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Toxicity to soil macroorganisms except arthropods

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Description of key information

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:
30.4 mg/kg soil dw

Additional information

For the assessment of the toxicity to soil macroorganisms except arthropods in total 5 studies with Klimisch 2 are available. These studies are publications and it is not stated if the studies were performed under GLP. These publications provide information on short term- toxicity and - to a limited extend - also for long-term toxicity.

In addition to the above mentioned 5 publications, in total 8 further disregarded studies are available. These studies were disregarded since the test design had major differences to the modern test guidelines and/or the lack of sufficient information on methods and results and/or an non standard test species (Enchytraeus albidus) was used for an acute test. These studies will not be discussed here.

 

It should be noted that Chloroacetamide is listed as reference substance in OECD 207, but not in the newer OECD 222.

 

Short-Term Toxicity Data

The 5 studies were performed with artificial soil and the test design of these studies was similar to the OECD 207. Since the studies were more or less similar in the test design and the provided information, the results of these studies are considered to have equal relevance and hence a weight of evidence approach was followed, i.e., the mean of the LC50 of all relevant studies was calculated. Since the data were all within the same range, no data were excluded from this data set.

Table 1: LC50 values provided in the relevant publications.

Author

Year

Duration

[days]

LC50

[mg/kg dw]

Comment

Yeardley, R.B., et al.

1995

14

33.1*

In total six tests performed, the mean was reported

Gibbs, M.H., et al.

1996

21

29

Test duration longer than stated in the OECD 207 but considered as relevant since this LC50 represents a worst case. Indication that NOEC reproduction is 15 mg/kg dw.

Heimbach

1984

28

24

Test duration longer than stated in the OECD 207 but considered as relevant since this LC50 represents a worst case.

Neuhauser, E.F., et al.

1985

14

26

 

Gestel et al.

1988

14

40

 

Mean of LC50 with test duration >= 14 days

 

 

30.4

 

*For the calculation of the mean LC50 the data from Yeardley, R.B., et al. (1995) were considered as one study even it was the mean of six experiments.

 

The LC50 of 30.4 mg/kg dw will be used for the risk assessment.

In the study from Yeardley, R.B., et al.(1995) 7 day and 14 day LC50 values were provided which allows a first assessment of the evolution of mortality after exposure to Chloroacetamide. The 7 day LC50 was 33.3 and the 14 day LC50 was 33.1 mg/kg dw. Hence, there was only a minor change from 7 to 14 days. It can be concluded that the main mortality of Chloroacetamide occurred within the first 7 days. This supports that the 21 and 28 day LC50 values can also be used for the risk assessment of short-term toxicity.

 

Long-Term-Toxicity Data

In the study from Gibbs, M.H., et al. (1996) the adults were exposed for 21 days (OECD 222 reproduction test: 28 days). The exposure of the juveniles and cocoons was performed for additional 42 days (total test duration 63 days) (OECD +28 days after adult exposure). Juvenile production and cocoon hatching were relatively low and did not met the validity criteria outlined in the OECD 222 for the number of cocoons and juveniles. The number of juveniles was less than the validity criterion of at least 3 juveniles per adult worm. It must be stated that the test design showed some deviations to the OECD 222, (e.g. adult exposure for 21 instead of 28 days) which was adopted only in the year 2004 and was hence not available when the study from Gibbs et al (1996) was performed. This limits the interpretation of the results and hence, the results of this study are considered to be not relevant as long-term toxicity data. The reported NOEC for reproduction is 15 mg/kg dw. The data indicate that at 10 and 25 mg/kg dw the number of cocoons was lower when compared to the other groups. Not clear concentration response was observed. Hence, no effect on reproduction was observed up to 25 mg/kg dw.However, a significant decline of the percent of replicates which showed reproduction was observed at 10 and 25 mg/kg dw (even if statistics were difficult due to the low number of cocoons/juveniles).This effect was not observed at 15 mg/kg dw.It was concluded that this study showed not effects on survival including 15 mg/kg dw. Sublethal effects were observed but the evaluation might be limited due to the low number of cocoons and juveniles. There is no indication that reproduction and sublethal effects are observed below 15 mg/kg dw. Hence, the LC50 of 29 mg/kg dw and the NOEC reproduction (15 mg/kg dw) are relatively close together (Gibbs, M.H., et al. ,1996). This would indicate that the mortality caused by Chloroacetamide within the first days of exposure is the driving factor for long-term toxicity including reproduction. This is supported by the finding that the mortality is mainly observed within the first 7 days (Yeardley, R.B., et al. 1995).

Due to the deviations to the OECD 222, the results are considered as not relevant as long-term toxicity data.