The hurricane is expected to generate a storm surge as great as 14 feet along parts of the Florida Panhandle, where it made landfall early Wednesday afternoon. That part of the coast that has seen some of the worst concentrations this year of red tide, a variety of algae that kills fish and releases toxins that cause respiratory symptoms in humans similar to tear gas.

Hurricane Michael could carry that algae past the beaches and into neighborhoods, scientists warn.

“A storm surge or king tide could bring red tide up onto land,” Larry Brand, a professor in the Department of Marine Biology and Ecology at the University of Miami, said by email. “The toxin would get into the air and people would be breathing it.”

Red tide is made up of Karenia brevis, an organism that can trigger attacks in people with asthma, according to Richard Pierce, program manager and senior scientist at the Mote Marine Laboratory & Aquarium in Sarasota. Even people who don’t have asthma can suffer from choking, coughing and stinging eyes. Some have reported lingering headaches and flu-like symptoms.

Pierce said this is the first time the state has had a severe red tide and severe hurricane at the same time, which makes the health effects harder to predict. But one risk is that the breaking waves could turn the algae into an airborne toxin, spreading the risk beyond the reach of the storm surge.

“Bubbles make an excellent surface for them,” Pierce said. “It’s a very efficient mechanism for getting toxins from the water onshore.”