The former landfill at Fort Dorset, Seatoun - now housing - is on the list, though noted as acceptably managed or remediated.

Throw a stick in Wellington and you are likely to hit one of its 2263 contaminated sites.

Placement on the ever-expanding list means a property's toxic rating is listed on publicly available files for potential buyers to see – and once on the list, there is no way off, even after the original problem has been fixed.

Greater Wellington Regional Council has released, under an official information request, details of all sites in the region that have been used for the storage or disposal of hazardous substances.

It includes explosives, cemeteries, petrol stations, chemical factories, and former landfills, some of which are now homes, public parks, and business areas. Each is deemed to have a current or past risk to human health or the environment.

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Several schools, including Newtown, South Wellington Intermediate, Kena Kena, Kelburn Normal, and Greenacres, are all on there, and only at Kelburn is it noted as being fixed or at an acceptable level.

ROSS GIBLIN/STUFF The site of the former Fort Dorset landfill in Seatoun is now occupied by high-end homes. The Greater Wellington database says the contamination is now acceptably managed or remediated - but the properties remain on the Slur list.

That list has grown from 1700 in 2009 to 2263 now, and could easily double in the years to come, Greater Wellington Regional Council environmental scientist Philippa Crisp said.

The council would soon start adding every past and present farm that had sheep dips which used arsenic.

"We don't want them to end up in someone's backyard and they plant their veges in it," Crisp said.

ROSS GIBLIN/STUFF Te Mome Stream in Lower Hutt was once ranked as one of New Zealand's 10 most-contaminated sites. Now off the top 10, it is still listed as contaminated.

Being on the list meant a site had a verified history of contamination, but did not necessarily mean they were still contaminated.

Even so, placement on the list shows up on Land Information Memorandums (Lims) and would probably affect property values. And worst of all, there is no way off.

Files could be altered to show an issue had been remediated, Crisp said.

ROSS GIBLIN/STUFF Newtown School made the list, along with several other Wellington schools.

Property owners were notified they were about to go on the list – called the Selected Land Use Register (Slur) – and placement on it came with three pieces of evidence.

"People don't like it, unfortunately. It is not a nice thing to have to send them a letter about."

Sally Beagles, whose home in Wellington's eastern suburbs had been used as a meth lab when she rented it out while overseas in 2003, was not aware of the Slur listing but knew of the contamination, which had since been fixed.

Alexander Turnbull Library/EP/1958/2624-F The former Miramar Gasworks on Cobham Drive is one of Wellington's worst toxic sites.

"I supposed it is not the best [to have the rating on a Lim report], but it is the truth," she said.

Sites on the Slur are based on an Ministry for the Environment Hazardous Activities and Industries List (Hail) that has 53 activities and industries that warrant inclusion.

Council environment committee chairwoman Sue Kedgley said new rules meant it was much less likely new sites were being approved that would eventually appear on the list.

"Many years ago we had to fight to get this contamination register. It is all about people's right to know when buying a house."

She was not aware that sites could not come off the list, even with remediation, but thought this should be looked at.

It had been proven in places such as Waitangi Park – which is on Slur as having a "verified history of hazardous activity or industry" – that once-toxic sites could be cleaned up.

Craig Lowe, of Lowe & Co Realty, was yet to come across a property on the Slur, but said contamination was an emotive issue for buyers, and it was important they were told of it and could seek independent advice.