Chloramide

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72h-EC50  based on the inhibition of the growth rate  and expressed as monochloramine were 0.014 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.014 mg/L

EC10 or NOEC for freshwater algae:

0.007 mg/L

Additional information

Very few data were available in the open literature for this trophic level and furthermore, the studies available do not correspond to a standard assessment endpoint used in REACH. Indeed, Bender et al., 1977 found the lowest reported observed effect concentration produced by residual chlorine on the unicellular alga Pyramimonas virginica (marine species) with a 15-minute EC50 (carbon uptake) at 0.01 mg/L . Toetz et al 1977 performed a study on the inhibition of inorganic nitrogen uptake on Closterium sp and de Chrysophyta sp. Maruyama et al.(1988) found 10-days EC50s (growth) of 0.014 and 0.02 mg/L for the multicellular red alga Porphyra yezoensis.

 

Thus these studies described above were not considered as fully valid due to lack of description or/and the non compliance with standard assessment endpoint used in REACH (inhibition of biomass or growth rate during 72 or 96 hours; Toetz et al 1977) or/and the very short exposure duration (Benderet al., 1977).

Therefore as available data were only partially relevant for the toxicity assessment toward aquatic plants, two supplementary acute toxicity tests were performed.

The first one was performed by Carso (Garrivier et al 2009) on Pseudokirchneriella subcapitata under static conditions according to the ISO Guideline 8692 (not GLP compliant). This study assessed the adverse effects of monochloramine on the growth rate of the freshwater green algal species over several generations. Exponentially growing algal cells were exposed for a period of 72 hours.Following a preliminary range-finding test,green algal was exposed to an aqueous solution of the test item at nominal concentrations of 0.005, 0.01, 0.02, 0.04 and 0.08 mg/L eq. Cl₂  for 72 hours, under constant illumination and shaking at a temperature of 23 ± 2°C.Experiment was conducted with 3 replicates for each concentration tested, and 6 replicates for controls.In this test, analytical determination of concentration of TRC (Total Residual Chlorine) was carried out but except for the two highest doses all the measured concentrations were below the LoQ ( Limit of Quantification 0.05 mg/L eq. Cl₂). Measured concentrations of the two highest doses were in the same range as the nominal concentrations. However as all the other measured concentrations were below the LoQ results were based on the nominal concentrations.

The 72h-EC50 and the 72h-EC10 based on the inhibition of the growth rate relative to control were 0.019 and 0.009 mg/L eq Cl₂ respectively expressed as TRC (Total Residual Chlorine).

In this study only measurement of the TRC was performed, no measurement of FRC was performed. TRC is the sum of the FRC (Free Residual Chlorine) and the CRC (Combined Residual Chlorine). CRC is composed of the 3 species of inorganic chloramines, mono-, di- and trichloramine).

However, according to the test conditions (pH above 8 and preparation of test solutions with a mass ratio Cl₂/N of 4.8), it could be considered that the FRC should be around 0 and the predominant species of inorganic chloramines (CRC) should be the monochloramine.

Therefore in the conditions of the test, it is considered that concentration in TRC is representative of the concentration of Monochloramine. Therefore as a worst case approach, acute toxicity toward algae could be assigned to monochloramine.

Thus as the results were expressed as TRC, the concentrations of monochloramine could be calculating by multiplying the TRC concentrations provided as eq Cl₂/L by the factor of 0.725. The 72h-EC50 and the 72h-EC10 based on the inhibition of the growth rate relative to control were 0.014 and 0.007 mg/L respectively expressed as monochloramine.

This study is classified as acceptable with restriction as a static test design is not recommended for an unstable substance and as results are expressed in nominal concentrations.

The second acute toxicity test SGS (Bellemain et al 2010) was performed on Lemna minor. This study is presented in § 6.1.6

Conclusion:

The study of SGS (Bellemain et al 2010) performed on Lemna minor was preferentially chosen for Classification and Labelling and for Risk Assessment because it was performed under continuous flow instead of static conditions and the LC50s values were based on measured concentrations instead of nominal concentrations, confederating a more robust study.