Harford County government said it has received "numerous calls" this week about cloudy or discolored tap water experienced by customers of the county's public water system.
Despite the concerns raised, the county is advising residents the water is safe to drink and the discoloration is a temporary seasonal condition caused by elevated levels of manganese in the water source.
At least 20 complaints have been received since Monday, Bob Thomas, spokesman for the county, said Tuesday evening.
According to a news release issued by the county, "the cause is manganese, a naturally occurring mineral that is present in water, soils, foods and the atmosphere."
"The source of the higher than normal levels in the County water system is likely the source water, Loch Raven Reservoir," the release continues. "The condition is temporary and the Division of Water and Sewer is taking steps to reduce the condition including enhanced chemical treatment and flushing of some mains."
Thomas said he did not have information yet on the geographic distribution of the complaints. The county's main water treatment plant in Abingdon is supplied with raw water from Loch Raven in Baltimore County. The reservoir, which is supplied by Little Gunpowder Falls, is owned by Baltimore City.
Joel Caudill, deputy director of the county's water and sewer division, said manganese in water is not uncommon in the U.S. and it depends on the source of water.
"None of our source waters are typically prone to it, so we don't generally expect to have it," he said, explaining that Baltimore City changed where it was drawing water from in Loch Raven Reservoir, which is what caused the manganese to enter.
After the city realized what happened, it took steps to change it back, he said.
Manganese is a naturally-occurring mineral that many people take in daily supplements, he pointed out.
No health issues have been directly linked to manganese even at high concentrations, but very high levels would make water "unpalatable," he said.
Citizens who believe their water has an aesthetic quality problem, are being encouraged to contact the Division of Water and Sewer Maintenance Department at 410-612-1612 for further assistance.
"There are no known health effects associated with these elevated manganese levels in drinking water," the county news release states. "High levels of these contaminants can result in discolored/cloudy water and an unpleasant metallic taste to the water."
The U.S. Environmental Protection Agency has not set maximum contaminant levels for manganese in the National Primary Drinking Water Regulations, the news release notes, "however, manganese is monitored for aesthetic (taste and appearance) reasons."