Microplastics are all over the news lately. Actually, these plastic bits 0.2 inches (5 mm) wide or smaller are all over everything— from our food to the insides of animals, and especially in the oceans.
Most plastic is non-biodegradable. When something biodegradable breaks down, it chemically changes into new substances. Bacteria and other microbes will digest a banana peel over a few weeks until it becomes soil. By contrast, plastic stays plastic forever. But it can still physically break into smaller pieces. This happens fastest outside, because the ultraviolet light in sunlight weakens and cracks plastic. Eventually, it breaks into smaller pieces. There’s no limit to how small those pieces can get, and that’s how we end up with microplastics. Bigger microplastics might look like individual grains of dust, just barely big enough to see with your eyes. Others are invisible without a microscope. These may be the size of human blood cells, or even around 10 times smaller than that, which is the size of some viruses!
So why all the attention? Microplastics are a newly discovered pollutant, and scientists around the world are worried that they can hurt animals and spread chemical pollutants around.
Problems for Animals Periodically, big sea animals like turtles or whales accidentally eat plastic debris. Similarly, very small animals in the ocean called zooplankton sometimes eat microplastics. To them, a piece of plastic might smell and taste good, because chemicals that smell like their normal food form on the surface of microplastics. But these critters can’t digest plastic, so one of two things happens. Hopefully, the plastic goes right through the zooplankton unchanged and, ahem, comes out the other end. But if a jagged piece of plastic gets stuck inside their guts, it can hurt or even kill them.
Microplastics can soak up toxins from the ocean around them like a sponge. These chemicals come from things like pesticides and fossil fuels. We know microplastics can soak them up because plastics are hydrophobic substances, which means they repel water. In the ocean, microplastics want to stick to other hydrophobic stuff, because then they don’t touch as much water. Similarly, hydrophobic toxins want to stick to other hydrophobic stuff. So these molecules will stick to plastic when they bump into it. Researchers worry this could expose animals that eat microplastics to higher amounts of these toxins,some of which cause cancer and birth defects.
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