An algae bloom is creating a toxic chemical in two lakes in Montgomery County, Maryland, and officials and a veterinarian said it could harm people and their pets.
Increased levels of blue-green algae, which can release a toxin known to cause liver damage if ingested, have been found in Lake Needwood and Lake Frank in Rock Creek Regional Park.
The toxin microcystin can be harmful to humans, and it can kill dogs that drink it.
"An algal bloom toxicity can be very dangerous and possibly lethal if not treated when clinical signs start occurring," Dr. Matthew Antokowiak, a veterinarian at AtlasVet in Washington, D.C., said in an email.
In a statement issued Monday, Montgomery Parks advised pet owners to keep their dogs on leashes and to make sure the animals stay out of the water.
Antokowiak advised dog owners to be careful.
"When you are near a body of water and are tempted to let your dog go swimming, if you notice anything weird, slimy, gross or unusual floating in the water, it would be better for both you and your pet to stay on dry land," he said.
Signs that a dog has been affected include excessive drooling, panting, fainting, vomiting and seizures.
Pollutants usually cause algal blooms, including fertilizers from homes and farms, Montgomery County natural resource specialist Matt Harper said.
Warnings about algal blooms in the two Maryland lakes have been issued every summer since 2009, he said.
Algae grows in the lakes year-round. In the summer months, the lakes get more direct sunlight and warmth. These, coupled with pollutants in stormwater runoff, create "the perfect storm" for algae growth, Harper said.
The algae lets off microcystin, which Montgomery Parks monitors. If microcystin is measured at more than 10 parts per billion, it has potential health risks, and the department issues warnings.
Once increased levels of microcystin are detected, there’s not much officials can do to stop it.
Better management of stormwater could potentially prevent future algal blooms, Harper said.
"I don’t think [the lakes] have necessarily been prioritized," he said.
The lakes are still safe to enjoy, Harper said. Swimming is always prohibited, but boating and fishing are allowed.
"I would definitely not hesitate to still use [them]," Harper said.
"This is more of a precaution," he continued. "I would take my kids out there on the weekends without any hesitation."
Still, visitors are advised to wash their hands after being in or near the lakes.