Case 2

HYGIENE STANDARDS

1. Introduction

We have seen that most of the chemical and physical agents found in industry today are potentially harmful if they are not handled correctly or are present in excessive quantities in the workplace environment. The aim of occupational hygiene is to prevent or reduce exposure to such agents.

Hygiene standards or occupational exposure limits (OELs) are useful measures with which exposures to chemical and physical agents in the workplace environment can be compared. There are a few key points to remember about hygiene standards, namely:

 They are not an index of toxicity.

 They do not represent a fine demarcation between good and bad practice.

 They are based on the current best available information and are liable to change.

 If there is not a hygiene standard set for a chemical substance, it does not mean that substance is safe.

 Good occupational hygiene practice is to keep airborne contaminants to as low a level as possible, not to just below the relevant hygiene standard(s).

 They apply to occupational exposure of adults. They are not applicable to environmental exposure where more susceptible groups exist e.g. pregnant women, children, infirm.

 For chemicals they generally relate to airborne concentrations i.e. they only take into account the inhalation route of entry.

 They generally refer to single substances, although some guidance may be given on mixed exposures.

2. Setting of Hygiene Standards and Exposure Limits

There are three main types of hygiene standards, those for chemical agents such as gases, apours, fumes, mists, dusts and aerosols. Those for physical 76 agents such as noise, vibration, heat, cold and radiation (ionising and non-ionising) and finally biological exposure indices. When setting hygiene standards for hazardous agents, the effects the agents might have on the body have to be considered namely:-

 Contact

 Local toxic effects at the site of contact (skin, eye, respiratory...