Associated with sure, but at what exposure levels? Can we expect all microplastics to have this affect? What if the lower fertility rates are tolerable compared to the benefits of plastic use overall?

From your first source: >Data are still preliminary but suggest that ingested MPs bio-accumulate in mammalian tissue, including the testis, with outcomes on semen quality in rodents, as a consequence of inflammatory state and oxidative stress damage.

>The mechanisms decreasing fertility rate during the lifespan are still poorly understood.

>Taken together, although studies in mammals are still limited, preliminary observations point out a possible risk of MPs for male fertility.

The evidence is still "preliminary" and data "suggests" some outcomes but nothing is close to definitive. There are lots of confounding factors that can cause lower fertility that are explicitly noted in the that source. For example they even suggest that the microplastics themselves might not be causing harm, but rather that they act as "sponges" or vehicles for concentrating other pollutants that are actually decreasing fertility.