Environmental persistence of chemicals

Area of Science:

• Environmental Chemistry
• Chemical Risk Assessment
• Environmental Modeling

Background:

• Persistence is a key environmental hazard criterion for chemicals.
• Direct measurement of environmental persistence is not feasible.
• Persistence estimation relies on models integrating half-lives, partitioning, environmental characteristics, and release scenarios.

Purpose of the Study:

• To review and discuss the hazard criterion of persistence in environmental chemistry.
• To propose a preferred method for estimating chemical persistence.
• To evaluate the utility of different environmental fate models for persistence assessment.

Main Methods:

• The study proposes average residence time as the preferred persistence criterion.
• It analyzes how degradation kinetics, mode-of-entry, and partitioning influence multimedia environmental persistence.
• The suitability of Level II, III, and IV environmental fate models for persistence estimation is examined.

Main Results:

• Average residence time is independent of chemical quantity and introduction type (steady- or unsteady-state) if processes are first-order.
• Multimedia persistence is influenced by degradation, entry mode, and partitioning.
• Level II models suffice for screening, Level III for average persistence, and Level IV for persistence distribution.

Conclusions:

• Regulating chemicals based on persistence requires sophisticated modeling.
• Using only degradation kinetics or media-specific half-lives can be misleading and inefficient.
• A strategy employing Level II, III, and IV models is recommended for accurate and economical persistence assessment.