Science & Technology, Canada (Commonwealth Union) – A novel framework for assessing plastic pollution emissions, akin to the established global standard for greenhouse gas emissions, has been developed by researchers at the University of Toronto. The removal of microplastics from the environment has been a key concern for researchers from across the world.
This innovative approach promises to enhance the identification of major contributors to plastic pollution at various scales, ranging from local to national, thereby refining strategies for global emission reduction.
By utilizing Toronto as a prototype, the pioneering framework estimates that Canada’s largest urban city released approximately 4,000 tonnes of plastic pollution within a single year.
According to Alice (Xia) Zhu, the lead author of the study detailing this method in Environmental Science & Technology, this equates to approximately 400 garbage trucks’ worth of plastic seeping into the environment annually across the city.
“Assigning responsibility for the pollution to a jurisdiction with the ability to enact laws means there is no hiding where the pollution came from. It presents an opportunity to identify major sources of plastic pollution within the area and inform measures to curb these emissions.”
Zhu, a PhD candidate in the Department of Physical and Environmental Sciences at U of T Scarborough, collaborated with Assistant Professor Chelsea Rochman from U of T’s Department of Ecology and Evolutionary Biology in the Faculty of Arts & Science to develop a groundbreaking framework. This collaborative effort involved colleagues from U of T and the Rochester Institute of Technology.
Inspired by the established guidelines of the United Nations’ Intergovernmental Panel on Climate Change for compiling emissions inventories of greenhouse gases, the researchers adapted a similar approach. They tailored the methodology to accommodate the physical disparities between greenhouse gases and plastic waste. The process involved identifying the primary sources of pollution in a specific area, quantifying the pollution generated by each activity over a defined period, and addressing uncertainties associated with each source.
This innovative framework came at a crucial time, the coincided with international discussions in Ottawa from April 23 to 29. These discussions aimed to formulate a binding global agreement on plastic pollution, led by the UN’s Intergovernmental Negotiating Committee on Plastic Pollution.
Zhu emphasized the aim of creating a versatile accounting mechanism accessible to any level of government. Additionally, the team hopes their tool will facilitate the establishment of a system akin to national emissions inventories for plastic pollution. She further indicated that such a system could be overseen by an international body, like the United Nations, to monitor progress toward a universally defined reduction target.
Presently, neither national emissions inventories nor a globally defined target for mitigating plastic pollution exists.
To showcase the practicality of the framework, the researchers constructed a plastic pollution emissions inventory for the City of Toronto in 2020. This inventory was developed using publicly accessible data obtained from municipal litter audits and other relevant sources. Covering nine distinct sources, such as littering, tire dust from airplanes and vehicles, washing machines, paint from road markings, and house exteriors, they approximated that between 3,531 and 3,852 tonnes of plastic pollution were emitted within the city’s limits during the specified timeframe.
Among these sources, littering constituted the largest portion of the total emissions, accounting for 3,099 tonnes. Additionally, artificial turf emerged as the primary emitter of microplastics—particles with a diameter under 5 millimeters—contributing 237 tonnes to the overall emissions.
“It is not surprising that larger materials – known as macroplastics, and in this case from mismanaged waste such as littering – made up the majority of the mass. But it overshadows the small stuff: microplastics,” explained Rochman, who is a co-author of the study and also the PhD supervisor of Zhu. “Microplastics tend to be the highest by count in terms of actual pieces. This suggests that policies relevant to microplastics, in addition to macroplastics, are critical to reduce plastic emissions in the City of Toronto.”
The researchers opted for Toronto as their testing ground for the framework due to its status as Canada’s largest city and the fourth-largest in North America.
Zhu pointed out that Toronto serves as a bustling urban center with diverse activities, where high population density and numerous activities naturally lead to significant pollution. She further indicated that selecting such a location ensures a rich and informative case study, as it encompasses a wide array of pollution sources. This allows us to pinpoint which sources warrant priority in pollution reduction efforts, effectively demonstrating the practical value of an emissions inventory in shaping local policies.”
