Synopsis: The great majority of measurements toxic contaminant deposition to the Great Lakes are made in rural areas in an effort to provide an estimate of the “background” levels of these contaminants that is minimally influences by local sources. However, this approach has made it difficult to fully understand the influence that urban areas within the Great Lakes region have on the adjoining lakes. This project is studying the influence of the Toronto urban area on the input of toxic chemicals to Lake Ontario, both through water discharge and runoff, and through direct atmospheric deposition. The project will work closely with large efforts to develop lake-wide contaminant loading and mass balance efforts to incorporate information about the urban influence.

Chemicals Studied: The project is studying polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs) and synthetic musk compounds.
PCBs were produced for use in electrical equipment, building sealants and many other purposes prior to the late 1970s, when production and new uses were banned. They are among the most studied environmental contaminants and concentrations in Great Lakes fish remain above safe consumption amounts, 30 years after their ban.

PBDEs have been produced mainly for use as a fire retardant in a wide array of consumer products, including electronics, furniture and plastics. Production of some mixtures has been voluntarily stopped by industry in recent years. Levels in Great Lakes fish and human tissues have been shown to be increasing dramatically in recent decades. Understanding of their entry into and impacts on the Great Lakes is still very incomplete.
PAH are produced from a very wide variety of combustion processes, including industrial operations, such as steel manufacturing and power generation, and residential activities, such as wood or trash burning. Although controls on many industrial releases have been put in place, concentrations in lake sediments continue to increase and are frequently above levels of concern for wildlife health.

Synthetic musks have been manufactured to mimic the fragrance of natural musk compounds, but posses many potentially harmful attributes, such as an ability to survive for long periods in the environment and to accumulate and be passed through the food chain. Relatively little is known about the amount of these chemicals entering the lakes or their impact on human and wildlife health.
Geographic Areas: This project will take samples in and around the Toronto urban area, including over Lake Ontario. The results will be very informative for other urban areas bordering the Great Lakes, including Chicago, Detroit, Cleveland, Milwaukee, Rochester and others.
Project Duration: The project began in the summer of 2007. Samples will be taken from the fall of 2007 through the end of 2008. Project results will be finalized in 2009.

Methods Used: Samples will be taken of air, precipitation, particulate matter, stream water and waste water to determine the amounts of the studied toxic substances in the Toronto environment. Several computer models will be used, including the Multimedia Urban Model (MUM-Fate) and the Mesoscale Boundary Layer Forecast Model (BLFM-Meso), to estimate the movement of these chemicals within the urban environment and the loading from the Toronto area to Lake Ontario.

Potential Results and Implications: This will be the most comprehensive study to date of the influence of a large city on the atmospheric deposition of the Great Lakes. It will fill one of the most important gaps in understanding where toxic pollution that enters the Great Lakes is coming from and will identify possible means of reducing the amount of these substances that urban centers within the region are releasing to the lakes. By studying both atmospheric inputs and water-borne inputs to the lake, a very complete picture will be obtained of the importance of urban sources on nearby Great Lakes.

Project Contact:
Miriam Diamond, Ph.D.
University Of Toronto
Dept. of Geography
100 St. George Street
Toronto, Ontario M5S 3G3
Phone: (416) 978-1586
Email: miriam.diamond@utoronto.ca