Registration Dossier
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EC number: 202-804-9 | CAS number: 99-96-7
Endpoint summary
Administrative data
Description of key information
Additional information
Tests without pH neutralisation:
Any tests without pH neutralisation revealed effects at concentrations in treatments with pH values significantly below 6. EC50/ LC50 were in the same range for all tested organisms:
EC50 (48 h) Daphnia magna = 67 mg/L (Biermann, (2009a),
LC50 (96 h)/ (14 d) Oryzias latipes (not considered as chronic toxicity test)= 92.8 mg/L/ 66.5 mg/L (Toray, 1997a/b),
ErC50 (72 h) Algae = 92 mg/L (Biermann, 2009b)
The pH-values in these tests were outside the acceptable range for validity or recommendations in the guidelines. It can be expected that the effects are mainly due to the low pH, which leads to an unphysiological milieu. Therfore, the effect concentrations of tests without pH-adjustments will not be used as key values for hazard assessment.
In tests with pH-adjustments to neutral values:
Tests with pH adjustments exhibited no effects/ effects at much higher concentrations. Therfore, the effect concentrations of tests without pH-adjustments will not be used as key values for hazard assessment.
No effects were observed at 100 mg/L for fish (Oryzias latipes, 14 days and 96 h, Toray (1997a/b)) and Daphnia magna (21 days, Toray (1997c). EC50 (48 h) Daphnia magna = 1690 mg/L. No effects were observed at 1000 mg/L in a study with Daphnia magna (48 h). In a study with algae (72 h) ErC10/EC50 was ca. 249 mg/L/>1000 mg/L
(Biermann, 2009b). 100 mg/L can be used as a no observe effect concentration as a worst case for chemical safety assessment.p-HBA (pKa=4.57) is considered a week acid. It can be expected from the Henderson Hasselbalch equation that the non-ionised form of p-Hydroxybenzoic acid will be the dominating species at pH-values below the pka of ca. 4.57.
The ionised form of p-HBA which is available at pH > pKa (pHBA) of 4.57 is less toxic than the non-ionised form. Further, the log P of both forms are different, (non-ionised: log P = 0.878, ionised form: log P = - 1.57). The substance in the form with higher logP should be more bioavailable.
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