Pentachlorophenol (PCP) and dioxin are two toxic substances contained in a timber treatment used in sawmills until 1988. Both toxins are now likely to be present in soil at most current and former sawmill sites, although the level of contamination will vary significantly from site to site. Contamination may also be present at other sites where sawdust or soil from sawmills has been dumped.

Exposure to PCP and dioxin can cause serious health problems, so it is important that anyone managing or developing a contaminated site understands the potential health risks to workers and takes appropriate steps to manage them.

At these contaminated sites, the risk of workers being exposed to harmful toxins is directly linked to disturbance of the soil. The risk can be minimised by sealing the affected area, for example, with asphalt. If the soil is undisturbed - for example, if workers are walking on grassed or sealed areas - the risk of exposure is thought to be extremely low.

However, if the soil is disturbed or dug up dust may be created and the risk of exposure may increase. This may occur if there is a change in land use - for example if a former sawmill site is redeveloped or cultivated - or if a site is being remediated or "decontaminated". Using these sites to growing fruit and vegetables for consumption should definitely be avoided.

Employers have an important role to play in preventing exposure. Under the Health and Safety in Employment Act, employers, site managers and developers have legal obligations to keep employees and contractors safe. That means they have an obligation to identify any hazard posed by known soil contamination, and to take all practicable steps to eliminate, isolate or minimise the risk of harm.

The steps needed to protect employees and contractors from exposure will depend on the circumstances. But the basic principles are to:

• Prevent disturbance to the soil that could cause dust.
• Where possible seal the contaminated area.
• If the material is disturbed, make sure measures are taken to avoid dust and to ensure material is not moved off site - for example on the wheels of earthmoving equipment and other vehicles.

Guidelines for assessing risks at sawmill and timber treatment sites were published in 1997 by the Ministry for the Environment and Ministry of Health. The guidelines - called the Health and Environmental Guidelines for Selected Timber Treatment Chemicals - provide practical information for landowners, occupiers, regulators and assessors of sites.

In August 2006, the Ministry for the Environment issued the Contaminated Land Management Guideline No. 4: Classification and Information Management Protocols to help local authorities identify and monitor contaminated land.

Where the Department of Labour is made aware of health and safety risks at a workplace it can become involved in providing advice about how to keep workers safe. Any employee concerned they are being exposed to PCP/dioxin can contact the Department through our website www.dol.govt.nz or contact centre 0800 20 90 20.

Note, the Department's role relates to health and safety in the workplace. Owners and managers of contaminated sites may also have responsibilities relating to the environment and public health. For more information contact the relevant regional council or the Ministry of Health.