OHS Code Explanation Guide

Published Date: July 01, 2009
Bookmark this page

Part 4 Chemical Hazards, Biological Hazards and Harmful Substances

Section 21 Potential worker exposure

The purpose of the hazard assessment is to determine the exposure, or potential for exposure, of workers to a harmful substance at their work site. An exposure hazard cannot be controlled without knowing the identity of the harmful substance and the extent to which workers are exposed to it. The toxicity of the substance – type of action, route of exposure and target organs – must be known, as well as the duration of exposure. Other factors that may contribute to the degree of hazard include:

(a) the nature of the process in which the material is used or generated;
(b) the possibility of reaction with other physical or chemical agents;
(c) the degree to which controls such as ventilation and enclosure are effective; and
(d) the type and degree of toxic response in both the “average” and highly susceptible worker.

Almost every work environment has potential or actual hazards that need to be recognized, measured and monitored. An initial assessment should be performed in any work area where there is a potential for exposure, or there have been complaints of health effects experienced by workers. The assessment should include a walk-around survey of the operation, identification of all the chemicals used at the work site, talking to workers about past experiences and safety concerns and measurement of contaminants in air.

Consider the raw materials being used, how they are modified and the finished product. Each process step from raw material to finished product must be evaluated under normal and anticipated emergency conditions. Re-assessments should be conducted on an annual basis and when

(a) new equipment or work processes that could affect worker exposure are introduced to the work site;
(b) work practices or procedures change; or
(c) workers complain of adverse effects during or after work shifts.

The hazard assessment must be performed by a competent individual. Workers should be permitted and encouraged to observe and participate in monitoring activities as long as doing so does not interfere with the activities. Workers frequently have the experience to identify sources of exposure, indicate when exposure may differ from “normal” and identify conditions that are routine or not routine.

Once hazards at the workplace have been identified, the employer must take steps to eliminate, or if this is not possible, control the hazards. To eliminate the hazard, the employer may substitute a less hazardous substance or modify equipment or processes to eliminate emissions. If elimination of the hazard is not possible, various control strategies can be used.

The employer should always investigate engineering controls first, then administrative controls, and finally the use of appropriate personal protective equipment. Engineering controls minimize or eliminate exposure by altering or removing the source. Administrative controls influence exposure by modifying the circumstances of the worker’s exposure. Personal protective equipment should only be considered when other control measures are not practicable or do not sufficiently reduce the hazard.

Workers who may be exposed to a harmful substance must receive training in the procedures that minimize their exposure to the substance. The training must, at a minimum, include

(a) information describing the health hazards associated with exposure to the substance, and
(b) training in the procedures to be used to reduce exposure.

If the hazard assessment indicates that there is a potential for a worker to be exposed to a substance in excess of its OEL, the employer must measure the airborne concentrations of the substance. Measurements must be made in accordance with NIOSH analytical methods or methods acceptable to a Director of Occupational Hygiene (refer to the explanation of section 20). The resulting measurement will be important when establishing effective control measures to minimize worker exposure.

Informing the worker and records

Once measurements have been made, section 21 requires that any worker who may be affected by the harmful substance be informed of the measurement and the results. A hard copy of the measurement report must be available at the work site. Section 8 of the OHS Regulation requires the report to be in writing and available to affected workers. Both the employer and the prime contractor, if there is one, are responsible for ensuring this is done. Further, a record of the results must be maintained for at least three years from the date the measurement was taken. The results should be readily available for review by an officer or a Director.