Chloramide

Short-term toxicity to aquatic invertebrates

Description of key information

The most relevant 48h-LC50 was determined to be 0.0118 mg/L (monochloramine) for the Ceriodaphia dubia.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.012 mg/L

Additional information

A number of publications are available regarding the toxicity of monochloramine on freshwater and marine invertebrates.

Freshwater

All the studies summarized below were selected and retained for the short-term toxicity assessment because the protocol design and the test conditions (particularly the pH and the ratio of Cl₂/N) were designed to obtain predominantly monochloramine in the test solutions. Therefore, in all of these studies, the LC50s or TLms could be assigned to monochloramine.

Depending on studies, LC50 values were expressed either as monochloramine or as TRC (Total Residual Chlorine) or combined chloramines (CRC Combined Residual Chlorine).Indeed, due to the difficulties to perform analytical monitoring on monochloramine, TRC or combined chloramines were often used as surrogate of monochloramine for the analytical monitoring. Thus due care was taken on the expression of the results (i.e. expressed as mg eq Cl₂/L for TRC or combined chloramines or as mg/L of monochloramine).

The acute toxicity toward several invertebrates belonging to different phyla (arthropods, molluscs, annelids) has been tested.

The LC50 values for invertebrates ranged from 0.010 mg/L (as monochloramine) for the freshwater water flea, D. magna (24-hour LC50), to 0.754 mg eq Cl₂/L (TRC) for the benthic invertebrate, Asellus aquaticus (96-hour LC50) (Wan et al 2000b; Kaniewska-Prus, 1982).

 

According to the priority substances list of the Canadian EPA and after studying data from literature, it appeared that D.magna was among the most sensitive invertebrates and that the reported LC50 values forD. magna varied considerably (e.g., 24-hour LC50 values ranged from 0.010 to 0.110 mg/L).The rotifer, Keratella cochlearis and the Australian water flea, C. dubia (were observed to be as sensitive as the D. magna to continuous monochloramine exposures in two studies (Beeton et al., 1976 and Taylor, 1993) with a 24-hour LC50 of 0.0135 mg eq Cl₂/L (TRC) and of 0.012 mg/L (as monochloramine), respectively.

Wan et al (2000a) performed a 24-h and a 48-h toxicity tests of inorganic chloramines on Daphnia magna in accordance with the standard method of Environment Canada 1990 (EPS 1/RM/14 similar to OECD 202). Tests were performed under semi-static conditions (i.e. each test solution was renewed every 24h), in reconstituted fresh water during 48 hours. Daphnids were exposed to control and test solutions at nominal concentrations of 0.020, 0.060, 0.30 and 2.60 mg/L (monochloramine). Monochloramine concentrations were analytically determined using both DPD-FAS and HPLC techniques. The results, based on mortality and on measured concentration of monochloramine, were 0.019 mg/L and 0.017 mg/L (monochloramine) for the 24h and 48h-LC50 values respectively.

 

Another test conducted by Wan et al (2000b) was performed in two type of freshwater; reconstituted water and well water. This test was also carried out in accordance with standard method of Environment Canada 1990 (EPS 1/RM/14). Tests were performed under semi-static conditions (i.e. test solutions were renewed every 3 hours) during 48 hours. Chemical analyses were conducted at 0hour and 3hours (fresh and old test solutions). For the reconstituted water analytical monitoring was performed on monochloramine and for the well water analytical monitoring was performed on CPO. The 3-h test solution renewal regime indicated for inorganic chloramines a48h-LC50 of 0.010 mg/L (monochloramine)for the reconstituted water and 0.016 mgeq Cl₂/L (CPO)for the well water. Toxicity with this exposure regime was higher than with a 24-hour renewal regime. However this study had several limitations as the number of animals per replicates and not enough details were reported for the analytical monitoring.

In a study of Kaniewska-prus (Kaniewska-prus et al 1982), 24-h LC50s were 0.0595 mg eq Cl₂/L for D. magna and 0.754 mg eq Cl₂/L (TRC) for Asellus aquaticus for solutions containing 90% monochloramine and 10% trichloramine and 0.018 mg eq Cl₂/L and 0.315 mg eq Cl₂/L respectively for solutions containing 80% monochloramine and 17% dichloramine and 3% trichloramine.

 

In addition, as found in the literature C. dubia was also among of the most sensitive freshwater invertebrates. Thus, supplementary tests were performed by the Canadian EPA using the same protocols as for D. magna and state-of-the-art analytical chemistry material (like in the study of Wan et al 2000a). Thus in Farrell et al 2000, monochloramine toxicity to the freshwater invertebrate Ceriodaphnia dubia was studied with time-to-lethality tests at 26 different concentrations. This test was performed with a standardized protocol for toxicity testing with C.Dubia however due to the rapid decay of monochloramine the test solutions were replaced every hour. Results of these tests allowed the determination of a simple exponential equation predicting the LC50 and LC20 for third-generation neonate (12–24 hours old). For C. dubia.: the results were as follows: LC50 (mg/L) = 61.6t^–1.08  and LC20(mg/L) = 53.9t^–1.10. So the values of 24h-LC50 and 48h- LC50 were estimated to be 0.024 and 0.0118 mg/L (monochloramine) respectively.

Taylor (Taylor et al 1993) tested the acute toxicity of various forms of free and combined chlorine (whose monochloramine) to Ceriodaphnia dubia in standard 24h toxicity tests .These tests were performed either under static conditions or under flow-through conditions. Static tests were carried out with and without food and the flow-through test was carried out without food. These toxicity tests were performed using pure solutions of monochloramine. Measurement of monochloramine concentrations were made with an amperometric titration method. In the test with food, the decay of monochloramine was very rapid (4h) so this test was not taken into account. Results of the static test without food and the continuous flow toxicity test showed a 24h-LC50 of 0.012 mg/L (monochloramine) for the static test without food and a 24h-LC50 of 0.016 mg/L (monochloramine) for the continuous flow toxicity test.

All these studies resulted in the same range of LC50 values for Daphnia magna and Ceriodaphnia dubia (between 0.010 to 0.017 mg/L). These two species were considered as the most sensitive of invertebrate species.

The studies of Wan (Wan et al 2000) and of Farrell (Farrell et al 2000) were considered more robust than the other studies since they satisfy the guideline requirements for an acute study with freshwater invertebrates and because they were performed with the state-of-the-art of the analytical monitoring.

 

Saltwater

As with freshwater invertebrates, available acute toxicity data for marine/estuarine invertebrates are highly variable.

Data obtained from open literature showed that species seemed to be sensitive to monochloramine (i.e., 48-hour LC50 of 0.32 mg eq Cl₂/L (TRC) for juveniles and larvae of an oyster, Crassostrea virginica, and 48-hour LC50 of 0.001 mg eq Cl₂/L (TRC) for larvae of a clam, Mercenaria mercenaria (Capuzzo, 1979; Benderet al., 1977).

Capuzzo et al (1979) performed flow-through bioassay with Brachionus plicatilis, Acartia tonsa, and larvae of Crassostrea virginica with exposure periods of 30 minutes at various temperatures. With these very short-term exposure, for the tests performed at the acclimation temperature LC50s, measured 48 hours after exposure, were 0.02, 0.32 and 0.01 mg eq Cl₂/L (TRC) respectively.Capuzzo et al (1976), in a previous study, performed an acute test in the same conditions above with Homarus americanus larvae and obtained a LC50 of 0.69 mg eq Cl₂/L (TRC). Due to the very short exposure duration, this study of Capuzzo was considered as not adequate to determine a LC50 useful for the assessment of short term toxicity under the REACH regulation. Furthermore, amperometric titration does not distinguish chlorine from bromine compounds. Nevertheless, these data are useful as supportive data because they give an outline of monochloramine potential to produce acute toxic effects in marine invertebrates.

Bender et al (1977) (results from Roberts et al.1975) tested four invertebrate species using estuarine river water, in flow through or static systems. Results were expressed as TRC. The lowest lethal concentrations to be used as supportive information are extrapolated values for Mercenaria mercenaria larvae (48h TL50 = 1 μgeq Cl₂/L (TRC), in the static test) and Crassostrea virginica juveniles (96h-EC50 (shell deposition) = 23 μg/l (TRC), in the flow through test).Amperometric titration used in this study does not distinguish chlorine from bromine compounds. Therefore it was judged not relevant to assign the toxicity observed in this study to monochloramine.

 

Wan et al (2000) performed an acute toxicity tests of CPO (Chlorine-produced Oxydants) under semi-static conditions (i.e. each test solution was renewed every 12 h), in sea water having a pH range of 7.5 ± 0.1. Testing was carried out at two temperatures: 10°C ± 0.1°C (A. virginiana) and 15°C ± 0.1°C (E. washingtonianus) in total darkness and without sediments. The estimated LC50s based on measured concentration of CPO toA. virginiana were 0.99 mg/L and 0.63 mg/L, for 24-h and 48-h respectively. The respective equivalent for E. washingtonianus was 1.85 mg/L and 0.567 mg/L CPO. In the presence of bromide, as in seawater, reactive chlorine atoms can be completely or partially replaced by bromine atoms. The collection of reactive chlorine and bromine species is called chlorine-produced oxidants (CPO). Therefore CPO was not judged as a good surrogate for the determination of the monochloramine concentration. This study was therefore judged not relevant for the toxicity risk assessment of marine invertebrates.

   

Conclusion:

Freshwater:

Different studies are available nevertheless acute studies performed according to standard test protocol and performed in conjunction with the best available analytical chemistry are considered as the most robust studies (Wan et al 2000a and Farrell et al 2000). Since the study of Farrell had the most conservative LC50 this study was chosen as key study.

Marine water:

No key study was indentified for this marine water due to either not enough detail on composition of test solutions or a misfit analytical method or a too short exposure period.

 

  

Value use for CSA.

48h-EC50 for freshwater invertebrates: 0.0118 mg/L.

Thus monochloramine is considered as very toxic to aquatic invertebrates.