Landfill risk assessment incomplete

The Smooth Hill landfill site looking south with (from left to right) Big Stone and McLaren Gully...
The Smooth Hill landfill site looking south with (from left to right) Big Stone and McLaren Gully roads. PHOTO: STEPHEN JAQUIERY
The Dunedin City Council may have underestimated the risk to human health posed by a proposed landfill near Brighton, an Otago Regional Council report says.

Tonkin + Taylor human health risk assessment technical lead Dr Lyn Denison highlighted several areas where evidence or analysis was missing from the city council’s assessment of the health risks the proposed Smooth Hill landfill could pose for people using Otokia Creek or Brighton Beach, where the creek goes to sea.

The hearing for the city council’s application to build the proposed landfill was adjourned in May so the council could do the assessment after an expert submitter identified it as missing.

Lyn Denison.
Lyn Denison.
City council consultants GHD subsequently submitted a 93-page water quality analysis, including a human health risk assessment, as new evidence for the hearings at the end of last month. That report was then reviewed by the expert from EHS Support New Zealand on behalf of a group of Brighton residents who oppose the site the city council has selected for the city’s next landfill.

The Brighton residents’ expert review of the city council’s new human health risk assessment found it to be incomplete.

Now, Dr Denison, on behalf of the regional council, has also raised concerns about it.

The overall approach to the city council assessment was appropriate and consistent with national and international approaches to human health risk assessments, Dr Denison said.

It included a review of the risk a key group of manufactured chemicals could pose to human health if they leaked from the landfill and entered the creek.

However, Dr Denison questioned why potential contaminants from the landfill such as arsenic, lead and mercury were not part of the new report.

Like the manufactured chemicals included in the new assessment, these chemicals could be found in leachate that could leak from landfills and could also build up in things living in the creek.

Not including them in the analysis could lead to underestimating "the total risk to human health" if the landfill liner failed.

Dr Denison went on to note in the new assessment there was no discussion about the potential for those key manufactured chemicals to contaminate groundwater and the potential risk to human health that possibility posed.

Due to the concern internationally about the health impacts of these manufactured chemicals (found in a variety of items such as cleaning products, nonstick cookware and water resistant clothing), there was a large amount of new research into them, she said.

Between 2020 and 2022, reviews had been done by several major international regulatory agencies, she said.

Apart from the limited use of data from one, no reference had been made to the reviews by the others, she said.

One agency classified some of the chemicals as carcinogens in 2020.

"This should have been included as part of the hazard assessment," Dr Denison said.

The city council’s assessment instead relied on studies published by Food Standards Australia and New Zealand in 2017 and earlier, she said.

Overall, the city council’s human health risk assessment concluded there was a low risk to human health from manufactured chemicals arising from the failure of the liner of the landfill, Dr Denison said.

If more recent data from international sources had been used, the estimated risks would be higher, she said.

The hearing remains adjourned while the city council prepares replies to a wide range of other concerns raised about the proposal during the hearing.

--  hamish.maclean@odt.co.nz

 

 

 

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