Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals that have been used in manufacturing since the 1940s. They are valued for their resistance to water, oil, and heat — which is why they end up in non-stick coatings, waterproof fabrics, and yes, wearable bands.

The problem: PFAS do not break down naturally. They persist in soil, water, and the human body for decades — which is how they earned the name "forever chemicals." Exposure has been linked to hormonal disruption, immune system impairment, liver damage, developmental issues in children, and increased cancer risk.

Regulatory bodies across the EU, US, and UAE are increasingly restricting PFAS in consumer products. But most wearable bands on the market have not caught up.