The harmful effects that fossil fuels have on our environment are well documented — a study from March found that global fossil-fuel emissions account for nearly 70% of climate cooling. But cars appear to be polluting in a way that hasn’t been deeply studied. According to a study from the San Francisco Bay Microplastics Project, the biggest source of microplastic pollution in California’s coastal waters may come from car tires. Microplastics are defined by the National Oceanic and Atmospheric Administration (NOAA) as fragments of plastic that are less than 5 mm in length (think the size of a sesame seed). Microplastics have been found in the stomachs of a number of marine organisms, and chemical additives from microplastics can also bleed out into the ocean, according to the NOAA. It is also possible that contaminants from the water may adhere to microplastics. The San Francisco Estuary Institute teamed up with the 5 Gyres Institute to complete a three-year study in what they claim is the first comprehensive regional study of microplastic pollution. The study found that more than 7 trillion pieces of microplastics wash into the San Francisco Bay each year, with much of it comin...