Confidential reports have just been released revealing residents on Nelson's Port Hills may be exposed to dangerous levels of toxic methyl bromide gas.
The Environment Court today released reports from an air quality scientist, which were withheld by the Nelson-Marlborough District Health Board.
In October, a parliamentary select committee recommended stricter controls on the use of the chemical after more than 1400 people signed a petition for it to be banned.
The petition, signed by Nelson-based Campaigners Against Toxic Sprays (Cats) chairwoman Claire Gulman and 1452 others, followed the controversial use of the fumigant at the Port of Nelson.
It has been blamed for ill health and deaths suffered by workers and nearby residents.
The DHB commissioned studies into the public risk of the gas' use, but then refused to release them and said the matter was before the Environment Court.
Today it was revealed the author of the report, Auckland-based Air and Environment Science's Craig Stevenson, said there was a likelihood gas from the Port may have exceeded safety standards as it drifted into residential parts of the surrounding hills.
He said more testing and analysis was necessary.
Methyl bromide is used in the agriculture industry to kill pests including micro-organisms, insects and weeds.
It is mainly used to fumigate infested imported goods, and as a pre-shipment treatment for some exports including fruit and wood, and by horticulturists to fumigate soil under susceptible crops.
Methyl bromide has been blamed for causing a cluster of cases of motor neurone disease by a group of Nelson widows whose husbands died of the disease after working at the port.
However, a study by Nelson's medical officer of health, Ed Kiddle, found no link between the gas and the men's deaths.
Modelling used in Dr Stevenson's reports predicts that after a three-minute discharge from Shed Two at the port under "worst-case meteorological conditions", concentrations of methyl bromide could be as high as 581 milligrams per cubic metre in parts of the Port Hills.
This is more than twice the level of 285mg allowed under workplace exposure standards.
Methyl bromide fumigation was moved from Shed Two to Shed Three, which is further away from the hills, in 2005.
But the reports indicated that discharge levels from Shed Three could still be too high.
Dr Stevenson wrote that further assessment could conclude that only a "low probability" of exposure existed.
Until this was shown, "serious consideration should be given to restricting the ventilation discharge of methyl bromide to times when the wind direction is not towards the Port Hills".
Campaigners Against Toxic Sprays released the reports yesterday after Environment Court Judge Jon Jackson ruled that they were not subject to mediation privilege.
Dr Ed Kiddle said he hoped that the documents would give the public a better understanding of the issue.
The service had not released them previously because a court-appointed mediator had earlier decided that they were confidential.
He would not comment further while mediation was under way.
Port Nelson chief executive Martin Byrne said he had not seen the reports before today and it would be inappropriate to comment until mediation was over.