Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

The aquatic toxicity profile of DOTE has been well characterized through several short-term tests and one long-term Daphnia reproduction test. The analysis of the existing data tends to demonstrate that test implementation is complex based on DOTE’s intrinsic properties such as low water solubility and in water. The protocols were designed to address those technical issues.

 

In the key study conducted in fish, a Water Accommodated Fraction (WAF) was prepared at a loading rate of 100 mg/L and subsequent dilutions containing 0.1, 1.0 and 10 % of the WAF were also prepared. DOTE induced no visible effects in zebra-fish (Brachydanio rerio) at or below a WAF prepared at the loading rate of 100 mg/L over 96 hours. Based on average measured concentrations the NOEC corresponded to 24.8 mg DOTE per litre (3.91 mg tin per litre).

The analytical methodology followed was the analysis of total tin, from which the DOTE concentration was calculated. In this context, the 96 h LC50 > 24.8 mg/L, therefore no effects were observed up to the water solubility limit of DOTE.

 

In the key study conducted in daphnia, it can be concluded that the 48 hour acute median effective concentration (EC50) of DOTE on Daphnia is 24.12 mg/L

 

In the key long-term Daphnia reproduction test (21 days) daphnids were exposed to the test material at concentrations of 33, 134, 286, 1448 and 3213 µg/L. Effects were noted at the two highest test concentrations; however it was determined that the effects cannot necessarily be attributed to the parent compound. It was therefore concluded that up to the water solubility of DOTE there is no toxicity. The NOEC was determined to be 0.286 mg/L.

The study was conducted with a test item containing ca. 3 -4 % of Ethylhexylthioglycolate (EHTG, CAS: 7659 -86 -1, EC: 231 -626 -4) as impurity EHTG is better soluable in water as DOTE and shows the following ecotoxicity: EC50 (48 h) Daphnia = 0.38 mg/L EC50 Algae = 0.41 mg/L and is thus classified as Aquatic Acute 1 H400 and Aquatic Chroinic H410 Is likely that the observed effects in the study are caused or exacerbated by the impurity EHTG

 

In the Key study withPseudokirchneriella subcapita and under the experimental conditions employed, it can be concluded that the growth rate ErC50and inhibition in the yield EyC50for the test item DOTE was greater than 100.0 mg/L.The No Observed Adverse Effect Concentration (NOAEC) over the 72 hours exposure period was also greater than 100.0 mg/L of DOTE.

 

The 3 hour EC50 for DOTE for inhibiting the respiration of aerobic wastewater bacteria has been determined to be > 100 mg/L.

 

Discussion

In several of the studies, exposure concentrations were not stable over the test period. Loss of the test material may be due to adsorption onto test vessels or incorporation of the test material in the algae biomass. The test material is poorly soluble in water but contains reactive ligands that can be readily hydrolysed in water, resulting in more-soluble compounds (e.g., hydroxides and oxides). Organotin impurities, including these hydrolysis reaction products, will be present in solution along with the named substance. At least some of these impurities are more soluble in water than the named substance. Poor solubility and the occurrence of hydrolysis reactions present significant challenges to testing organotin compounds in aqueous solutions. It is highly probable that any toxicity seen is not entirely due to the named substance only.