Biological monitoring MSc in Occupational Hygiene

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Biological monitoringMSc in Occupational Hygiene

• Finlay Dick
• Department of Environmental Occupational
  Medicine
• University of Aberdeen

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Some definitions

• Biological monitoring (BM) - the measurement of a
  substance or its metabolite in a biological
  medium such as blood, urine or breath
• Biological effect monitoring (BEM) - the
  measurement of pre-clinical effects in exposed
  workers

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Exposure, absorption and effects
Ambient monitoring
Exposure
Internal dose
Adverse effects
Biological monitoring
Biological effect monitoring
Adapted from Cassarett Doulls Toxicology 5th
Edition, ed. Klassen CD pp995. McGraw Hill, 1995
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Objectives

• Evaluate control measures
• Detect early adverse effects
• Assess immunity (biological agents)

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When is biological monitoring appropriate?

• significant exposure is likely
  and there is a
• likelihood of adverse effects

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What can be measured?

• The substance - Trichloroethylene
• A metabolite - Urinary TCA
• An adverse effect - ? liver enzymes

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The ideal test

• Valid technique - reliable - reproducible
• Sensitive and specific
• Acceptable to workers
• Safe, easy to perform
• Non-invasive

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Ethical issues

• Informed consent of employees
  - what is proposed
  - what are the risks
  - what are the
  consequences -
  who gets to see results
• Discussion with Trades unions

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Practical considerations

• Is the metabolite unique to that agent?
• Are there possible confounders
  - alcohol
  - diet
  
  - age
• What to sample - blood
  - urine -
  breath

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Sampling time
Half-life lt 2 hours 2-10 hours 10 - 100
hours gt 100 hours
Optimum sampling time Elimination too rapid to
measure Post- shift or before next shift End of
shift, end of week Random (timing not critical)
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Practical considerations 2

• How much to sample
• Special containers - metal free tubes
  - preservatives
• Storage - refrigerate?
• Quality control - laboratory QA schemes

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Interpreting results - population versus
benchmarking

• Biological exposure indices (BEI) - ACGIH
• Biological monitoring guidance values (BMGV) -
  HSE - Health Guidance value (HGV)
  - Benchmark Guidance Value (BGV)
• Lead monitoring - HSE
  - action level
  
  - suspension level
• Biological Tolerance Values (BAT) - DFG

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Feedback of results

• Employees - individual and group
• HSE - certain agents e.g. lead
  - individual and group
• Employers - anonymised, group data
• Safety committee - group data
• Trades Unions - group data

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Audit and review

• Are results satisfactory
• Is control satisfactory
• Are the trends downwards
• Can we do better

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Useful texts

• Biological monitoring in the workplace (HSG
  167) HSE Books
• Industrial Chemical Exposure - Guidelines for
  Biological Monitoring 3rd Edition. RR Lauwerys, P
  Hoet. CRC Press 2001
• Guidance on Laboratory techniques in
  Occupational Medicine 8th Edition Health
  Safety Laboratory 1999