Final answer:
The EPA has issued regulations against 17 top priority chemicals under its 33/50 Program. In addition, the EPA has implemented regulations through various other programs. The total number of chemicals against which the EPA has issued regulations is not specified.
Step-by-step explanation:
The EPA has issued regulations against 17 top priority chemicals under its 33/50 Program, a voluntary program that companies committed to reducing their releases of these chemicals. These regulations aimed to reduce pollution and were implemented between 1992 and 1995. In addition to these 17 chemicals, the EPA has issued regulations against other chemicals through programs like WaterSense, Safer Choice, Environmentally Preferable Purchasing, Green Chemistry, and the SmartWay Transport Partnership Program. The total number of chemicals against which the EPA has issued regulations is not specified in the provided information.