Thunderstorm Asthma & Climate Change – The Lightning Bolt Moment

Dr Seb Gray, Paediatric Consultant. Twitter: @SebJGray; Email: Sebastian.Gray@nhs.net

The term “thunderstorm asthma” has been used since the early 1980’s when there were reports of asthma symptoms which seemed to coincide with thunderstorm activity.

Since then, thunderstorm asthma has become a well-recognised but rare phenomenon (the perfect storm of environmental, meteorological and specific population factors need to coincide) – however, as climate breakdown progresses, thunderstorm asthma is likely to become much more common.

Who’s at risk of Thunderstorm Asthma?

It mostly affects young people under 30 years – 50% occurs in children. Theoretically, you don’t have to have asthma already to be at risk of thunderstorm asthma – although prior diagnosis, poorly controlled asthma (lower FEV₁, higher FeNO) and asthmatic patients not compliant with treatment are all at increased risk.

People with asthma that hasn’t been formally diagnosed at the time of the episodes are understandably at increased risk, (although I wouldn’t recommend a thunderstorm-tolerance test becomes part of the asthma diagnostic process). The other at-risk group is patients with seasonal allergic rhinitis/ hay fever. For more details, the TAISAR (Thunderstorm asthma in seasonal allergic rhinitis) study has explored risk factors in excellent detail and Xu et al have performed a paediatric specific retrospective analysis on thunderstorm asthma in Yulin, China.

How do thunderstorms cause breathing problems?

Thunderstorms happen more during Spring or Summer – which is also when pollen counts are peaking. The process of how a thunderstorm forms helps to explain the associated breathing problems, so let’s take a look.

1. During spring/summer, there is a warmer layer of wetter air (responsible for that “it’s a bit muggy” sensation) nearer the earth below much cooler air higher in the atmosphere.
2. This warm air rises quickly (up-draft) causing the cooler air to flow downwards (down-draft).
3. The rising warm air quickly cools and the moisture forms clouds and water molecules.
4. The falling cold air generates a strong cross wind across the earths’ surface which picks up pollen grains and fungal spores (like an over-zealous grandparent ruffling the hair of a hair lice and dandruff ridden child).
5. These aero-allergen loaded air currents are then caught in the up-draft and amalgamate into the storm clouds.
6. Within the clouds, the moisture and electricity break the pollen grains and fungal spores into smaller particles, like a natural nebulisation device.
7. As the thunderstorm rains down, the micro-particles shower down and can be more deeply inhaled triggering asthma symptoms.

The above explains most of thunderstorm asthma, but there are other things that also might be contributing:

• Anxiety/stress: It’s not just dogs that get scared by thunderstorms – the link between emotions and asthma exacerbations is indisputable.
• Change in temperature: Any good personal asthma action plan has this trigger on the list; the meteorological process described above can cause sudden changes in temperature which may be the trigger irrespective of all the nebulised pollen!
• Lightning: Ozone can be produced at ground level when lightning strikes. A puff of nitrogen oxide gas can react with sunlight and other gases producing ozone which can independently act as an airway irritant. The ozone layer is very important for climate control when it’s in the right place, but ground level ozone is not a good thing to be inhaling.

What’s the big deal – is this just a storm in a teacup?

The thunderstorm asthma surges have been called epidemics, and the most serious reported episode was in Melbourne in November 2016.

Emergency departments were overwhelmed with thousands of acute respiratory presentations and ten deaths. There was a disproportionate number of people of ethnic minorities who died – with 6 out of the 10 deaths occurring were people of Asian or Indian heritage. Commentary in The Lancet suggests health-seeking behaviour may play a role, but epigenetic factors are also discussed.

Emergency department presentations are probably the tip of the iceberg when it comes to population impact – primary care and emergency services are also badly affected; this study reported a 7-fold increase in respiratory distress symptoms, 50% increase in out of hospital cardiac arrest and 1.5-fold increase in caseload for the ambulance service. The second biggest thunderstorm asthma outbreak was in London in June 1994 involving over 100 admissions, 5 ICU admissions and one death.

What’s Climate Change got to do with it?

Climate change affects all three parts of the thunderstorm asthma triad:

1. Meteorological Factors:

Lightning strikes somewhere on the Earth’s surface 44 times every second and is created by intense heating of the Earth’s surface. Lightning is more common in areas where it’s hot and humid. With climate change increasing both the temperature and humidity, lightning strikes are going to become much more frequent.

In 2014, it was predicted that the number of lightning strikes would increase by 12% for every degree rise in global average air temperature. The mean temperature in the UK has risen by 0.8°C between 1961 and 2020. Whilst we haven’t quite seen this dramatic a rise in lightning strikes, the volatility of weather recently does look ominous. Last year (2022), there were 26,718 lightning strikes in the UK between 14th and 18th August – this is more than half

the total number of lightning strikes during the previous 12 months (total of 49,439).

Geographically, there is a North-South divide with 15-19 days of thunder on average in the South-East compared to 5 days or less in the Northern parts of Scotland (figure below from the Tornado and Storm Research Organisation; TORRO).

2. Environmental Factors:

Pollen seasons are directly affected by global heating – phenological trends show longer and more intense pollen seasons. Ongoing climate change will further change the timing, production and distribution of aeroallergens as the reproductive cycles of plants and fungi are disrupted.

The increasingly temperate climate – alongside increasing atmospheric CO2 – interact to make it a hay fever sufferer’s worst nightmare. Increased CO₂ doesn’t just boost atmospheric pollen but also the spore count of allergenic fungi. Weeds are also likely to proliferate and could become more of a prominent trigger.

Evolution has allowed aero-allergen producing plants and fungi to adapt, survive and thrive despite being exposed to increasing air pollution. More resilient species might be worse for causing allergic rhinitis AND could have more irritant micro-particles, making them a bigger contributor to the thunderstorm asthma triad.

3. Population Factors:

We know that asthma incidence and exacerbation rates will increase as the climate emergency escalates. Increased global temperatures, CO₂ levels, ozone levels, air pollution and aeroallergens will all have detrimental effects on the 339 million people currently diagnosed with asthma worldwide – and the prevalence rates will also increase. The only question is, by how much?

Preparing for the Storms…

Meteorologists can now predict storms so effectively that they’re often named before they are felt or heard. But what should we be advising patients with asthma to do in preparation?

Asthma + Lung UK, as always, offer some great practical tips that focus on getting basic asthma care correct:

• Take your preventer inhaler (this study demonstrated a significant reduction in need for emergency medical care during the Melbourne 2016 thunderstorm asthma epidemic if patients were taking their preventative medicines compared to bronchodilators only; 21% vs 103% respectively)
• Carry your reliever inhaler (and spacer)
• Use a written personalised asthma action plan
• Ensure you go for regular asthma reviews
• If needing your reliever 3 or more times a week, book an asthma review
• Take your usual hay fever treatments during pollen season
• If affected by thunderstorms, stay indoors before, during and after the storm & keep windows closed

May we also suggest…

• Not going to Lake Maracaibo in Venezuela… the most lightning-struck location in the world (with as many as 40,000 lightning strikes in one night!)

• Avoid helicopters – the process of flying acquires a negative charge which can trigger a lightning strike if flying too close to positively charged cumulonimbus cloud.
• Definitely don’t go for a helicopter ride around Lake Maracaibo 🙂
• And some more practical suggestions…
• If on a MART (maintenance and reliever therapy) regimen, ensure the personalised asthma action plan includes information on increasing treatment if thunderstorms imminent.

• Set up “Enable Notifications” (in the weather app of most smart phones) to be informed of any Met Office issued weather warnings (screenshot from the popular fruit-based phone device below)
• The old wives’ tale of how to tell how far away a thunderstorm is DOES actually work (and is endorsed by The Met Office); count the number of seconds between the flash of lightning and the following boom of thunder; divide by 5 for number of miles away or 3 for kilometres.

It’s important to forecast risk and provide early warnings to those at risk. We already have the DAQI (daily air quality index) which helps guide activity levels for asthmatic patients and gives daily pollen counts to prepare for hay fever/allergic rhinitis symptoms. There’s potential for future AI-augmented personalised asthma care based on environmental, meteorological and personal factors. Any solution needs to ensure we don’t widen health inequalities already prevalent in asthma (previously discussed – Health inequalities, poverty and asthma – PaediatricFOAM).

In Summary

Patients and clinicians need to be more aware of the risk thunderstorm asthma – further epidemics are very likely. Use the mnemonic CALM to help advise asthma patients of how to reduce their risk:

C – Continue basic asthma management (take medications as prescribed, carry reliever and spacer, use a personalised asthma action plan, attend asthma reviews regularly, increase treatment if regular SABA use, treat co-morbidities – especially hay fever/allergic rhinitis)

A – Alerts set up to warn about potential thunderstorms

L – Lower risk by staying indoors with windows closed before, during and after the storm

M – Manage worsening symptoms as per the personal asthma action plan seeking help when needed

As paediatricians we are advocates for the children and young people we look after and we therefore have a responsibiliy to continue to fight for change. To find out how you can get involved in tackling the climate emergency have a look at the RCPCH Climate Change Working Group “how to get involved” page and resources for child health professionals.

Dr Seb Gray, Paediatric Consultant at Salisbury NHS Foundation Trust & CYP Asthma Lead for Bath, North East Somerset, Swindon & Wiltshire (BSW)