RACHEL BECKER CalMatters California is poised to issue the worldâs first guidelines for microplastics in drinking water despite no data on how plentiful they are in the state, no scientific agreement on how to test water for them and little research on their health risks. The pieces of plastic â smaller than an ant, some so tiny they can be seen only with a microscope â have contaminated wildlife and human bodies through their food, air and water. Under a 2018 state law, California must require four years of testing for microplastics in drinking water, and the state must consider guidelines to help water providers and consumers determine what levels may be safe to drink.