The Greater Wellington Regional Council may prosecute a Petone battery recycling plant for its second air emissions breach this year.
On Monday Exide Technologies admitted breaching permitted lead-air emission levels at its Petone plant in the three months to November 25.
Last month Exide was fined $5000 bythe Environment Court after it pleaded guilty to discharging excessive lead into the air in March, April and May of this year.
Greater Wellington environmental regulation manager Al Cross said the second suspected breach was being investigated by Exide.
"It's a hell of a concern," he told the Dominion Post.
"Obviously we'll need some answers."
The council, which brought the first prosecution against Exide, had asked the company for a formal explanation before deciding whether to prosecute again, Mr Cross said.
Exide said in a statement on Monday emissions had reached 4.19 micrograms of lead per cubic metre of air in the week to November 25, exceeding the permitted limit of 1.5mcg.
While the plant had averaged 1.63mcg in the quarter, it blamed the "single, abnormally high reading on one monitor" for raising the average level of emissions.
"While these readings are slightly higher than allowable levels, the company believes the results do not represent a health threat to people in the community or in the Exide facility."
It said it was disappointed by the results and believed its baghouse, a device that filters plant air through a stack before it is released to the outside environment, was a contributing source.
Exide announced last week it would install a new baghouse at the Petone facility.
The plant has been a source of protest in the Petone community.
Neighbour Julie Wake called for harsher penalties that would hurt Exide.
She was skeptical about the company's claims that neither breach would cause adverse health effects.
"They've been saying that for years. Nobody believes them," she told the Dominion Post.
"They make promises and they never keep their word. We don't believe them when they say they're keeping us safe."
