In front of the United Nations African headquarters in Nairobi, a 30-foot-high artwork featuring a faucet “spewing” a long stream of plastic waste dramatically illustrates the worsening flow of plastic fouling the world. Inside the main hall, 175 UN delegates took the first formal steps on Wednesday to turn off the tap. They agreed to negotiate the first comprehensive global treaty to curb plastic pollution—a move hailed as the most significant environmental agreement since the Paris climate accord in 2015.

The framework of the agreement was hammered out last week ahead of the delegates’ vote. It creates a road map for treaty negotiations that are set to begin in May. Inger Andersen, who heads the UN Environment Program, told the delegates: