Kevin Ka-Lun Lau

Developing Street-Level PM2.5 and PM10 Land Use Regression Models in High-Density Hong Kong with Urban Morphological Factors

Monitoring street-level particulates is essential to air quality management but challenging in high-density Hong Kong due to limitations in local monitoring network and the complexities of street environment. By employing vehicle-based mobile measurements, land use regression (LUR) models were developed to estimate the spatial variation of PM2.5 and PM10 in the downtown area of Hong Kong. Sampling runs were conducted along routes measuring a total of 30 km during a selected measurement period of total 14 days. In total, 321 independent variables were examined to develop LUR models by using stepwise regression with PM2.5 and PM10 as dependent variables. Approximately, 10% increases in the model adjusted R(2) were achieved by integrating urban/building morphology as independent variables into the LUR models. Resultant LUR models show that the most decisive factors on street-level air quality in Hong Kong are frontal area index, an urban/building morphological parameter, and road network line density and traffic volume, two parameters of road traffic. The adjusted R(2) of the final LUR models of PM2.5 and PM10 are 0.633 and 0.707, respectively. These results indicate that urban morphology is more decisive to the street-level air quality in high-density cities than other cities. Air pollution hotspots were also identified based on the LUR mapping.

Incorporating wind availability into land use regression modelling of air quality in mountainous high-density urban environment

Abstract Urban air quality serves as an important function of the quality of urban life. Land use regression (LUR) modelling of air quality is essential for conducting health impacts assessment but more challenging in mountainous high‐density urban scenario due to the complexities of the urban environment. In this study, a total of 21 LUR models are developed for seven kinds of air pollutants (gaseous air pollutants CO, NO2, NOx, O3, SO2 and particulate air pollutants PM2.5, PM10) with reference to three different time periods (summertime, wintertime and annual average of 5‐year long‐term hourly monitoring data from local air quality monitoring network) in Hong Kong. Under the mountainous high‐density urban scenario, we improved the traditional LUR modelling method by incorporating wind availability information into LUR modelling based on surface geomorphometrical analysis. As a result, 269 independent variables were examined to develop the LUR models by using the “ADDRESS” independent variable selection method and stepwise multiple linear regression (MLR). Cross validation has been performed for each resultant model. The results show that wind‐related variables are included in most of the resultant models as statistically significant independent variables. Compared with the traditional method, a maximum increase of 20% was achieved in the prediction performance of annual averaged NO2 concentration level by incorporating wind‐related variables into LUR model development. Graphical abstract Figure. No Caption available. HighlightsLUR application in the mountainous high‐density urban scenario.Wind environment were quantified by using the surface geomorphometrical analysis.Wind availability information was incorporated into LUR modelling.Wind variables show in most resultant models as significant independent variables.A maximum increase of 20% is achieved in the annual averaged NO2 model performance.

Spatial Variability of Geriatric Depression Risk in a High-Density City: A Data-Driven Socio-Environmental Vulnerability Mapping Approach

Previous studies found a relationship between geriatric depression and social deprivation. However, most studies did not include environmental factors in the statistical models, introducing a bias to estimate geriatric depression risk because the urban environment was found to have significant associations with mental health. We developed a cross-sectional study with a binomial logistic regression to examine the geriatric depression risk of a high-density city based on five social vulnerability factors and four environmental measures. We constructed a socio-environmental vulnerability index by including the significant variables to map the geriatric depression risk in Hong Kong, a high-density city characterized by compact urban environment and high-rise buildings. Crude and adjusted odds ratios (ORs) of the variables were significantly different, indicating that both social and environmental variables should be included as confounding factors. For the comprehensive model controlled by all confounding factors, older adults who were of lower education had the highest geriatric depression risks (OR: 1.60 (1.21, 2.12)). Higher percentage of residential area and greater variation in building height within the neighborhood also contributed to geriatric depression risk in Hong Kong, while average building height had negative association with geriatric depression risk. In addition, the socio-environmental vulnerability index showed that higher scores were associated with higher geriatric depression risk at neighborhood scale. The results of mapping and cross-section model suggested that geriatric depression risk was associated with a compact living environment with low socio-economic conditions in historical urban areas in Hong Kong. In conclusion, our study found a significant difference in geriatric depression risk between unadjusted and adjusted models, suggesting the importance of including environmental factors in estimating geriatric depression risk. We also developed a framework to map geriatric depression risk across a city, which can be used for identifying neighborhoods with higher risk for public health surveillance and sustainable urban planning.

Characterizing prolonged heat effects on mortality in a sub-tropical high-density city, Hong Kong

Extreme hot weather events are likely to increase under future climate change, and it is exacerbated in urban areas due to the complex urban settings. It causes excess mortality due to prolonged exposure to such extreme heat. However, there is lack of universal definition of prolonged heat or heat wave, which leads to inadequacies of associated risk preparedness. Previous studies focused on estimating temperature-mortality relationship based on temperature thresholds for assessing heat-related health risks but only several studies investigated the association between types of prolonged heat and excess mortality. However, most studies focused on one or a few isolated heat waves, which cannot demonstrate typical scenarios that population has experienced. In addition, there are limited studies on the difference between daytime and nighttime temperature, resulting in insufficiency to conclude the effect of prolonged heat. In sub-tropical high-density cities where prolonged heat is common in summer, it is important to obtain a comprehensive understanding of prolonged heat for a complete assessment of heat-related health risks. In this study, six types of prolonged heat were examined by using a time-stratified analysis. We found that more consecutive hot nights contribute to higher mortality risk while the number of consecutive hot days does not have significant association with excess mortality. For a day after five consecutive hot nights, there were 7.99% [7.64%, 8.35%], 7.74% [6.93%, 8.55%], and 8.14% [7.38%, 8.88%] increases in all-cause, cardiovascular, and respiratory mortality, respectively. Non-consecutive hot days or nights are also found to contribute to short-term mortality risk. For a 7-day-period with at least five non-consecutive hot days and nights, there was 15.61% [14.52%, 16.70%] increase in all-cause mortality at lag 0–1, but only −2.00% [−2.83%, −1.17%] at lag 2–3. Differences in the temperature-mortality relationship caused by hot days and hot nights imply the need to categorize prolonged heat for public health surveillance. Findings also contribute to potential improvement to existing heat-health warning system.

Near-extreme summer meteorological data set for sub-tropical climates

Building performance simulation requires representative weather data of specific locations. Test Reference Year (TRY) and Typical Meteorological Year (TMY) are common hourly dataset for typical year conditions. In sub-tropical climates, overheating is very common in buildings due to high temperature and intense solar radiation. However, there are no universal approaches to develop a dataset for estimating summer discomfort in naturally ventilated and free-running buildings. This article employs the concept of Summer Reference Years (SRY) in order to represent the near-extreme summer conditions in Hong Kong. The derived SRY is able to capture the near-extreme conditions in the multi-year series. The SRY was found to represent the high Tdry values reasonably well during daytime when such near-extreme conditions occur. On the contrary, according to the number of HN-DHs, the SRY does not satisfactorily represent high night-time Tdry. It is possible to incorporate the sorting of Tdry-min in the SRY adjustment in order to better reflect night-time situations in sub-tropical climate. Further studies are therefore required to confirm whether such modifications give more accurate results in the assessment of building energy performance. Nonetheless, the SRY dataset can be applied in building performance simulation and the assessment of indoor thermal comfort. Practical application : The present study found that there are deficiencies for the SRY to represent the high night-time Tdry, which affects the building performance assessment in sub-tropical climates. It suggests potential improvement to the existing adjustment of SRY for representing the near-extreme summer conditions in order to obtain more accurate results of building assessment.

Defining the environmental performance of neighbourhoods in high-density cities

ABSTRACT The regenerative design framework aims to ‘engage a broader range of possibilities by moving beyond the immediate building and site boundaries’. It implies that the environmental performance of buildings requires a revised definition so that it considers not only the building itself, but also its contribution beyond its own boundary, i.e. neighbourhoods. In high-density cities, outdoor spaces are culturally considered as the extension of one’s living spaces. The environmental performance of neighbourhoods is particularly important to the health and wellbeing of urban inhabitants. This paper aims to define the environmental performance of neighbourhoods in high-density urban context based on the experience acquired in previous studies in Hong Kong over the last 15 years. These studies cover a wide range of environmental issues including urban climate, outdoor thermal comfort, and daylighting design in high-density cities. Subsequent development of the assessment tools for environmental performance of neighbourhoods in Hong Kong is also presented. The framework of stakeholder engagement, as an integral part of the neighbourhood assessment tool, is discussed. This paper highlights the distinctive features of the environmental performance of neighbourhoods in high-density urban context and how it influences the professional practices in Hong Kong.

Design for climate resilience: influence of environmental conditions on thermal sensation in subtropical high-density cities

ABSTRACT Although outdoor thermal comfort has gained increasing research attention, meteorological conditions and thermal sensation in different urban settings in high-density cities have not been systematically studied from the perspective of urban planning and design. Considering the potential relationship between environmental quality and thermal sensation in outdoor spaces— an emerging topic in perceived comfort, this study offers a new approach for planning and design for climate resilience in cities. This paper presents the results of an outdoor thermal comfort survey conducted on hot summer days in Hong Kong. Diverse patterns of PET-comfort ratings relationships were found in different urban settings. The study revealed that air temperature, subjective assessments of solar radiation and wind environment were strong determinants of thermal sensation and evaluation. In our analysis, wind condition showed a significant indirect effect on comfort through subjective perception. Statistical modelling showed that subjective perceptions on microclimate condition and comfort are moderated by various aspects of environmental quality. The findings of this study help inform future design for climate resilience in outdoor urban spaces in hot-humid subtropical cities.

Associations between Perceived Neighborhood Walkability and Walking Time, Wellbeing, and Loneliness in Community-Dwelling Older Chinese People in Hong Kong

This study examined the cross-sectional associations between perceived neighborhood walkability and walking time, physical activity, wellbeing, and loneliness, and examined which components of walkability were most strongly associated with better wellbeing and less loneliness in older adults. Participants were community-dwelling Chinese adults aged 60+ (n = 181). Walkability was measured using nine items selected from the Chinese version of the abbreviated Neighborhood Environment Walkability Scales (NEWS) and NEWS for Chinese Seniors. Outcomes were walking time, physical activity, wellbeing (life satisfaction, happiness, sense of purpose and meaning in life), and loneliness. The mean age of the participants was 71.7 ± 7.8 years. Walkability was positively associated with walking time (p = 0.001, p for trend <0.001) but not with physical activity. After adjusting for socio-demographic characteristics, health conditions, lifestyle, and negative life events, those who perceived their neighborhoods as walkable had higher scores for life satisfaction (p = 0.002) and happiness (p = 0.002), and lower scores for loneliness (p = 0.019), compared with those who perceived their neighborhoods as less walkable. However, perceived neighborhood walkability was not associated with sense of purpose and meaning in life. Among components of walkability, land use mix-access, infrastructure and safety for walking, and traffic safety showed the strongest associations with the measures of wellbeing. The results of this study support the importance of neighborhood walkability for health behavior and wellbeing of older adults. The wellbeing of older adults may be enhanced through the improvement of land use mix-access, infrastructure for walking, and traffic safety.

Neighbouring green space and mortality in community-dwelling elderly Hong Kong Chinese: a cohort study

Objective Green space has been shown to be beneficial for human wellness through multiple pathways. This study aimed to explore the contributions of neighbouring green space to cause-specific mortality. Methods Data from 3544 Chinese men and women (aged ≥65 years at baseline) in a community-based cohort study were analysed. Outcome measures, identified from the death registry, were death from all-cause, respiratory system disease, circulatory system disease. The quantity of green space (%) within a 300 m radius buffer was calculated for each subject from a map created based on the Normalised Difference Vegetation Index. Cox proportional hazard models adjusted for demographics, socioeconomics, lifestyle, health conditions and housing type were used to estimate the HRs and 95% CIs. Results During a mean of 10.3 years of follow-up, 795 deaths were identified. Our findings showed that a 10% increase in coverage of green space was significantly associated with a reduction in all-cause mortality (HR 0.963, 95% CI 0.930 to 0.998), circulatory system-caused mortality (HR 0.887, 95% CI 0.817 to 0.963) and stroke-caused mortality (HR 0.661, 95% CI 0.524 to 0.835), independent of age, sex, marital status, years lived in Hong Kong, education level, socioeconomic ladder, smoking, alcohol intake, diet quality, self-rated health and housing type. The inverse associations between coverage of green space with all-cause mortality (HR 0.964, 95% CI 0.931 to 0.999) and circulatory system disease-caused mortality (HR 0.888, 95% CI 0.817 to 0.964) were attenuated when the models were further adjusted for physical activity and cognitive function. The effects of green space on all-cause and circulatory system-caused mortality tended to be stronger in females than in males. Conclusion Higher coverage of green space was associated with reduced risks of all-cause mortality, circulatory system-caused mortality and stroke-caused mortality in Chinese older people living in a highly urbanised city.