See how Houston is counting pollen and mold spores for allergy season

Every weekday, rain or shine, a microbiologist starts the morning by going to the rooftop of the Houston Health Department lab.

She’s not there for the view of the nearby Texas Medical Center. She controls a machine that samples the air so they can begin the hours-long process of determining daily pollen counts and mold spores.

Houston residents who have allergies may be familiar with the counts, which provide a valuable prediction of when they are at higher risk for symptoms. But those counts are not done by a machine. A microbiologist uses a microscope to count individual pollen and mold spores, then uses a mathematical formula to calculate the data, which will be released Monday through Friday at around 9:30 a.m. on the health department’s website.
The process has taken longer lately because Houston is in the middle of tree pollen season, explains Christina Utz, one of two Houston Health Department microbiologists who count pollen and mold spores. Tree pollen counts have been “heavy” or “extremely heavy” every day for the past week.
‘If it’s not a tree [pollen] season, it takes me about an hour. But when it does, it can take two to four hours, depending on how bad it is,” Utz said. “That’s why the count doesn’t always come out at 9:30 p.m.”

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Allergy season is underway in Houston almost year-round, but data shows the problem has gotten worse over time.
An analysis by the nonprofit organization Climate Central found that climate change is causing allergy season to start earlier, last longer and be more intense. In Houston, warm weather caused the 2023 pollen season to arrive earlier than usual.

“We’ve had a slew of patients come in with significant nasal and eye symptoms for allergies,” said Dr. Sanjiv Sur, a professor of medicine in the section of immunology, allergy and rheumatology at Baylor College of Medicine.
Utz noticed the difference during her trips to the roof this month. The machine that samples the air collects small particles on a piece of foil. The film is clear, but develops a distinct hue during the pollen season.
“It’s definitely yellow this time of year,” Utz said. “Everything is yellow.”

Performing the count

The Houston Health Department provides counts for 18 types of tree pollen, nine types of weed pollen, and 20 types of fungi, in addition to a count for grass pollen. The prevalence of each depends on the time of year. For example, oak pollen is heaviest in February, March and April, while ragweed is heaviest in September and October.
Utz has been counting pollen and mold spores for seven years. Her colleague from the Houston Health Department, microbiologist Rasmita Patel, has been calculating for some time. They usually alternate months.
The process starts early, around 6 or 7 in the morning. The stairs to the roof are outside, so it’s harder when it’s cold, Utz said.
The Burkard Spore Trap on the roof works by sucking in air as a vacuum as the windvane rotates. Airborne particles, including pollen and mold spores, are trapped on a greased piece of film inside the machine.
The film is removed from the machine and taken to the laboratory. Utz and Patel then place it on a slide and add some food coloring that turns the pollen spores pink because it makes them easier to count, Utz said.

The microbiologists use a microscope to view the individual pollen and mold spores. To the untrained eye it may look like a jumble of dots and jagged shapes, but Utz and Patel took courses and exams to become licensed barristers. They also have a reference book with pictures of each spore, in case they have trouble identifying them.

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Utz counts all tree pollen at the same time and then moves on to fungal spores. She uses a counter top to keep track and taps keys as if she were using a typewriter.
She can’t see the entire slide under the microscope, so she counts portions at a time, from left to right. Each time she reaches a new field of view, she starts counting by looking at the 3 o’clock position and then moving clockwise. She follows the same process every day.
“When I switch it up, I forget something,” she said.
After she finishes counting the pollen and mold spores, Utz converts each count into a formula to calculate the number of spores in every cubic foot of air. The results are the final counts posted online each day.
The number doesn’t usually change drastically from day to day, Utz said, although rain can wash away pollen and lead to more mold.
While rain can reduce pollen counts, it can have a detrimental effect on symptoms, Sur said. Rain can break pollen into smaller particles, and that makes it easier for them to enter the lungs and other areas, he said.

“We view rain as a good thing,” Sur said. “Well, there’s a downside where it can’t be such a good thing.”

Prediction of allergy symptoms

Pollen and mold spores counts can be a valuable resource for someone who wants to avoid being exposed to whatever triggers their allergy symptoms, said Dr. Albert Wu, an allergist at the Kelsey-Seybold Clinic.
“Avoidance is very helpful,” he said. “One way to do that is to monitor the pollen count and avoid the things you’re allergic to.”
Wu and Sur also recommend keeping track of what time of year you usually have allergy symptoms. You can prevent or limit symptoms by starting to take allergy medication a few weeks before, they said.
If you’re having a flare-up, over-the-counter medications like nasal sprays and antihistamines can help reduce symptoms. Decongestants are also helpful, although anyone with high blood pressure or heart disease should avoid using a decongestant.

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The health department is not required to provide the pollen and mold counts. It is one of about 80 counting stations in the US that provide data to the National Allergy Bureau, a division of the American Academy of Allergy, Asthma & Immunology.
Many of these counting stations are managed by allergists or researchers; only a handful are run by government agencies, Utz said. But the health department provides the service because Houston’s allergy season is practically year-round due to the area’s warm climate and vegetation.
“We are the only counting station in the city. If we didn’t count, no one would get the count,” Utz said. “Someone has to count. I think it’s me.’

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See how Houston is counting pollen and mold spores for allergy season

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