From Vox: In the 1970s, acid rain was one of the most serious environmental threats in North America and Europe. The air was so laden with pollution from coal power plants and cars at the time that it turned the rain toxic. Now, however, there’s another problem with our rain — and it’s even more alarming. While precipitation has become less acidic, a growing body of evidence suggests that it’s now full of many other pollutants that pose a risk to public health, including microplastics. And unlike the compounds that cause acid rain, these pollutants are almost impossible to get rid of.