Hexamethylenediamine

Toxicity to soil microorganisms

Description of key information

The test item had no adverse effects on N-transformation (OECD 216; GLP; RL1; 2017) in lucerne amended soil during 28 days at test item concentrations of up to and including 1000 mg/kg soil dry weight. Due to the lacking of adverse effects inhibitory concentrations (ICx) could not be calculated. Consequently, ICx are considered to be higher than 1000 mg/kg soil dry weight which was the highest tested concentration. Accordingly, LOAEC and NOAEC are > and ≥ 1000 mg/kg soil dry weight, respectively.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

1 000 mg/kg soil dw

Additional information

A valid nitrogen transformation test was performed with the submission substance in 2017 according to OECD 216, compliant with GLP (RL 1).

Five test item concentrations were tested against an untreated control (C) with four replicates, each: 62.5, 125, 250, 500 and 1000 mg/kg soil dry weight. The soil test was amended with ground lucerne grass green meal (5.0 g/kg soil dw) except for treatment TC which consisted of soil without lucerne and was treated with the test item at 250 mg/kg soil dw. Nitrate of the soil was measured after test item application on day 0, and 28 days after test item application.

The following results were obtained for the submission substance:

Mean nitrate concentration at test start (day 0) ranged from 57.6 to 59.6 mg/kg soil dry weight (control and test item treatments T1 to T5). Mean nitrate concentration for soil without lucerne was 43.7 mg/kg soil dw (bulk soil) and 43.3 mg/kg soil dw (treatment TC).

Nitrate concentration in soil increased considerably in all test soils from day 0 to day 28 thus confirming the existence of a metabolically active microbial biomass in the soil.

Mean nitrate concentration on day 28 had increased to 112.8 mg/kg soil dw (control). In the test item treated soils it ranged from 149.4 mg/kg soil dw to 698.6 mg/kg soil dw (206.9 mg/kg soil dw in treatment TC).

Nitrate concentration in soil on day 28 increased with the test item concentration. This observation strongly suggests that nitrogen from the test item was transformed to nitrate by the soil microorganisms.

No adverse effects of the test item on nitrate formation were observed at any of the test item concentrations up to and including 1000 mg/kg soil dw which was the highest tested concentration.

Due to the lack of any adverse effects, inhibitory concentrations (ICx) could not be determined. Consequently, IC50, IC20 and IC10 can be considered to be higher than 1000 mg/kg soil dry weight. Accordingly, LOAEC and NOAEC are >1000 mg/kg soil dw and ≥1000 mg/kg soil dw, respectively.