What does 40 CFR part 156 primarily address?

The correct answer pertains to the criteria for labeling pesticides, which is the primary focus of 40 CFR part 156. This regulation provides detailed guidelines on how pesticides must be labeled to ensure that users understand the potential hazards and safe handling practices associated with these chemical products. This includes mandatory information that must be present on the label, such as active ingredients, directions for use, precautionary statements, and first aid instructions. The purpose of these labeling requirements is to protect human health and the environment by ensuring that pesticides are used properly and safely.

In contrast, the other options address different aspects of pesticide regulation. For instance, packaging criteria are covered in another part of the regulations and focus on how pesticides are physically contained, while worker protection standards pertain to regulations designed to protect agricultural workers from occupational exposure to pesticides, detailing safety measures and training. Experimental use permits refer to specific permissions required for the use of pesticides that are still under development or testing, which is governed by separate regulations rather than those focused on labeling.