Module 3: Toxicology - Section 4: Biological Monitoring

TOX 4.4: Questions and Answers on Biological Monitoring

Biological monitoring: Answers to questions

Question 1:

What is the relationship of biological monitoring to medical surveillance?

Answer 1:

Medical surveillance is the broader concept and encompasses all regular examinations, including interviews, biological monitoring and clinical investigations such as lung functions and audiometry. Biological monitoring is reserved for the laboratory measurement of substances in body fluids.

Question 2:

How much carboxyhaemoglobin do smokers have?

Answer 2:

Typically 4-5%, up to 10%. This needs to be taken into account in assessing an occupational effect of carbon monoxide and methylene chloride.(Back to page 2)

Question 3:

What is the ACGIH? What is their relationship to the US government?

Answer 3:

American Conference of Governmental Industrial Hygienists. Confusingly, they are a non-governmental organisation. Their standards are regarded as authoritative, although the standards may or may not coincide with American statutory (OSHA) limits. Their standards have been criticised as too subject to corporate influence. This critique will be covered in a later block. (Back to page 2)

Question 4:

You find that two workers exposed to arsenic have urine arsenic concentrations of 60 µg/g creatinine and 300µg/g creatinine respectively. Describe the steps you would take and what you would tell the workers. (Back to page 2)

Answer 4:

Ideally, workers will know in advance what the programme is about so that a finding that their concentration are above the BEI will not require starting at the beginning. It is important to emphasise that these results do not mean that they have been adversely affected or that they ill.

In the first case, the level is just above the BEI and is probably within biological and/or technique variability. The second one is much higher than the BEI and if accurate, suggests a real overexposure. One would probably want to repeat these tests.

If the results persist, then action needs to be taken to reduce exposure if this is ongoing. Management needs to be informed.

If one uses the approach to lead as a standard, then the workers need to be moved out of the exposure area until their BEI returns to below the acceptable level. In the meantime, the workplace/work station/work practice controls need to be investigated to see where the breakdown was.

Question 5:

What biological monitoring would you do for toluene? When would you take the specimen? What practical problems might you encounter in setting up a procedure for the regular monitoring of toluene? (Back to page 2)

Answer 5:

Urinary hippuric acid or urinary toluene. The half-life of hippuric acid is 1 to 2 hours, so it has to be done at the end of the shift. An important practical problem arises if exposures are not continuous. You then have to set up a procedure that is able to anticipate when exposures are taking place and is flexible enough to respond to changing exposure circumstances. This requires that the occupational health nurse be closely in touch with production circumstances.