Stuffy nose? Watery eyes? Spore count details allergies
Houston Health Department’s pollen calculations done by hand daily
Every weekday, rain or shine, a microbiologist begins the morning by heading up to the roof of the Houston Health Department’s laboratory.
She isn’t up there for the view of the nearby Texas Medical Center. She is checking a machine that samples the air so she can begin the hours-long process of determining the daily pollen and mold spore count.
Houston residents who have allergies might be familiar with the counts, which provide a valuable forecast of when they’re at a higher risk for symptoms. But those counts aren’t 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 that is released on the health department website around 9:30 a.m. Monday through Friday.
The process has taken longer lately because Houston is in the midst of tree pollen season, explained Christina Utz, one of the two microbiologists at the Houston Health Department who count pollen and mold spores. Tree pollen counts have been “heavy” or “extremely heavy” every day for the past week.
“When it’s not tree [pollen] season, it takes me about an hour. But when it is, it can take me from 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.”
Allergy season is nearly a year-round affair in Houston, but data suggests the problem has become worse over time.
An analysis by the nonprofit Climate Central found that climate change is causing allergy season to arrive earlier, last longer and be more intense. In Houston, warm weather caused pollen season to arrive earlier than usual in 2023.
“We’ve had a whole bunch of patients who are coming in with significant nasal and eye symptoms for allergies,” said Dr. Sanjiv Sur, a professor of medicine in the section of im
munology, allergy and rheumatology at Baylor College of Medicine.
Utz has noticed the difference during her treks up to the roof this month. The machine that samples the air collects tiny particles on a piece of film. The film is clear, but it develops a distinct hue during pollen season.
“This time of year, it is absolutely yellow,” Utz said. “The whole thing 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 mold, in addition to a count for grass pollen. The prevalence of each depends on the time of year. Oak pollen, for example, 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 at the Houston Health Department, microbiologist Rasmita Patel, has been counting for even longer. They typically alternate months.
The process begins early, around 6 or 7 a.m. The stairs to the roof are outdoors, so it’s tougher when it’s cold, Utz said.
The Burkard Spore Trap on the roof works by sucking in air like a vacuum as its wind vane 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 inside to the lab. Utz and Patel then place it on a slide and add some dye that makes the pollen spores turn pink, because that makes them easier to count, Utz said.
The microbiologists use a microscope to see the individual pollen and mold spores. To an untrained eye it might look like a jumbled mess of dots and jagged shapes, but Utz and Patel took courses to become certified counters. They also have a reference book that contains pictures of each spore, in case they’re struggling to identify them.
Utz counts all the tree pollens at the same time, then moves on to mold spores. She uses a benchtop counter to keep track.
She can’t see the full slide under the microscope, so she counts portions at a time, moving from left to right. Each time she reaches a new field of vision she begins her count by looking to the 3 o’clock position, then moving clockwise. She follows the same process every day.
“If I switch it up, I’m going to forget something,” she said.
After she finishes counting the pollen and mold spores, Utz puts each tally into a formula to calculate the number of spores in each cubic meter of air. The results are the final tallies that are posted online each day.
The count typically doesn’t change drastically from day to day, Utz said, though rain can wash away pollen and lead to more mold.
Although rain can reduce the pollen count, it can have an adverse effect on symptoms, Sur said. Rain can break up pollen into smaller particles, and that makes it easier for them to penetrate the lungs and other areas, he said.
“We think about rain as being a good thing,” Sur said. “Well, there is a flip side to this where it can be not such a good thing.”
Forecast allergy symptoms
The pollen and mold spore counts can be a valuable resource for someone who is looking to avoid being exposed to whatever is causing their allergy symptoms, said Dr. Albert Wu, an allergist at Kelsey-Seybold Clinic.
“Avoidance is very helpful,” he said. “One way to do that is to check pollen counts and try to avoid the things that you’re allergic to.”
Wu and Sur also recommend keeping track of the time of year when you usually have allergy symptoms. You can prevent or limit symptoms by starting to take allergy medications a few weeks before then, they said.
If you do have a flare-up, overthe-counter medications like nasal sprays and antihistamines can help reduce symptoms. Decongestants are also helpful, though anyone with high blood pressure or a heart condition should avoid taking a decongestant.
The health department is not required to provide the pollen and mold counts. It is one of about 80 counting stations across the U.S. that provide data to the National Allergy Bureau, a division of the American Academy of Allergy, Asthma & Immunology.
Many of those counting stations are run 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 warm climate and vegetation.
“We’re the only counting station in the city. If we didn’t count, nobody would get the count,” Utz said. “Somebody needs to count. I guess it’s me.”