Over the last month there have been two stories in the news that have shown a strong link between chemical fertilizers and diseases. The first is a study that showed that breast cancer may be caused by high cadmium levels in food Cadmium in Diet May Increase Breast Cancer Risk: MedlinePlus. The second is a report from Ohio State University reporting that some people are have strong allergic reactions to the metal nickel in their foods http://medicalcenter.osu.edu/mediaroom/releases/Pages/Nickel-Food-Allergies.aspx.
Apparently, the heavy metals arsenic, cadmium, lead, mercury and nickel are all present in fairly large amounts in chemical fertilizers. The amounts that can be applied are regulated by federal and state governments. But, since all these metals are present in small amounts in the environment and it is not clearly understood how the man-made metal compounds build up in the soil or are transferred to our food and water, chemical fertilizer manufacturers can find some scientists willing to state that the fertilizers are safe.
It takes years for the metals to build up in the soils and migrate from the soil into our food and then accumate in our bodies. I would expect more similar stories over the next decades showing the stupidity of introducing additional heavy metals into our diets.
Of course, buffalo and chicken manure would make a more sensible fertilizer.