Toxicity of C10-, C11-, C12-, and C14-Polychlorinated Alkanes to Japanese Medaka (Oryzias Latipes) Embryos

Abstract

Japanese medaka (Oryzias latipes) eggs were exposed to aqueous concentrations of six polychlorinated n-alkane (PCA) standards () of known carbon chain length and chlorine content to assess their toxicity. Eggs were also exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to act as a positive control. Chlorinated paraffins are complex industrial products for which there is a lack of toxicological data on individual congeners. High aqueous concentrations of C 10 H 15.5 Cl 6.5 and C 10 H 15.3 Cl 6.7 (9,600 and 7,700 ng/ml, respectively) caused 100% mortality in eggs, but no other significant mortalities or lesions were observed at lower concentrations or in any eggs exposed to the other PCAs. Larvae from eggs exposed to high concentrations of the C 10 -, C 11 -and C 12 -PCAs were extremely lethargic or did not move, although a heart beat was present. The concentrations in these exposures and the tissue concentrations of the larvae were at levels that should elicit narcosis. Concentrations of the C 14 -PCAs in larvae did not reach narcotic levels, and larvae in these exposures appeared normal with no signs of narcosis. The TCDD was found to be extremely embryotoxic, consistent with past work using Japanese medaka eggs. The ratio of LC50 of TCDD to the LC50 of the PCAs, based on acute toxicity and TCDD results, were all Ͻ0.0001, and most were Ͻ0.000001. These results suggest that the acute mechanism of toxicity of lower chlorinated, short (C 10-13 ) and medium (C 14-18 ) carbon chain PCAs is narcosis and that chlorine substitution on the terminal carbons of PCAs does not significantly increase nor decrease the toxicity of C 10 -and C 14 -PCAs. However, additional work is needed to assess a greater range of PCAs as well as their sublethal effects and chronic toxicity.

Dietary accumulation and quantitative structure‐activity relationships for depuration and biotransformation of short (C10), medium (C14), and long (C18) carbon‐chain polychlorinated alkanes by juvenile rainbow trout (Oncorhynchus mykiss)

“…Body and liver growth rates and liver somatic indices did not vary between PCA-exposed and control rainbow trout, and no mortalities occurred in any treatment group (Table 2). Concentrations in the trout were much less than the lowest observable effects concentrations reported for short-and medium-chain PCAs in Japanese medaka (Oryzias latipes) embryos [12]. Based on these criteria, exposure to PCAs at the concentrations used in this experiment did not affect the health of the rainbow trout.…”

“…These standards consist of numerous PCA compounds with the same carbon-chain length but differing numbers of chlorine atoms ( Table 1). The synthesis methods are described in Fisk et al [12]. In brief, [ 14 C]-alkanes were chlorinated by adding a quantity of SO 2 Cl 2 into the respective n-alkane standard that would provide the desired chlorination (ϳ6-7 Cl atoms per alkane).…”

“…Polychlorinated alkanes (PCAs) are a class of high-molecular-weight organochlorines used for a variety of industrial processes, including high-pressure lubricants, plasticizers, and flame retardants. Commercial PCA formulations, which are also known as chlorinated paraffins, are complex mixtures of chlorinated n-alkanes with carbon-chain lengths of between 10 and 30 and chlorine contents of between 30 and 70% by weight that are categorized by the carbon-chain length: short (C [10][11][12][13], medium (C [14][15][16][17] ), or long (C [18][19][20][21][22][23][24][25][26][27][28][29][30] ). The PCAs are one of the last high-molecular-weight organochlorines and one of the largest groups of chlorinated hydrocarbons being produced and used in North America and western Europe [1].…”

Early Life Stage Bioactivity Assessment of Short-Chain Chlorinated Paraffins at Environmentally Relevant Concentrations by Concentration-Dependent Transcriptomic Analysis of Zebrafish Embryos

“…Short-chain chlorinated paraffins (SCCPs) are a large and complex family of chlorinated n-alkanes with carbon chain lengths of 10–13 and chlorine content of 30–70% by mass or weight, for example, an SCCP mixture with 60% chlorine by weight can comprise more than 4200 congeners . Because of their widespread use and diverse applications, SCCPs are ubiquitous in aquatic ecosystems and can be accumulated and biomagnified through the food web in aquatic organisms, − likely posing risks to high-trophic-level wildlife and even humans. ,− …”

“…A large number of SCCP mixtures or congeners are frequently found in aquatic ecosystems with a wide range of concentrations. ,, The concentrations of total SCCPs detected in surface water generally range from ng/L to μg/L, , and in aquatic organisms, the concentrations range from 0.1 ng/g lipid weight to 24 μg/g lipid weight . Adverse developmental toxicity was observed in fish in the early life stage upon exposure to SCCPs, for example, sheepshead minnow (Cyprinodon variegatus) larvae showed significantly decreased growth after 32 days of exposure to commercial SCCP mixtures (C 10–13 , 58% Cl) at 620.5 and 280 μg/L, Japanese medaka (Oryzias latipes) eggs exposed to high concentrations of C 10 H 15.5 Cl 6.5 and C 10 H 15.3 C l6.7 (9.6 and 7.7 mg/L, respectively) exhibited 100% mortality . However, most toxicological studies of SCCPs in fish have focused on only a few specific SCCP mixtures or congeners and examined the acute toxicity upon exposure to high concentrations; there is limited toxicological information available on SCCPs at low, environmentally relevant concentrations (ng/L to μg/L).…”