Can someone tell me how to understand the ppm. It is on the bags of some of my stuff for goats but what does the ppm stand for? I'm not dum just somethings I do not understand what it stands for. Always learning more and more. On this map does the dark blue stand for low or high in selenium? Selenium in Counties of the East-Central US Thanks for the help and advice. I've got to learn this very important for my goats and friends of mine too.