A macro-plastic is the largest of the three classifications of plastic. It is anything you can clearly see. Some examples are plastic bags, water bottles, nets, etc. These generally are the easiest to see and are relatively easy to collect. While they still have a negative impact on the environment, they are less likely to get into the food chain because they are hard to ingest due to their size.
The next classification of plastic is micro-plastic. While there is not a strict formal definition micro-plastics are generally considered to have a diameter of one to five millimeters. There are two main types of micro plastic, primary and secondary. Primary micro-plastics are things like the micro-beads in cosmetics, or plastic pellets. Secondary micro-plastics are formed as macro-plastics breakdown. Micro-plastics can easily be incorporated into the food chain, and because of this have become the main focus of environmental conversation.
There is a third classification of plastic that is becoming a more popular research topic, nano-plastic. Nano-plastics are created by the degradation of micro-plastics. They can be smaller than 1 μm. Due to the extremely small size of nano-plastics they are highly likely to enter the food chain, as they can be consumed at the most base parts of the food chains. Nano-plastics also have a high surface area to volume ratio making them more likely to absorb organic pollutants and other hazardous contaminants. Much is still unknown about nano-plastics, but they are considered to pose a significant threat to the environment and human kind.
Preventing further plastic pollution and cleaning up what is there are the first major steps to solving the problem. Both micro- and nano- plastics are created by the degradation of macro-plastics. By preventing macro-plastics from entering the environment, it will prevent it from degrading into the smaller more dangerous plastics. Another way to cut down on micro-plastics is to not use products that contain them. Make sure that cosmetics are micro-bead free. One of the best way to prevent micro- and nano- plastics from damaging the environment is by preventing them from being there in the first place.