Gauging the polluting effects of holy smoke


Although not as severe as in some Mainland cities, Hong Kong’s pollution problems are well documented and pose a significant risk to the health of the population. Local road and marine traffic, as well as regional industry, are cited as primary culprits, but there are also noxious contributions from less frequently publicised sources.


Backed by a HK$500,000 grant from the Environment and Conservation Fund, Professor Paulina Wong, of Lingnan’s Science Unit, is currently studying ‘Fine particulate matter pollution from incense burning at temples in Hong Kong’. The two-year project, which she began working on in June 2019, will examine the areas affected by the PM2.5, or the fine particulate matter, emissions from this source, and the way in which the effects fluctuate over time.



Professor Paulina Wong


The inspiration for this study stemmed from an interesting and unexpected finding from another piece of research work Professor Wong was involved with. Led by Dr Benjamin Barratt from King’s College London, the project, titled ‘A Dynamic Three-Dimensional Air Pollution Exposure Model for Hong Kong’, considered the spread of traffic pollution amid Hong Kong’s high-density, high-rise urban topography that features deep ‘street canyons’.


In order to assess pollution levels and fluctuations not just at street level but in three dimensions, this study also took readings from homes on the upper floors of Hong Kong’s soaring residential buildings. As expected, the pollution levels recorded differed according to the relative proximity to traffic of a building, and to the altitude being monitored, and also rose and fell at different times of the day. However, Professor Wong and the rest of the team were surprised to find that on two specific nights their monitors registered a big spike in pollution levels. When they went back and asked the residents if anything unusual had been happening on those nights, the researchers discovered they coincided with the Hungry Ghost Festival. In Hong Kong this celebration is marked by the burning, on small roadside fires, of ‘offerings’ and incense for deceased ancestors.


Given that incense is routinely burned at the city’s temples, Professor Wong then wondered how these emissions played into Hong Kong’s overall pollution problem. One of the challenges she faces in her latest study is distinguishing between the pollutants that originate in the temples and those coming from passing vehicles, as the temples are often located, not only in tightly-packed residential areas, but also by busy roads. Another challenge has been gaining the access she needs, as some of the temple authorities have concerns that recommendations that might arise from Professor Wong’s study could lead to calls for their temples to be relocated.


The goals of her project are to not only collect evidence of the ambient air pollution created by incense burning at temples, evidence which can then be used to estimate the health exposure of people living nearby, but also to contribute to methodological advances in the field of environmental health and provide support for future policies.


To know more about Professor Wong's research projects, please click Lingnan Scholars.