José Comino (ANEPA): Radon gas requires effective management in the workplace

What is radon gas?

Radon is a radioactive gas belonging to the noble gases group, scientifically known as Rn-222. It is formed naturally through the decay of radioactive elements such as uranium, found mainly in granite and volcanic soils. It is colourless and odourless, which means it cannot be seen or smelled. Although its presence in outdoor air is not usually a problem, it can become a risk when it accumulates in enclosed spaces, such as homes or workplaces.

In Spain, some regions have a higher risk of radon concentration due to their geological characteristics. The granite regions of Galicia, Castile and León, Extremadura, Madrid, Catalonia and Andalusia may present high radon levels, as may the volcanic areas of the Canary Islands.

What occupational risks can be associated with this gas?

Radon is a carcinogenic gas, classified as such by the International Agency for Research on Cancer (IARC) and the United States Environmental Protection Agency (USEPA). According to the World Health Organization (WHO), between 3% and 14% of lung cancer cases worldwide are attributable to radon. 

It is the second most important cause of lung cancer after tobacco, and the leading cause among non-smokers. It is estimated that in Spain, radon could be responsible for between 1,500 and 2,000 deaths annually from lung cancer.

Inhaling alpha particles resulting from the radioactive decay of radon gas can damage lung cells and increase the risk of lung cancer. This makes the gas a public health issue both in the workplace and for the general population.

What regulations related to this issue currently exist in Spain?

In Spain, radon exposure is regulated by several sets of regulations. Since 2001, the Regulation on Health Protection Against Ionizing Radiation has generically regulated exposure to this gas, together with specific public standards and guidelines issued by the Nuclear Safety Council (CSN) for the implementation of this regulation, such as Instruction IS-33, Guide 11-04, etc.   

Royal Decree 1029/2022 of 20 December, which approves the Regulation on health protection against risks arising from exposure to ionizing radiation, establishes the obligation of the employer or activity holder to estimate the annual average level of radon concentration in enclosed workplaces located at ground level or below ground, where workers must regularly access or remain. It also establishes a reference value of 300 becquerels per cubic metre of air (Bq/m³) for radon concentration in workplaces, and sets out measures for protection against radon gas in the workplace if this reference value is exceeded.

Instruction IS-47 of 9 April, issued by the Nuclear Safety Council, approves the list of municipalities requiring priority action against radon and establishes guidelines for radon measurements in the indoor air of workplaces located within them. Under IS-47, municipalities classified as Zone II municipalities under the 2019 Technical Building Code are considered priority municipalities for radon measurement. Likewise, the priority period for radon measurements is established between the months of October and May, avoiding the summer period.

In the field of construction, the DB-HS6 Document “Protection Against Radon” was approved in 2019, establishing measures for new and renovated buildings. Its objective is to prevent radon concentrations from exceeding 300 Bq/m³. This document identifies priority areas for radon measurement and control.

What aspects are considered necessary for proper risk management?

Proper management involves preventing radon risk, for which awareness and education about its hazards are essential. It is important to inform individuals and companies about the risk posed by this gas, as well as to understand the actions that can be taken to reduce its presence.

The first phase of prevention is carrying out an appropriate assessment to estimate radon concentrations in workplaces and determine whether reference values (300 Bq/m³) are exceeded. If high levels are detected, appropriate remediation actions must be taken, including technical or organisational measures, to reduce radon concentration and/or exposure.

If, after implementing remediation measures, reference values are still exceeded, the doses received by workers must be calculated to determine whether the level of 6 mSv/year may be exceeded, in order to classify the exposure as controlled. Based on this, measures such as radon zone signage, specific health surveillance, notification to the competent authority, etc., must be adopted. These dose calculations must be carried out by authorised Radiation Protection Technical Units (UTPR) approved by the CSN.

 What methodologies exist for measuring radon concentrations?

To estimate the annual average level of radon gas in workplaces, a prior planning study is required, including an appropriate sampling strategy. This involves identifying the areas within workplaces where measurements should be taken (ground-floor or below-ground areas with regular access/occupancy, i.e., more than 50 hours per year), the number of measurement points, and the placement of detectors, following the provisions of Instruction IS-47 and CSN Guide 11.04.

Due to the temporal variability of radon gas, long-term measurements must be performed using passive track detectors. The detectors are placed for at least three months (avoiding the summer period). If necessary, measurements are carried out over a full year, especially in underground workplaces, in quarterly periods. After this period, the detectors are analysed in accredited laboratories according to ISO-EN-UNE 17025 for radon analysis. There are also real-time monitoring devices, useful for planning and assessing the effectiveness of mitigation strategies.

Based on the results obtained, a report is prepared, the content of which is established in Instruction IS-47. This report compares the results with the regulatory reference value and provides appropriate recommendations regarding the obligation to implement remediation and control measures to reduce radon concentration or exposure, as well as other obligations that may apply to the employer depending on current regulations.

What is the practical experience of External Prevention Services in measuring, analysing and implementing mitigation measures against high radon concentrations in workplaces?

External Prevention Services play a key role in the different phases of risk management in the workplace. First, they provide information and advice to employers regarding their obligations under current regulations, as well as carry out actions to raise awareness and sensitise the workforce about the risks of radon gas, its prevention and control. Second, they advise and support employers in developing an appropriate strategy to estimate the average radon level in workplaces. And third, they carry out specific actions to manage radon gas risk as part of occupational risk prevention, treating it as one more hazard within the broader framework of workplace health and safety.

For this purpose, actions such as the following must be developed: identification of the hazard in the general risk assessment (physical agents/ionising radiation); specific evaluation as a hygiene risk (definition of the measurement strategy, execution of measurements, and preparation of reports by qualified technicians); information, consultation and participation of workers in accordance with Article 18 of Law 31/1995 on Occupational Risk Prevention and Article 8 of CSN Instruction IS-47; advisory support on possible radon remediation and control measures within the company’s risk control action plan; training of workers on radon gas risks and prevention, in accordance with Article 19 of Law 31/1995 on Occupational Risk Prevention and Royal Decree 1029/2022; health surveillance of workers (those exposed to radon gas, under controlled exposure, with doses above 6 mSv/year); and advisory support on the signage of radon areas (where radon concentrations may lead to an effective dose above 6 mSv/year).

What other radon-related measures should be considered in building construction?

It is important to note that in new buildings, as well as in their renovation, construction techniques must be implemented to minimise radon infiltration. These measures vary depending on whether the buildings are located in Zone I or Zone II municipalities according to the Technical Building Code (CTE). Among the remediation measures that can be implemented are the installation of radon barriers, ventilation and extraction systems, air renewal systems and ground depressurisation systems, among others. In addition, it is important to regularly measure radon levels to ensure they remain within established limits, following the periodicity set out in current regulations.