2-[methyl[(nonafluorobutyl)sulphonyl]amino]ethyl methacrylate

Endpoint summary

Description of key information

Aquatic toxicity of C4 sulfonamido methacrylate (Target chemical) is addressed by readacross from C4 acrylate (Source chemical). The Target chemical and the Source chemical both contain the nonafluorobutylsulfon-N-methylamidoethoxyl (i.e., C4 sulfonamido alcohol) functionality. The Target chemical contains this structure esterified with methacrylic acid. The Source chemical contains the same group esterified with acrylic acid. The Source chemical and the Target chemical have similar molecular weight. Water solubility differs between the two chemicals by approximately a factor of ten, while octanol-water partition coefficient differs by less than one log unit. Acrylate and methacrylate functionalities are electrophilic and both may participate in Michael addition reactions. Metabolism is expected to occur through the same pathways, hydrolysis by carboxylesterases and conjugation to gluthathione. Hydrolysis is similar across the acrylate family and enhances the elimination of the chemical upon exposure (McCarthy & Witz (1997), Toxicol. 116, 153). Enzymatic hydrolysis kinetic constants for methacrylate and acrylate esters are similar. The analogue hypothesis is that toxicity data for C4 sulfonamido acrylate, which is more electrophilic, can be read across directly to C4 sulfonamido methacrylate. The resulting readacross will be conservative, as the greater electrophilicity of acrylate esters leads to greater toxicity than that exerted by methacrylates. C4 acrylate has previously been registered in a higher tonnage band than C4 sulfonamido methacrylate, and more ecotoxicity data are available for readacross than is required for the methacrylate. Nevertheless, all available aquatic toxicity endpoints are reported to establish that D. magna is the most sensitive species (Table 1).

Table 1. Aquatic toxicity endpoints

Acute Toxicity to Fish (D. rerio)	Endpoint is not required at this tonnage band. Source chemical data included to demonstrate that D. magna is the most sensitive species.	Experimental: 96 hr test (OECD 203) No toxicity observed, loading rate 5 - 6 mg/L, analytically determined concentration 0.32 mg/L.
Acute Toxicity to Aquatic Invertebrates (D. magna)	Read-across: 48-hour EC50 (mobility): 1.2 mg/L   Rationale: While the source chemical is expected to be more toxic than the target chemical, its 48-hour EC50 is read across as such to account for uncertainties in molecular weight and hydrophobicity	Experimental: 48-hour EC50 (mobility) 1.2 mg/L (OECD 202)
Toxicity to Algae and Aquatic Plants (P. subcapitata)	Read-across: No toxicity to algae expected   Rationale: Acrylates and methacrylates are toxic via a Michael addition pathway, where acrylates are somewhat more electrophillic and somewhat more toxic. No toxicity observed for Source chemical at a loading rate above its water solubility limit. The Target chemical is 10X less soluble, in addition to its lesser expected toxicity.	Experimental: No effect on growth rate, loading rate 5 mg/L, analytically determined concentration 0.34 mg/L. (OECD 201)
Toxicity to Microorganisms (activated sludge respiration)	Endpoint is not required at this tonnage band. Source chemical data included to demonstrate that D. magna is most the sensitive species.	Experimental: 3h EC50 >1000 mg/L (OECD 209)

Please see Analogue Reporting Format, IUCLID Section 13, for further information justifying the readacross.