Biological monitoring in the workplace

Information for employees on its application to chemical exposure


What does your employer have to do?

Many jobs involve using chemicals which can harm your health if they are not properly handled. Under the Control of Substances Hazardous to Health Regulations 1994 (COSHH) your employer has to look for the risks to your health from chemicals in the workplace. Your employer must make sure that your exposure to chemicals is either prevented, or properly controlled. To do this he or she may need to measure your amount of chemical exposure.

How can chemicals enter your body?

The main ways that chemicals can enter your body are:

  • by breathing them in;
  • by absorbing them through the skin; or
  • by swallowing them. This can happen if your hands become contaminated at work and you do not wash them before eating, drinking or smoking.

If you are exposed to chemicals in the job you do, the most common way of finding out how much you are exposed to is to measure how much of the chemical is present in the air you breathe in. However, this does not tell you how much of the chemical has actually entered your body. In particular, it does not measure how much has entered your body through the skin or by swallowing. This is why we sometimes recommend biological monitoring for certain chemicals.

How can the amount of chemicals absorbed into your body be measured?

Biological monitoring can be used to indicate how much of a chemical has entered your body. It involves measuring the chemical you are exposed to at work (or what it breaks down into) in a sample of your breath, urine or blood. Which of these three samples is used depends on how the chemical you are exposed to is processed by your body. Biological monitoring is often used together with air monitoring.

Biological monitoring is especially useful when:

  • there is likely significant absorption through the skin; and
  • control of your exposure depends on personal protective equipment and your employer needs to check it is protecting you.

Why should you take part in a biological monitoring programme?

You do not have to take part in a biological monitoring programme*. However, taking part is in your interests because it shows you how much of the chemical you work with has been absorbed by your body.

If your result is high it does not necessarily mean that you will become ill, but it does indicate that your exposure may not be properly controlled. Under these circumstances your employer will probably need to look at how the chemical is being handled to see how exposure can be reduced. To help assess the results from biological monitoring, we publish Biological Monitoring Guidance Values for some substances in the publication EH40 Occupational exposure limits (EH40/97 ISBN 0 7176 1315 1, this is updated annually). * Under some circumstances, where your employer is required under health and safety law to carry out biological monitoring, there is an obligation on you to co-operate. In particular, if you work with lead your participation is required by the Control of Lead at Work Regulations 1980 (to be replaced by new regulations in 1998).

How should your rights as an individual be protected?

If you decide to take part in a biological monitoring programme your employer needs to obtain your agreement before you provide a sample. We recommend that this is done using a consent form. The consent form is an agreement between you and your employer to ensure that:

  • you understand what the test results mean and what action might be taken on the basis of them;
  • you can decide who has access to your result (for example, doctor, safety representative, health and safety manager);
  • you can decide, for example, whether people see your individual result or whether your result is anonymous and pooled with other people's results;
  • the sample you provide will only be analysed for the chemical (or breakdown products of it) that you are exposed to at work;
  • the result of the test will not affect your conditions of employment.

We recommend that your employer involves an occupational doctor in the biological monitoring programme. As well as filling out the consent form you may also wish to discuss with an occupational doctor any risks that are associated with providing the sample, and any concerns over the interpretation of your results.

How can you find out more?

If you have any concerns or questions about taking part in a biological monitoring programme, you should raise them with your employer, safety representative, union representative or the person responsible for organising the biological monitoring programme. More information about your employer's requirement to control your exposure to chemicals which can harm your health can be found in the COSHH Regulations 1994:

COSHH a brief guide to the Regulations: What you need to know about the Control of Substances Hazardous to Health Regulations 2002 (COSHH) Leaflet INDG136 HSE Books 2005 (single copy free or priced packs of 5 ISBN 9 7807 1766 4863) Web version:

HSE publishes a more detailed guide about biological monitoring Biological monitoring in the workplace:

Biological monitoring in the workplace: A guide to its practical application to chemical exposure HSG167 HSE Books 1997 ISBN 0 7176 1279 1

This leaflet is available in priced packs of 15 from HSE Books, ISBN 0 7176 1450 6. Single free copies are also available from HSE Books.

HSE priced and free publications are available by mail order from HSE Books, TSO Customer Services, PO Box 29, Norwich, NR3 1GN, Tel: +44 (0)333 202 5070 Website: (HSE priced publications are also available from bookshops and free leaflets can be downloaded from HSE's website:

Further advice can be obtained from HSE offices (see under Health and Safety Executive in the telephone directory). For other enquiries write to HSE's Information Centre, Broad Lane, Sheffield S3 7HQ.

This document contains notes on good practice which are not compulsory but which you may find helpful in considering what you need to do.

This document is available at:

© Crown copyright This publication may be freely reproduced, except for advertising, endorsement or commercial purposes. First published 10/97. Please acknowledge the source as HSE.

Printed and published by the Health and Safety Executive INDG245 10/97 C250

Added to the web Site 1/04/98

Is this page useful?