In their cluster randomised controlled trial (doi:10.1136/bmj.b95), Dobbinson and colleagues assess whether students in 51 secondary schools in Australia use or avoid newly shaded areas created by sun sails.1 They found that a significantly higher number of students used the shaded areas during their lunch breaks in intervention schools. This shows that sun sails are a practical way of passively reducing sun exposure in teenagers. The results are encouraging, but it is hard to measure the benefit of the intervention because we do not know how many students used the shaded and unshaded outdoor areas or stayed indoors instead during the breaks.

The results are in line with a non-randomised controlled Swedish study in preschool children, in which situating the playground under a canopy of trees reduced ultraviolet radiation doses by up to 41%.2 In Toowoomba, Australia, optimising the timing of morning and lunchtime breaks in schools has …