I think there are ways they can clean up that stuff nowadays, if they take the time and want to market it as a healthy garden product. I'll check my sources for any discussion of the subject.
John, thanks for sending along the citation. This is primarily out of curiosity and for comparison purposes--sometimes things you discover from decades past are found to be leathal mixes, yet other times you find that old remedies are just what you were looking for and fit your modern needs exactly.