chemical fertilizers have numbers on them like 10-20-10. this is the ratio of the particular chemicals making up the fertilizer. they stand for n-p-k or nitrogen-phosphorus-potassium. the middle number, phosphorus, is the stuff these phosphor plants are making. even after heating the mined phosphorus and making the fluoride escape into the scrubber stacks, not all of the fluoride is extracted. up to 20% of the "P" number in the fertilizer can be pure fluoride. this is one of the things that makes chemical fertilizer to grow food so dangerous. it is not bad enough to spray it on the plants and produce, it is grown in it and taken into the plant through the roots.