Radon In The Workplace & School

Radon-222 is one of the decay products of uranium-238 which occurs naturally in many rocks and soils. Radon is a gas and high levels within the air in soil are possible, especially if the local geology contains rocks with higher levels of uranium. Granite tends to have high levels of uranium and so radon levels are particularly high in some granite areas within the UK. However, it is important to recognise that high radon levels can be found outside granite areas and conversely that not all granite areas are associated with high radon levels.

Radon can seep out of the ground and build up in confined spaces. High concentrations can also be found in buildings because they are usually at slightly lower pressure than the surrounding atmosphere and so tend to suck in radon (from the soil) through cracks or gaps in the floor.

Most radon gas breathed in is immediately exhaled and presents little radiological hazard. However, the decay products of radon (radon daughters) are solid and are themselves radioactive. These decay products attach to atmospheric dust and water droplets which can become lodged in the lungs and airways when breathed in. They are thus likely to irradiate the respiratory tract. Some radon daughters are alpha emitters and will cause significant damage to the cells of the respiratory tract. The relative amounts of radon daughters to radon gas depends radon ingress rates. Radon gas is measured in Becquerels per cubic metre, Bq/m 3 (ie air activity concentration).

Radon is now recognised to be the second largest cause of lung cancer after smoking and is estimated to cause 2,500 cancer related deaths in the UK every year. Radon contributes by far the largest component of background radiation dose received by the UK population and, while the largest radiation doses arise in domestic dwellings (due to the longer time spent there), significant exposures are possible in workplace or school.

Legal requirements

Under the Health and Safety at Work etc Act 1974, the employer bears the principal duty to ensure the health and safety of employees and others who have access to their work environment. The Management of Health and Safety at Work Regulations 1999 require the assessment of health and safety risks and this must include radon if a workplace is located in a radon Affected Area, or is an underground workplace likely to be affected. For ground floor and underground workplaces this risk assessment will almost certainly require radon measurements to be carried out. Additionally, the Ionising Radiations Regulations 1999 come into effect where radon is present above the defined level of 400 Bq/m3 and employers are required to take action to restrict resulting exposures. The HSE and Local Authorities are responsible for enforcing these regulations in various workplaces and schools.

Testing

Radon surveys should be conducted in any building where its location and characteristics suggest elevated levels may be found. AlphaLab's fully validated three month long-term alpha-track test should be deployed for measuring radon in the workplace or school. If however employees or parental groups are agitated and have raised concerns AlphaLab's activated charcoal short-term radon screening test may be deployed to provide a quick indication of radon levels.

The Building Regulations 2000 ( England and Wales), the Building (Scotland) Regulations 2004 and Building Regulations Northern Ireland (as amended 1990), supported by BRE reports BR211, BR376 and BR413 respectively require that buildings and buildings extensions (workplaces and dwellings) constructed after 2000 in radon affected areas have protective measures installed during construction. These measures are described below. However, since it isn’t possible to accurately assess the severity of a radon problem on a particular site until the building has been constructed and occupied, employers must still test as described irrespective of the age of the building.

Experience has shown that radon concentrations in adjacent buildings, even adjoining ones, can differ by as much as a factor of ten (for many reasons including local geology or building design and construction), so measurement results from neighbouring properties are unfortunately not a reliable indicator.

What will the test results mean?

Where the workplace measurements show radon levels below 400 Bq/m3, then the only further action required is decide when the risk assessment will be reviewed. This figure of 400 Bq/m3 is comparable with the Action Level of 200 Bq/m3 for homes, taking into account that most people spend much more time in their home than at work. For occupied areas with levels above 400 Bq/m3, the employer may need to immediately take steps to manage occupational exposures pending any decision they may take to reduce the radon levels by engineered means.

Practical control of radon levels in buildings

Radon enters a building primarily by airflow from the underlying ground and protection measures for reducing levels inside workplaces vary depending upon the severity of the problem and the type of building construction. New buildings can be protected during construction by installing a ‘radon proof barrier’ within the floor structure and, in more seriously affected areas, provision of a ventilated sub-floor void or a 'radon sump' (A radon sump is a small, bucket sized, cavity under the floor with an electric pump drawing air from it. This reduces the normal under floor pressure with respect to radon in the soil and vents the radon gas outside the building where it quickly dissipates).

In existing buildings, it is not possible to provide a radon proof barrier and so alternative reduction measures are used depending upon the severity of the problem. Such measures include improved under floor and indoor ventilation in the area, sealing large gaps in floors and walls in contact with the ground, positive pressure ventilation of occupied areas, and installation of radon sumps and extraction pipework.

If it is necessary to reduce radon levels by engineered means, the employer should ensure that the radon levels in the area are remeasured immediately after installation in order to verify its effectiveness.

What next?

As with all health and safety risk assessments, their applicability should be kept under review. Where significant changes are made to the fabric of a building or to the work processes carried out within it, then the need to remeasure the radon levels should be considered. If neither these or any other significant changes occur, it is still suggested good practice to assign a maximum period upon which remeasurement of the radon levels will occur. Whilst it is the employer, in consultation with the Radiation Protection Adviser where appropriate, who is best placed to determine the frequency of any remeasurements, HSE suggests the following as a guideline only:

1/ where radon levels were found to be significantly less than 400 Bq/m3 at the initial measurement, the period of remeasurement might be of the order of once every 10 years;

2/ where radon levels were just below 400 Bq/m3 at the initial measurement the suggested period for remeasurement will be every 3 years;

3/ where radon levels were above 400 Bq/m3 at the initial measurement and measures taken to reduce radon exposures (Eg. engineered systems or occupancy restrictions), the remeasurement period will need to be frequent.

If engineered systems are fitted to reduce levels then procedures must be in place to ensure that they are working correctly and kept switched on!

Domestic radon exposure of employees

In radon Affected Areas, employees could also be receiving significant exposure at home. Employers are strongly encouraged to recommend home testing to their employees who live in the radon Affected Area.