Monitoring shows low risk of methyl bromide exposure

Wednesday 18 May 2005

Fumigation operations at the Port of Nelson involving methyl bromide can be carried out safely, and with a low risk of exposure to port workers, a Department of Labour audit into the port has shown.

DoL surveyed fumigation operations at Shed 3 in March, to evaluate any methyl bromide exposure to workers during the fumigation process and subsequent ventilation of the shed. The results of the audit were released at a public meeting in Nelson today.

DoL national operations manager for health and safety, Mike Cosman, said the audit showed methyl bromide was being effectively contained during the fumigation process, and that the port's forced air extraction system efficiently controlled the gas during the ventilation stage.

Mr Cosman said there was no evidence that methyl bromide was leaking from the shed and affecting the health of nearby workers, as had been alleged when fumigations were carried out in Shed 2. Measurements taken outside the shed picked up very low amounts of 'volatile organic compounds', which may or may not have been methyl bromide.

'Under most conditions methyl bromide rapidly dissipates into the atmosphere when released, so suggestions that high levels of methyl bromide exist some distance from the fumigation shed can't be supported by these findings,' he said.

While the audit showed fumigations were being carried out safely in Shed 3, DoL has recommended modifications to the operation to improve systems further. These modifications include increasing the height of the extraction flue, increasing the length of time of ventilation, improved use of personal protection equipment, and the installation of a third extractor fan. DoL recommends these improvements happen before the next fumigation season starts, in October.

Mr Cosman said the audit was specific to one day's fumigation operations at the port, and for Shed 3 only. Changes in operations at the port meant that all fumigations had been moved away from neighbouring workplaces, from Shed 2 to Shed 3, in early March.

He said DoL was planning further monitoring at the port, to gain a more comprehensive picture of the overall fumigation operations.

In a separate study, carried out in conjunction with Stevedoring Services Ltd, the blood of port workers has been tested for signs of methyl bromide exposure. Dr Bill Glass, a highly experienced occupational physician working for the Department of Labour, has reviewed the test results, which he says are some of the most comprehensive ever carried out.

Methyl bromide occurs naturally in blood, and the recorded levels show no particular elevation outside of acceptable workplace exposure levels. However, Dr Glass stated that although little was currently known about the relationship between workplace exposure and blood levels, the results did confirm that there was no evidence of significant exposure to methyl bromide.

'We are in largely unexplored territory here and this research is ground-breaking,' Mr Cosman said.

'We hope to repeat the tests later in the year, after fumigation has ceased for the winter, to try to assess the background levels for these workers. Even if they are a lot lower than the current results we will not be able say whether this is significant in terms of possible health effects. However the combined effect of all the studies being carried out in Nelson is adding to the sum of our knowledge in an area where little previous research has been carried out.'