Topical gels like diclofenac, better known under the brand name Voltaren, are used to treat skin inflammations, joint pain and swelling, containing an active anti-inflammatory ingredient that targets the pain locally. After applying it to the aching area, we automatically go on to wash our hands to get off the sticky residue, but that allows the active ingredient to enter the sewage system. That’s a problem, as wastewater treatment plants are unable to remove diclofenac from the sewage water, meaning residues can end up in nature where they pose a risk to animals and plants, Germany’s Environm…