title: Acute toxicity of the cationic surfactant C12-benzalkonium in different bioassays: how test design affects bioavailability and effect concentrations.
abstract: Using an ion-exchange-based solid-phase microextraction (SPME) method, the freely dissolved concentrations of C12-benzalkonium were measured in different toxicity assays, including 1) immobilization of Daphnia magna in the presence or absence of dissolved humic acid; 2) mortality of Lumbriculus variegatus in the presence or absence of a suspension of Organisation for Economic Co-Operation and Development (OECD) sediment; 3) photosystem II inhibition of green algae Chlorella vulgaris; and 4) viability of in vitro rainbow trout gill cell line (RTgill-W1) in the presence or absence of serum proteins. Furthermore, the loss from chemical adsorption to the different test vessels used in these tests was also determined. The C12-benzalkonium sorption isotherms to the different sorbent phases were established as well. Our results show that the freely dissolved concentration is a better indicator of the actual exposure concentration than the nominal or total concentration in most test assays. Daphnia was the most sensitive species to C12-benzalkonium. The acute Daphnia and Lumbriculus tests both showed no enhanced toxicity from possible ingestion of sorbed C12-benzalkonium in comparison with water-only exposure, which is in accordance with the equilibrium partitioning theory. Moreover, the present study demonstrates that commonly used sorbent phases can strongly affect bioavailability and observed effect concentrations for C12-benzalkonium. Even stronger effects of decreased actual exposure concentrations resulting from sorption to test vessels, cells, and sorbent phases can be expected for more hydrophobic cationic surfactants.
authors.affiliation: Institute for Risk Assessment Sciences, Utrecht University, The Netherlands.
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.forename: Marc
authors.initials: M
authors.lastname: Geurts
authors.forename: Sascha B
authors.initials: SB
authors.lastname: Sjollema
authors.forename: Nynke I
authors.initials: NI
authors.lastname: Kramer
authors.forename: Joop L M
authors.initials: JL
authors.lastname: Hermens
authors.forename: Steven T J
authors.initials: ST
authors.lastname: Droge
mesh_terms: D000327:Adsorption; D000818:Animals; D001548:Benzalkonium Compounds / Q000633:toxicity*; D001681:Biological Assay / Q000379:methods*; D000460:Chlorophyta / Q000187:drug effects / Q000378:metabolism; D003621:Daphnia / Q000187:drug effects; D019015:Geologic Sediments / Q000737:chemistry; D006812:Humic Substances / Q000633:toxicity; D009835:Oligochaeta / Q000187:drug effects; D017686:Oncorhynchus mykiss; D045332:Photosystem II Protein Complex / Q000378:metabolism; D052617:Solid Phase Microextraction; D013501:Surface-Active Agents / Q000633:toxicity*; D023382:Toxicity Tests, Acute / Q000379:methods*; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D001548:Benzalkonium Compounds; D006812:Humic Substances; D045332:Photosystem II Protein Complex; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D014867:Water
keywords: Bioavailability; Cationic surfactant; Equilibrium partitioning; Sorption