Of the many milestones that mark our transition to autumn – the first brown leaves, the first crumble, the first "Shall we put the heating on?" – there is perhaps none as significant as First Tights Day. It’s simultaneously comforting and discombobulating, the first time you give in and pull on a pair of black opaques in the morning – 'bobulating' being the operative part of that word, since it’s what all your tights have been doing since you shoved them away in a drawer back in March.After years of the truly chic shivering their way through winter in bare legs and hiking socks, hosiery's finally back on the fashion menu too. And it's making up for those wilderness years; tights were splashed with logos at Fendi, Gucci and Saks Potts, spotted in Crayola-bright shades on the cobbles of fashion week and in lacy, netted swirls on the pins of influencers not old enough to have worn them during the Great Goth Revival of 2002. Even white tights, once the preserve of unlucky bridesmaids and sexy nurse costumes, suddenly look modishly cool again.But there’s a catch, and not just the snaggy-toenail kind. Fashion might be conspiring with the weather to tell us that it’s time to put our tights back on, but our growing environmental anxiety is saying the opposite.Tights are mostly made from nylon, a plastic-based synthetic fibre derived from coal and crude oil. You don’t need to know much about climate science to know that lots of the words in that last sentence are Not Good Things. Nylon production is thirsty, energy-hungry and generates nitrous oxide – a greenhouse gas 300 times more potent than CO2. It takes at least 30 years to decompose , often longer, meaning every single pair of laddered pantyhose we’ve thrown in the bin will still be sitting in landfill somewhere.While the durability of synthetic fibres can sometimes be a point in their favour, we can hardly argue that tights are made to last. In excess of 103,000 kg of hosiery waste is created worldwide every year, with that stubbornly linear lifespan – buy, wear, rip, repeat – earning it a reputation as the single-use plastic of the fashion industry. And we all know how we feel about straws these days.Does this mean cold legs are the only option for a clear conscience? Thankfully, no. We can do our bit to prolong our tights by washing them less (oh yes) and using a delicates bag like Guppyfriend to keep bobbles at bay. Meanwhile brands both new and established are doing the legwork to make tights in a more sustainable way. Here are six of the best.