title: Mode of action and aquatic exposure thresholds of no concern.
abstract: Threshold concepts of toxicological concern are based on the possibility of establishing an exposure threshold value for chemicals below which no significant risk is to be expected. The objective of the present study is to address environmental thresholds of no toxicological concern for freshwater systems (ETNCaq) for organic chemicals. We analyzed environmental toxicological databases (acute and chronic endpoints) and substance hazard assessments. Lowest numbers and 95th-percentile values were derived using data stratification based on mode of action (MOA; 1 = inert chemicals; 2 = less inert chemicals; 3 = reactive chemicals; 4 = specifically acting chemicals). The ETNCaq values were derived by multiplying the lowest 95th percentile values with appropriate application factors; ETNCaq,MOA1-3 is approximately 0.1 microg/L. A preliminary analysis with complete MOA stratification of the databases shows that in the case of MOA1 or MOA2, the ETNCaq value could be even higher than 0.1 microg/L. A significantly lower ETNCaq,MOA4 value was observed based on the long-term toxicity information in the European Centre for the Ecotoxicology and Toxicology of Chemicals database. Application of the ETNCaq value in a tiered risk-assessment scheme may help chemical producers to set data-generation priorities and to refine or reduce animal use. It also may help to inform downstream users concerning the relative risk associated with their specific uses and be of value in putting environmental monitoring data into a risk-assessment perspective.
authors.affiliation: DuPont, B-2800 Mechelen, Belgium. watze.de-wolf@bel.dupont.com
authors.forename: Watze
authors.initials: W
authors.lastname: de Wolf
authors.forename: Angela
authors.initials: A
authors.lastname: Siebel-Sauer
authors.forename: Andre
authors.initials: A
authors.lastname: Lecloux
authors.forename: Volker
authors.initials: V
authors.lastname: Koch
authors.forename: Martin
authors.initials: M
authors.lastname: Holt
authors.forename: Tom
authors.initials: T
authors.lastname: Feijtel
authors.forename: Mike
authors.initials: M
authors.lastname: Comber
authors.forename: Geert
authors.initials: G
authors.lastname: Boeije
mesh_terms: D000818:Animals; D019992:Databases as Topic; D004781:Environmental Exposure; D004784:Environmental Monitoring; D005618:Fresh Water; D006801:Humans; D019055:No-Observed-Adverse-Effect Level; D009930:Organic Chemicals; D018570:Risk Assessment; D014874:Water Pollutants, Chemical / Q000009:adverse effects* / Q000032:analysis
chemical_list: D009930:Organic Chemicals; D014874:Water Pollutants, Chemical