Module 1: Occupational Hygiene - Section 3: OH Standards
OH2.1: Introduction to Occupational Hygiene Standards


The objective of this Module is to introduce the concept of occupational hygiene standards and their application in evaluating working conditions.


  • understand the basis for development of occupational standards;
  • differentiate between the various occupational exposure limits;
  • apply an occupational hygiene standard in evaluating risk of developing adverse health effects; and
  • understand the strengths and limitations of occupational hygiene standards.


Occupational hygiene standards are standards against which occupational exposure to various substances are judged. The first set of occupational hygiene standards was first proposed in the late 19th century. They were for organic solvents and irritant gases. However, it was not until the late 1920s that the first list of national standards was published in the USSR. Hygiene standards are designed as an aid in preventing occupational diseases.

The hygiene standard is a numerical value defining an acceptable level of exposure of an individual to a specific substance or agent. An occupational hygiene standard is used as a practical measure of compliance. For example, if a workplace meets applicable standards that implies that the health of workers is assured.


Different countries have published various lists of occupational hygiene standards and they are referred to according to the country of origin. In the US the most widely known limits are the Threshold Limit Values (TLVs) , Maximum Allowable Concentrations (MACs) in the USSR and Occupational Exposure Limits (OELs) in the United Kingdom. Few countries have taken up the challenge of standard setting due to it being costly, complex and time-consuming. South Africa has adopted the Occupational Exposure Limits developed in the United Kingdom in its current legislation.

The difference in exposure standards is a reflection of the approach taken in standard setting (no deviation from 'normal' vs. prevention of diseases); conflicting interpretation of scientific evidence; political pressure; economic pressure; and worker concerns.

Basically there are two types of occupational hygiene standard, namely, voluntary and compulsory standards.

Voluntary standards:

Voluntary standards are generally published by private sector or non-governmental organisations. These standards, as the name implies, do not have the force of the law and they serve as recommendations or guidelines. Voluntary standards are designed to protect nearly all workers and as such they tend to be more stringent than compulsory standards. Examples of voluntary standards are the TLVs published by the American Conference of Governmental Industrial Hygienists,an organisation of professional occupational hygienists. Because voluntary standards are revised or amended frequently and more easily (in the case of occupational health professional organisations with less obstruction by interested parties), they are more likely to be up-to-date with respect to incorporation of current scientific knowledge.

Compulsory standards:

Compulsory standards are promulgated by government or state agencies and are therefore legally enforceable. Compulsory standards are not intended to protect every worker in the workplace due to a social compromise between government, industry and worker organisations. Unlike voluntary standards, compulsory standards are infrequently revised due to delays in the process of updating legislation attendant on a complex and contested political process. This, in many instances, causes government standards to be outdated as far as protection of workers' health is concerned. Some voluntary standards developed by NGOs have been incorporated into law.For example in the 1980s in the USA, many of the ACGIH TLVs were accepted by the Occupational Health and Safety Administration.


1. Pepper A and Evans G. Occupational Exposure Limits; Principles of Air Sampling; Particle Behaviour. In: Module C, NEBOSH Diploma. Published by University of Portsmouth, 1992.

2. Ehrlich R. The Hazardous Chemical Substances Regulations: Occupational Health Comes of Age in South Africa. OccHSA Vol 1 No 6, Nov/Dec 1995.

3. American Conference of Governmental Industrial Hygienists. Documentation for Threshold Limit Values and Biological Exposure Indices. Volumes I and II, 1995.

4. Todd AL. Evaluation of the Work Environment. In: ILO Encyclopaedia of Occupational Health and Safety Published by the International Labour Office.

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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