Does BPS in BPA-free plastics disrupt thyroid function and reproduction?

What's actually in it

BPS (bisphenol S) replaced BPA in most plastics after BPA was restricted. It's now in water bottles, food storage containers, baby bottles, and thermal paper receipts. Like BPA, it leaches from plastic into food and is absorbed through skin from receipts.

BPS is structurally similar to thyroid hormones and can bind to thyroid hormone receptors, interfering with thyroid function throughout the body.

What the research says

A 2026 study in Chemosphere examined the long-term effects of early-life BPS exposure on thyroid function and adult reproductive outcomes. Animals exposed to BPS during a critical early-life developmental window showed disrupted thyroid hormone levels that persisted into adulthood, even after BPS exposure stopped.

The reproductive effects were also lasting. Adult females exposed to BPS early in life showed altered estrogen cycling, reduced fertility markers, and changes in reproductive organ structure. The thyroid disruption contributed to these reproductive effects because thyroid hormones regulate the menstrual cycle and reproductive hormone balance.

This study demonstrates what's sometimes called the "regrettable substitution" problem. BPA was removed because of health concerns, but the BPS that replaced it causes the same types of harm. If you already own BPA-free plastic containers, you likely have BPS containers, which carry the same risks.