Microplastics & air quality

Two exposures have moved quickly in the research since most fertility advice was written.

Microplastics reach the ovary. Microplastics were detected in 69% of follicular fluid samples from women undergoing fertility evaluation — the immediate environment of the developing egg — and have also been found in placenta, breast milk and semen. Associated effects include altered folliculogenesis, disrupted ovarian hormone levels and impaired oocyte quality, though most causal data remain animal or in-vitro. It does turn "avoid heating plastic" from precaution into something more concrete.

Air quality affects conception, not just IVF. In a large North American preconception cohort of naturally conceiving couples, particulate matter exposure was associated with reduced fecundability. In IVF, higher PM2.5 and ozone during ovarian stimulation were associated with lower fertilization rates, fewer top-quality embryos and reduced live birth rates, with follicular fluid metabolite changes as the proposed pathway.

What to actually do: the practical steps are ones you may already have — glass rather than plastic for food, never microwaving in plastic, filtered water, and a HEPA purifier in the bedroom if you live somewhere with poor air quality or cook on gas. The advice hasn't changed; the reason behind it got considerably stronger.