Micro plastics are small plastic particles that are of 5mm length or below. Some scientists have raised their objection to the loose definition of micro plastics with respect to the size — it seems 5mm is not small enough to be called micro. However, this should not be much of a concern when speaking of the general health effects of tiny plastics.

One of the argument against considering micro plastics to be harmful to human body is that there isn't empirical scientific evidence that establishes it. Most assertions of the harm of micro plastics are based on inferences and suppositions. While this is true to an extent, the argument that it needs to be considered safe, or one shouldn't considered micro plastics as harmful is pretty moot. This is because scientific evidences are merely a subset of facts and it is foolish to consider only the subset as facts.

Now, back test this argument. Consider you are in 1920s and told to smoke cigarettes because of the lack of scientific evidence proving tobacco causes cancer. How right would that be?

Since there isn't an empirical evidence for the harmfulness of micro plastics, we can only rely on suppositions based on logic. Ours go this way: since there is no scientific evidence for the harmlessness of micro plastics upon consumed, and since there are evidences that non micro plastics and their chemical constituents cause cancer and offspring deformities, it is sensible to preemptively consider that micro plastics are dangerous.

The other argument in this domain is that human bodies are already contaminated with micro plastics, and so there is no need to be paranoid about it. It is true that paranoia doesn't really help with anything but bad health, being already contaminated with micro plastics is no reason not to be concerned about it and stop/reduce the contamination, especially since they are considered dangerous (as discussed earlier).