A health advisory for Fernan Lake by the Panhandle Health District and the Idaho Department of Environmental Quality remains in effect.

Water samples confirmed the presence of blue-green algae that can produce toxins harmful to humans and animals.

The public is advised to avoid swallowing or inhaling water and to avoid direct contact with water containing visible algae.

Drinking water from the lake is especially dangerous and the toxins cannot be removed by boiling or filtering the water. Children and pets are particularly susceptible.

According to the Centers for Disease Control and Prevention, humans who drink or swim in water that contains high concentrations may experience gastroenteritis, skin irritation, allergic responses or liver damage.

Symptoms of exposure in humans are rare and include numbness, tingling, skin irritation and nausea. If symptoms persist or worsen, people should seek medical attention. Pets and livestock should also avoid the area.

The public will be advised when the concern no longer exists.

With proper precautions to avoid water contact, people are encouraged to enjoy other activities near the lake, including camping, hiking, biking, catch-and-release fishing and bird watching. If people choose to eat fish from this area, it is recommended that they remove all fat, skin and organs before cooking; toxins are more likely to collect in those tissues.

Blue-green algae are naturally-occurring, microscopic bacteria. Many species occur in Idaho surface waters and only some species release toxins under certain conditions. Blooms occur in waters with high levels of nutrients such as phosphorus and nitrogen.

The physical appearance of blue-green algae blooms can be unsightly, often causing thick green mats along shorelines. Often excess nutrients associated with algae blooms are caused by pollution from human activities.

Water quality improvements can be expected to reduce future algae blooms so the Idaho Department of Environmental Quality is working with residents and landowners to implement nutrient-reduction projects.