Willing
There are many reasons why we study parts per million. It is very important because parts per million along with parts per billion and parts per trillion are the most commonly used terms to describe very small amounts of contaminants in our environment. It may be a little difficult to explain to my friends what parts per million or parts per billion were. I think that the way that I would explain these equations to them is that they took something they found on the street and wanted to know if it was edible then they could measure it in either parts per million or parts per billion to find out if the item is toxic and if it is toxic, how toxic it is.