Dialuminium chloride pentahydroxide

Endpoint summary

Description of key information

According to the available read-across studies, the most sensitive aquatic organism seems to be the fish Salvelinus fontinali (long-term toxicity test), with a 60-days NOEC of 13 µg/L based on geometric mean of measured concentrations of aluminium sulphate (Cleveland, 1989).

Both key studies (activated sludge respiration inhibition tests) available to evaluate the toxicity on microorganisms (using polyaluminium chloride hydroxide sulphate and aluminium chloride) did not show any effect on microorganisms. An EC10 of 200 mg/L was obtained with aluminium chloride.

Additional information

Two valid transformation/dissolution studies were conducted with an analogue (aluminium sulphate). The first 24h study was performed at nominal pH 6 and 8, in ISO 6341 reconstituted test medium 10x diluted (pH6) or undiluted (pH8), and aluminium concentrations dropped from 8.8 to 7.5 mg Al/L and 0.36 mg Al/L, respectively. This drop was less than expected due to the considerable reduction from the target pH (especially at pH6, which descended to 4.75 within a couple of minutes) caused by the capacity of aluminium to consume the alkalinity of the test medium (approximately 0.5 mg/L of alkalinity as CaCO3 per mg/L of alum according to Pernitsky and Edzwald, 2003).

For this reason a second 28 -day TDp study was performed at a more environmentally realistic concentration of 1 mg/L at pH 6 (in diluted ISO 6341). In this case pH 6 was selected as the solubility was found to be the higher of the 2 pHs tested. In this study the original nominal concentration of 1 mg/L as aluminium sulphate (88 µg as elemental aluminium) dropped to 16 µg/L as elemental aluminium within 7 days and just 12 µg/L after 28 days and can therefore be considered as insoluble when added to environmental media within a few hours.A supporting publication reports consistent information on significant pH- and speciation-dependency, in deionised water,with a minimum solubility of 29µg Al/L(pH=6.3) or52 µg Al/L(pH=6.4) respectively for polyaluminium chloride sulphated of medium and high basicity grade.

According to the available long-term fish read-across studies, the most sensitive aquatic organism seems to be the fishSalvelinus fontinali,with a 60-days NOEC of 13 µg/L based on geometric mean of measured concentrations of aluminium sulphate (Cleveland, 1989).The tested concentrations were 0, 38, 50, 75, 100, 150, 200, 300, 400 µg/L [nominal] ; 5 (background), 4, 8, 29, 57, 68, 88, 142, 169, 292, 350 ug/L [measured total aluminium].According to Brouwers (2015) water solubility study on sulphate-14-hydrate, 12 µg AI/L was left in the solution at the end of the experiment (study started at 1 mg/L, lasting 28 days). The NOEC obtained in the long-term fish study of 13 µg/L appears to be under the minimum solubility and should consequently not cause any effect to the fish as it is not soluble. Plus, it is precised in the water solubility study that aluminium sulphate can be considered insoluble when added to environmental media within a few hours.