I’m looking at sand from the seafloor down a microscope. Oh dear! What am I seeing?
Like other types of plastic, these microplastics don’t go away. They build up in the sand and mud of coastlines and on the sea floor. Where there are sand dunes, the wind will blow them inland so they become part of the soil. They don’t decay because plastics don’t do that. But they do enter the food chain. Because microplastics (including nurdles) seem like food to the myriad little animals that normally filter-feed in sand and mud, they get eaten by them. But they are not food and can block up the animals’ digestive systems so they starve to death.
These tiny sea creatures (like worms, molluscs and crustaceans at the bottom of the food chain are very sensitive to toxic substances (like plasticisers) and these toxins then pass up the food chain… and humans are at the top of the chain! Scientists don’t yet know much about the damage done by these ‘invisible’ microplastics but suspect that they will turn out to be serious. They already know that microplastics can ‘suck up‘ and carry with them toxic chemicals (e.g. persistent organic pollutants, POPs. These man-made chemicals already pollute the oceans.
The 12 worst of these POPs were banned in 2004 but they are very stable and take many years to disappear. Because of their stability, they get spread all around the world via the atmosphere and oceans. Many end up in the Arctic, far from their source, and are bad news for the Inuit peoples and polar bears because POPs ‘bioaccumulate’ (or ‘biomagnify’) in both plants and animals. This is critical for meat-eating animals at the top of the food chain such as people and polar bears. POPs become concentrated in animals’ body fat so if a person eats meat from an animal like a fish which has ‘bioaccumulated’ POPs from its own food, the chemicals become concentrated and can reach up to 70,000 times the levels you would find in the environment.
Before human industry, there were no POPs anywhere. They are not natural chemicals. But some POPs are useful to industry which is why they are made
- because some can be used to kill crop pests like insects
- because they are needed in many industry products (e.g PCBs )
Unfortunately some POPs form because of the burning of trash containing plastics at waste tips and incinerators dioxins are the best known ‘nasty’ which get unintentionally made when PVC plastic burns).
For more on POPs, including the “dirty dozen” worst offenders, visit the US EPA website.
Poor cow. Little does she know what’s under the grass…
So humans have to do something to stop plastic pollution. Just a century ago, there was no plastic and no pollution problem. Now it’s everywhere — in the ocean, on every coastline, on the sea floor and blowing in the wind to eventually wind up on city streets, parks, trees, fences and farmland.
Molluscs? What are they?
These are an enormous group of animals without backbones (invertebrates) which make up around a quarter of all sea creatures. They include many kinds of filter-feeding shellfish — snails, abalone, limpets, and conches — right up to the intelligent, free-swimming animals like octopus and squid
What are crustaceans?
These are a large group of arthropods (animals with ‘outside’ skeletons and jointed legs) such as crabs, lobsters, crayfish, shrimp, krill and barnacles
These are chemicals which are added to plastics to make them softer and more flexible. Best known are the pthalates, and some of these are known to be toxic
Meaning absorb and make stronger; concentrate