October 22, 2026, 11:58 am | Read time: 7 minutes
Many dangers to our health are invisible. Often, they lurk in the air. Researchers have now discovered that a naturally occurring gas could increase the lifetime risk of lung cancer (up to age 85) by about 50 percent. The culprit is climate change. However, there are simple methods to protect against it.
Climate change and the associated global warming directly and indirectly pose health risks to people. Increasingly, extreme weather events are being linked to it.1 Many people also suffer directly from extremely high temperatures and drought in the summer. What is rarely discussed: Those who retreat indoors to escape the heat are often more exposed to radon. Researchers have now calculated that the risk of lung cancer in Europe (pooled data for Germany, France, and Italy) could increase by 49 percent for individuals up to age 85.2
What Exactly Is the Study About?
Researchers from Europe and the U.S. have investigated a previously overlooked side effect of climate change. Their hypothesis is that people who protect themselves from heat inhale more harmful radon. Those who spend more time indoors during heat waves, use air conditioning more frequently, or retreat to a cool basement are exposed to higher radon concentrations there.
The scientists first evaluated scientific publications from 2015 to 2025 to determine how weather, buildings, and human behavior affect indoor radon exposure. They then calculated how much the risk of lung cancer could increase in the U.S. and Europe (France, Germany, and Italy). They emphasize that this is not a forecast that will necessarily come true. Instead, they highlight the impact of changed behavior on people’s health, in this case, the risk of developing lung cancer.
Why Does Radon Increase the Risk of Lung Cancer?
According to the Federal Office for Radiation Protection, radon is a radioactive gas that forms during the natural decay of uranium in the soil.3 Its short-lived decay products emit alpha radiation to the lungs and bronchi when inhaled. The International Agency for Research on Cancer (IARC) classifies radon as a known carcinogen, and worldwide, an estimated three to 14 percent of lung cancer deaths are attributed to radon. The radiation directly damages the genetic material of cells in the bronchi, among other things, through double-strand breaks. Smoking significantly amplifies the effect.
In Germany, approximately 6.3 percent of all lung cancer deaths are statistically attributed to radon in homes. Since the gas is invisible and odorless, its concentration in a home can only be determined through measurement. The concentration is particularly high in basements and lower floors, as well as in enclosed spaces that use air conditioning. Air conditioners typically recirculate existing indoor air and cool it. If there is not enough fresh air, radon can accumulate in enclosed spaces.
How Did the Researchers Calculate the Health Risk?
To calculate the lung cancer risk from radon, the researchers used a typical model house. In it, the radon concentration is 74 Bq/m³ (becquerels per cubic meter) on the ground floor and 185 Bq/m³ in the basement. Based on these values, four scenarios were simulated:
- First Scenario: This reflects the current situation, where people spend an average of 21 hours a day indoors and three hours outdoors.
- Second Scenario: Here, air conditioning is used more frequently during three summer months, increasing indoor radon concentration by about 60 percent.
- Third Scenario: Here, people spend four more hours daily in the basement and, on average, one hour less outdoors.
- Fourth Scenario: In this case, both Scenario 2 and Scenario 3 occur simultaneously.
The concentrations were converted into a radiation dose over time, measured in “Working Level Months.” The authors calculated using all 8,766 hours of a year, both indoors and outdoors. For the lung cancer risk, they used the BEIR VI model from the U.S. National Academy of Sciences, which weights the radiation based on how long ago it occurred, the person’s age, and the concentration level.
The researchers combined this with national data on lung cancer mortality and survival rates from 2015 to 2019 for people up to age 85. The result is given per 10,000 people. To verify the results, they used two other models, one including miner data and the other residential studies.
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What the Data Analysis Revealed
The data analysis showed that in the current scenario, the risk of death from lung cancer (caused by radon) in the U.S. is 91 out of 10,000 people. If more people use air conditioning, the risk rises to 104 deaths. And if more people spend time in the basement, it could be 119 deaths per 10,000 people. In the fourth scenario, where people spend more time in air-conditioned rooms and the basement, it leads to 137 lung cancer deaths per 10,000 people.
For Europe (pooled for France, Germany, and Italy), the researchers calculated slightly lower numbers:
- In the current scenario, there are about 86 deaths from radon-induced lung cancer per 10,000 people up to age 85.
- The second scenario, with more use of air conditioning in living spaces, would lead to 98 deaths.
- In the third scenario, with more time spent in basements, there would be 112 deaths per 10,000 people.
- In the fourth, combined scenario, there would be 128 deaths. This means that the risk of lung cancer in Europe for people up to age 85 could increase by about 49 percent if they use more air conditioning in enclosed spaces and simultaneously spend time in basements. Notably, there is a synergy effect: The combination of air conditioning and basement time disproportionately increases the risk–the increase in the fourth scenario (+42 cases) is greater than the sum of the two individual effects (+38 cases).
The authors emphasize that the estimates were cautiously calculated. Effects such as warmer soils, droughts, floods, and thawing permafrost are not included. They also point out important limitations: The use of air conditioning in Europe is currently lower than in the U.S., and everyday influences (such as radon levels at workplaces) were simplified in the model.
How to Reduce the Risk of Lung Cancer from Radon
In evaluating the study, the researchers explain that these are hypothetical calculations and not already observed additional cases of radon-related illnesses. Nevertheless, their study draws attention to an underestimated factor in lung cancer cases. It also shows that there are ways to reduce radon exposure. The Federal Office for Radiation Protection recommends the following measures:
- Regular measurement: There are passive measuring devices (costing around 30 to 50 euros) that can be placed in living spaces. These can measure the exact radon exposure in individual rooms over months. This is especially important in winter months when rooms are closed and more radon accumulates.
- Assess values: The reference value in Germany is 300 Bq/m³ on an annual average.
- Ventilation: As an immediate measure, regular shock or cross-ventilation helps, where the indoor air is exchanged within minutes.
- Sealing: Seal pipe penetrations, cracks in the floor slab and basement walls, and the transition from the basement to the ground floor. Otherwise, radon can spread throughout the house through damage in the basement and ground floor.
- Technical solutions: If that is not enough, there are experts who can extract soil air from under the house.
The study authors emphasize that cool rooms and air conditioning should not be avoided during extreme heat to prevent heat strokes. However, they recommend technical solutions such as controlled residential ventilation with heat recovery to keep radon levels low even with closed windows. They also point out that smoking and radon mutually reinforce each other. Those who avoid tobacco also reduce the lung cancer risk from radon. Following these tips can significantly reduce the risk of lung cancer from radon.