High radon levels in Extremadura

Researchers at the University of Extremadura have measured levels of the radioactive gas radon in 130 workplaces in the Spanish region of Extremadura. The results revealed that 13% of shops, schools, offices, museums and other buildings exceeded EU recommended levels. The record for the highest level of radon is held by a cave in the north of Cáceres in Western Spain.

Along with Galicia and provinces in the Sistema Central mountain range, Extremadura is one the areas in Spain with the highest radon levels. This radioactive gas that naturally emanates from the ground is believed to be the second risk factor in developing lung cancer after smoking.

In order to analyse its presence, a team of physicists from the University of Extremadura (UEX) took 200 radon concentration samples from 130 workplaces across the region ranging from health centres and spas to museums, wine cellars and car parks.

Published in the Journal of Environmental Radioactivity, the study concluded that 13% of workplaces have radon levels higher than 400 Bq/m3. This figure rises to 16% in workplaces that initially do not pose any particular risk, such as shops, theatres, schools, offices, cathedrals and construction material companies. Furthermore, 18% of the places tested showed values of between 200 and 400 Bq/m3.

The European Union recommends that annual average radon concentrations should not exceed 400 Bq/m3 inside existent buildings or 200 Bq/m3 inside newly built constructions. Until now the Spanish Nuclear Safety Council (CSN) also recommended the same reference values. However, this year it has increased protection levels for employees in the workplace to 600 Bq/m3 and to 300 Bq/m3 for buildings where people stay for a prolonged period of time (hospitals, schools or prisons). The WHO has reduced the reference concentration to 100 Bq/m3.

In any case, the study in Extremadura highlights that many facilities exceed recommended limits. In two museums belonging to a small city, radon levels have reached up to 1,182 and 4,337 Bq/m3, respectively. "This data only relates to some rooms but not others where workers usually are. These rooms have levels lower than 200 Bq/m3", states Alejandro Martín, lecturer at the UEX and co-author of the study.

The researcher reiterates that radon gas emanates from the ground and can head towards one place or another, depending on the amount of cracks, the typology of the land, the buildings itself and ventilation. In fact, no large differences have been found between data recorded in underground facilities and those above or at ground level.

Ten minutes of ventilation

In order to avoid its harmful effects in the workplace, experts recommendations are clear: "A good way is to ventilate rooms where you live or work for ten minutes each day even though each room has its own characteristic which should not be forgotten," outlines Martin.

The team was surprised not to find high levels of radon in car parks and wine cellars, where the average has stood at 68 Bq/m3. The study explains that those in charge of facilities should ensure that they are well ventilated in order to avoid problems with carbon monoxide and dioxide concentrations.

The results reveal that in general the granite areas of the northeast and centre of Extremadura naturally have higher radon concentrations due to the rock itself. Granite contains radioactive uranium isotopes which firstly transform into radium and then radon.

Levels of 40,000 Bq/m3 in a cave

The highest gas levels by far (40.000 Bq/m3) have been detected in a cave in the north of Cáceres that is of particular tourist interest. The researchers have chosen not to reveal any details of its location but they have confirmed that the person who spends the most time there (the guide) now only goes into the cave to accompany scientists on sporadic visits and takes care not to exceed to the annual radiation dose.

In this type of cave, poor ventilation can pose a risk for the spectacular geological formations that are common inside.

To carry out the study, scientists used active charcoal canisters (for quick measurements over 48 hours) and nuclear track detectors, which are plastic films from where radon impacts over three months can be counted.

Source University of Extremadura