Great Lakes drinking water study links gastro bugs to heavy storms


A new study of environmental and health data shows that the risk of stomach bugs in four North American cities around the Great Lakes can spike following heavy storms and that more centralized data sharing could benefit human health.

The study looked at 2009 to 2014 health, weather and water quality data for Hamilton and Toronto in Canada, as well as Green Bay and Milwaukee on the U.S. side. Both sides of the border combine to deliver some 40 million people their treated drinking water from the Great Lakes.

Dr. Elaine Faustman, U.S. co-chair of the International Joint Commission’s Health Professionals Advisory Board, and professor and director of the Institute for Risk Analysis and Risk Communication at the University of Washington, said the study found that heavy precipitation following dry periods — no matter which season — resulted in more reported cases of people sick from the waterborne germs giardia or cryptosporidium three to seven weeks afterwards.

The study suggests that climate change is expected to impact several factors linked to drinking water and gastrointestinal illness, “giving some urgency to assessing our capacity to detect and monitor this relationship.”

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The Phase 1 report, completed in 2017 for the IJC, confirmed the feasibility of collecting comparable, binational water quality and population health data. The Phase 2 report, completed in 2021, modelled potential exposure sources and weather events, revealing spatiotemporal patterns of waterborne acute gastrointestinal illness cases.

In Toronto, the study pulled data from the Clark, Harris, Horgan and Island water treatment plants. The city has seven active raw water intake pipes drawing water from Lake Ontario across  the Greater Toronto Area from Etobicoke to Scarborough. Hamilton has one water treatment facility and two active raw water intake pipes in Lake Ontario.

No connection between gastro bugs and heavy storms was detected in the Green Bay data, the study found.

As a result of the study, the IJC’s Health Professionals Advisory Board recommends a centralized data portal for binational drinking water source quality that cities could use to develop partnerships with water utilities and water monitoring organizations.

“One of the big challenges doing this study was that the data were scattered across many agencies, and so one of the board’s recommendations is to have a binational clearinghouse of these data indicators,” noted Dr. Laurie Chan, Canadian co-chair of the board, professor and Canada research chair in toxicology and environmental health at the University of Ottawa.

The board was assisted by the cooperation of water utilities and public health agencies in the four study cities that provided the requested data.

The study’s authors say the next step should be to evaluate the connections between weather and gastrointestinal illnesses in other Great Lakes cities such as Thunder Bay, Sarnia, Windsor and London.

The Health Professionals Advisory Board also recommends that the Canadian and U.S. governments include indicators of source water quality as part of their reporting.


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