Land surrounding a former mine on the Isle of Man has been closed to the public because of concerns about the disturbance of historic waste material.
Cross Vein in Foxdale, a popular spot for off-road motorcyclists in the south of the island, was shut on Monday.
Dion Meechan, of the Isle of Man Schoolboy Motocross Club, said it had let “young riders cut their teeth”.
But the public access ban will reduce the amount of contaminated silt ending up in Peel Marina, the government said.
Although the mine, locally known as Snuff the Wind, was closed nearly 140 years ago, spoil heaps in the surrounding area still contain heavy metals including lead and zinc.
Tim Baker MHK, of the Department of Environment, Food and Agriculture, said: “The decision is backed up scientific analysis and absolutely makes sense from an environmental, health and marina perspective.
“Motorcycles churning up fine dust is dangerous to the rider’s health and has damaging ecological effects.”
A spokesman for Isle of Man Friends of the Earth said the contaminants were “particularly horrific things” that were “getting into shellfish and crabs”.
“Rain takes it down, it’s very small stuff you can’t see it, so in the dust it disappears into the rivers,” he added.
Mr Meechan said aspiring motocross riders must have somewhere to learn that was “accessible” and “very central to the island”.
He said: “It’s been a fantastic facility which has been enjoyed for decades by lots of different people, all hours of the day, no restrictions.
“It’s been a fantastic facility for young people to start riding on.”