EXTREME HEAT AND RESPIRATORY HEALTH: WHY SUMMER IS A RISK FOR YOUR LUNGS

In recent years, climate change has turned heatwaves from exceptional events into increasingly frequent and intense occurrences. While the effects of heat on cardiovascular health are now well-known, its impact on the respiratory system is perhaps less familiar.

For people with asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, bronchiectasis, or chronic respiratory failure, periods of extreme heat can be a significant risk factor for flare-ups, hospitalizations, and, in the most severe cases, increased mortality.

The summer season therefore requires special attention to patients with chronic respiratory diseases.

Why does heat put stress on the lungs?

The body has numerous mechanisms to keep body temperature constant. During a heatwave, these systems are heavily challenged and can also affect respiratory function.

High temperatures actually cause:

- increased breathing rate;
- greater loss of fluids through respiration;
- dehydration of the bronchial mucous membranes;
- increased oxidative stress;
- heightened inflammatory response.

In people with chronic respiratory diseases, these phenomena can lead to a worsening of symptoms and lung function.

The role of ozone: a 'summer' pollutant

One of the indirect effects of heat is the increase in tropospheric ozone (O₃).

Unlike the ozone in the stratosphere, which protects against ultraviolet rays, the ozone that forms at ground level is a powerful respiratory irritant.

It develops during the hottest and sunniest days through photochemical reactions involving:

- nitrogen oxides;
- volatile organic compounds;
- sunlight.

Exposure to high concentrations of ozone can cause:

- airway irritation;
- bronchoconstriction;
- worsening of asthma; increase in COPD flare-ups; reduction of lung function even in healthy individuals. For this reason, air quality reports become particularly important during the summer months.

Particulate Matter and Wildfires

Heat waves also contribute to the increase in wildfires.

The smoke from these fires contains high concentrations of:

PM2.5;

ultrafine particles;

carbon monoxide;
toxic organic compounds.

These particles can easily reach the lung alveoli and may lead to:

inflammation of the airways;
increased susceptibility to infections;
worsening of respiratory function;
increased hospital admissions.

More and more studies show that smoke from wildfires is now one of the main new sources of particulate exposure.

Who is most at risk?

The most vulnerable groups include:

patients with COPD;

people with asthma;

individuals with pulmonary fibrosis;

patients on home oxygen therapy;
elderly people;
children;
people with cardiovascular diseases.

In these individuals, even relatively modest changes in temperature or air quality can lead to significant clinical consequences.

Does heat also promote respiratory infections?

Although many respiratory infections are more common during the winter months, intense heat can affect the airway defense mechanisms.

Dehydration of the mucous membranes actually reduces the efficiency of mucociliary clearance, the natural system that helps eliminate particles and microorganisms.

Furthermore, heat stress can create conditions that increase the risk of certain infections, especially in fragile patients.

How to protect respiratory patients during the summer

Some simple precautions can significantly reduce the risk of complications. It is advisable to: avoid intense physical activity during the hottest hours; stay well hydrated; stay in cool and well-ventilated environments; check daily air quality levels; limit outings when ozone or particulate peaks are expected; regularly follow the prescribed therapy. For patients with chronic respiratory diseases, it is important not to stop medications on their own during the summer period. Climate change is now a respiratory health issue. More and more international scientific societies consider climate change one of the main future challenges for pulmonology. Rising temperatures, air pollution, and wildfires are changing the epidemiology of respiratory diseases and require new attention to prevention.

The lung is indeed one of the organs most exposed to environmental effects and acts as a true 'biological sensor' for climate changes. As pulmonologists, we are used to thinking of cigarette smoke as the main enemy of respiratory health. Today, however, we need to broaden this view. Extreme heat and air pollution are becoming increasingly important risk factors, especially for those living with a chronic respiratory disease. Protecting patients means not only prescribing the most appropriate therapy but also teaching them to recognize and reduce environmental exposures that can worsen their condition.