Chloramide

Endpoint summary

Additional information

Monochloramine is an inorganic substance and thus no ready biodegradation test was performed in accordance with REACH Annex VII column 2. Moreover, monochloramine is always used in an aqueous solution at low concentrations and primarily in water treatment. Therefore, surface water is considered as the target compartment of monochloramine and most of the available data concern kinetics of the substance in water.

It was established that both monochloramine autodecomposition and reaction with natural organic matter are significant in typical drinking water conditions (Duirk, 2005). As for natural surface water, several studies have shown that depending on the conditions the substance can stay quite long in rivers by comparison with other chloramines species (Yamamoto, 1988) and that illumination characteristics can have significant effects on monochloramine kinetics in water (Lin, 1983). The rate of monochloramine loss can also vary depending on pH conditions. The rate loss increases when pH decreases, which is attributed to the formation rate of dichloramine at pH < 8 (Vikesland, 2001). It is generally accepted that monochloramine persists for hours to days in water (Johnson, 1978; Pasternak, 2003; EPA, 1999). This low persistence is supported by several hydrolysis data showing high hydrolysis constants which correspond to a T1/2 of ca. 10 hours (Margerum, 1978; Vikesland, 2001).

Based on all the relevant data on hydrolysis and decomposition in water and based on the T1/2 value of 10 hours, the substance is considered as rapidly degradable in surface water according to the criteria of the Regulation (EC) No 1272/2008 of the European Parliament and of the Council on classification, labelling and packaging of substances and mixtures.

Inorganic chloramine loss from the water column may also occur via adsorption and reaction with suspended solids and bottom sediments (EPA, 1999). Stream beds may be covered with active biological materials in the form of slimes, sludges and algae, particularly at wastewater outfalls. This biological material has a capacity for uptake of residual chlorine. The rate of pollutant uptake in this layer (or the rate produced by benthic demand) will be influenced by the type of biological material, temperature, flow and sediment characteristics and depth but it is very difficult to make generalizations regarding chloramine loss rate. Nevertheless, EPA (1999) has obtained decay rate constants of 0.50 to14.83 per day (half-lives of 1.4 - 0.05 days) on monochloramine. Thus, although no adsorption/desorption test was performed due to technical difficulties (instability of the substance and difficulty in assessing results), the substance is considered as not persistent in sediments.

Considering the use of the substance in water treatment system (aquatic environment will be directly exposed) and that the substance is considered as rapidly degradable in water and not persistent in sediment, it is considered that both direct and indirect exposure of soil is unlikely.

Holzwarth et al. (1984) studied the behaviour of the substance regarding the atmospheric compartment. A Henry law's constant was determined to be 0.45 (dimensionless) at 20°C. This value was converted and a Henry law's constant of 0.824 Pa.m3/mol at 20°C was found. Thus monochloramine presents a volatilisation potential.

Finally, bioaccumulation is not considered relevant for monochloramine as it is an inorganic substance. The BCF value for inorganic substances will be mainly influenced by water chemistry (e.g. pH, hardness, temperature, redox conditions) and generally only dissolved ions will be potentially available for direct uptake. Monochloramine is soluble in water, used in an aqueous solution at low concentrations in water treatment and consequently highly diluted when entering the aquatic environment. As stated above, hydrolysis (T1/2= 10h) and/or degradation (T1/2 depending on factors such as pH, T, light conditions) of monochloramine in the aquatic environment will limit the amount of bioavailable monochloramine.

 

In conclusion, monochloramine in aqueous solution is considered as rapidly degradable in surface water, not persistent in sediment and not bioaccumulable in aquatic organisms. Moreover, both direct and indirect exposure to soil is considered unlikely. However, monochloramine presents a volatilisation potential.