Whanganui health protection officers are keeping a watching brief on the stench coming from Wanganui's wastewater treatment plant.
The smell has been wafting across the city on and off since early December, when a large amount of protein waste was dumped into the treatment plant, causing it to malfunction.
Health protection officer Bruce Butters said an offensive smell was one of the things that could be considered a nuisance under the Health Act.
"But ultimately, the local authority is responsible for dealing with the smell," he said.
Mr Butters said he was not aware of any medical issues relating to the smell from the wastewater treatment plant.
"We are waiting to hear about cases, although there is not much chance of the smell causing any serious problems," he said.
He said the smell, if it became very strong, could possibly exacerbate asthma or cause eye irritations.
"If you have either of those problems, you should go to your GP," Mr Butters said.
Some residents at Kaitoke and Marybank, where the smell has been particularly strong, have told the Wanganui Chronicle they have suffered sore throats as a result of the stench.