Some retailers are installing blue lights in bathrooms to make it more difficult for people to see their veins and inject drugs, the Associated Press reports.

The city of Philadelphia has begun distributing kits to residents that include a blue bulb for the front porch. The kit also has no-trespassing signs, a tool to pick up used syringes, a box to dispose of needles, and contact information for social services.

Some studies have questioned the effectiveness of blue lights as a deterrent to drug injection, and many public health experts say the lights make people more likely to hurt themselves, the article notes. Some experts recommend installing needle disposal containers in bathrooms, as well as stall doors that swing outward to make it easier to reach a person who has overdosed and needs medical help.