Is There a Link Between Climate Change and Rhinosinusitis? Researchers Explore Possibilities

Carol Yan, MD, an otolaryngologist–head and neck surgeon and assistant professor of surgery at the University of California, San Diego, sometimes has patients whose chronic rhinosinusitis (CRS) has flared after returning from trips to hotter environments and higher pollen counts.

“Their symptoms are often immediately worse, or they suffer from a prolonged exacerbation even upon returning to San Diego,” she said. “This can be seen in both medically managed and post-surgical patients with CRS.” The inflammation in the sinus leads to more thick discharge, a greater polyp burden, and even systemic therapy, she said.

We will likely see even greater clinical collaboration amongst otolaryngologists, allergist-immunologists, and pulmonologists.

—Carol Yan, MD

Although she can’t definitively connect the dots between climate change and the disease, “I think that is very much a possibility,” she said.

Whether, and to what extent, otolaryngologic diseases can be connected to climate change is still unclear, but it’s certainly a topic generating more interest in the field. Researchers are putting real numbers to the effects that human-induced environmental changes are having on the amount of pollution in the air from wildfires, on the length of our pollen seasons, and on pollen counts. They’re also establishing that there are associations between those changes and health, including conditions such as CRS.

The Climate Connection

The potential effects of these climate-related conditions pose challenges for otolaryngologists, who are treating increasingly stubborn disease. But researchers hope that clarifying the problems can also help guide the way to better management.

“In the last five years, our understanding of the link between climate change—and its downstream effects—and CRS have really grown,” said Murray Ramanathan, MD, professor of otolaryngology–head and neck surgery at Johns Hopkins University in Baltimore.

In what is thought to be the first time, researchers have shown that environmental conditions are linked to developing CRS. Dr. Ramanathan and his colleagues last year compared 2,000 people with CRS to 4,000 people without CRS. To gauge their exposure to fine particulate matter—PM 2.5, or particulate matter with a diameter of 2.5 microns or smaller—researchers used environmental data and residential zip codes. (PM 2.5 includes airborne particles such as car exhaust and smoke.)

The researchers looked back at PM 2.5 exposure rates one year, two years, three years, and five years before the date when subjects were diagnosed with CRS. (The CRS was validated with CT scans, and the control subjects were verified not to have CRS on CT scan as well.) Exposure at all time points correlated with CRS, averaging out to about 1.3 times the risk. Exposure was associated even more strongly with severe CRS, at about three times the risk after adjusting for smoking status (Am J Respir Crit Care Med. 2021;204:859-862). The association was most pronounced for the ethmoid sinus. Although a cause couldn’t be ascertained from the findings, the study offers a definitive association between the two, Dr. Ramanathan said. One weakness of this study, however, was that almost all of the patients were from the Northeastern U.S.

The link was also found in another study by Dr. Ramanathan and his colleagues. They looked at data on military personnel around the United States, finding a 3-fold increase in CRS for every 5 microgram per cubic meter increase in PM 2.5 exposure. The findings are persuasive, he said, especially because of the reliability of military data.

“We know exactly where the military personnel are, and they’re required to get routine physical exams,” he said. “I think this is one example of how climate change and related air pollution are associated with a high incidence of CRS.”

Particulate Matter and CRS

In the clinic, rhinologists are noticing the effects of exposure to these conditions, added Dr. Ramanathan. “You’ll find that patients who are in highly polluted areas do tend to be more symptomatic,” he said, “and, retrospectively, you begin to see that they have this type of exposure.”

Recent research has also shown that environmental conditions seem to play a role in the severity of disease. Researchers at the University of Pittsburgh looked at 113 patients with CRS with nasal polyps, 96 patients with CRS without polyps, and 25 patients with aspirin-exacerbated respiratory disease. They found that patients exposed to vapors, gases, dusts, fumes, fibers and mists, or diesel fumes required more steroid use than those without such exposure. In addition, those with higher levels of exposure were more likely to undergo functional endoscopic sinus surgery compared to those who were not exposed (Int Forum Allergy Rhinol. 2020;10:175-182). “We’re seeing a lot of people who have had CRS who are doing well, but the ones who are in environments where they’re exposed to higher levels of air pollution are more prone to exacerbations,” Dr. Ramanathan said.

In the Central Valley of California, researchers are examining the effects that these conditions are having on the body. “In some of the cohorts that we have, the asthma rates are up to 20 to 25 percent, which is much higher than the national or even state average,” said Mary Prunicki, MD, PhD, senior director of air pollution and health research at Stanford University. “Even though the [air quality] regulations have improved, we continue to have poor air quality.”

“The Central Valley is similar to a basin,” added Juan Aguilera, MD, PhD, MPH, director of translational environmental and climate health at Stanford University. “Basically, air pollution stagnates, and the Valley has several contributors coming from nearby air pollution sources, such as heavy traffic. Also, during wildfire season, the smoke tends to stall longer around the Central Valley.”

In one recent study, Dr. Aguilera and his colleagues enrolled 186 women who were 20 weeks pregnant and lived in Fresno, one of the nation’s most highly polluted cities due to its topography and exposure to wildfires and agricultural pollutants. They found that T-helper immune cells were influenced by exposure to fine particulate matter, nitrogen dioxide, carbon monoxide, and polycyclic aromatic hydrocarbons. The findings show the negative effects of air pollution exposure during pregnancy and the need for more epigenetic studies. (Clin Epigenetics. 2022;14:40) “It throws off the immune system,” said Dr. Aguilera. “Patients will have fewer of the beneficial immune cells that keep your immune system in balance.”

Pollen and CRS

Another aggravator of rhinologic conditions is pollen, and this topic is looking bleak as well. University of Michigan researchers assessed how temperature and precipitation changes affect pollen season and grass season length, as well as pollen emissions. Based on these patterns, they said, models predict that pollen emissions will increase by 200% by the end of the century, increasing the likelihood of seasonal allergies (Nat Commun. 2022;13:1234).

Climate change isn’t something in the future or in distant parts of the world—it’s here with us now. And in every breath that we take in the spring, we’re inhaling climate change-driven exacerbations of pollen. —William Anderegg, PhD

In findings published in 2021, researchers found that pollen seasons have lengthened by 20 days and pollen concentrations have increased by 21% across North America, and that these concentrations were strongly correlated with global warming. Human influences on the climate system, they determined, contributed about 50% of the trend in the pollen season length and about 8% in the trend of increasing pollen concentrations (Proc Natl Acad Sci USA. 2021;118:e2013284118). “It’s a really clear example that climate change isn’t something in the future or in distant parts of the world—it’s here with us now,” said William Anderegg, PhD, associate professor of biological sciences at the University of Utah in Salt Lake City and the lead author of the study. “And in every breath that we take in the spring, we’re inhaling climate change-driven exacerbations of pollen.”

Researchers in Belgium and Sweden looked at 12 patients with grass pollen-sensitized CRS, 12 grass pollen-allergic rhinitis patients, 12 patients with CRS with nasal polyps, and 12 controls. On provocation testing with grass pollen, the test was positive in six of 12 patients with CRS with nasal polyps who were grass pollen-sensitized, with another four showing allergic symptoms not rising to test positivity. This contrasted with all the patients with allergic rhinitis having a positive test, one in the control group with a positive test, and two in the nonsensitized CRS with nasal polyps group having a positive test. “These results,” researchers wrote, “show that allergen exposure induces an attenuated clinical response in patients with CRS with nasal polyps and sensitization to grass pollen as compared with grass pollenallergic rhinitis patients” (Clin Exp Allergy. 2016;46:555-563).

Dr. Anderegg and other climate researchers said they hope their work sparks tangible changes. One possibility, noted Dr. Anderegg, is better planning regarding urban vegetation, perhaps planting species that produce less pollen. Early-warning systems of high pollen counts are another idea.

“Just having folks aware that pollen seasons are changing and starting earlier can be really big,” he said. “When I talk to a lot of allergists, I hear from them that many of the worst impacts happen when people get caught by surprise.”

Dr. Yan said she hopes prospective, longitudinal research will be done establishing the direct impact of climate change on CRS exacerbations. Once those connections are established, studying how immunological changes come about could help guide development of targeted therapies.

“We will likely be seeing even greater clinical collaboration amongst otolaryngologists, allergist-immunologists, and pulmonologists,” Dr. Yan said. “As physicians we may also end up with increased continuity of care in treating these patients as they return to our clinics, potentially on a seasonal basis despite prior medical or surgical therapies.”

Dr. Aguilera said that the new attention to air quality brought on by COVID-19 might be beneficial when it comes to climate effects. “There was more awareness regarding air quality and how particles are dispersed in different environments,” he said. “It wasn’t until the pandemic that we started to see increased attention on better filtering systems for schools, or better use of better protective barriers.”

“The big goal of this is awareness—awareness of patients that their environment can be a driver of some of these diseases,” Dr. Ramanathan said. “Also, awareness that climate change is real, there are downstream effects from it, and there’s a need for increased regulation of air quality to mitigate a real health hazard. I think that’s probably the most powerful message that can come out of this.”

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Thomas R. Collins is a freelance medical writer based in Florida.