|
Module 3: Toxicology -
Section 4:
Biological Monitoring |
TOX 4.2: Lecture:
Biological
Monitoring and Biological Effect Monitoring |
LEGISLATION:
-
OHSA: Regulations
for hazardous chemical
substances 1995. (Open up the
book "Regulations", and then open the book "Hazardous Chemical
Substances Regulations", 1995).
"an
employer shall ensure that an employee is under medical surveillance if
the employee may be exposed to a substance listed in Table 3"
Table 3:
Substances for which BEIs exist..
- OHSA:
Lead Regulations,
2001. (Open up
the book "Regulations", and then open the book "Lead Regulations,
2001").
DIFFERENT TYPES OF WORKPLACE
MONITORING:
Environmental monitoring:
Concentration of a substance in
air, on surfaces, etc. (province of occupational hygiene).
Biological monitoring:
Concentration of a substance in
body tissue /excreta.
Biologic effect monitoring:
Reversible physiological
effects of a substance on an organ system.
Screening:
Early disease, or a marker of acquired or genetic susceptibility
(overlaps with biological effect monitoring).
Question
1:
What is the relationship of biological monitoring to medical
surveillance? (
Answer)
SUBSTANCES WITH BEIs IN TABLE
OF THE HCS REGULATIONS:
Metals:
arsenic*, cadmium, chromium VI*, mercury*, lead*;
Aromatic
solvents: benzene*, ethyl
benzene, chlorobenzene, nitrobenzene, phenol*, toluene*, xylene*;
Chlorinated
solvents: Perchloroethylene*,
trichloroethylene*, methylchloroform*;
Other
solvents: carbon disulfide,
dimethylformamide, methanol*, methyl ethyl ketone (MEK)*, methyl
isobutyl ketone, n-hexane*, styrene;
Pesticides:
parathion*, pentachlorophenol;
Miscellaneous:
Aniline, carbon monoxide*, fluorides, furfural.
* You are more likely to
encounter these in practice.
SUBSTANCES IN TABLE 3 FOR
WHICH BIOLOGIC EFFECT MONITORING CAN BE DONE:
- Cholinesterase*
(organophosphate, carbamates);
- Carboxyhaemoglobin* (carbon
monoxide, methylene chloride);
Question
2:
How much carboxyhaemoglobin do smokers have? Why is this relevant to
biological monitoring? (
Answer)
- Methaemoglobin (aromatic
amines and nitro-compounds);
Note:
The iron in haemoglobin is normally in "ferrous" form, i.e. Fe2+.
Methaemoglobinaemia is a pathological (cyanotic or "blue blood") state
in which the iron is oxidised to the "ferric" form, i.e.Fe3+.
(If you cant remember which way around this goes, suffice to say that
"in methaemoglobinaemia the iron is chemically altered so that the
molecule malfunctions".)
- Zinc protoporphyrin* (lead);
- Urinary enzymes e.g. beta 2
microglobulin for (cadmium), N-acetyl glucosaminidine (NAG) (lead);
- Mutagenic / ?
precarcinogenic changes.
* Likely to encounter in practice.
BIOLOGICAL EXPOSURE INDEX
(BEI):
- ACGIH concept
Question
3:
What is the ACGIH? What is their relationship to the US government? (
Answer)
- The BEI is a reference level
for occupational exposure
- Linked to TLV for inhaled
substances
Task::
Revise your understanding of TLV.
- BEI = concentration observed
in a healthy worker doing (non-strenuous) work for 40-hour work week at
TLV-TWA
- Thus incorporates both a
measure of exposure and of risk (via the TLV equivalence).
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. (
Answer)
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? (
Answer)
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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