What is the "downside" to extensive use of synthesized nitrogen-containing fertilizers?

An extensive use of synthesized fertilizers can cause over fertilization as then the nutrients are readily available to the plant. The repeated use of these fertilizers can promote alagal growth,  build up of toxic chemicals like arsenic, cadmium, and uranium in soil. These harmful chemicals can indirectly reach your body through fruits and vegetables. It can also change the PH of the soil. Furthermore, the extensive use of these fertilizers can release greenhouse gases and attracts pest.

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