Reaction mass of 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-inden-5-yl isobutyrate and 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-inden-6-yl isobutyrate

Short-term toxicity to aquatic invertebrates

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1.2 mg/L

Additional information

The acute Daphnia toxicity is based on a WoE approach of two acute tests and one acute value from the long-term test. The executive summaries of the acute Daphnia tests with Elendt medium, with ISO-medium and the derived value from the long-term test also in ISO medium will be presented. From these three the geometric mean will be used to derive the final result.

The acute Daphnia toxicity with Elendt medium (2020)

The acute toxicity for Daphnia magna was assessed in a semi-static test design with closed vessel test according to OECD TG 202. The nominal and arithmic mean measured test concentrations were 0, 3.3, 4.1, 5.1, 6.4 and 8.0, mg /L (spacing factor 1.25), 0, 1.8, 2.2, 3.02, 3.53 and 4.58, 3.53, 3.02, 2.20, respectively. At 24h 10 and 50% of the Daphnia were immobile at 3.53 and 4.58 mg/l. After 48 hours 50, 60, 75,80 and 85% was immobile at 1.8, 2.2,3.02, 3.53 and 4.58 mg/l. The 48-hour EC50 value was calculated to be 1.78 mg/L.

Acute Daphnia test with ISO Medium (2018)

The acute toxicity to Daphnia magna of the substances was conducted in an OECD TG 202 test under GLP. The test solutions were prepared in ISO-water. A standard stock solution was prepared with 25mg substance in 5L to have a stock solution of 5 mg/l. This solution was stirred for 24h under sealed conditions after which further dilutions were made. The nominal concentrations were 0.1, 0.18, 0.32, 0.56, and 1 mg/l. The geometric mean concentrations were 0.11, 0.218, 0.372, 0.653, and 1.181 mg/l all slightly higher than nominal. At 24h at 0.56 and 1 mg/l nominal 2/20 and 8/20 Daphnia become immobile. After 48h the toxicity increased: at 0.32, 0.56 and at 1 mg/l, 5/20, 10/20 and 19/20 Daphnia became immobile. pH and temperature were within the criteria of the test guideline. This resulted in an EC50 of 0.536 mg/l (0.446 -0.642 mg/l) based on geometric mean concentrations.

Acute Daphnia derived from Long term Daphnia test (2019)

The acute Daphnia EC50 after 48h was derived from an long-term Daphnia test and considered to be equivalent to an OECD TG 202 under static conditions because renewal time was after 2 days. The stock solutions were stirred for 23.5 to 24 hours. Then adequate volumes of the stock solutions were mixed into test water to obtain the desired test concentrations. The nominal concentrations were 0.03, 0.1. 0.32, 0.9 and 3.0 mg/l. The TWA measured concentrations during the whole 21d exposure period with semi-are considered to be applicable after 2 days exposure. These concentrations are 0.00891, 0.0307, 0.164, 0.462, 1.83 mg/l. No Daphnia were immobilised after 2d in this test and therefore the EC50 is > 1.83 mg/l.

WoE for deriving acute 48h EC50 Daphnia

The value from the acute Daphnia EC50 study with ISO-medium (2018 study) is about a factor 3 lower compared to the acute EC50 values derived from the studies with Elendt medium: one long-term and one acute toxicity study (EC50 values of > 1.83 and 1.78 mg/l, respectively). Both acute values with Elendt and ISO-medium could be considered to be within the experimental variability of these studies (1.78 and 0.535 mg/l, respectively). The results of the acute and long-term ISO-medium studies show a fairly normal difference between acute and long-term effects: 1.78 and 0.46 mg/l, a factor of 3.9. The long-term NOEC of the Elendt medium and the acute ISO medium are almost the same 0.46 and 0.535 mg/l, respectively, which is remarkable. However, the ISO-medium acute value cannot be ignored as such. Therefore a WoE is applied for the three EC50 studies 1.78 and >=1.83 mg/l in Elendt medium and 0.535 in ISO medium. Using equal weight of all studies these acute values can be multiplied and taking the 3rd Root the EC50 Daphnia value results in 1.2 mg/l.