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Ecotoxicological information

Toxicity to soil microorganisms

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Description of key information

A study performed according to the OECD TG 216 and under GLP is available. The OECD TG 216 recommends to consider the quantity of nitrate formed to interpret the results for non-agrochemicals. The 28d EC10 and EC50 were estimated at 19.5 and 60.1 mg hydroquinone/kg dry soil, respectively. The NOEC was determined as 10.0 mg hydroquinone/kg dry soil.

Key value for chemical safety assessment

Short-term EC50 for soil microorganisms:
60.1 mg/kg soil dw
Long-term EC10 or NOEC for soil microorganisms:
19.5 mg/kg soil dw

Additional information

One reliable key study is available for this endpoint. This study determined the effects of hydroquinone on the nitrogen transformation activity in a LUFA standard soil type 2.3, according to procedures described in OECD Guideline 216 (2000) and under GLP.

The soil used in the study had a sand content of 59.7%, a pH (measured in water) of 6.6, an organic carbon content of 0.67% w/w and a microbial biomass of 2.11 % of the total organic carbon (TOC).

A range finder assay was conducted across a concentration range of 0.01 µg hydroquinone /kg to 1000 µg hydroquinone/kg dry soil. Based on the result of the range finding assay, the concentrations used for the definitive test were as follows; 0.10, 1.00, 10.0, 100 and 1000 mg hydroquinone/kg dry soil. The test item was prepared in acetone and the test solutions dried down onto fine quartz sand. The soil was amended with powdered lucerne and the soil dosed with the treated sand. Each treatment group was replicated three times. The products of the process of mineralisation of organic nitrogen were extracted from the soil on Day 0 and then 28 after treatment and incubation at 20°C ± 2°C in the dark.

 

The solutions for extracted soil were analysed on Day 28 for nitrate, nitrite and ammonium nitrogen concentrations.

Hydroquinone at 100 and 1000 mg hydroquinone/kg dry soil showed a significant inhibitory effect on soil nitrogen mineralisation compared to the pooled control treatments in terms of both the amount of nitrate produced at the end of the 28 day test and the rate of nitrate production period (Dunnett’s two tail, p=0.05).

For the concentration on nitrate produced at day 28 , the EC10 and EC50 were estimated at 19.5 and 60.1 mg hydroquinone/kg dry soil, respectively. The NOEC was determined at 10.0 mg hydroquinone/kg dry soil and the LOEC at 100 mg hydroquinone/kg dry soil.

For the rate of nitrate production from 0 to 28 days , the EC10 and EC50 were estimated at 17.6 and 54.2 mg hydroquinone/kg dry soil, respectively. Again the NOEC and LOEC were determined as 10.0 mg and 100 mg hydroquinone/kg dry soil, respectively.

At day 28 there was some ammonium present in the soil in the 100 mg hydroquinone/kg dry soil treatment. The accumulation of ammonium indicates that the process of nitrification (ammonium to nitrate) had been inhibited. The rate of nitrate production in this treatment and the 1000 mg hydroquinone/kg dry soil treatment at day 28 compared to the control treatments was greater than 25% which suggests there has been some long term effect on the soil microorganisms.

 

All validity criteria for the study were met, as the variation in nitrate concentration in replicate water and solvent control samples ranged by -1.3 to +0.6 % and -1.8 to +2.1 % at Day 28, respectively, which was no greater than +/-15 % for either control.