High levels of pollen in Miami are nothing to sneeze at

A mango flower blooming full on a mango tree. Photo: eakrin rasadonyindee/iStock
By Robert C. Jones Jr.

A mango flower blooming full on a mango tree. Photo: eakrin rasadonyindee/iStock

High levels of pollen in Miami are nothing to sneeze at

By Robert C. Jones Jr.
Pollen counts in the city have been on the rise since mid-February, signaling a return of allergy season. And human-induced climate change is making it worse.

Pollen-measuring sensors are not the only tools Naresh Kumar uses to determine whether levels of the fine, powdery substance are spiking in the Miami air. Sometimes, the University of Miami public health scientist can tell by using a different kind of gauge—his eyes.

“Before coming to Miami, I didn’t have any allergies to pollens,” said Kumar, an associate professor of environmental health at the University of Miami Miller School of Medicine. “Now, when I go outside without goggles during high pollen seasons, my eyes burn and itch terribly.”

For Kumar, that burning and itching sensation is once again at its worse, as the pollen count in Miami has increased and remained at unusually high levels since mid-February, signaling an early return to allergy season in Florida.

“Last year, pollen levels in the city were extremely high,” said Kumar, “and this year they’re even worse.” Forecasts from pollen.com and Kumar’s own sensors bear that out.

The levels started rising during the second week of February and have been intensifying since then, he said. 

Just how bad is it? One day late last month, the concentration of pollen in Miami registered at 2,949 pollen grains per cubic meter. “And that’s pretty high,” Kumar said. “Even if one to two pollen grains make their way to your eyes or nasal cavity, they can trigger an allergic response.”

Exposure to pollen can trigger allergies, result in allergic conjunctivitis, and exacerbate asthma. It also can worsen COPD and eye, nose, and throat inflammation, according to Kumar.

The high levels will only linger. “It’s a perennial issue in Miami. We’ve been seeing high concentrations from March through May,” said Kumar, noting that his research group has been monitoring the levels since 2018, storing data that will be used to analyze pollen distribution in different parts of the city.

Florida, said Kumar, rarely experiences a hard freeze. So, plants pollinate in the state year-round.

“All of the trees and most of the rest of the plants in Miami produce pollen,” said Barbara Whitlock, an associate professor of biology in the College of Arts and Sciences, whose research focuses on the origins of plant diversity. “People are sensitive to different kinds of pollen, but trees produce more pollen. So that’s usually what we blame for allergies,” she added. “Most of Miami was built on pine rocklands. There are not a lot of our native slash pines left, but the occasional tree can still produce a lot of pollen.”

Live oaks, which are planted all over Miami, are the other big pollen producers. “They are flowering now, and producing a lot of pollen,” said Whitlock, noting that for the past two weeks she has parked her car under a large oak tree, only to find it covered in pollen later in the day.

Mango trees are also flowering right now. “Their flowers are tiny, and a single flower does not produce much pollen. But there are a lot of flowers,” Whitlock explained. “A lot of people claim to have allergic reactions to mango flowers, myself included. Julia Morton, who was a botanist at UM for many years, claimed that this was a reaction to vaporized oils from the flowers and not from pollen. Mangos are in the same family as poison ivy and the irritant in poison ivy is an oil, so this is believable.”

For allergy sufferers, more bad news comes in a recent study in the Proceedings of the National Academy of Sciences (PNAS) of the United States, which reports that human-induced climate change is worsening and lengthening pollen seasons across the U.S. and Canada.

Climate change can alter the timing, duration, and intensity of pollen production, said Kenneth Feeley, associate professor and Smathers Chair in Tropical Trees in the Department of Biology. “Lots of plant species use climate as a cue for when to produce flowers and pollen, so as the climate changes, so will the timing of pollination,” Feeley explained. “Likewise, climate can determine how much energy plants have, and it may also influence what proportion of that energy plants invest in pollen production.”

Whitlock said the PNAS study is convincing, calling it an “important first step” to examining the effects of climate change on pollen and pollen allergies. “It makes sense that plants will respond to rising temperatures and higher carbon dioxide levels,” she said. “One of the strengths of the study is that they use pollen data from 60 different sites across the U.S. and Canada.” While Miami was not included in the study, the city of Tampa was, “and Tampa shows a strong signal for more pollen and a longer pollen season,” Whitlock said. “It would be very interesting to see if the trend holds for Miami.”

Feeley said it is also important to note that at the same time we are changing the climate, we are also changing the environment in other ways. “We have intentionally and unintentionally introduced many flowering plant species into South Florida, and some of these exotic plants produce the pollen that is leading to people’s allergic reactions,” he said. “For example, mango trees are not from the U.S. They are originally from India and were introduced to South Florida in the 1930s by David Fairchild.”

If people with allergies cannot avoid the outdoors, Kumar recommends they use modern antihistamines that prevent seasonal allergy symptoms with few side effects.

And mask-wearing, which has proved effective in preventing the spread of COVID-19, can also help reduce exposure to pollen, said Kumar. He will soon release a study showing that masks can filter out most pollens when used properly. “Masks and skin-fit goggles will protect you from both COVID-19 and pollens and most mold spores as well,” he said.