Module 3: Toxicology - Section 4: Biological Monitoring

TOX 4.3: Lecture: Biological Monitoring and Biological Effect Monitoring - (Continued)

ENVIRONMENTAL (AIRBORNE) MONITORING HAS SOME ADVANTAGES OVER BIOLOGICAL MONITORING:

1. Can collect large volume of air
2. Air homogeneous, simple matrix
3. Much experience accumulated in occupational hygiene
4. Exposure response relationships between air levels of a substance and its adverse health effects are known in some cases
5. Regulations are usually based on airborne standards
6. Relatively non-invasive/fewer ethical problems.

ADVANTAGES OF BIOLOGICAL MONITORING :

By integrating all recent/past exposures and indicating actual absorption, reflects:

1. All routes of absorption: skin, gastrointestinal, and not only inhalation;
2. Relevant properties of the substance which influence absorption, such as solubility, particle size;
3. All exposures over a particular time period, not only at the time of monitoring;
4. Worker’s individual kinetics;
   
   
   Revise your concept of toxicokinetics.  NOTE THAT YOU WILL HAVE TO USE THE TABLE OF CONTENTS TO GET BACK TO THIS POINT - TOX 4.3
   
   
5. The effectiveness of control measures, PPE.

The results that are obtained are thus closer to the concept of dose in toxicology.

PITFALLS OF BIOLOGICAL MONITORING:

1. The laboratory and the test:
   
• Sensitive? - can the test detect low concentrations?
• Repeatable or precise? - If the specimen is split, will the same result be obtained (within or across laboratories)?
• Valid? - does the test give the same result as that obtained by a reference laboratory using the same technique?


2. Collection:

   You have to understand the toxicokinetics of the substance! This includes the half-life, so that the timing is appropriate.

   Question: What biological monitoring would you do for toluene? When in the week would you take the specimen? What practical problems might you encounter doing this?  Answer

   Confounders: (e.g. smoking, diet). Are there any special restrictions that workers need to observe? (Difficult to monitor).

   Contamination / preservation requirements? Work with laboratory to ensure proper collection and transport.

3. Interpretation:

   The BEI is a benchmark - you need to understand the concept. What will you infer about risk from the result? (And what will you tell workers and management?)

   Individual variability may be important. (E.g. some workers may be "slow excretors" and tend to have higher levels for the same exposure. Review this concept in toxicokinetics).

4. Ethics and acceptability:
   • Consent is needed - workers need to understand the whole exercise.
   • Only limited, if any, confidentiality is possible - the whole point is to enable management to act on the results.
   • Will job security be threatened by an abnormal result?
   • Do the workers think you are doing, alcohol, drug or even HIV testing?
   • Are there religious or psychological sensibilities concerning frequent blood testing?

5. Administrative:
   • Must have plan of action if you find abnormal results.
   • Need to have communication worked out.

6. Bottom lines:
   • Biologic monitoring is expensive. It is not a substitute for environmental controls and training.
   • If you don’t know what to do with abnormal results, don’t test.
   • If the results do not result in risk assessment or risk reduction, waste of time and money.
   • You need to write a programme and procedures with all the elements in place.

Answer

What biological monitoring would you do for toluene?    Urine Hippuric Acid

When in the week would you take the specimen?  Within 2 hours of the last shift

What practical problems might you encounter doing this?  Scheduling and logistical problems of collecting specimens from the exposed group.

Postgraduate Diploma in Occupational Health (DOH) - Modules 3: Occupational Medicine & Toxicology (Basic) by Profs Mohamed Jeebhay and Rodney Ehrlich, Health Sciences UCT is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 South Africa License. Major contributors: Mohamed Jeebhay, Rodney Ehrlich, Jonny Myers, Leslie London, Sophie Kisting, Rajen Naidoo, Saloshni Naidoo. Source available from here. For any updates to the material, or more permissions beyond the scope of this license, please email healthoer@uct.ac.za or visit www.healthedu.uct.ac.za. Last updated Jan 2007.
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