Did you know that polyester has been tied to miscarriages, sterility and impotence? No? Well, one group of researchers called polyester a “100% effective contraceptive” in men.

Let’s take a look at the studies behind these claims.

Polyester: bad news for your balls


Over recent months we’ve been examining the negative effects of a wide variety of common substances on human fertility and health.

Xenoestrogens, industrial chemicals that mimic the effects of the human hormone estrogen, have been a particular focus for us, because of their ubiquity. They are quite literally everywhere: in the food, in the plastic containers you put the food in, in the water and even in the air. Yes, that’s right: in the air.

A few weeks ago we talked about the potentially toxic effects of touching thermal paper, most commonly used in receipts, and of cooking with non-stick pans.

While some people naturally shrink away from man-made fibers, few are likely to do so because of the potential damage they could be doing to your chances of having children.

Some forms of polyester are natural and biodegradable, but here we’re talking about synthetic polyesters, which are not biodegradable. It’s already well known that polyester can be bad for your skin, for instance.

Skin exposure to polyester has been linked to rashes, itching, eczema, dermatitis and blistering, as well as making pre-existing skin conditions worse for those who already have sensitive skin.

You may also know that polyester has been fingered as a cause of widespread insomnia. Polyester sheets don’t let your body regulate its temperature properly, leading to a bad night’s sleep and all the other negative effects that entails.

But what about these more spectacular claims about fertility?

In one study, the effects of different textiles were studied on 35 pregnant bitches, divided into one control group and four experimental groups.

“The bitches wearing cotton, wool and polyester-cotton mix as well as five of the seven wearing pure polyester garments had normal serum estradiol and progesterone during pregnancy and produced normal offspring. The remaining two animals of the group wearing pure polyester showed low serum progesterone levels in the first month of pregnancy and had spontaneous abortions.” 

The bitches who had previously worn the polyester then had the garment removed and were able to mate and give birth successfully. Their hormone levels returned to normal.

In another study, men were made to wear a polyester sling over their scrotums for a period of 12 months. All 14 of the men in the study became functionally sterile – i.e. producing no sperm – within a mean of 139.6 +/- 20.8 sd days.

Although reproductive hormones showed no changes, the scientists noted degradation of the seminiferous tubules, decreased testicular volume and changes to the rectal-testicular temperature difference.

After removing the sling, sperm concentration returned to normal levels after a mean period of 156.6 +/- 14.8 sd days and the other measures also returned to normal. Subjects who wanted to conceive with their partners were then able to.

The researchers are quite clear that they believe polyester underwear to be a safe and 100% effective form of contraception for men.

To conclude, fertile men can be rendered azoospermic by wearing the polyester sling. It is a safe, reversible, acceptable and inexpensive method of contraception in men.

Contraceptive efficacy of polyester-induced azoospermia in normal men – PubMed (nih.gov)

So what is it about polyester than makes it an effective contraceptive?

The effects seem to be due to two things: the creation of an electrostatic field (i.e. static electricity) in the area, and disordered thermoregulation, which we talked about earlier with regard to sleep disruption.

Why you should avoid touching receipts: trust the broscience (in this case)


So you care deeply about your health. You work out. You filter your tap water. You buy local organic produce. Looks like you’re gonna make it, right?

But then, at the checkout, the cashier hands you the receipt.

Dive in slow-motion bullet time to get out of the path of the incoming receipt?

Drop your shopping and run screaming from the store?

Don a special glove to receive the receipt and then carefully deposit it in a lead-lined box you carry specifically for the purpose?

Accept the receipt meekly and slowly dissolve into a puddle on the floor like something out of an ’80s body-horror movie?

So far, so silly. But the truth is, measurable levels of the powerful endocrine disruptor BPA are found in the thermal paper used in receipts (including from ATMs and card machines), airline boarding passes, movie tickets, prescriptions labels and food labels.

BPA is added to many kinds of thermal paper to allow them to produce visible text or colour when heat is applied.

Click here to read more

It’s worth noting that these studies are not the only ones that have substantiated these effects (see for instance this study and this one).

A number of other studies have claimed that polyester is toxic and some have recommended that babies should be kept away from it.

One of the biggest problems, it is claimed, occurs when polyester is heated, which releases antimony oxide (Sb2O3), a known carcinogen. And we aren’t just talking about heat from, say, a washing machine – we mean body heat. Sweat can then dissolve the antimony oxide, which is absorbed into the body.

The gases released when polyester is heated included perfluorochemicals, which can cause lung problems and headaches. Worse still, a big study from New Zealand linked fire retardants in cribs – some of which are the same as the chemical gases released by polyester – to sudden infant death syndrome.

So our advice is: ditch the polyester and plump for cotton instead. It’s that simple.

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