1,2,3,6-tetrahydro-3-methylphthalic anhydride

Endpoint summary

Additional information

Various studies have been undertaken on tetrahydromethylphthalic anhydride (MTHPA). This is a structural analogue of 3-MTHPA D4 in which the methyl substitution is not defined or fixed in a specific position on the carbon cyclic structure, as opposed to 3-MTHPA D4 where the methyl substitution is fixed at the 3C position. 3-MTHPA D4 is regarded as a specific isomer of MTHPA.

 

Acute toxicity

The 48–hour acute toxicity to Daphnia Magna has been studied under static conditions. Daphnids were exposed to control and test chemical at nominal concentration of 0, 32, 56, 100, 180, 320 mg/L for 48 hours. Mortality/immobilisation and sublethal effects were observed daily. The 48 – hour LC50/EC50 was 130 mg /L. The 48 – hr NOEC based on immobilisation was 87 mg/L.

In a 72 hour study, cultures of Selenastrum capricornutum were exposed to nominal concentrations of 10, 18, 32, 56 and 100 mg/L under static conditions in accordance with OECD Guideline 201. An EC50 of 68 mg/L (growth rate) and 64 mg/L (biomass) were reported and the NOEC value determined was 27.5 mg/L (growth rate and biomass).In accordance with ECHA guidance on information requirements and chemical safety assessment,Chapter R.7b: Endpoint specific guidance, theErC50 endpoint is used in DNEL derivation. This is because use of values based on biomass cannot be applied to an analysis of results from a system in exponential growth without logarithmic transformation.

In a 96-hour acute toxicity study, Medaka (Oryzias latipes) were exposed to a nominal limit concentration of 100 mg/L under flow through conditions. The EC50 and NOEC values, based on mortality/sublethal effects, were> 100 and = 100 mg/L, respectively. Sublethal effects were not observed in the groups exposed to 100 mg/L of tetrahydromethylphthalic anhydride.

An activated sludge test has been conducted following OECD test methds. An EC50 value of 69.87 mg/L was determined. An accurate NOEC value could not be determined, being lower than the lowest concentration of 10 mg/L investigated. Respiration rates were influenced (inhibited) dose dependently over the whole concentration range.

Chronic toxicity

The 21 -day-chronic toxicity to Daphnia Magna was studied under semi-static conditions in two Daphnia magna reproduction tests conducted in accordance with OECD test methods.In a new key study of 2010 , daphnids were exposed at nominal concentrations of 1.25, 2.5, 5, 10, 20 and 40 mg/L. The NOEC was 20 mg/L and the LOEC was 40 mg/L. An older study of 1997 is regarded as of lower quality as the available study report does not give enough experimental details and analytical measurements are equivocal. In this study daphnids were exposed at nominal concentrations of 1.3, 4.1, 13, 41 and 130 mg/L. The 21 day LC50 for parenteral animals was >110 mg/L and the EC50 based on mortality/sublethal effects was 9.2 mg/L. Both studies revealed comparable LC50 values (> 110 mg/L and > 40 mg/L) and, at high concentrations, a reduced number of juveniles. The weight of evidence from these studies justifies a NOEC of 20 mg/L for chronic Daphnia toxicity.

 

The 14 -day-chronic toxicity to Oryzias latips has been studied under flow through conditions. Fish were exposed to control and test chemical at nominal/measured concentrations of 0 and 100 mg/L. The 14 day LC50/EC50 based on mortality was > 100 mg/L. The 14-day NOEC was 100 mg/L. It is recognised that 14-days exposure is not currently regarded as a chronic study. Upon contact with water hydrolysis of MTHPA to the corresponding dicarboxylic acid rapidly occurs and, therefore, not long-term but acute toxicity effects are relevant, in particular changes of pH. Moreover, the available information about production and processing of MTHPA, and the uses identified, indicates that direct releases to the aquatic compartment can be excluded. With consideration of these aspects, no further testing is indicated and would not be in agreement with concerns regarding animal welfare and the use of animals for experimental purposes.