Fertility and plastic additives

Most of what we write is about plastic particles; the microscopic and nanoscopic fragments turning up in blood, placenta, and food. This piece is about something different. Not the plastic itself, but the chemicals inside it. The softeners that make a shower curtain drape. The resins that keep a can from rusting. The compounds that leach out of plastic long after the plastic is made.

They have names most people have heard in passing. Phthalates. BPA. And the fertility literature keeps circling back to them.

What these chemicals actually do inside plastic

Phthalates are plasticizers. They turn a rigid polymer like PVC into something soft and bendable. Think vinyl flooring, medical tubing, fragrance carriers in personal care products, the coatings on some pill capsules. They are not chemically bonded to the plastic, which is why they steadily migrate out of it into food, dust, and skin ^[1].

Bisphenol A (BPA) is different chemistry with a similar life story. It is a building block of polycarbonate plastic and epoxy resins, including the linings inside most metal food and beverage cans. Like phthalates, it leaches, especially when the plastic is heated or scratched ^[2].

Both classes of chemical have been detected in the urine of nearly every person tested in national surveys. Exposure is not exceptional. It is the baseline.

Why the body reads them as hormones

The reason these chemicals matter for fertility comes down to shape. Phthalates and BPA look, at a molecular level, enough like the body's own sex hormones that they can slip into hormone receptors and either activate them weakly or block them entirely ^[2]. Endocrinologists call this endocrine disruption.

Reproduction is not the only system for which this matters. We have written more broadly about how plastic chemicals may be quietly rewiring hormones (here and here). Reproduction is exquisitely sensitive to hormonal timing. Ovulation, sperm production, implantation, and the growth of a fetus each depend on hormone signals delivered at the right dose, in the right window, in the right sequence. A chemical that nudges those signals — even by a small amount, and even at very low doses — has a plausible route to affect outcomes downstream.

That is the theory. The human evidence is what makes the theory hard to dismiss.

What the fertility studies show

In men, urinary phthalate levels have been linked for two decades to lower sperm concentration and reduced motility ^[3]. More recent work in mixed-exposure cohorts has extended the pattern, and animal studies show phthalates disrupting the blood-testis barrier and testosterone production in ways that at least partly recover once exposure stops ^[4]. The story is not that any one man is doomed by his exposure. It is that the average signal, across large populations, points the same direction.

In women, BPA has been associated with lower egg quality in fertility clinics, reduced ovarian reserve, and — in one careful clinical study — a higher risk of miscarriage among women already being followed for pregnancy loss ^[5-6]. A broader review across dozens of epidemiological studies concluded that the weight of evidence supports a real, if modest, effect on female fertility ^[6]. Newer work from IVF clinics has extended the picture to particles themselves — we walked through what the first human studies of microplastics in follicular fluid actually show here.

Pregnancy is where the numbers get large. A pooled analysis of more than 6,000 US pregnancies linked higher DEHP breakdown products in maternal urine to roughly 12 to 16 percent higher odds of preterm delivery ^[7]. A 2026 global modeling exercise estimated that DEHP alone was statistically tied to nearly two million preterm births worldwide in 2018 ^[8]. We wrote about what that number does and does not mean here.

And fathers are in the frame too. Animal work published in early 2026 showed that male mice fed phthalates or microplastics before mating passed altered small RNA signatures through their sperm, with metabolic effects visible in the next generation. We covered the paternal window in detail.

The regrettable-substitution problem

When regulators flag a specific phthalate — as the US EPA did in January 2026 for DEHP and four related compounds ^[9] — industry tends to swap it for a close chemical cousin. DEHP gave way to DiNP. A 2023 systematic review found that DiNP shows hormone-disrupting activity in a similar range to the compound it replaced ^[10].

That pattern is worth naming. A single chemical getting banned rarely means the exposure goes away. It usually means the exposure is now spelled differently on the label.

So what does this mean

Plastic additives are not the same conversation as plastic particles, but they travel together. A plastic fragment in food packaging can be both a particle exposure and a chemical exposure at the same time, since the chemicals migrate out of the material carrying them. That overlap is the through-line connecting this piece to our work on reproductive health more broadly, on fertility and pregnancy, and on what probiotics might do about BPA and phthalates specifically.

Where Winnow fits in

The upstream fix for plastic additives is systemic — cleaner packaging defaults, tighter class-wide regulation, and honest labeling of what replaces what. Downstream of that, sensible personal moves add up: fewer heated plastic containers, fewer canned foods where the lining is uncertain, glass or stainless where it is easy to swap. Winnow's role is narrow and honest. Our formulation is built around probiotic strains shown in laboratory testing to bind micro- and nanoplastics It is not a treatment for endocrine disruption, and any read-across to hormone chemistry is a hypothesis for future research — not a claim we make about the product.