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EC number: 233-658-4 | CAS number: 10294-34-5
Long-term toxicity to aquatic invertebrates
Administrative data
Link to relevant study record(s)
Description of key information
The decreased pH caused by the formation of HCl during hydrolysis of BCl3 is decisive for the long-term toxicity to aquatic invertebrates.
The "LC50" of pH = 6 is best described in pH-units and not by the concentration, in case of more or less buffered aquatic environments.
Key value for chemical safety assessment
Additional information
Relevant information for the 2 degradation products:
Hydrogen chloride:
According to column 2 of Annex IX of REACH "Long-term toxicity testing shall be proposed by the registrant if the chemical safety assessment according to Annex I indicates the need to investigate further the effects on aquatic organisms."
The main effect of hydrochloric acid is to lower the pH. It is not relevant to determine toxicity in terms of mg/L due to the varying buffering capacity of different test systems and different aquatic ecosystems. The constituents of HCl in water are the naturally occurring ions H+ and Cl-. No other than pH effects are expected.
Relevant aquatic organisms need a pH in the range of 6 to 9. If the pH is lowered by the test substance to <6, a toxicity at least to some of the aquatic organisms is foreseen. This is one of the basic assumptions in the EC directive 2006/44/EC on the quality of fresh waters needing protection or improvement in order to support fish life, which state that the pH of the fish water has to be in the range of 6 to 9.
In the case of HCl it is therefore not necessary to perform long-term investigations because a toxic effect can be predicted if the pH falls below 6. There is no "need to investigate further the effects on aquatic organisms".
A pH of 6 corresponds theoretically to NOEClong-term = 0.036 mg HCl/L or 0.039 mg BCl3/L in pure, unbuffered water. In natural water a NOEClong-term >0.039 mg BCl3/L would be obtained, depending on the buffer capacity of the water and the species concerned.
Boric acid:
15 long-term fish toxicity test are reported in the IUCLID on boric acid, NOEC ranging from 0.1 to 86 mg B/L, equivalent to 0.57 to 490 mg B(OH)3/L. Most of the results are in the range of 2 to 20 mg B/L, therefore a NOEClong-term = 2 mg B/L, equivalent to 11 mg B(OH)3/L, transcribed to 22 mg BCl3/L is adopted,
Endpoint conclusion:
The decreased pH caused by the formation of HCl during hydrolysis of BCl3 is decisive for the toxicity to aquatic organisms, compared to that of boric acid. Toxic acute and long-term effects can be predicted if the pH is <6, caused by HCl.
A pH of 6 corresponds theoretically to a NOEClong-term = 0.036 mg HCl/L or 0.039 mg BCl3/L in pure, unbuffered water. In natural water a NOEClong-term >0.039 mg BCl3/L would be obtained, depending on the buffer capacity of the water and the species concerned.
Three times this value is considered to reflect more practical conditions for classification: NOEClong-term = 0.12 mg BCl3/L.
For a risk assessment a NOEClong-term of pH = 6 is considered to be the choice for each of the aquatic organisms, as not a systemic, species specific effect is the mechanism of toxicity but the acidity of the medium.
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