Heat and sweat are part of a workout, and heat is also what makes some plastics give off more. PVC yoga mats need plasticisers, and the amount they give off rises with temperature. In a lab study, hot water made polypropylene bottles shed more microplastics. Protein powder is the other question: two studies found more lead in plant-based powders than in dairy-based ones, and the swap page explains why their numbers differ. These three swaps are a natural rubber mat, a stainless steel shaker, and a dairy-based protein, each with the studies behind it. If you’re plant-based, the protein swap says what to look for instead: a maker that publishes lot-by-lot heavy-metal results.
