Radon Awareness

Dr Julian MacDonaldRadiation Protection AdviserMedical Physics Department

Radon

• Radiation and Radioactivity• What is Radon ?• What are the dangers of Radon ?• Radon affected areas• Duties of employers• Grosvenor Road specific issues

Radiation and Radioactivity• Everything in the world is made of elements, the smallest part of which

is an atom.• Some atoms are unstable and change into other stable atoms (decay).• During this decay, the atoms emit energy in the form of radiation, e.g.

alpha, beta and gamma radiation.• Materials consisting of such unstable atoms are said to be ‘radioactive’.• Different forms of elements exist – isotopes – and those which are

radioactive are called radioisotopes.• The radioactivity of a material tells you how many unstable atoms are

decaying.• The more unstable atoms, the higher the radioactivity, the more

radiation is being emitted.• Radioactivity is measured in Becquerels (Bq), which is the number of

atoms decaying every second.

Radiation Doses

• When radiation enters tissue, it deposits energy as it interacts and this causes damage to the atoms that make up cells in the body.

• Cell damage can lead to induction of cancer.• Radiation dose is a measure of the amount of energy

deposited by radiation.• The higher the radiation dose, the more damage is done to

cells in the body.• Radiation dose is measured in microSieverts (Sv)

Background RadiationUK average annual radiation dose from background is 2700 Sv.

What is Radon ?• Radon (radioisotope Rn-222) is a naturally occurring radioactive

gas that seeps out of the ground.• It is produced through the decay of naturally occurring

radioactive materials in the ground, i.e. Uranium-238.• U-238 (and hence Rn-222) is found predominately in: light-

colored volcanic rocks, granites, dark shales, sedimentary rocks that contain

phosphate and metamorphic rocks derived from these rocks • It has a half-life of 3.8 days, which gives it time to escape from

the ground and accumulate in buildings.

What is Radon ?• Radon (radioisotope Rn-222) is a naturally occurring radioactive

gas that seeps out of the ground.• It is produced through the decay of naturally occurring

radioactive materials in the ground, i.e. Uranium-238.• U-238 (and hence Rn-222) is found predominately in: light-

colored volcanic rocks, granites, dark shales, sedimentary rocks that contain

phosphate and metamorphic rocks derived from these rocks • It has a half-life of 3.8 days, which gives it time to escape from

the ground and accumulate in buildings.• It can build up to high levels in underground premises

(basements and caves) and at ground-level (due to them being at slightly lower pressure than surrounding atmosphere).

Radon Levels

• Radon levels are measured in the amount of radioactivity per unit volume, i.e. Bq/m3.

• Outdoor levels are about 4 Bq/m3.• Indoor levels range are about 20 Bq/m3 on average (range 5 –

>10,000).• The Action Level for domestic premises is 200 Bq/m3.• The Action Level for work premises is 400 Bq/m3 (equivalent to the

domestic level of 200 Bq/m3 taking into account differences in residence time)

Variations in Radon Levels• Radon levels vary over time; there are seasonal variations due

to changes in pressure within buildings (e.g. due to heating in winter) and ventilation (more in summer months)

• The winter levels determine the need for action – so measurements performed at other times of the year have to be seasonally adjusted

Where is Radon Found ?

• Radon-affected areas are those in which 1% or more of homes are above the Action Level (200 Bq/m3), i.e. any non-white areas

What are the Dangers of Radon ?• Radon undergoes further radioactive decay to produce other

radioactive materials, some of which are in solid form:

• As a gas, Radon is inhaled by people occupying buildings where radon accumulates.

What are the Dangers of Radon ?• Most of the actual Radon is exhaled

harmlessly, but the solid-form daughter products attach to dust and water droplets and remain lodged in the lungs.

• The decay of these daughter products results in further radiation (mainly alpha particles ()), which are then deposited in the lungs, delivering a radiation dose.

• This radiation dose has the potential to cause lung cancer.• Radon is the 2nd largest cause of lung cancer in the UK.• It has been estimated that over 1,100 lung cancer deaths each

year in the UK are due to Radon exposure.• However smoking causes over 28,000 lung cancer deaths p.a.

Grosvenor Road – Levels and Risks

• Exposure at work depends on radon level, how long you have worked there, and number of hours worked per week.

• “Project Workers Meeting Room”• 2012 Actual measured value – 300 Bq/m3

• => Winter-corrected maximum value - 520 Bq/m3

• Assume occupancy of 4 hours per working day day for 5 years at 500 Bq/m3

• The additional risk of lung cancer is around 1 in 10,000 (non-smokers)• Natural risk of lung cancer is around 40 in 10,000 (non-smokers)• (1 in 3 people in the UK get cancer in their lifetime)

Duties of Employers

• HSW Act 1974 – “employers must, so far as is reasonably practicable, ensure the health and safety of employees and others who have access to their work environment”

• Employers must assess health and safety risks, including radon.

• Ionising Radiations Regulations 1999• Below ground – all occupied workplaces• Above ground – ground-floor rooms in buildings in Radon-

Affected Areas

Radon Assessment – How ?• Radon levels can be assessed using a variety of detectors:

• Alpha Track Detectors (ATDs) are small plastic passive detectors which contain a thin polymer film onto which tracks from alpha particles are etched.

• ATDs are typically left in place for 3 months and are then sent to an accredited laboratory for analysis.

• Continuous monitors• Can give hourly readings but..• Interpret readings with caution –

due to significant variations in radon levels over short time periods

If Radon Exceeds Action Level

• If the radon levels exceed the 400 Bq/m3 action level, immediate action:– The HSE must be notified.– Staff must be advised.– Remedial action must be undertaken promptly to reduce Radon levels.– Otherwise a Radiation Protection Adviser consulted and doses to workers must be

restricted through reduced occupancy until remedial work is undertaken.• e.g Grosvenor Road – ensure occupancy is less than 400/520~ 6 hours per day

Engineered Solutions• There are several solutions that can be employed to reduce

radon levels.• Mainly involve increasing ventilation to remove radon or

sealing against radon entering in the first place.

Re-assessing Radon• A continuous programme of monitoring should be carried

out with maximum periods between re-assessments determined by initial measurements:

Initial level: HSE Guidelines Advised Monitoring Period (RPA):

“significantly less than 400 Bq/m3”

“of the order of once every 10 years”

10 years

“just below 400 Bq/m3”

“less than 10 years” 5 years

above 400 Bq/m3 (and following engineered solution)

“significantly more frequent” 2-3 years

• Re-assessment should also be performed if there are any significant changes to the building or its occupation