Rising plastic waste pollution issues are a growing concern around the world. Buildup of plastic debris in oceans for example is a very visible problem across the Asia-Pacific region, and has prompted APEC and numerous governments to take regulatory action. Not all plastic waste is easily visible however – tiny microplastics particles broken off of products such as clothing, car tires, and drink bottles are also building up not only in oceans but in drinking water supplies as well, raising concerns about potential impact on human health. Washington Core took a look at the first effort to regulate microplastics in drinking water, undertaken by the state of California. In June 2020, the California State Water Resources Control Board (SWRCB) released the world’s first official definition of the physical characteristics of microplastics particles for drinking water. Washington Core spoke with Dr. Scott Coffin – a scientist with the Division of Drinking Water at the SWRCB and main author of the definition – about this development and its implications for the environment and industry.