Some sneaker tops are made from natural sources like leather, but tanning this material relies on chromium; a carcinogenic chemical that can damage freshwater ecosystems.

有一些运动鞋的鞋面是由皮革等自然资源制成的，但是需要依靠铬为材料进一步上色，而铬是一种能够破坏淡水生态系统的致癌化学物质。