Introduction to Occupational Hygiene

Module 1: Occupational Hygiene - Section 1: Introduction to Occupational Hygiene

OH1.6: Standards in Occupational Hygiene

OCCUPATIONAL HYGIENE STANDARDS:

Exposure standards are maximum levels of exposure to substances or agents which are considered acceptable on health and safety grounds in light of current knowledge.

There are two types of exposure standards used by occupational hygienists. These are Threshold Limit Values and Occupational Exposure Limits.

Threshold Limit Values are voluntary standards published by the American Conference of Government Industrial Hygienists, (ACGIH) ⁶. Because they are voluntary, it is not compulsory for companies to comply with them. Instead they are used as recommendations. There are three types of TLVs and these are the time-weighted average (TWA), the short-term exposure limit (STEL) and the ceiling limit (C).

Occupational exposure limits (OELs) are published by the SA Department of Labour and as such they are compulsory. They were first published in 1995 and are contained in Tables 1 and 2 of the Regulations for Hazardous Chemicals Substances. There are two types of OELs, namely, Recommended Limits and Control Limits. These are currently being revised by the Department of Labour.

[For an in-depth discussion of occupational hygiene standards refer to the module on occupational exposure limits]

QUANTIFYING AIRBORNE CONCENTRATION OF CHEMICAL AGENTS:

BY VOLUME:

atmospheric concentration in parts per million (ppm)
usually used for expressing the concentration of gases and vapours

BY WEIGHT

milligrams of a substance per cubic meter of air (mg/m³)
commonly used for expressing the concentration of dusts, fumes or other particles in air

THERE IS A CORRELATION BETWEEN THE TWO:

NUMERICAL

the number of fibres per cubic centimetre of air is used for expressing the concentration of airborne asbestos fibres fibres per millilitre of air (f/cc)

REFERENCES

6. American Conference of Governmental Industrial Hygienists. Documentation of the Threshold Limit Values and Biological Exposure Indices. Volumes I and II, 1996. Published by ACGIH.

9. Department of Labour. Regulations for Hazardous Chemical Substances . Government Gazette No 5549, Published by Government Printers, 25 August 1995.

General Introduction to Occupational Health: Occupational Hygiene, Epidemiology & Biostatistics by Prof Jonny Myers is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 South Africa License.