Chinese artist Ai Weiwei carpeted the floor of the Turbine Hall with 100 million porcelain seeds and invited the public to walk across them.

But within days of the work’s grand unveiling, staff reported a fine dust rising from the seeds as people crunched them underfoot. According to health and safety experts, prolonged exposure to the dust could exacerbate conditions such as as asthma.

Read More: Tate Modern closes sunflower seed exhibit to the public – Telegraph.