By RNZ
Experts discovered arsenic in the smoke plume that drifted over Auckland CBD during the SkyCity international convention centre fire.
GNS Science tested samples taken by Auckland Council and a university researcher close to the fire site.
The tests measured levels of PM, or particulate matter (PM10) the term for a mixture of solid particles and liquid droplets found in the air.
It was found that for the first time in a decade, the air quality in central Auckland exceeded national standards on Wednesday 23 October, the second day of the fire.