CDC begins new study on the health effects of cyanotoxins


ATLANTA, GA – The Centers for Disease Control and Prevention (CDC) will start a new study in south Florida during the 2021 algal bloom season to assess the health effects of exposure to cyanotoxins in the air. This study, called the Cyanotoxins in Air Study (CAST), will look at exposures to cyanotoxins among people who live or work near the following areas:

  • Lake Okeechobee,
  • St. Lucie River,
  • Caloosahatchee River, and
  • Cape Coral Canals.

CDC is conducting this study to determine if breathing in cyanotoxins can make people sick or cause symptoms. Cyanotoxins are toxins (poisons) that are sometimes produced when small, plant-like organisms called cyanobacteria (also known as blue-green algae) rapidly grow out of control, or bloom. Cyanobacterial blooms most often occur in fresh water, such as lakes, rivers, and streams. People are most often exposed while swimming, boating, or doing other activities in or near water with a cyanobacterial bloom. Harmful algal and cyanobacterial blooms, an emerging public health issue, are the rapid growth of algae or cyanobacteria in salt and fresh waters that can cause harm to people, animals, or the local ecology.

Previous research and personal reports show that people exposed to cyanotoxins in the air may experience symptoms of upper respiratory irritation, such as wheezing, coughing, chest tightness, or shortness of breath.

“This is an important opportunity to study a critical emerging issue affecting millions of Americans,” said Dr. Patrick Breysse, Director of the CDC’s National Center for Environmental Health and the Agency for Toxic Substances and Disease Registry. “A broader understanding of the risks from cyanobacterial blooms will enable CDC and its environmental public health partners to develop more targeted strategies to protect the health of people and animals from these exposures and to address an important climate change related health issue.”

As part of this study, researchers will meet with participants during a bloom season, which is about March through October. Participants will be asked to complete surveys about their symptoms, provide urine specimens and nasal swabs, perform a simple lung function test at home (called remote spirometry), and provide some blood specimens. CDC will test the urine specimens and nasal swabs for cyanobacterial toxins, and the blood samples for changes in liver and kidney function. CDC staff members will also work with participants to record air quality measurements and time spent outdoors. Because of the study design, we will recruit only one person per household.

The study will begin enrolling participants when we see signs of a cyanobacterial bloom forming. For more information about the Cyanotoxins in Air Study (CAST) visit: or call 561-297-4631.

In addition, people can take the following steps to avoid getting sick from cyanobacteria and the toxins they make:

  • If you see a bloom, stay out of the water and keep your pets out of the water. Do not fish, swim, boat, or play water sports. You cannot tell if a bloom is harmful by looking at it, so it is best to use caution and stay away.
  • Do not go into or play in water that: smells bad, looks discolored,, has foam, scum, mats, or paint-like streaks on the surface, or has dead fish or other animals washed up on its shore or beach.
  • Check for and follow local shellfish and fish advisories before eating any fish or shellfish you collect.
  • If you are notified of a bloom in a nearby body of water or in your public drinking water supply, follow local or state guidance to reduce your chances of getting sick.

For more information about cyanobacterial blooms, visit or call 800-CDC-INFO (800-232-4636).

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