PYRETHROIDS IN SOUTHERN CALIFORNIA COASTAL SEDIMENTS WENJIAN LAO,* LIESL TIEFENTHALER,DARRIN J. GREENSTEIN,KEITH A. MARUYA,STEVEN M. BAY, KERRY RITTER, and KENNETH SCHIFF Southern California Coast Water Research Project, Costa Mesa, California, USA (Submitted 9 January 2012; Returned for Revision 16 February 2012; Accepted 23 March 2012) Abstract —Little is known about pyrethroid fate and effects in estuarine and marine environments. In the present study, the extent and magnitude of pyrethroids in coastal embayments of the Southern California Bight (SCB), USA, were assessed. Using a stratified probabilistic design, 155 sediment samples were collected from four embayment habitats (estuaries, marinas, open bays, and ports) and analyzed for eight common-use pyrethroids. Total pyrethroid concentrations ranged from less than 0.5 to 230 mg/kg dry weight (area-weighted mean concentration ¼ 5.1  3.1 mg/kg) and were detected in 35% of the total SCB embayment area. Estuaries and marinas had the greatest areal extent of detectable concentrations (up to 65%) and the greatest area-weighted mean concentrations (22.1  26.5 mg/kg). Sites with the greatest pyrethroid concentrations were located near sources of runoff from urban watersheds. Bifenthrin and cyfluthrin were detected in 32 and 15% of all samples, respectively, whereas the other six pyrethroids were detected in 5% of samples. Permethrin and bifenthrin had the highest concentrations at 132 and 65 mg/kg. Toxic units estimated for the marine amphipod Eohaustorius estuarius ranged from 0 to 5.8, exceeding unity in 9 and 32% of the total and estuary habitat areas, respectively, and were not correlated with mortality, suggesting that other factors (e.g., co-occurring contaminants, reduced bioavailability) may affect the predictive capability using a single test species. Environ. Toxicol. Chem. 2012;31:1649–1656. # 2012 SETAC Keywords —Pyrethroid Sediment Embayment Mass inventory Toxicity INTRODUCTION Synthetic pyrethroids have become the dominant current-use pesticides in both agricultural and nonagricultural applications since the phase-out of organophosphates over the past 20 years [1]. Between 1999 and 2008 in five southern California coastal counties, total annual sales of pyrethroid pesticides for professional (i.e., licensed) application increased from 65 to 153 metric tons (www.cdpr.ca.gov). However, these usage figures underestimate total pyrethroid sales, because they do not include direct over-the-counter sales to consumers for residential use. In southern California, with more than 17 million residents and 6 million housing units (http://quickfacts. census.gov), approximately 73% of pyrethroids had nonagri- cultural applications, such as structural pest control and landscape maintenance (www.cdpr.ca.gov). Due to their hydrophobicity (log K OW ¼ 5–6) and particle reactive nature [2,3], sediments in urban and agricultural runoff are the predominant sink of pyrethroids in California receiving waters [4,5]. Pyrethroids have been measured in sediments from California, Texas, and Illinois; and stormwater runoff has been implicated as a primary source [1,4,6–8]. In much of urbanized California, stormwater and wastewater treatment systems are separate; therefore, wet and dry weather runoff receive no treatment before discharging to the coastal ocean. Moreover, the flood-control system has been highly modified to reduce flooding [9]. As a result, storm flows can change by orders of magnitude in a matter of minutes and carry large quantities of sediment. For example, approximately 700,000 metric tons of suspended solids, with 89% carried by storm flow, were discharged to the coastal ocean of the Southern California Bight (SCB) from 1994 to 1995 [10]. Pyrethroids can be highly toxic to nontarget aquatic species [1]. In several California urban creeks, bifenthrin concentra- tions ranged from 2.19 to 219 mg/kg dry weight, and most samples with greater than 0.5 toxic units (TUs) exhibited substantial toxicity to the freshwater amphipod Hyalella azteca [11]. In central Texas, pyrethroids were reported as the likely cause of toxicity to H. azteca in the sediments of urban streams [7]. In Illinois, pyrethroids occurred at levels up to 56 mg/kg with up to 2.9 TUs and were toxic to H. azteca in sediments of urban waterways [12]. Although pyrethroid use in California is widespread, and the potential for environmental impact is substantial, a limited number of comprehensive studies have evaluated the occurrence, extent, or magnitude of pyrethroids in the coastal environment. Two relatively small-scale, site-specific studies have been conducted in southern California marine habitats indicating that concern regarding pyrethroid impacts in marine systems is warranted [13,14]. One study in Ballona Creek (Los Angeles, CA), an intensely urbanized coastal estuary, reported pyrethroid concentrations up to 473 mg/kg dry weight and corresponding toxicity to a standard invertebrate toxicity test species, Eohaustorius estuarius [13]. The first objective of the present study was to assess the extent and magnitude of pyrethroid concentrations in marine embayments across the entire SCB. The second objective was to assess the influence of receiving water classification and dis- charge sources by comparing pyrethroid concentrations among different habitats, including estuaries, marinas, ports, and open bays. The third objective was to determine if a TU approach was predictive of toxicity observed for E. estuarius in sediment toxicity tests using splits of the same samples to quantify pyrethroid concentrations. Environmental Toxicology and Chemistry, Vol. 31, No. 7, pp. 1649–1656, 2012 # 2012 SETAC Printed in the USA DOI: 10.1002/etc.1867 All Supplemental Data may be found in the online version of this article. * To whom correspondence may be addressed (waynel@sccwrp.org). Published online 2 May 2012 in Wiley Online Library (wileyonlinelibrary.com). 1649