You might want to think twice before purchasing a ultraviolet (UV) light steriliser that claims to kill the bacteria and viruses, including coronavirus, according to a new investigation. Consumer group Which? says some UV light products sold on online marketplaces may be ineffective or could pose safety risks to users. These include 'potentially dangerous' handheld UV 'wands', freestanding lamps, smartphone containers, tumble dryers and even mattresses. It has long been known that UV light has a sterilising effect because the radiation damages the genetic material of viruses and their ability to replicate. But UV light is a human health hazard because it can damage cells in our skin, potentially causing skin cancer, or eye problems like cataracts.