Concerns that the fumigation of logs and lumber might be linked to motor neurone disease have no scientific basis, says the forest industry.
"Methyl bromide gas is obviously toxic at the doses used to fumigate logs. But outside fumigation envelopes or containers it poses no risk to the public or to wharf workers who follow normal safety procedures," Stakeholders in Methyl Bromide Reduction (STIMBR) spokesman Gordon Hosking said.
Dr Hosking was reacting to reports of research at Canterbury University that showed a reaction when methyl bromide was mixed with glutathione, a protective chemical found in living cells.
The scientists' hypothesis was that if the human cells were exposed, it would reduce the cells' ability to protect against repeated exposure.
Toxicologist professor Ian Shaw said exposure of nerve cells to the chemical could trigger motor neurone disease.
However, Dr Hosking said Prof Shaw's findings did not prove that motor neurone disease and methyl bromide were linked. "But the possibility that they might has alarmed maritime and wharf workers," he said.
"No-one knows what causes motor neurone disease. So it is understandable that family members and fellow workers should see possible exposure to the gas as an explanation for cases involving workers at sites where fumigation is carried out.
"Their concerns were fully investigated in an official inquiry five years ago and no link was found. Further reassurance comes from more recent investigations by the Institute of Environmental Science and Research, Environmental Risk Management Authority (Erma) and the Ministry of Health that also found no link," Dr Hosking said.
Methyl bromide is used at some ports to fumigate logs and lumber for export and some imported food products, such as garlic from China and grapes from Australia.
"Internationally, it is the most widely accepted biosecurity fumigant, because it is effective against a wide range of pests and diseases, safe when used correctly, and does not harm the treated produce. However, because it damages the planet's ozone layer, the hunt is on world-wide to find alternatives," Dr Hosking said.
"In the meantime, however, we have no alternative but to continue using methyl bromide as it is so effective in keeping our country protected against biosecurity pests and enabling our valuable exports to be accepted overseas."
