A playground has been closed to the public after a dangerous chemical was detected in the sand.

A small amount of thallium — a metal more toxic than mercury or lead — was found during environmental testing at the Fraser Gregory Park Playground in Beachlands, in Geraldton’s inner west.

The concerning discovery was made during soil and surface dust sampling program across the coastal regional city, which was prompted by complaints of excessive dust in the area.

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The Department of Water and Environmental Regulation (DWER) alerted the Geraldton council that an “isolated low-level detection result for thallium” was detected “in the soft fall.”

The City of Greater Geraldton then decided to cordon off the contaminated playground.

“While it is a low-level amount, the City is exercising caution by closing the playground until the soft fall has been removed and replaced,” the council said.

“Members of the community are requested to exercise caution and obey all warning signs and directions from authorised City personnel and contractors.”

Thallium was only found in the single sample at the playground, and not at the adjacent oval, and nearby playgrounds.

The exact source of the thallium that has contaminated the playground is not yet known.

“Thallium can be released from some industrial processes, including metals and cement manufacture,” DWER said.

“There is currently no information to suggest an ongoing source affecting the playground.”

“While the Department has received and assessed a substantial body of information, further technical assessment is required before conclusions can be reached regarding sources of dust emissions or potential regulatory action.”