On aspects of the dynamic behavior of persistent chemicals in a multimedia environment related to exposure-based hazard assessment
ABSTRACT The present research study focuses on the analysis and characterization of certain aspects of the dynamic behavior displayed
by persistent chemicals in a multimedia environment (chemodynamics), which is jointly determined by the inherent physicochemical
properties of the chemical substance under consideration, as well as underlying environmental processes such as degradation
in different phases/media (soil, water and air) coupled with intermedia transport (interphase mass transfer). In particular,
dynamic multimedia environmental models are considered with constant source terms describing steady chemical release/discharge
rates into various environmental media of interest, and key risk-related aspects of the dynamic behavior of persistent chemicals
are analyzed using perturbation theory techniques under conditions where degradation rates in different media are considerably
slower than intermedia transport rates. Under the above conditions, the problem of defining physically meaningful and practical
quantitative measures of overall persistence of chemicals in a multimedia environment is revisited, given its role as a key
exposure-based indicator within all major chemical risk assessment frameworks, and a proof is provided that rigorously establishes
equivalence between two important and popular persistence measures, namely the characteristic time at steady state and the
inverse of the associated chemodynamics overall decay rate (slowest chemodynamic mode).
KeywordsChemical dynamics-Multimedia environmental models-Persistence-Exposure-based hazard assessment-Perturbation theory
- SourceAvailable from: mit.edu[show abstract] [hide abstract]
ABSTRACT: The United Nations Environment Programme (UNEP) is currently coordinating negotiations to develop a binding global agreement by late in the year 2000 to prohibit, restrict, or reduce the production, use, or release of certain persistent organic pollutants (POPs). POPs are a small subset of organic chemicals whose characteristics of persistence in the environment, accumulation in biological organisms, and toxicity make them priority pollutants and environmental risks to humans and ecosystems. Under the UNEP negotiation, representatives are developing criteria and procedures for the addition of substances, guided by the initial list of 12 substances or substance groups selected for global action. It is therefore timely to investigate the scientific foundation for POPs screening criteria that have been used in other international, regional, and national programs, focusing on the properties of persistence, bioaccumulation, toxicity, and long-range transport in a policy context. The theoretical, empirical, and multimedia modeling approaches used reveal that guidance for setting POPs screening criteria can be developed using a combination of science and policy input. These approaches suggest that criteria adopted under regional POPs agreements in North America and Europe are reasonable and tend to isolate a limited number of clearly hazardous POPs from the majority of organic chemicals, while not being so stringent that the ability to respond to as yet unidentified risks is seriously compromised.Environmental Science & Technology - ENVIRON SCI TECHNOL. 09/1999; 33(20).
- [show abstract] [hide abstract]
ABSTRACT: A method is suggested for rapid screening of chemicals for persistence in the environment. Physical−chemical equilibrium partitioning information between air, water, and octanol are used as a first screen to identify the media for which degradation half-lives are required and those for which half-lives may be unnecessary. An overall persistence under equilibrium conditions is then estimated using half-lives in air, water, soil, and sediment using a steady-state mass balance model. A graphical technique to identify the key half-lives is demonstrated using 233 chemicals. For chemicals of more extreme partitioning properties, some half-lives may not be needed.Environmental Science & Technology - ENVIRON SCI TECHNOL. 02/2000; 34(5).
- Second 01/2003; Springer Verlag.