Urea, Ammonium sulphate, Ammonium nitrate, potassium nitrate are toxic to human flesh and increase soil acidity. This is because when they are hydrolyzed they form strong acids H2SO4.HNO3 and HCl with high dissociating constants.The best ways out are to put on protective clothes, gloves,and boots as well as proper washing of bodies after application. Besides, there is need for soil testing to know the status of soils whether there is need for liming or not
I think that the incidence of cancerous diseases due to the use of chemical fertilizers that contain nitrogenous substances, as nitrates in the human intestine turn into nitrites that cause leukemia in the stomach and intestines.
Also, the decomposition of urea and the volatilization of ammonia gas lead to respiratory infections and infertility in men.
I so much appreciate every response made in regards to my question. I believe I now have in-depth knowledge concerning the choice of fertilizer. Thanks so much for the quick response.