A new study measuring microplastics in organs of the recently deceased found that about two dozen brain samples were 0.5% plastic by weight. Also, having an IUD inserted in the uterus is extremely painful for some people. The CDC now recommends that doctors use local anesthetics.

It only takes a quick look at our streets and waterways to be reminded that plastic pollution is a big problem. But that’s just the plastic that we can see. An increasing amount of scientific literature points to microplastics accumulating inside our bodies, particularly in organs.

A recent preprint published by the National Institutes of Health found a staggering amount of microplastics in livers, kidneys, and brains of recently deceased cadavers. The brains, however, were the biggest shock: They had 10 to 20 times more microplastics than the other organs studied. Twenty-four of the brain samples measured were found to be about 0.5% plastic by weight.

Joining guest host Maggie Koerth is Tim Revell, executive editor of New Scientist based in London. The two discuss this and other top stories of the week, including a possible explanation for an “alien” radio signal, a look into how orb spiders use fireflies to lure other insects, and a study that says playing video games is good for you, actually.

The Centers for Disease Control and Prevention recently announced updated guidelines for managing pain from inserting a popular form of birth control called an intrauterine device, or IUD. The recommendations now advise doctors to consider using local anesthetics like lidocaine to help manage patients’ pain.

An IUD is a small T-shaped device that is passed through the vagina and cervix and placed in the uterus, where it can remain for several years. Figures vary, but this insertion process can be very painful for roughly 10%-20% of patients. In recent years there’s been an outpouring of patients speaking out on social media about just how painful their IUD insertions were. Many people have recounted how their doctors did not provide anything to help mitigate their pain or, in some cases, dismissed their experiences altogether.

Guest host Maggie Koerth talks with Dr. Beverly Gray, associate professor of obstetrics and gynecology at Duke University to discuss the significance of these new guidelines.

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