Why is plastic bottles bad for the earth but aluminium isnt?
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Elemental aluminum is fairly inert. Rather, it forms a protective oxide layer that makes it inert. That means even if it’s ingested by some critters it will most likely just get pooped out and not interfere with biological processes. Plastic breaks down into a bunch of chemicals that can interfere with those processes and affect health. There are plenty of *super* toxic compounds that contain aluminum, but the kind of elemental aluminum that most things are made of doesn’t break down into anything other than smaller pieces of aluminum. At the smallest scale, it’s all just aluminum atoms (and some inert oxides). Plastics are made from a huge variety of molecules, many of which break down not just into smaller pieces of plastic but different chemical compounds, some of which are more toxic than the original molecule.
Aluminum is very dense, which means when it gets into waterways it tends to sink to the bottom, get buried, and stay there. Even plastic that is more dense than water tends not to be *that much* more dense, and it can get picked up by currents. This is especially true for microplastics. Floating plastic is more likely to be ingested by aquatic life or interfere with the ecology (for example, providing an unnaturally ample surface for certain planktons to grow on near the surface). Microplastics can even be light enough to get picked up into the air – recent studies have found microplastics inside our lungs. To be clear, aluminum dust is absolutely not good for your lungs, but because aluminum is so dense it will probably settle out of the air unless you are in an environment where it is being created (like a factory).
Speaking of, aluminum doesn’t tend to break down into tiny bits like plastic. It absolutely *can*, but it usually doesn’t because it isn’t soft like plastic. Each atom in the aluminum is bound pretty tightly to the atoms around it in a crystal lattice. Plastics are made from chains of long molecules – the individual bonds within those molecules may not be as strong as the bonds holding the aluminum atoms; and, many of the chains are not *chemically* bound at all, just tangled up together. Plastic is more vulnerable to damage from UV light, too, which helps break it down into smaller, more mobile pieces of plastic that can travel through the environment.
Again, to be clear, getting pure aluminum atoms inside of you is not good for you, but that is almost never going to happen. The aluminum quickly reacts with oxygen in the air and forms an oxide layer that is already “pre-reacted” so it can’t really interact with anything else. If you cut or grind that oxide layer off, a new layer will very quickly form. If you ate a chunk of aluminum, your body can’t really do anything to it because the oxide layer protects the rest of the pure aluminum underneath, so you just have a big ball of aluminum that does nothing, interacts with nothing, and can’t be absorbed into your body before it gets passed. As stated, there are compounds containing aluminum that are very toxic, but we don’t make cans out of those for obvious reasons so you don’t find those compounds outside of, like, industrial waste. And that really is not good for the environment, but it doesn’t happen at the sheer scale that plastic pollution happens.
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