Harmful Algal Bloom (HAB)

Most algae are harmless and are an important part of the food web. Certain types of algae can grow quickly and form blooms, which can cover all or portions of a lake. Even large blooms are not necessarily harmful. However some species of algae can produce toxins that can be harmful to people and animals. Blooms of algal species that can produce toxins are referred to as harmful algal blooms (HABs). HABs usually occur in nutrient-rich waters, particularly during hot, calm weather.

What are the potential health effects of blue-green algae and blue-green algal toxins?

Some blue-green algae can produce toxins, some do not. However, exposure to any blue-green algae blooms can cause health effects in people and animals when water with blooms is touched, swallowed, or when airborne droplets are inhaled. Exposure to high levels of blue-green algae and their toxins can cause diarrhea, nausea or vomiting; skin, eye or throat irritation; and allergic reactions or breathing difficulties.

How do I know if I am being exposed to blue-green algae?

People should suspect that harmful blue-green algae blooms could be present in water that is noticeably discolored or that has surface scums. Colors might include shades of green, blue-green, yellow, brown, purple, white, or red. Water affected by harmful blue-green algal blooms often is so strongly colored that it can have a paint-like appearance. When it comes to drinking water, unpleasant tastes or odors are not reliable indicators of blue-green algal toxins, or other toxic substances.

What should I do if I suspect a bloom and/or if I suspect I’ve been exposed to a bloom?

If you are exposed: 

  • Rinse off yourself, children, and animals with clean water if exposed to blooms or surface scums, or water that is noticeably discolored.
  • Stop using the water and consider medical attention if people or animals have symptoms and might have touched, swallowed, or inhaled surface waters with possible blooms. Symptoms include diarrhea, nausea or vomiting; skin, eye or throat irritation; and allergic reactions or breathing difficulties.

More Information can be found on the following sites:

NYS Department of Health

NYS Department of Environmental Conservation

US Centers for Disease Control and Prevention

US Environmental Protection Agency


Contact Info

Jennifer M. Priebe, M.S.

107 Nott Terrace
Schaffer Heights
Schenectady, NY 12308
(518) 386-2818