Abstract
3,4-dichloroaniline (3,4-DCA) is one of the most widely produced anilines world-wide, used in plastic packaging, fabrics, pharmaceuticals, pesticides, dyes and paints as well as being a degradation product of several pesticides. 3,4-DCA has been detected in freshwater, brackish and marine environments. Although freshwater toxicity thresholds exist, very little toxicological information is available on marine and cold-water species. In this study, we exposed Atlantic cod (Gadus morhua) embryos (3-7 days post fertilization) to 3,4-DCA concentrations ranging from 8-747 μg/L for 4 days followed by a recovery period in clean sea water until 14 days post fertilization (dpf). The cod embryos were significantly more sensitive to acute 3,4-DCA exposure compared to other species tested and reported in the literature. At the highest concentration (747 μg/L), no embryos survived until hatch, and even at the lowest concentration (8 μg/L), a small, but significant increase in mortality was observed at 14 dpf. Delayed and concentration-dependent effects on surviving yolk-sac larvae, manifested as cardiac, developmental and morphometric alterations, more than a week after exposure suggest potential long-term effects of transient embryonic exposure to low concentrations of 3,4-DCA.
Highlights
3,4-dichloroaniline (3,4-DCA) is one of the most widely produced anilines world-wide, used in plastic packaging, fabrics, pharmaceuticals, pesticides, dyes and paints as well as being a degradation product of several pesticides. 3,4-DCA has been detected in freshwater, brackish and marine environments
At the end of the recovery period (14 dpf), all 3,4-DCA-exposed groups displayed significantly higher cumulative mortality than controls (Fig. 2 D) and in a more concentration-dependent manner, and the LC50 was estimated at 310.3 μg/L
This study of Atlantic cod embryos demonstrates that the early life stage of this cold-water marine fish species is more sensitive to 3,4-DCA than freshwater species previously studied
Summary
3,4-dichloroaniline (3,4-DCA) is one of the most widely produced anilines world-wide, used in plastic packaging, fabrics, pharmaceuticals, pesticides, dyes and paints as well as being a degradation product of several pesticides. 3,4-DCA has been detected in freshwater, brackish and marine environments. The cod embryos were significantly more sensitive to acute 3,4-DCA exposure compared to other species tested and reported in the literature. 3,4-DCA is a precursor and intermediate product in the chemical synthesis of several industrial products, including herbicides, dyes and paints [3,4]. It is, for example, an intermediate of 3,4-dichlorophenylisocynate, used for the production of phytosanitary products such as propanil, linuron, diuron and neburon [1]. Concentrations causing acute toxicity in ELS of other freshwater fish species vary, with reported 96h-LC50 values ranging between 940 μg/L in Arabian killifish (Aphanius dispar) and 33 000 μg/L in Javanese medaka (Oryzias javanicus) [24,25]. Ibrahim and co-authors [65] (2021) further documented reduced spawning rates and lowered gonadosomatic indices (GSI) in female Javanese medaka (O. javanicus), and 3,4-DCA exposure has been shown to cause delayed development, altered heart rates, peri cardial and yolk sac edema and various skeletal deformations fish em bryos and larvae [24,32]
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