The Department of Labour Workplace Exposure Standards

The Department of Labour is the primary agency responsible for setting Workplace Exposure Standards (WES) as part of the administration of the Health and Safety in Employment Act (HSE), 1992. 

WES relate to worker exposure to airborne substances in workplaces.

WES are health-based values. In assigning the WES value, defining a level that will achieve freedom from adverse health effects is the major consideration.
Employee exposure to hazardous substances should be controlled to a level as far below the relevant WES as practicable by applying the hierarchy of control required by the HSE Act. Section 10(2)(c) of the Act requires that where significant hazards are minimised, the employer must monitor the employees exposure to the hazard.  WES can be used by those involved in occupational health practice as guidelines for evaluating exposure to airborne hazards. Compliance with the designated value does not, however, guarantee protection from discomfort or possible ill-health outcomes for all workers.

As New Zealand does not have prevalent epidemiological studies of the working population, New Zealand’s standards reflect international experience.  The formaldehyde and soft wood dust WES were chosen for review as they are inconsistent with some international workplace exposure guidelines.

Formaldehyde WES

Currently a WES-Ceiling limit of 1ppm is set for formaldehyde.

The following reasons prompt a review of this WES:

• Human studies on acute inhalation of formaldehyde indicate adverse health effects including: mucous membrane irritation, shortness of breath, upper airway irritation and sore throats, at concentrations below 1ppm (source ACGIH Formaldehyde TLV Chemical Substances Documentation 7th Edition).
• Formaldehyde is classified as a 6.7A substance (known or presumed human carcinogen) under the HSNO Act. 
• Monitoring against a Ceiling limit can be problematic in terms of sampling methodology and detection limits.
• An 8-hour WES-TWA of 0.3ppm and a WES-STEL of 0.6ppm are being considered.  These levels are intended to minimise the potential for sensory irritation, chiefly of the eye and upper respiratory tract. However, even at these levels, some workers may be responsive to the irritant effects of formaldehyde due to increased sensitivity.

Soft wood dust WES

Currently an 8-hour Time Weighted Average WES of 5mg/m3 is set for soft wood dust.

The following reasons prompt a review of this WES:

• Human studies on the health effects from chronic inhalation of soft and mixed wood dusts indicate adverse health effects including: impaired lung function and lower and upper respiratory symptoms, at concentrations below 5mg/m3 (source ACGIH Formaldehyde TLV Chemical Substances Documentation 7th Edition).
• In industries where a variety of wood types are commonly used or multi-tasking with different wood types occurs, a different WES-TWA for hard and soft wood dusts can be problematic in terms of exposure monitoring.
• An 8-hour WES-TWA of 1mg/m3 is being considered.  This level is intended to prevent decreases in pulmonary function.