Why is the movement of chemicals across borders significant in PEC evaluations?

The significance of the movement of chemicals across borders in PEC evaluations stems primarily from the potential to introduce previously unseen risks to local environments. When chemicals are transported from one region to another, they may interact with different ecological systems, which may not have been previously exposed to those particular substances. This can lead to unexpected ecological impacts, such as toxicity to local species, disruption of food chains, or contamination of local water sources.

Additionally, regions may have varying regulations, environmental conditions, and biodiversity levels, which can influence how a chemical behaves and its potential effects. Thus, it becomes crucial for PEC evaluations to consider these risks to ensure environmental safety and effective risk management, particularly in regions that may lack robust regulatory frameworks or prior exposure to certain chemicals.