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Heavy Storms Linked to Germs in Great Lakes Drinking Water: IJC Health Professionals Advisory Board Report

Picture of Jennifer Boehme
Jennifer Boehme
Picture of Allison Voglesong Zejnati
Allison Voglesong Zejnati
intake cribs lake michigan water quality

The governments of Canada and the United States committed to maintaining the Great Lakes as a source of safe, high-quality drinking water when they signed the Great Lakes Water Quality Agreement. Both human activities and natural phenomena can negatively impact the waters of the Great Lakes in ways that affect our health. The latest research from the IJC’s Health Professionals Advisory Board provides evidence that heavy storms can indicate an elevated risk of germs in treated drinking water sourced from the Great Lakes.

Heavy storms can lead to high levels of undesirable pathogens like bacteria that close Great Lakes beaches due to public health risks.

For example, a few days or weeks after a big rainstorm, you might see a temporary sign posted at your nearest Great Lakes beach stating that it’s closed and unsafe for swimming due to high levels of bacteria that may pose a risk to your health. However, waterborne illness does not only lurk at the beach. The board’s new report looked into the connection between the water quality of the Great Lakes as a source of treated drinking water, and the issue of waterborne acute gastrointestinal illnesses.

Monitoring and reporting on water quality is vital to understanding potential health risks to the 40 million Canadian and US residents whose treated drinking water comes from the Great Lakes. The board’s latest project combined water quality monitoring data with public health disease counts and climate data for four Great Lakes cities. The board’s research found that heavy precipitation events following periods of dry weather were an indicator of a subsequent increase in residents who reported getting sick with one of two stomach bugs (Giardia and Cryptosporidium) within one to seven weeks after the heavy storm.

Storms, drains and germs: the domino effect

The intensity of rainstorms in the Great Lakes region is predicted to increase with our changing climate. Heavy storms can carry pollutants directly into the Great Lakes and overwhelm sewage treatment systems, leading to the dumping of untreated wastewater. 

Untreated sewage contains a variety of pollutants, including pathogens that can pose health risks. The domino effect of heavy downpours overwhelming infrastructure and increasing germs in sources of drinking water can, in turn, increase exposures to diseases in recreational water and sources of treated drinking water, such as the Great Lakes.

The HPAB looked at Cryptosporidium and Giardia, two acute gastrointestinal illness-causing pathogens, because they are particularly resistant to commonplace water treatment processes and therefore may be temporarily present in treated drinking water supplies.

A cause for additional analysis, not alarm

One of the initial purposes of the study was simply to assess the availability of the data needed to assess human health hazards and figure out if there were suitable environmental or water quality indicators to predict or prevent public health risks of illness,” said Dr. Tim Takaro, professor of health sciences at Simon Fraser University who served as the Canadian co-chair of the board from 2015 to 2020.

The HPAB study looked at water quality, public health and weather data from 2009 to 2014 for Toronto and Hamilton, Ontario, which get their drinking water from Lake Ontario, and two US cities that treat drinking water from Lake Michigan: Green Bay and Milwaukee, Wisconsin.

Ultimately, it proved challenging to get data that we could compare over time and across jurisdictions. Unfortunately, weather, water quality and disease data are rarely integrated for analysis. The data challenge is why the board also recommends a binational drinking water source quality indicator clearinghouse to standardize and centralize the data,” said Takaro.

The study findings are a first in the Great Lakes, but confirm a similar pattern identified in a 2017 study from Metro Vancouver in British Columbia, Canada, by Takaro, Dr. Bimal Chhetri and others.

This study suggests a time relationship between heavy rains and cases of two gastrointestinal diseases that are frequently waterborne,” said Dr. Seth Foldy, co-author of the HPAB report, board member and former director of epidemiology, informatics and preparedness at the Public Health Institute at Denver Health.

“Lake water later treated for drinking showed simultaneous quality changes, so drinking water could be the source of at least some of these infections. To prove this relationship requires more data and analysis.”

Foldy added: “Unfortunately, stronger rainstorms are predicted from climate change in the region. Disease rates and water treatment challenges could rise over time. This is why health, water quality and climate data should be routinely integrated for ongoing review and analysis across the Great Lakes basin.”

Understanding these patterns better can help address vulnerabilities in drinking water systems in Canada and the United States.

Adapting to climate change

Climate change is not only expected to increase the extremes in wet and dry weather in the region but also shift physical, biological and chemical-related factors that impact how utilities manage stormwater, sanitary sewage and drinking water treatment.

Climate change also is expected to impact several factors linked to gastrointestinal illness, giving some urgency to assessing the capacity to monitor this relationship. Climate change impacts underscore the need to increase capacity of drinking water utilities to adapt and respond to climate change to reduce the risk for the millions who rely on the Great Lakes for drinking water.

thunderstorm chicago hpab report

Pedestrians caught in a thunderstorm jump over pooling water on a Chicago Street. Credit: Charles Edward Miller/Flickr

Monitoring and reporting on source water quality under conditions of changing climate, combined with data on disease trends, is vital to understanding how the health of people is dependent on the health of the lakes and on governments’ progress toward achieving objectives of the Great Lakes Water Quality Agreement.

With such knowledge, jurisdictions may better plan and manage water and waste treatment in the face of climate change, while working to better understand and adapt to the causes and effects of rapid climate change. 

For more, see an illustrated executive summary, news release and full report on the HPAB website.

Picture of Jennifer Boehme
Jennifer Boehme

Jennifer Boehme is a senior environmental scientist at the IJC’s Great Lakes Regional Office and serves as chair of the GLOS Board.

Picture of Allison Voglesong Zejnati
Allison Voglesong Zejnati

Allison Voglesong Zejnati is public affairs specialist at the IJC’s Great Lakes Regional Office in Windsor, Ontario.

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