Primary sources of microplastics are those which are produced for industrial or business purposes. The most prevalent are used in cosmetics, textiles, and commercial use. Just because they start out as microplastics, does not mean they do not continue to break down, eventually becoming nanoplastics. According to a study by the IUCN, approximately two thirds of microplastic pollution in the ocean comes from the primary sources of textiles or microfibres. Through erosion, these synthetic particles are transported from land areas to the oceans and waterways. Read more about the ways in which industries and consumerism contribute to primary sources of microplastic pollution.
As we can see here, modern consumerism and manufacturing has exacerbated the severity of microiplastic pollution. By changing our behaviors, even in small ways, we can lower these numbers.