Some fertilizers can be harmful to your health. It depends on what kind of fertilizer you're using and what's in it. Chemicals like lead, arsenic, and mercury are used as ingredients in fertilizer, so it's important to know that they're there. Check the label when shopping for fertilizer. In good fertilizers, nitrogen, phosphorus, and lead are used as ingredients. In some fertilizers, mercury, arsenic, and lead are used as ingredients.