Hydroquinone

Long-term toxicity to fish

Description of key information

A study performed according to the OECD TG 210 and under GLP is available. No effect on the reproduction were observed up to and including the highest tested concentration. The NOEC is 100 µg/l expressed in target concentration and 66 µg/l expressed in average concentration measured in the highest tested group.

Additional information

One reliable key study is available for this endpoint. The purpose of this study was to estimate the possible lethal and sub-lethal effects of Hydroquinone during the embryonic and early larval development of the fathead minnow. This study was conducted according to the Fish early-life stage toxicity test under flow-through conditions and the GLP.

 

The study procedures were based on the OECD guidelines for Testing of Chemicals: Guideline No. 210, 2013. In addition, the procedures were designed to generally meet the test methods of the EPA Ecological Effects Test Guidelines, OPPTS 850.1400, Fish Early-Life Stage Test 'Public Draft', EPA 712-C-96- 121, April 1996.

 

The batch of Hydroquinone tested consisted of a white crystalline solid and the test item was completely soluble in test medium at the target concentrations tested. The test was performed using a flow-through system with target concentrations of 4.6, 10, 22, 46 and 100 µg/l, which were based on the results of a preceding range-finding test and a subsequent first invalid full study. An untreated control was also included.

 

In the flow-through system the dilution water was dosed separately from the test item stock solutions into mixing vessels. Stock solutions were prepared in purified water with a pH adjusted to 5. The dosed volumes of stock and the dilution water were mixed under continuous stirring in the mixing vessels before entering the test vessels. The dosing was computer controlled, and the system was checked daily.

 

The test was performed with four replicates containing 20 eggs per replicate for each concentration and control. The test started by placing fertilised eggs in stainless steel test vessels. During the embryonic and larval phases, the eggs/larvae were observed for survival and effects on development, appearance and swimming behaviour. At the end of the test (day 32), the surviving fish were measured and weighed.

 

Samples for chemical analysis of the actual Hydroquinone concentrations were taken one day before the start, at the start, at weekly intervals and at the end of the test. In addition, samples were taken at the same intervals to assess the concentration of the degradant p-benzoquinone in solution.

 

Analyses of samples taken from the target concentrations on a weekly basis showed that measured Hydroquinone concentrations were just below the target concentrations at the start and after 7 days of exposure with recoveries that generally ranged between 70 and 100%. The recoveries decreased as exposure progressed with recoveries dropping to 60-70% after 14 days and recoveries from day 21 ranged between approximately 35 and 60% relative to the target concentrations. The range tested based on the arithmetic mean measured concentrations was 2.5, 5.7, 14, 28 and 66 µg/l.

 

The study met the acceptability criteria prescribed by the study plan and was considered valid.

 

The present study assessed the possible lethal and sub-lethal effects of Hydroquinone during the embryonic and early larval development of the fathead minnow. The results led to the following conclusions for Hydroquinone:

 

1) Hydroquinone did not induce any significant, visible effects on the development of fathead minnow embryos at target concentrations up to and including 100 µg/l, corresponding to average measured concentrations up to and including 66 µg/l.

2) Hydroquinone did not significantly affect time of hatching or the hatching success at target concentrations up to and including 100 µg/l, corresponding to average measured concentrations up to and including 66 µg/l.

3) Hydroquinone did not affect survival, growth or development of the larvae during the whole test period at target concentrations up to and including 100 µg/l, corresponding to average measured concentrations up to and including 66 µg/l.

 

Hence, the NOEC of Hydroquinone for the early life stages of fish under the conditions of the present study is 100 µg/l expressed in target concentration and 66 µg/l expressed in average concentration measured in the highest tested group.

The OECD Testing Guideline No 210 recommends that when the measured concentrations do not remain within 80-120% of the nominal concentration, the effect concentrations should be determined and expressed relative to the arithmetic mean concentration for flow-through tests.

At the highest target concentration of 100 µg/l, analyses showed that recoveries of hydroquinone decreased as exposure progressed with recoveries ranging from 35% to 96%. However, the degradation product p-benzoquinone can also induce effects. Hence the contribution of this degradation product to the test item concentration should be considered.

The contribution of the degradation product p-benzoquinone in solution varied from 6.4 to 42 % (i.e. relative to the measured Hydroquinone concentration). Globally it has been observed that the contribution of p-benzoquinone decreases as test item concentration increases. At the highest target concentration of 100 µg/l of hydroquinone, its contribution was between 8 and 19% (i.e. relative to the measured Hydroquinone concentration). Considering the measured concentrations of both hydroquinone and p-benzoquinone, the recoveries ranged from 45 to 107%, consequently still outside the accepted range of 80-120%. However, it should be highlighted that the analytical method development and validation demonstrated that there is a rapid interconversion between hydroquinone and p-benzoquinone in samples, and therefore the real concentration of both substances is uncertain.

Hence, the NOEC of Hydroquinone can be expressed both in arithmetic mean concentration as recommended by the OECD Testing Guideline No 210, and in nominal concentration to take into account the effects of the degradation product and the uncertainties of the analytical measurement.