Polyurethane

Polyurethane is a plastic coating or film, the material behind most so-called vegan leather, typically made by dissolving PU resin in the heavy solvent DMF (dimethylformamide) and softening it with plasticizers. DMF is a known liver toxin and reproductive hazard listed as a Substance of Very High Concern in Europe, and it can leave residual contamination on the finished product.

Here is the honest part the marketing skips: vegan leather is almost always polyurethane or PVC plastic, not a clean natural alternative, and it is the high-hazard end of the spectrum. The plasticizers that keep PU and PVC supple are commonly endocrine-disrupting phthalates that can be absorbed through the skin, and some phthalate plasticizers have been restricted over carcinogenicity and links to breast cancer. PVC versions add chlorine chemistry and dioxin concerns, and residual DMF solvent can linger in cheaper PU. Worn against warm, sweaty skin, a watchband, jacket, or bag lining, these are exactly the conditions that promote plasticizer migration.

If you want a leather alternative, look for water-based PU (it eliminates the DMF solvent) and OEKO-TEX certification that caps phthalates and DMF, and treat any unlabeled vegan leather as plastic until proven otherwise.

Polyurethane and PVC are fossil-based plastics that do not biodegrade and shed plastic particles as they wear and flake.