As government regulators focused on reigning in air pollution, companies were busy generating new sources of pollution, including plastics and PFAS, the so-called forever chemicals. PFAS, which stands for perfluoroalkyl and polyfluoroalkyl substances, are a large group of compounds used, among other things, to make fabric stain-resistant and pans nonstick.

Over time, these modern-era substances — which famously take decades to millennia to degrade — have leached into the environment, reaching every corner of the planet, no matter how tall or deep. Microplastics, PFAS, and some other compounds, such as pesticides, are now so widespread that they’ve essentially become part of our biome, not unlike bacteria or fungi.

They’re so common, in fact, that they’re even found in the rain.