Officials issued a water ban overnight Friday that affected about 400,000 people in Toledo, Ohio, after tests revealed an unsafe concentration of a toxin likely caused by an algae bloom in Lake Erie.
The city advised residents not to use water for drinking or brushing their teeth, though showers and baths were fine for adults. Boiling the water, officials said, would only increase the concentration of the toxin.
The warning came just after midnight, when tests at one water treatment plant showed the presence of microcystin above a safe level for consumption.
Microcystin are toxins released by blue-green algae, which feeds off the phosphorus in farm fertilizer runoff, sewage and livestock pens.
The city's public advisory said Lake Erie may have experienced a bloom of harmful algae. Consumption of the fouled water could lead to vomiting and diarrhea, among other problems.
Summer blooms have become more frequent around the western end of Lake Erie, and the microcystin these blooms leave behind contributes to oxygen-deprived dead zones where fish can't survive.
Toledo Mayor D. Michael Collins said at a news conference that the city should know more details by late Saturday and asked residents not to panic.
Toledo police, however, were called to respond to “disorders over bottled water,” the Toledo Blade, a local newspaper, reported.
Emily Ellis, 28, a Toledo city resident and school psychologist, told Al Jazeera that people at local churches were handing out water and that city officials had established emergency water distribution points. Even so, she said she fears for the community's most vulnerable.
"I am afraid for disabled residents and people without cars," she said, adding that long lines remained at the local Costco and Kroger grocery stores, which had sold out of water and where large crowds waited for additional shipments.
Most water treatment plants along the western shoreline of Lake Erie, which supplies water for about 11 million people, treat their water to combat the algae. The city of Toledo reportedly spent about $4 million last year on chemicals to treat its water and combat the toxins.
Still, Ellis said residents blame the city's water treatment plant, which she called outdated, saying suburban areas have better water management systems.
Toledo isn't the first place to have contamination issues in the area. Last summer, toxins from algae in Lake Erie prompted a water ban for a town of 2,000 east of Toledo.
A sample of water was being flown to the U.S. Environmental Protection Agency in Cincinnati for additional testing, officials said.
Federal law requires officials to identify potential sources of contamination around sources used for drinking water, Maya Nye, Executive Director of People Concerned About Chemical Safety — an organization dedicated to reducing threats from toxic chemicals — told Al Jazeera.
"This is a national issue, and represents somewhat of an unfunded mandate from Congress. A lot of cities never followed through with the appropriate measures," Nye said.
Nye lives in West Virginia, where a toxic chemical spill near Charleston in January prompted a water ban for hundreds of thousands of residents. Several residents were hospitalized after exposure to the contaminated water following Elk River accident.
Nye said that legislation and plans to protect source water, though helpful, do not get to the core of the issue.
"We're using a lot of toxic chemicals in our environment, and we're using them more than we have the ability to contain," she said. "It's important to prevent chemical disasters before they occur, and obviously reducing how many of these we use in our world is going to assist with that."
Al Jazeera's Wilson Dizard contributed reporting with wire services