Amoxicillin

Toxicity to aquatic algae and cyanobacteria

Description of key information

Weight of evidence. Test method ISO 8692 (1989). No GLP. The 7-days EC50 for M. aeruginosa was 0.0037 mg/L (based on growth inhibition, nominal concentration).
Weight of evidence. Test method ISO 8692 (1989). No GLP. The 72h-EC50  for Rhodomonas salina was estimated to be 3108 mg/L (based on growth inhibition, nominal concentration).
Weight of evidence. Test method ISO 8692 (1989). No GLP. The 72h-EC50 and NOEC for Selenastrum capricornutum was 250 mg/L (based on growth inhibition, nominal concentration).
Weight of evidence. Test method according to EPA Algal Growth Test. No GLP. Test item was not toxic to P. subcapitata in concentrations ranging from 5 ng/L to 50 mg/L during 96 hours of exposure (based on growth inhibition).
Weight of evidence. Test method according to EPA Algal Growth Test. No GLP. Test item was not toxic to Closterium ehrenbergii in concentrations ranging from 5 ng/L to 50 mg/L during 96 hours of exposure (based on growth inhibition).
Weight of evidence. Test method according to EPA Algal Growth Test. No GLP. Test item was not toxic to Cyclotella meneghiniana in concentrations ranging from 5 ng/L to 50 mg/L during 96 hours of exposure (based on growth inhibition).
Weight of evidence. Test method according to EPA Algal Growth Test. No GLP. The 96h-LOEC, NOEC and EC50 for S. leopoliensis were 0.00156, 0.00078 and 0.00222 mg/L respectively (based on growth inhibition, nominal concentration).
Weight of evidence. Test method similar to OECD 201. No GLP. The 72h-EC10 for P. subcapitata showed was > 1500 mg/L (based on growth inhibition, nominal concentration).
Weight of evidence. Test method similar to OECD 201. No GLP. The 72h-EC50 for Anabaena CPB4337 was 53.3 mg/L (based on luminescense, nominal concentration).

Key value for chemical safety assessment

EC50 for freshwater algae:

0.002 mg/L

EC10 or NOEC for freshwater algae:

0.001 mg/L

Additional information

The algae growth-inhibiting effect of amoxicillin was investigated by Holten-Lützholft et al. (1999) according to a modified test procedure based on the ISO 8692 (1989) protocol. 1x10+4 cells/mL of Rhodomonas salina (cryptophyte) and Microcystis aeruginosa (freshwater cyanobacteria), were exposed to three concentrations of amoxicillin for 72h days. The tests were

performed in 250 mL Erlenmeyer flasks containing 100 mL algal culture. Algal growth was measured as increased chlorophyll concentration by extraction with ethanol followed by measurement of fluorescence. Results were quantified in terms of growth rates using the Weibull equation to describe the concentration response relationship. The 72h-EC50 for Rhodomonas salina and Microcystis aeruginosa were found to be 3108 mg/L and 0.0037 mg/L respectively. No data on analytical monitoring was reported. In the same study, Selenastrum capricornutum (freshwater green algae) was exposed to three concentrations of amoxicillin for 7 days. The NOEC (7 days) was determined to be higher than 250 mg/L.

Andreozzi et al. (2004) exposed Pseudokikneriella subpicata (freshwater green algae) and Synechococcus leopoliensis (Cyanophyte), Cyclotella meneguiniana (Bacillariophyceae), Closterium ehrengergii (freshwater green algae) up to 50 mg/L amoxicillin for 96 hours exposure. The experiments were carried out in quadruplicate, and the results were evaluated on the basis of three tests. The EC50 was determined by regression using log-logistic models and NOEC and LOECs by hypothesis test. P. subpicata was insensitive to amoxicillin within the tested range. Moreover, the authors concluded that amoxicillin was not toxic to eukaryotic algae but had a marked toxicity toward the blue-green alga S. leopoliensis (NOEC = 0.78 μg/L, LOEC = 1.56 μg/L and EC50 = 2.22 μg/L).

The aquatic toxicity of amoxicillin was examined in two organisms representative of the aquatic environment, the cyanobacterium Anabaena CPB4337 as a target organism and the green alga Pseudokirchneriella subcapitata as a non-target organism by González-Pleiter et al. (2013). Algae and cyanobacteria were exposed to amoxicillin in concentrations ranged from 0.01 to 1500 mg/L for 72 h. The toxicity to bioassay using Anabaena CPB4337 was based on the inhibition of constitutive luminescence, while the determination of algal toxicity followed the algal growth inhibition according to the OECD Guideline 201. The tests were conducted in

four replicates in three independent series of assays. According to the authors, amoxicillin was not toxic to P. subpicata since no effect was observed at the end of the exposure at the highest tested concentration (72h-EC10 > 1500 mg/L). By contrast, in the cyanobacterium test a complete concentration-response relationship was recorded, being the 72h-EC10 equal to 6.16 mg/L and the 72h-EC50 equal to 56.3 mg/L. It should be pointed out that amoxicillin was found to be unstable in test media based on HPLC analysis, no characterization of the degradation products was conducted and the results were presented based on nominal concentrations.