Chemical fertilizers are made up of various artificial ingredients, including nitrates, phosphates, ammonium sulfate, urea, sulfur, potash, and many more. They're usually applied at higher rates than organic fertilizers. These chemicals have been proven safe for humans; however, some people may still experience negative effects like skin irritation, nausea, vomiting, diarrhea, headaches, dizziness, breathing difficulties, and even death if used improperly.