Because of climate change, heat waves, storms, heavy rainfalls, and floods are now occurring in areas that seldom experienced these phenomena before. “Extreme weather events are rare, but in terms of their extent, duration, and scale, they are unusual. And they are increasing due to climate change,” said Andrea Elmer, MD, an internal medicine and pulmonology specialist at the DKD Helios Clinic in Wiesbaden, Germany. She spoke at the Congress of the German Society for Pneumology and Respiratory Medicine.
Elmer referred to the 2023 status report by the Robert Koch Institute and the 2023 Synthesis Report by the Intergovernmental Panel on Climate Change, in which the likelihood of extreme weather events was acknowledged to be significantly higher than previously recognized. “Knowing about such extreme weather events is important to assess the consequences for our patients and to identify possible medical care needs,” said Elmer. She focused on the effects of platanus (plane tree) cough and thunderstorm asthma.
Platanus Cough
The severe symptoms of 40 students at a comprehensive school in Wiesbaden, including shortness of breath, coughing, and irritated eyes, led to a major operation involving the fire brigade and police on May 11, 2022. The symptoms worsened when the children left the building and waited in the schoolyard. Initially, a chemical attack with irritant gas was suspected because the school is located near an industrial area. There were no indications of a pollen cloud.
Eventually, doctors and firefighters found that the symptoms were caused by platanus cough, which is induced by the fine star-shaped hair found on young platanus leaves, bark, young branches, and buds. If strong winds move the leaves after prolonged dryness, these trichomes can break off when touched, creating platanus dust.
At that time, there were unusual climatic conditions. The temperature was 29 °C, it was dry, and wind gusts reached 50 km/h. The schoolyard was enclosed and densely planted with tall, old plane trees. Initial symptoms occurred in classrooms with open windows.
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A total of 25 children had to be admitted to the hospital. Treatment included lorazepam and salbutamol. All students had normal oxygen levels, and the symptoms were reversed.
Cough or Allergy?
The clinical differential diagnosis for an allergy is quite simple, said Elmer. Platanus cough mainly shows symptoms of irritation, a feeling of a foreign body, and scratching in the eyes, throat, and nose. Coughing can also occur. In an allergy, there is often a runny nose and itching in the eyes and nose. Such allergic symptoms do not occur with platanus cough.
It should also be noted that the sensitization rates for a platanus allergy in Germany range between 5% and 11%. “Having so many platanus allergy sufferers in one place was relatively unlikely,” said Elmer.
She expects an increase in cases of platanus cough, especially in cities with dense construction, such as in narrow schoolyards. High concentrations of platanus dust can occur, especially when it is warm, dry, and windy. “Platanus cough does not occur every time we walk under plane trees. It strongly depends on warmth, dryness, and wind,” said Elmer.
Patients can protect themselves by avoiding skin and mucous membrane contact under appropriate climatic conditions and by wearing protective glasses and masks. Leaves and branches should not be swept but vacuumed. “Under no circumstances should plane trees be cut down. We need trees, especially in cities,” said Elmer. Moreover, the trichomes act as biofilters for air pollutants. In critical environments such as schoolyards, seasonal spraying of plane trees with a mixture of apple pectin and water can prevent the star hair from breaking off.
Thunderstorm Asthma
For patients with asthma, wildfires, storms, heavy rainfall, and thunderstorms can lead to exacerbations. Emergency room visits and hospital admissions generally increase after extreme weather events.
A study examining the consequences of the fires in California from 2004 to 2009, for example, reported that hospital visits related to asthma increased by 10.3%. Those related to respiratory problems increased by 3.3%. Infants and children up to age 5 years were most affected.
Thunderstorms are increasing because of global warming. Thunderstorm asthma arises under specific meteorological conditions. It typically occurs in patients with aeroallergies (eg, to pollen and fungal spores) in combination with thunderstorms and lightning. Large pollen grains, which normally remain in the upper airways, ascend into higher atmospheric layers and break apart due to updrafts. These very small particles are pushed back to ground level by downdrafts, enter the lower airways, and cause acute asthma.
Worldwide, cases of thunderstorm asthma are rare. About 30 events have been documented. Thunderstorm asthma was first observed in 1983 in Birmingham, England. Fungal spores were the trigger.
The most significant incident so far was a severe thunderstorm on November 21, 2016, in Melbourne, Australia. Worldwide attention was drawn to the storm due to an unusually high number of asthma cases. Within 30 hours, 3365 patients were admitted to emergency rooms. “This is also a high burden for a city with 4.6 million inhabitants,” said Elmer. Of the patients in Melbourne, 35 were admitted to the intensive care unit and five patients died.
Elmer calculated the corresponding number of patients for Wiesbaden and Mainz. “Assuming a population of 500,000 in this region, that would be 400 patients in emergency rooms within 30 hours, which would be a significant number.”
Such events are mainly observed in Australia, where two events per decade are expected. However, due to climate change, the risk could also increase in Europe, leading to more cases of thunderstorm asthma.
Risk Factors
The following environmental factors increase the risk:
High pollen concentrations in the days before a thunderstorm
Precipitation and high humidity, thunderstorms, and lightning
Sudden temperature changes
Increases in aeroallergen biomass and extreme weather events because of climate change
In Australia, grass pollen was often the trigger for thunderstorm asthma. In the United Kingdom, it was fungal spores. In Italy, olive pollen has a similar potential.
Patients with preexisting asthma, uncontrolled asthma, and high serum-specific immunoglobulin E levels are at risk. The risk is also increased for patients with poor compliance with inhaled steroid (ICS) therapy and for patients who have previously been hospitalized because of their asthma.
Patients with hay fever (ie, seasonal allergic rhinitis) have a significantly higher risk. As Elmer observed, 88% of patients in the emergency room in Melbourne had seasonal allergic rhinitis. “Fifty-seven percent of the patients in the emergency room did not have previously known asthma, but more than half showed symptoms indicating latent asthma. These patients had latent asthma but had not yet been diagnosed.”
Elmer emphasized how important it is not to underestimate mild asthma, which should be treated. For patients with hay fever, hyposensitization should be considered.
Reducing Risk
Many factors must come together for thunderstorm asthma to develop, according to Elmer. Because this convergence is difficult to predict, however, preparation and risk reduction are important. They consist of individual precautions and public health strategies.
The following steps can be taken at the individual level:
Identify risk groups, including patients with allergic rhinitis and high serum-specific immunoglobulin E levels. Patients with hay fever benefit from hyposensitization.
Avoid outdoor activities on risky days.
Diagnose asthma, and do not underestimate mild asthma.
Improve therapy compliance with ICS therapy and use maintenance and reliever therapy. This way, the patient automatically increases the steroid dose with increased symptoms and is better protected against exacerbations.
Improve health literacy and understanding of asthma.
Thunderstorm asthma also affects healthcare professionals, Elmer warned. In Melbourne, 25% of responders themselves showed symptoms. Therefore, expect that some of these clinicians will also be unavailable.
Other steps are appropriate at the public health level. In addition to monitoring local pollen concentrations, one must identify risk groups, especially people working outdoors. “It is very difficult to predict an epidemic of thunderstorm asthma,” said Elmer. Therefore, it is important to increase awareness of the phenomenon and to develop an early warning system with emergency plans for patients and the healthcare system.
“Allergen immunotherapy is protective,” she added. “This has been well studied, and for Melbourne, it has been demonstrated. Patients with allergic rhinitis who had received immunotherapy were protected. These patients did not have to visit the emergency room. This shows that we can do something, and we should hyposensitize,” Elmer concluded.
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