Explanation

Option A is correct: Microbeads are manufactured solid polyethylene or polypropylene plastic particles measuring less than 5 mm, frequently added as exfoliating abrasives in cosmetic facial cleansers and toothpastes:

– Because of their minute size, microbeads pass unfiltered through municipal wastewater treatment plant screens and flow into rivers, lakes, and oceans.
– In aquatic environments, they adsorb hydrophobic persistent organic pollutants (POPs) and are mistaken for food by zooplankton, fish, turtles, and seabirds, leading to bioaccumulation and severe toxic damage across marine ecosystems and marine food webs.

Therefore, the primary concern is that They are considered harmful to marine ecosystems — Option A.