title: Comparison of two methods for obtaining degradation half-lives.
abstract: Given the paucity of experimental degradation half-life data for most organic chemicals, there is a compelling incentive to use available estimation software when undertaking assessments of chemical persistence and mass balance modeling studies. In this study, half-life data obtained from estimation software for a set of 233 organic chemicals in air, water, soil and sediments were shown to differ significantly from half-life data listed in handbooks. It is suggested that the widely available and used estimation software, EPIWIN (Estimations Program's Interface for Windows), overestimates the reactivity of persistent organic pollutants (POPs). Reasons for this overestimation are explored. It is concluded that the maximum "default half-life values" used by the EPIWIN software are too short for estimating half-lives of highly persistent chemicals such as PCBs. There is a need for estimation software such as EPIWIN to be more thoroughly calibrated against experimental derived half-life data for a wide range of chemicals, including potential POPs, thus improving their reliability.
authors.affiliation: Canadian Environmental Modelling Centre, Trent University, Peterborough, ON, Canada.
authors.forename: Todd
authors.initials: T
authors.lastname: Gouin
authors.forename: Ian
authors.initials: I
authors.lastname: Cousins
authors.forename: Don
authors.initials: D
authors.lastname: Mackay
mesh_terms: D002623:Chemistry Techniques, Analytical / Q000379:methods*; D004785:Environmental Pollutants / Q000032:analysis*; D006207:Half-Life; D009930:Organic Chemicals / Q000032:analysis* / Q000737:chemistry; D012015:Reference Standards; D012984:Software
chemical_list: D004785:Environmental Pollutants; D009930:Organic Chemicals