Three staff exposed to unsafe levels of naturally occurring mercury vapour at OceanaGold Corporation's (ASX, TSX & NZX: OCG) processing plant at Macraes in East Otago prompted a $500,000 upgrade of its gold smelting room.
Chief operating officer Mark Cadzow said the incident, in January 2010, found no adverse effects to the three staff who were treated orally for removal of mercury and voluntary tests on a further up to 30 staff found no signs of raised mercury levels.
The incident prompted a critical report from the Department of Labour (DOL), citing breaches of health and safety regulations, but no prosecution was sought as OceanaGold had dealt with the issues.
Cadzow said the mercury vapour was not used as part of the gold processing system but naturally occurred in the ore being processed at the time, but he was unable to say why some ore would have higher mercury content levels than other ores.
“Routine testing during the past 20 years has not shown it [raised mercury levels] to be an issue,'' Cadzow said yesterday.
The incident in January 2010 was not reported to DOL until June, and was made public following an Official Information Request to the Labour Department by Fairfax media.
Cadzow said DOL was not told until June about the incident because once Oceana picked up the raised mercury levels in its routine audit process, it instigated more tests to confirm the higher levels, then informed DOL of its findings.
The three staff were reported to have been exposed to 20-times the safe mercury vapour levels.
“There were varying degrees of elevated levels recorded, but at all times the necessary protective equipment was worn by our OceanaGold employees, thereby negating potential harm,'' Cadzow said.
He said the gold room had been upgraded, at a cost of up to $500,000, including new ventilation systems and enhanced personal safety equipment. It is coincidental that a new smelting room is being built in the near future.
*Simon Hartley is senior business reporter for the Otago Daily Times.