Understanding the impact of microplastics
Leung was awarded a Croucher Fellowship in 2000 to pursue research at Royal Holloway, University of London. On his return, he joined the faculty of the University of Hong Kong and established a research group with a focus on aquatic ecology and toxicology at the Swire Institue of Marine Science. Since August 2020, at the City University of Hong Kong, he has been leading research on the environmental impact of new chemicals.
“The major challenge now is that we have more than 300,000 chemicals used daily and about 1000 of those are new chemicals. We don’t know their toxicity, their environmental persistence, how they impact marine life and affect us” he explains. “My major work is to study the ecotoxicology of those emerging chemicals of concern.”
Leung is co-leading the Global Estuaries Monitoring Program (GEM). This very large scale study is a component of the UN Decade of Ocean Science for Sustainable Development. Now in its first phase, GEM is developing standardised methods for sampling and analysing pharmaceutical residues in over 150 urbanised estuaries worldwide, to improve our currently limited knowledge of the environmental risks such contaminants pose to these habitats. A global analysis of 258 rivers, published in PNAS in 2022, found chemical concentrations exceeding the safety threshold in around a quarter of cases.
“We are interested in looking at the health status of our estuaries and finding the priority pollutants to tackle. Then we can inform governments and stakeholders to find a way to make the estuaries cleaner and safer.”
Eco-engineered habitats
Leung’s research resulting in experimental trials of eco-engineered structures which form habitats for marine species on urbanised shorelines is continuing to have an impact. His study published in Marine Pollution Bulletin in 2020 which found that the combined use of eco-tiles and rock oysters significantly increased species richness and abundance was recently adopted for consideration under a European Commission’s environmental policy framework. The eco-engineered tiles which resulted from the project have won several international awards.
Closer to home, a household incident recently led Leung to discover a serious, but overlooked, source of microplastic pollution: tumble dryers.
“A few years back, I turned on my tumble dryer to dry my clothes. Then the vent duct detached from the window while I was out shopping. When I returned to my house, there were fibers everywhere in my kitchen.”
Wondering how many microfibers the millions of dryers around the world were releasing into the environment, Leung lead the very first comprehensive study of this after joining CityU, measuring the airborne microfiber loads released from drying synthetic clothes. The results found that in just one 15-minute drying cycle, seven kilograms of synthetic clothing could release an estimated 561,810 microplastic fibers, with each tumble dryer releasing an estimated 120 million per year, making them a paramount source of airborne microplastics. Leung suggests that the problem could be controlled through improved filtration systems. The study was published in Environmental Science and Technology Letters in 2022.