Endosulfan and its metabolite, endosulfan sulfate, in freshwater ecosystems of South Florida: a probabilistic aquatic ecological risk assessment

Abstract

Endosulfan is an insecticide-acaricide used in South Florida and is one of the remaining organochlorine insecticides registered under the Federal Insecticide Fungicide and Rodenticide Act by the U.S.EPA. The technical grade material consists of two isomers (alpha-, beta-) and the main environmental metabolite in water, sediment and tissue is endosulfan sulfate through oxidation. A comprehensive probabilistic aquatic ecological risk assessment was conducted to determine the potential risks of existing exposures to endosulfan and endosulfan sulfate in freshwaters of South Florida based on historical data (1992-2007). The assessment included hazard assessment (Tier 1) followed by probabilistic risk assessment (Tier 2). Tier 1 compared actual measured concentrations in surface freshwaters of 47 sites in South Florida from historical data to U.S.EPA numerical water quality criteria. Based on results of Tier 1, Tier 2 focused on the acute and chronic risks of endosulfan at nine sites by comparing distributions of surface water exposure concentrations of endosulfan [i.e., for total endosulfan (summation of concentrations of alpha- and beta-isomers plus the sulfate), alpha- plus beta-endosulfan, and endosulfan sulfate (alone)] with distributions of species effects from laboratory toxicity data. In Tier 2 the distribution of total endosulfan in fish tissue (whole body) from South Florida freshwaters was also used to determine the probability of exceeding a distribution of whole body residues of endosulfan producing mortality (critical lethal residues). Tier 1 showed the majority of endosulfan water quality violations in South Florida were at locations S-178 followed by S-177 in the C-111 system (southeastern boundary of Everglades National Park (ENP)). Nine surface water sampling sites were chosen for Tier 2. Tier 2 showed the highest potentially affected fraction of toxicity values (>10%) by the estimated 90th centile exposure concentration (total endosulfan) was at S-178. At all other freshwater sites there were <5% of the toxicity values exceeded. Potential chronic risk (9.2% for total endosulfan) was only found at S-178 and all other sites were <5%. Joint probability curves showed the higher probability of risk at S-178 than at S-177. The freshwater fish species which contain tissue concentrations of endosulfan (total) with the highest potential risk for lethal whole body tissue residues were marsh killifish, flagfish and mosquitofish. Based on existing surface water exposures and available aquatic toxicity data, there are potential risks of total endosulfan to freshwater organisms in South Florida. Although there are uncertainties, the presence of tissue concentrations of endosulfan in small demersal fish, is of ecological significance since these fish support higher trophic level species, such as wading birds.

Assessment of the Occurrence and Potential Risks of Pharmaceuticals and their Metabolites in Fish and Water Using Liquid Chromatography Mass Spectrometry

“…The estimated 90th centile of exposure concentrations were compared to the estimated 10th and 5th centile concentrations from the acute SSDs (Solomon et al 2001). The 90th centile represents a concentration that would only be expected to occur 10% of the time and would represent episodic or pulsed exposures (Rand et al 2010). The estimated 50th centile exposure concentrations were compared to the estimated 10th and 5th centile concentrations of the chronic SSDs (Solomon et al 2001).…”

“…The 50th centile concentration was chosen as a comparison to chronic SSDs on the basis of that it might be more representative of background concentrations as 50% of the exposures are anticipated to be above or below this level at a site (Rand et al 2010).…”

Impact and Mitigation of Nutrient Pollution and Overland Water Flow Change on the Florida Everglades, USA

“…A 2015 study of agricultural chemicals in the water of the extended Lake Okeechobee and Everglades watersheds periodically detected trace levels (<0.00015 mg/L) of the herbicides 2,4-D, ametryn, atrazine, bentazon, diuron, metolachlor, metribuzin, along with the insecticide imidacloprid, however all detections were below the threshold of concern for aquatic toxicity [49]. Endosulfan, a persistent, bioaccumulative and toxic organochlorine insecticide and acaricide used in South Florida until its regulatory phase out at the end of 2014, is ubiquitous in the South Florida aquatic ecosystem and presents potential risk to freshwater organisms of the Everglades ecosystem [50,51].…”

Probabilistic risk assessment of diuron and prometryn in the Gwydir River catchment, Australia, with the input of a novel bioassay based on algal growth

“…163 records for EC 50 or LC 50 of diuron and 51 records of prometryn were selected. Where more than one toxicity value was available for a single species, the geometric mean was calculated to favor the more sensitive studies (Maltby et al, 2005;Rand et al, 2010). Toxicity data for 60 species by diuron and 35 species by prometryn were finally derived to construct the SSD for the two herbicides.…”