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“Biological Monitoring Guidelines” HSA 2011

by Tim O’Sullivan, Nifast Senior Consultant


Chemical Exposure and Biological Monitoring

The Safety, Health and Welfare at Work (Chemical Agent) Regulations, 2001, require employers to prevent, or adequately control, exposure to chemicals. The method typically used to check if chemical exposure is adequately controlled, is to measure the amount of the chemical in the employee’s breathing zone. The measured concentration is compared to the occupational exposure limit value (OELV), which must not be exceeded, and employee exposure should be maintained as low as reasonably achievable.

This air monitoring only gives a measure of the amount of a chemical that the employee is likely to inhale. Employees could also be exposed to the chemical by skin absorption or ingestion, and where these routes of entry are likely, air monitoring may not give an accurate picture of employee exposure.

Biological monitoring involves the analysis of blood, urine, hair or exhaled breath samples from workers, for a hazardous substance or its metabolites (breakdown products in the body). Biological monitoring data reflects the total absorption of a chemical by an individual through all routes of exposure (inhalation, ingestion, absorption through the skin) and thus represents the individual’s actual exposure level. The biological monitoring data can be used to demonstrate the effectiveness of the control measures in place.


Biological Limit Values and Biological Monitoring Guidance Values

Biological Limit Values must not be exceeded. Currently, only one chemical agent has been assigned a BLV – lead and its ionic compounds (70 µg Pb/100ml blood). In this case, biological monitoring must be undertaken if exposure monitoring has measured significant airborne lead concentrations, or previous blood tests have measured significant lead levels.

Compliance with a Biological Monitoring Guidance Value (BMGV) would provide further evidence to demonstrate adequate control.

Appendix 1 of the Guidelines gives a list of BLVs and BMGVs for selected hazardous substances.


Biological Monitoring Programme

The Biological Monitoring Programme must be managed by a competent person. The programme should include arrangements for:

  • - Obtaining the consent of the employee prior to collecting the samples (Appendix 2 of the Guidelines gives a sample consent form).
  • - Ensuring that samples are collected at the appropriate time. For some hazardous substances it is critical that the samples be collected at the end of the shift, samples for other substances can be collected at any time. Sampling times are included in Appendix 1 of the Guidelines.
  • - Quality assurance, covering sampling, storage and transportation. All sample analysis should be performed by a suitably accredited laboratory.
  • - Interpretation of the results, by an experienced medical practitioner.
  • - Reporting the results to the employees.
  • - Maintaining individual health records for each employee who undergoes biological monitoring.


For more information on the above topic, please contact Tim O’Sullivan at tim.o’


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