Types of Occupational Exposure Limits (OELs) and How to Search

An Occupational Exposure Limit (OEL) is the maximum allowable airborne concentration for a given chemical substance or biological agent in the workplace. In this article, we will help you understand different types of OELs and teach you how to find them.

Types of Occupational Exposure Limits (OELs)

There are three types of occupational exposure limits: the time-weighted average (TWA) exposure limit, the short-term exposure limit (STEL) and ceiling value.

• the time-weighted average (TWA) exposure limit - the maximum average concentration of a chemical in air for a normal 8-hour working day and 40-hour week;
• the short-term exposure limit (STEL) - the maximum average concentration to which workers can be exposed for a short period of time (usually 15 minutes) without suffering irritation, irreversible tissue damage, or "significant" narcosis;
• the ceiling value or maximum allowable concentration (MAC) - the concentration that should not be exceeded at any time.

It shall be noted that TWA OELs and STEL are not absolute limits, but rather time-weighted averages measured over an 8-hour period or 15 minutes. Ceiling value is the concentration that should not be exceeded at any time.

Occupational Exposure Limits in the United States

In the United States, there are mandatory and recommended occupational exposure limits. Many of OSHA's mandatory permissible exposure limits (PELs) are outdated and inadequate for ensuring protection of worker health. OSHA recommends that employers consider using alternative occupational exposure limits such as ACGIH TLVs, NIOSH RELs, etc.

• OSHA Permissible Exposure Limits (PELs)
• California OSHA Permissible Exposure Limits (PELs)
• ACGIH Threshold Limit Values (TLVs)
• NIOSH Recommended Exposure Limits (RELs)
• AIHA Workplace Environmental Exposure Levels (WEELs)

Occupational Exposure Limits in Europe

In Europe, there are two types of occupational exposure limits for chemical agents: EU community exposure limits and national occupational exposure limits. The community exposure limit values are set by the European Agency for Safety and Health at Work. The Member States are required to establish national occupational exposure limit values for listed chemical agents, taking into account the Community values. National exposure limit values may be different from the community values.

• EU Community Occupational Exposure Limits and National OELs;

How to Find Occupational Exposure Limits (OELs) for Chemical Substances Easily?

Recommended or mandatory occupational exposure limits (OELs) have been developed by many organizations in many countries for thousands of chemical substances. Unfortunately, those limits are not the same.

There are many databases for checking international occupational exposure limits. My favorite database is GESTIS. This free database contains a collection of occupational limit values for hazardous substances gathered from various EU member states, Australia, Canada, Japan, New Zealand, Singapore, South Korea, Switzerland, China, and the United States. Limit values of almost 1,800 substances are listed.

Read more at
http://www.chemsafetypro.com/Topics/OELs/Occupationa_Exposure_Limits_OELs_TWA_STEL_MAC_Databases.html