Visitors were barred Friday from contact with a leading Chinese artist's exhibition of more than 100 million porcelain "seeds" at Britain's international modern art gallery over health fears.
Ai Weiwei's "Sunflower Seeds" artwork covers 1,000 square metres (10,760 square feet) of the Turbine Hall at the Tate Modern in London. Walking on them was a key factor in the exhibition, but the public can no longer do so.
"Although porcelain is very robust, the enthusiastic interaction of visitors has resulted in a greater than expected level of dust in the Turbine Hall," a Tate spokeswoman said.
"Tate has been advised that this dust could be damaging to health following repeated inhalation over a long period of time.
"In consequence, Tate, in consultation with the artist, has decided not to allow visitors to walk across the sculpture."
Ai is one of China's leading conceptual artists.
The life-size seeds were individually sculpted and painted in workshops in Jingdezhen, eastern China.
Porcelain has traditionally been one China's most prized exports.
"'Sunflower Seeds' invites us to look more closely at the 'Made in China' phenomenon and the geo-politics of cultural and economic exchange today," Tate Modern said.
In publicising the exhibition, the Tate Modern said the seeds "form a seemingly infinite landscape.
"'Sunflower Seeds' is a sensory and immersive installation, which we can touch, walk on and listen to as the seeds shift under our feet.
"The casual act of walking on the work's surface contrasts with the immense effort of production and the precious nature of the material."
"Sunflower Seeds" runs until May 2, but the public will only be able to look at it.