were applied to correct the measured PM2.5 data set. In general, PM2.5 concentrations in all TMEs were significantly higher in winter than in summer. The mean PM2.5 concentration in winter was lower for underground sections of the Mass Transit Railway (MTR) metro system (31 μg/m3) than for other TMEs, whereas in summer TMEs had mean PM2.5 concentrations in the range of 10–15 μg/m3, with above-ground MTR train as an exception, at 23 μg/m3. PM2.5 concentrations measured in TMEs were strongly correlated with nearby air quality monitoring stations (AQMSs) measurements in winter, but in summer there was little correlation. The minimum sample size estimates varied more among TMEs in summer versus winter because of the differences in PM2.5 concentration distributions related to changes in ambient PM2.5 concentrations and ventilation practices. This study provides a feasible protocol on the calibration and application of portable monitors in TME air quality measurement and develops a method for estimating minimum sample size.

Studies have shown that socioeconomic and environmental factors have direct/indirect influences on TB. This research focuses on TB prevalence of Hong Kong in relation to its compact urban development comprising of high-rise and high-density residential dwellings caused by rapid population growth and limited land resources. It has been postulated that occupants living on higher levels of a building would benefit from better ventilation and direct sunlight and thus less likely to contract infectious respiratory diseases. On the contrary, those on lower floors amid the dense clusters of high-rises are more susceptible to TB infection because of poorer air quality from street-level pollution and lesser exposure to direct sunlight. However, there have not been published studies to support these claims. As TB continues to threaten public health in Hong Kong, this study seeks to understand the effects of housing development on TB occurrences in an urban setting.

In this study on-road gaseous emissions of vehicles are investigated using remote sensing measurements collected over three different periods. The results show that a high percentage of gaseous pollutants were emitted from a small percentage of vehicles. Liquified Petroleum Gas (LPG) vehicles generally have higher gaseous emissions compared to other vehicles, particularly among higher-emitting vehicles. Vehicles with high vehicle specific power (VSP) tend to have lower CO and HC emissions while petrol and LPG vehicles tend to have higher NO emissions when engine load is high. It can be observed that gaseous emission factors of petrol and LPG vehicles increase greatly within 2 years of being introduced to the vehicle fleet, suggesting that engine and catalyst performance deteriorate rapidly. It can be observed that LPG vehicles have higher levels of gaseous emissions than petrol vehicles, suggesting that proper maintenance of LPG vehicles is essential in reducing gaseous emissions from vehicles.

The study reported in this paper examined the concentrations of nineteen perfluorochemicals (PFCs), including perfluoroalkyl sulfonates, carboxylates, and sulfonamides in samples collected from Hong Kong wastewater treatment plants (WWTPs) and sediments. The study was the first to use an external isolator column to assist in the quantification of PFCs in environmental samples without having to make internal modifications to a liquid chromatography system. Perfluorooctanesulfonate was found to be the dominant PFC pollutant in Hong Kong, and the WWTP sludge was the major sink of PFCs discharged from the urban areas. Compared to discharge influenced by industrial activities, much less perfluorooctanoate was found in waste streams. The significantly lower level of perfluorodecanesulfonate in WWTP sludge reflects the important influence of consumer products on PFC distribution. The dominance of even-chain length perfluoroalkyl carboxylates in all of the WWTP sludge samples investigated further suggests the strong aerobic degradation of fluorotelomer alcohols in WWTPs.

Investigating the long-term trends of alkyl nitrates (RONO₂) is of great importance for evaluating the variations of photochemical pollution. Mixing ratios of C₁–C₅ RONO₂ were measured in autumn Hong Kong from 2002 to 2016, and the average level of 2-butyl nitrate (2-BuONO₂) always ranked first. The C₁–C₄ RONO₂ all showed increasing trends (p < 0.05), and 2-BuONO₂ had the largest increase rate. The enhancement in C₃ RONO₂ was partially related to elevated propane, and dramatic decreases (p < 0.05) in both nitrogen monoxide (NO) and nitrogen dioxide (NO₂) also led to the increased RONO₂ formation. In addition, an increase of hydroxyl (OH) and hydroperoxyl (HO₂) radicals (p < 0.05) suggested enhanced atmospheric oxidative capacity, further resulting in the increases of RONO₂. Source apportionment of C₁–C₄ RONO₂ specified three typical sources of RONO₂, including biomass burning emission, oceanic emission, and secondary formation, of which secondary formation was the largest contributor to ambient RONO₂ levels. Mixing ratios of total RONO₂ from each source were quantified and their temporal variations were investigated. Elevated RONO₂ from secondary formation and biomass burning emission were two likely causes of increased ambient RONO₂. By looking into the spatial distributions of C₁–C₅ RONO₂, regional transport from the Pearl River Delta (PRD) was inferred to build up RONO₂ levels in Hong Kong, especially in the northwestern part. In addition, more serious RONO₂ pollution was found in western PRD region. This study helps build a comprehensive understanding of RONO₂ pollution in Hong Kong and even the entire PRD.

Over the last decades, plastic debris has been identified and quantified in the marine environment. Coastal and riverine input have been recognized as sources of plastic debris, whereas oceanic gyres and sediments are understood to be sinks. However, we have a limited understanding of the fate of plastic debris in the nearshore environment. To investigate the movement and distribution of plastic debris in the nearshore environment, we collected samples at three distinct locations: below the high tide line, the turbulent zone created by the combination of breaking wave and backflush (defined as the boundary), and the outer nearshore. We estimated the abundance and physical characteristics (e.g. density, hardness, etc.) of macroplastic and microplastics. Four times and 15 times more macroplastics and microplastics are observed, respectively, at the boundary than in the outer nearshore waters, which suggests an accumulation driven by the physical properties of the plastic particles such as density, buoyancy and surface area. We further report that highly energetic conditions characteristic of the boundary area promote the long-term suspension and/or degradation of low density, highly buoyant or large surface area plastic debris, leading to their preferential accumulation at the boundary. Contrastingly, denser and low surface area plastic pieces were transported to the outer nearshore. These results emphasize the role of selective plastic movement at the nearshore driven by physical properties, but also by the combined effects of several hydrodynamics forces like wave action, wind or tide in the resuspension, as well as degradation and transport of plastic debris out of the nearshore environment.

We developed a novel indicator, daily excessive concentration hours (DECH), to explore the acute mortality impacts of ambient fine particulate matter pollution (PM2.5) in Hong Kong. The DECH of PM2.5 was calculated as daily concentration-hours >25 μg/m3. We applied a generalized additive models to quantify the association between DECH and mortality with adjustment for potential confounders. The results showed that the DECH was significantly associated with mortality. The excess mortality risk for an interquartile range (565 μg/m3*hours) increase in DECH of PM2.5 was 1.65% (95% CI: 1.05%, 2.26%) for all natural mortality at lag 02 day, 2.01% (95% CI: 0.82%, 3.21%) for cardiovascular mortality at lag 03 days, and 1.41% (95% CI: 0.34%, 2.49%) for respiratory mortality at lag 2 day. The associations remained consistent after adjustment for gaseous air pollutants (daily mean concentration of SO2, NO2 and O3) and in alternative model specifications. When compared to the mortality burden of daily mean PM2.5, DECH was found to be a relatively conservative indicator. This study adds to the evidence by showing that daily excessive concentration hours of PM2.5 might be a new predictor of mortality in Hong Kong.

Interactions between particulate matter with aerodynamic diameter less than or equal to 2.5 μm (PM2.5) and temperature on mortality have not been well studied, and results are difficult to synthesize. We aimed to assess modification of temperature on the association between PM2.5 and cause-specific mortality by stratifying temperature into low, medium, and high stratum in Hong Kong, using data from 1999 to 2011. The mortality effects of PM2.5 were stronger in low temperature stratum than those in high. The excess risk (%) per 10 μg/m3 increase in PM2.5 at lag 0–1 in low temperature stratum were 0.94% (95% confidence interval: 0.65, 1.24) for all natural, 0.88% (0.38, 1.37) for cardiovascular, and 1.15% (0.51, 1.79) for respiratory mortality. We found statistically significant interaction of PM2.5 and temperature between low and high temperature stratum for all natural mortality. Our results suggested that temperature might modify mortality effects of PM2.5 in Hong Kong.

Organic films were collected from indoor and outdoor window surfaces in two large cities in southern China, Guangzhou and Hong Kong, and analyzed to quantify the polycyclic aromatic hydrocarbons (PAHs). In the glass films, the highest concentration of total PAHs, predominantly phenanthrene, fluorene, fluoranthene, and pyrene, was found to be l400 ng/m². The concentrations of PAHs in Guangzhou were usually higher than those in Hong Kong. In general, higher concentrations of PAHs on exterior window films in comparison with interior window films in both cities indicated that the outdoor air acted as a major source of pollution to the indoor environment. However, indoor air was a major source of some light-weight PAHs. Measurements made over time indicated that the growth rates of light-weight PAHs on window surfaces were fast at the beginning and then gradually reached a consistent level, whereas heavy-weight PAHs exhibited near-linear accumulation during the 40 days sampling period.