The Ontario Ministry of Labour recently introduced changes to occupational exposure limits ("OELs") for various hazardous chemical substances present in workplaces. The changes included introducing an OEL for substances where an OEL had not previously been established and revising existing OELs, thus requiring a greater level of protection for workers.

OELs identify the maximum exposure concentration of a substance that a worker may be exposed to in a given time period. Generally, the more hazardous the substance, the lower the OEL because of the potential for adverse health effects. The changes to the OELs were made as part of an annual review process that was started in 2004 by the Ministry of Labour.

Labour Minister Steve Peters stated, "overexposure to hazardous substances is a major cause of occupational illness that also adds significant costs to businesses through lost time and higher workplace insurance premiums". Over exposure also puts an employer at risk of legal liability.

Regulation 833, Control of Exposure to Biological or Chemical Agents, lists over 700 different agents and their corresponding OEL, either as a time-weighted average exposure value, short-term exposure value, or ceiling exposure value.

The regulation also prescribes specific requirements for compliance with the limits.

Employers should identify, by way of conducting a hazard assessment, if their workplace contains or uses any of the hazardous substances listed in the regulation. If the workplace contains a hazardous substance listed in Regulation 833, the employer is required to ensure that any exposure to workers is in compliance with the OEL. This requires implementation of sound control measures and diligent and regular monitoring of worker exposure.

An action item for employers on this issue is to conduct a workplace hazard assessment to determine the presence of and extent of exposure to any hazardous materials and develop a written program to address how exposure to the substance( s) will be eliminated/minimized through control measures, monitored (personal and workplace) and handled in the event overexposure does occur.

Communication and training to workers on what practices they should employ to protect themselves and consistent follow up by management to ensure compliance is key to successful prevention of overexposure.