Zinc bis(dibutyldithiocarbamate)

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: read-across from a comparable to guideline and with acceptable restrictions study

Justification for type of information:

The long-term toxicity of zinc bis(dibutyldithiocarbamate) to aquatic invertebrates is based on read-across from the structural analogue zinc bis(diethyldithiocarbamate).

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

3.2 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Non-GLP-compliance, near guideline study, published in reviewed literature, minor restrictions in design and reporting, but otherwise adequate for assessment.

Qualifier:

no guideline followed

Principles of method if other than guideline:

The test was a pre-guideline 21-day reproduction study with neonate (<24 h) Daphnia magna, at least five concentrations were tested in five-fold including a blank control. Ten daphnids were used for each replicate sample. The test solutions were renewed three times a week and were prepared fresh at each renewal. The number of surviving females and number of neonates were recorded daily, the neonates being removed from the test vessels after counting.

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The test medium used was 50-µm filter UV-sterilised Lake IJssel water. Stock solutions were prepared in the test medium. The test solutions were renewed three times a week and were prepared fresh at each renewal. The ration of concentrations was 1.8; actual concentrations were not verified during the experiments. At least five concentrations were tested in five-fold including a blank control.

Test organisms (species):

Daphnia magna

Details on test organisms:

The experiment was started with newborn (< 24 h) daphinds from a laboratory stock culture. These were fed daily with 3E+08 cells/L of the unicellular green alga Chlorella pyrenoidosa.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

None

Hardness:

225 mg/L (as CaCO3)

Test temperature:

20 +/- 0.5 °C

pH:

8.1

Dissolved oxygen:

Not reported

Salinity:

Not relevant

Nominal and measured concentrations:

At least: 0, 3.2, 5.6, 10 and 18 µg/l

Details on test conditions:

The experiments were carried out in a temperature room at 20 ± 0.5 °C with a 12-h photoperiod. The tests were conducted in 800-ml vessels to which 500 ml of the test solution was added. The pooled neonates were randomly distributed into cohorts of ten animals each and transferred to the test vessels. The daphnids were fed daily 3E8 cells of the unicellular green algae Chlorella pyrenoidosa. The number of surviving females and number of neonates were recorded daily, the neonates being removed from the test vessels after counting. When daphnids appeared to be males, these animals were excluded from both fecundity and survival analysis. Oxygen concentrations and pH were measured at regular intervals.

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

3.2 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

10 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

LC50

Effect conc.:

14 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 13-15

Details on results:

The survival pattern of the daphnids was clearly related to the exposure concentration and a gradual decline of the LC50 with time was observed. Generally, the lower rate of population increase casued by certain concentrations of test compounds was due to both increased mortality and fewer clutches per female. The latter was also due to reduced parental survival.

Reported statistics and error estimates:

The results were summarized in life-table form. The intrinsic rate of natural increase, rm, was calculated for each cohort of ten animals by successive approximation from the equation:

Sum of lx.mx.e^-rm.x = 1

Where lx is the proportion of individuals surviving to age x, mx is the age-specific fecundity (number of females produced per surviving female at age x), and x is days. As rm calculated after 21 days is indistinguishable from rm estimated for the entire life-span, due to the great importance of early reproduction, all calculations were based on 21-day experiments. Finally, means and errors were calculated.
Differences in mean survival and rm between treatments and blank control were tested using the Willimas’ test. After verification of differences between blank and solvent control (Student’s t-test). Prior to the Willimas’ test, the data were tested for homogeneity of variances using the Bartlett test. Normailty was verified by means of a Shapiro-Wilk test, or graphivcally, by plots of ordered data against the normal order statistic. It should be noted that in case of survival data the arcsin square root transformation of the proportion of survivorsin each test vessel was used. The lowest concentration wwhich was significantly different from the control was denoted as LRCT (lowest rejected concentration tested; similar to the LOEC). Differences were considered significant at the p < 0.01 level. From the LOEC the NOEC was derived by applying a factor of 1.8. The LC50 values and their 95% confidence limits were determined according to Kooijman (1981).
Kooijman SALM (1981). Parametric analyses of mortality rates in bioassays. Water Res. 15: 107-119.

Description of key information

The 21-d NOEC of 3.2 µg/L in Daphnia magna will be used in the assessment.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

3.2 µg/L

Additional information

 No long-term tests are available with Daphnia for zinc bis(dibutyldithiocarbamate). The results from the structural analogue zinc bis(diethyldithiocarbamate) are used (for details see Reporting Format as attached to the respective IUCLID entry and CSR Appendix A.1). A 21-d NOEC value of 3.2 µg/L in Daphnia magna from a semi-static non-GLP, near guideline study without analytical monitoring (van Leeuwen et al., 1985a) is used in the assessment.