Mud and silt left behind at an Esk Valley property in Hawke's Bay on 17 February 2023 after Cyclone Gabrielle passed through. Photo: RNZ / Sally Murphy
Scientists have found a reassuringly low health risk from the silt dust caused by Cyclone Gabrielle in Hawke's Bay.
Ever since the cyclone in February 2023 dumped millions of tonnes of silt in areas like Esk Valley, residents worried the dust coming from it contained dangerous levels of silica.
However, a report from the Institute of Environmental Science and Research (ESR) shows the silt contains no more silica than normal garden soil, and less than most beach sand.
ESR Science leader Peter Cressey said: "While health effects may occur due to flooding events, this is most commonly due to direct contact with flood waters, rather than flood-deposited silt."
He said air quality monitoring in the Hawke's Bay region during September 2023 to March 2024 also showed a low level of concern for silicosis resulting from exposure to silt in the form of airborne dust.
"Those affected by Cyclone Gabrielle have a range of huge issues to deal with. All the evidence indicates that long-term health effects due to silt will not be one of those issues," he said.
The report was commissioned by Health New Zealand after the cyclone to better understand any longer-term impacts of silt or dust on human health, and Medical Officer of Health Dr Bridget Wilson said the findings also include an analysis from flooding events overseas, as well as in-depth local analysis on silt sampling and air quality.
"Impacted communities have been understandably concerned about the effect of silt and dust on their health and what that could mean longer term," Dr Wilson said.
She said it was extremely reassuring to find the public health impacts from silt and dust exposure was deemed low, but public health advice was still in place for people experiencing short-term symptoms like eye and airway irritations from dust.
"People continue to be advised to wear a mask when outside on dusty days or when undertaking clean up around their property that generates dust."