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Short-term toxicity to fish

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Description of key information

Key value for chemical safety assessment

LC50 for freshwater fish:
19.8 mg/L

Additional information

One study is available for Methyl Salicylate for this endpoint. This study (LICATA-MESSANA L., 2000) was performed to assess the acute toxicity of Methyl salicylate to freshwater fish (Danio rerio) under static conditions. This study was conducted in accordance with the method C.1 of the European Directive 92/69/EC and the OECD guideline 203. A group of ten fish was exposed to different concentrations of Methyl salicylate: nominally 1, 10 and 100 mg/L. Observations were made on the number of dead fish and the incidence of sub-lethal effects after 24, 48, 72 and 96 hours exposure. The 96h-LC50 for freshwater fish (Danio rerio) was found to be higher than 100 mg/L. Based on these results, Methyl salicylate is considered as not dangerous to the aquatic organisms tested in accordance with the Directive 67/548/EC.

 

However, the test item concentration levels were not checked although oily insoluble droplets were observed in the stock solution. Additionally, although not performed in the same test conditions, the stability study in the algal toxicity test showed that the concentrations of Methyl Salicylate decreased significantly within 72 hours.

 

Based on these observations, the results of the acute fish toxicity test for Methyl Salicylate should be used with caution. Therefore, a weight of evidence approach with results obtained on analog substances is applied for the assessment of the toxicity to fish of methyl salicylate. Ethyl salicylate (CAS RN 118 -61 -6) and salicylic acid (CAS RN 69 -72 -7) are used as analog substances.

 

One reliable key study is available for Ethyl salicylate for this endpoint. In this acute toxicity study (Geiger et al. 1985), fishes from the speciesPimephales promelaswere exposedunder flow-through conditionsto ethyl salicylate (CAS 1118 -61 -6).

The average measured concentrations tested were 0 (control), 2.73, 4.82, 7.70, 14.9 and 26.2 mg/L. Twenty five fish were tested in duplicate at each control and tested concentrations. The resulting LC50 (96h) was 19.8 mg/L, based on measured concentrations.

Therefore, ethyl salicylate is harmful to Pimephales promelas in the conditions tested.

This study was not performed according to GLP but authors followed a method similar to OECD 203 and gave sufficient details to check all validity criteria, which were all fulfilled. Therefore this study is considered as reliable with acceptable restrictions.

 

It is proposed to use this data for the assessment of the toxicity to fish of methyl salicylate as a read-across approach. The main assumption to justify the read-across approach is that both substances have a similar chemical structure. Both substances are 2-hydroxybenzoate, one being a methyl ester (i.e. methyl salicylate) and the second one being an ethyl ester (i.e. ethyl salicylate). Therefore, both substances have the same functional groups in their chemical structure, and the addition of an alkyl "CH2" in the ester function for ethyl salicylate compared to methyl salicylate is not expected to have a significant impact on the biological and physico-chemical properties of the substance.

 

This assumption is supported by the physico-chemical information which shows that both substances have very similar physicochemical properties (including water solubility and vapour pressure). The logKow value of ethyl salicylate is slightly higher than the one of methyl salicylate (i.e. 3.09 and 2.55 respectively). It can therefore be expected that ethyl salicylate has higher effect on the biological cells than methyl salicylate, and therefore applying the read-across approach would be a worst case and protective strategy. Even if not completely comparable due to different test conditions, the toxicity data to Daphnia magna of both substances show similar conclusion (i.e. 48hEC50 = 28 mg/L for Ethyl Salicylate and 24hEC50 = 50 mg/L for Methyl Salicylate).

 

To support the fact that methyl salicylate is expected to be less toxic than ethyl salicylate, data on salicylic acid is used to show that the 2–hydroxybenzoic acid is less toxic than the methyl ester, and therefore that the lower the 2-hydroxybenzoic form is substituted, the lower is the toxicity. The read-across approach is supported by the physico-chemical information which shows that both substances have very similar physicochemical properties (including logKow). But it should be noted that salicylic acid is more soluble in water than methyl salicylate (i.e. 1.5 - 2.6 g/L at 20°C - 25°C and 625 mg/L at 30°C respectively) and less volatile (i.e. 0.0208 Pa at 25°C and 13 Pa at 20°C respectively), but these differences are not expected to impact the results of the aquatic toxicity test at the concentrations tested.

 

The aquatic toxicity of salicylic acid is assessed based on its sodium salt to avoid pH effect. In the acute toxicity key study for this substance (Geiger et al. 1985), fishes from the species Pimephales promelas were exposedunder flow-through conditions tosalicylic acid sodium salt (CAS n° 54 -21 -7) at average measured concentrations of 0 (in duplicate), <50 (in duplicate), 497, 536, 837, 867, 1238, 1272, 2211, 2217, 3442 and 3573 mg/L.

The LC50 (96h) was 1370 mg/L (CI: 1270 - 1470 mg/L), based on measured concentrations.

Therefore, salicylic acid sodium salt is not dangerous to Pimephales promelas in the conditions tested.

 

In conclusion, the result obtained with ethyl salicylate is used in a worst case read-across approach to assess the fish toxicity of methyl salicylate.