XN000022-1993-01-29 — Page 11

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FRIDAY, JANUARY 29, 1993

"THE OELS REPRESENTED AIRBORNE CONCENTRATIONS OF INDIVIDUAL CHEMICAL SUBSTANCE," HE SAID.

"REFERENCE IS MADE TO AMERICAN CONFERENCE OF GOVERNMENTAL INDUSTRIAL HYGIENISTS' LIST OF THRESHOLD LIMIT VALUES AND STANDARDS OF OTHER OVERSEAS ORGANISATIONS IN ESTABLISHING THE OELS, HE ADDED.

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DR CHAN STRESSED THAT BEFORE APPLYING OR INTERPRETING THE OELS, IT WAS IMPORTANT TO STUDY THOROUGHLY SOME ASPECTS REGARDING THE OELS.

"THE OELS ARE NOT FINE DIVIDING LINES BETWEEN SAFE AND DANGEROUS CONCENTRATIONS, THEY ARE USED AS GUIDELINES TO ASSESS THE WORKING ENVIRONMENT AND TO INDICATE WHETHER ADDITIONAL CONTROL MEASURES ARE REQUIRED, HE POINTED OUT.

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"EXPOSURE TO AIRBORNE CHEMICALS SHOULD ALWAYS BE KEPT AS LOW AS REASONABLY PRACTICABLE EVEN THOUGH THE CURRENT OELS ARE NOT EXCEEDED, HE SAID.

DR CHAN SAID ONE OF THE REASONS WAS INDIVIDUAL SUSCEPTIBILITY, AS A SMALL PROPORTION OF WORKERS MIGHT STILL BE AFFECTED BY SOME CHEMICAL SUBSTANCES AT CONCENTRATIONS AROUND OR BELOW THE OELS.

ANOTHER REASON IS THAT MANY OF THE OELS WERE ESTABLISHED ON CURRENT BUT LIMITED SCIENTIFIC TOXICOLOGICAL KNOWLEDGE OF THE SUBSTANCES.

HE ALSO POINTED OUT THAT THE EVALUATION OR MONITORING OF HAZARDS OF ATMOSPHERIC CONTAMINANTS IN WORKPLACES WAS OFTEN A COMPLEX TASK.

"IT INVOLVES THOROUGH UNDERSTANDING OF THE WORK PROCESSES, GOOD KNOWLEDGE OF THE TOXIC EFFECTS OF THE CHEMICAL SUBSTANCES, ADOPTION OF APPROPRIATE SAMPLING STRATEGY, SUITABLE CHOICE OF SAMPLING AND ANALYTICAL

OTHER METHOD, CORRECT USE OF SAMPLING EQUIPMENT AND MANY FACTORS, HE SAID.

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"THEREFORE, IT IS ESSENTIAL THAT THOSE APPLYING OR INTERPRETING THE OELS IN SUCH HAZARD EVALUATIONS SHOULD BE SOMEONE WITH APPROPRIATE TRAINING, KNOWLEDGE AND EXPERIENCE IN OCCUPATIONAL HYGIENE PRACTICE, HE ADDED.

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DR CHAN ALSO SAID IT WAS IMPORTANT TO NOTE THAT THE OELS ONLY CONSIDERED ABSORPTION OF CHEMICALS BY INHALATION AND WERE VALID ONLY WHEN SIGNIFICANT SKIN ABSORPTION DID NOT OCCUR.

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**THEY ARE NOT RELATIVE INDICES OF TOXICITY OF THE CHEMICAL SUBSTANCES AND SHOULD NOT BR USED IN THE EVALUATION OF NON- OCCUPATIONAL EXPOSURES SUCH AS EVALUATION OF COMMUNITY AIR QUALITY, HE SAID.

"THE OELS MAY NOT ВЕ APPLICABLE DIRECTLY TO POLLUTION PROBLEMS BECAUSE THE EXPOSED POPULATION MAY HEALTH STATUS VERY DIFFERENT FROM WORKERS IN INDUSTRY.

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INDOOR AIR HAVE

THEIR

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