Dose monitoring, assessment and recording

Dose limits

Why have dose limits?

Dose limits are set to protect workers and members of the public from the effects of ionising radiation. They are set at a level that balances the risk from exposure with the benefits of using ionising radiation. The fundamental requirement is for employers to reduce all exposure to ionising radiations to as low a level as possible and this should be below the dose limits.

What are dose limits?

Dose limits are intended to reduce the risk of serious effects occurring, such as cancer, and are in place to protect the eyes, skin and extremities against other forms of damage. Dose limits are defined in UK legislation and can be found in Schedule 3 of the Ionising Radiations Regulations 2017.

There are different dose limits for different classes of people:

Should I notify my employer if I am pregnant?

It is in your interest and those of your baby to inform your employer as soon as you know you are pregnant. Your employer needs to know this so they can make any necessary changes to protection measures and apply the additional dose constraints. You are not legally required to inform your employer and can choose to keep this private. However, if your employer is unaware that you are pregnant they may not be able to take any further action.

Working safely with ionising radiation: Guidelines for expectant or breastfeeding mothers.  

Am I allowed to exceed a dose limit?

It is an offence under the Ionising Radiations Regulations 2017 to exceed a dose limit.

HSE produces statistics based on the dose information reported annually to the Central Index of Dose Information (CIDI).

Dose monitoring

The risk assessment you carry out for work with ionising radiation should consider the potential radiation exposures an individual may receive during the course of their work (including accidental exposures).

This will help you to:

Controlled areas

What is a controlled area?

A controlled area is one which has been designated by an employer to assist in controlling and restricting radiation exposures. Controlled areas will be designated because the employer has recognised the need for people entering an area to follow special procedures.

Who can enter a controlled area?

Entrance into controlled areas is strictly controlled by the employer. Employees designated as 'classified persons' and outside workers can enter the area where they have been authorised to do so by the employer and have received appropriate training.

If an assessment of the potential exposure shows that work in a controlled area could be done by employees who are not classified persons, HSE would normally expect entry into the controlled areas to be allowed under suitable written arrangements and monitoring to ensure exposures are kept as low as possible. Other workers should only be allowed conditional access and only in accordance with prior written arrangements.

What is a classified person?

An employer must classify an employee where they consider that their employee is likely to receive:

Employees can only be classified if they are aged 18 years or over.

What happens if I am 'classified'?

As a classified person, your employer is required to:

Your employer should periodically review if there is a continuing need for classification.

What happens if I work with radiation for more than one employer?

Where an employee has two or more employers, they should cooperate to ensure that relevant information, in particular relating to exposure, is shared.

The classification of the employee should be determined on the basis of the total dose that the employee is likely to receive from both employers. For example, an interventional radiologist working for both an NHS Trust and a private hospital could potentially receive a greater dose.

Examples of classification:-

Outcome: As entry to a controlled area is not required, neither designation as a classified person nor written arrangements are necessary.

Outcome: On this basis the employer has decided to designate the welder as a classified person.

Outcome: Although designation is unlikely to be appropriate, suitable written arrangements under IRR17 will be necessary to allow entry to the controlled area and the 2 employers should exchange relevant information. A record should be kept of any monitoring in the controlled area and assessment of dose.

Outcome: The firm uses the services of the licensee's radiation protection Adviser (RPA) and it is evaluated that the potential and actual dose would be far below that where designation would be required. The firm concurs with the evaluation and written arrangements under IRR17 (that include assessments of dose) are implemented to allow the technician to enter all required areas.

Outcome: As she is approaching 3/10ths of the appropriate dose limit of 500mSv per year, designation as a classified person will be necessary.

Outcome: The Trust revisited the risk assessment when only one radiologist remained to carry out all the work. This radiologist would now have a significantly increased interventional workload, and based on projected doses to the hands and lens of the eyes particularly, the Trust decided that this remaining individual should be classified. The continuing need for classification was then subject to periodic review.

Outside workers

What is an outside worker?

You are an outside worker under IRR17 when you are:

For example, an engineer (whether they are a classified person or not) works for a firm of maintenance contractors and goes into a controlled area in a hospital to service an accelerator. That engineer is an outside worker and these provisions apply both to their employer and the employer who has control of the controlled area in which they are carrying out the service.

You are not an outside worker when:

What information do I need to complete a risk assessment for outside work?

The employer of the outside worker and the employer in control of the supervised/controlled area should exchange information about the risks so adequate arrangements can be made for worker protection. The type of information that may need to be exchanged includes:

As a classified outside worker, you will use a personal dosemeter issued by your employer and have an estimate of any likely dose from working in another employer's controlled area recorded in your radiation passbook.

I have been issued with a radiation passbook. What does this mean?

You are a classified outside worker. Your employer will issue you with a radiation passbook before you begin working in the controlled area of another employer.

The employer for the controlled area will record in your passbook the relevant estimated dose(s), including all external, internal and non-uniform doses such as those to the lens of the eye, from each period you have worked in their controlled area. The passbook should be updated before you leave site or at agreed intervals for longer periods of work. Your employer's Approved Dosimetry Service will hold these doses in your dose record.

For non-classified outside workers the employer in control of the work area must provide you with suitable written arrangements, including personal dose monitoring or other suitable measurements to estimate dose, to ensure your doses are restricted to as low as possible. Records should be made of any dose monitoring.

How do I monitor my staff?

For your workers designated as classified persons, you must employ one or more approved dosimetry services (ADS) to make assessments of all radiation exposures that are likely to be significant. Dose records for classified persons must be held by an ADS that is specifically approved to keep such records.

You must send your ADS accurate information about your employees and tell them when a classified person ceases to be classified or leaves your employment. The ADS will send a termination record to give the leaving employee.

Make sure your employees know their dose information is being kept by your ADS and that summaries are held in HSE's Central Index of Dose Information (CIDI). Employees are entitled to request from the ADS copies of their own dose records and termination reports including a complete dose history.

Regulation 22 of IRR17 sets out the requirements – see the Approved Code of Practice and guidance on the Regulations.

What should I do with the worker dose summaries from my ADS?

Your ADS will provide you with dose summaries for all your classified workers. These provide you with valuable information to identify (and if necessary investigate) where:

These may point to a need for further training, a review of working conditions or even an investigation of a previously unidentified accident.

Regulation 22 of IRR17 sets out the requirements – see the Approved Code of Practice and guidance on the Regulations.

How do I find a dose monitoring service?

See our approved dosimetry services webpages for information, including a list of HSE-approved services.

How do I ensure the proper care and use of personal monitoring equipment?

You need to make sure that your employees receive adequate training and instruction about the care and proper use of dosemeters you provide so they know:

How should I store dosemeters?

When not being worn, make sure dosemeters are stored:

Make sure dosemeters are not screened by X-ray surveillance equipment such as mail/package monitors, otherwise they may register an incorrect dose.

What do I do if I think a worker has had an overexposure?

An overexposure is where a dose to a worker has exceeded a dose limit. Where you suspect an overexposure to a worker has occurred you must:

Regulation 26 of IRR17 sets out the requirements about investigation – see the Approved Code of Practice and guidance on the Regulations.

Unless the investigation shows beyond reasonable doubt that the overexposure did not occur you must:

What do I do if a worker has had an exposure over 6mSv (but below the dose limit)?

You must ask your ADS to carry out a dose assessment for the worker, including the examination of any personal monitoring device, and inform the worker and HSE of the result.

Updated 2021-10-06