Guanidinium thiocyanate

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

fish, juvenile growth test

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

For justification for read-across applying the analogue approach please refer to attached document in Chapter 13.2 "other assessment reports".

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

124 d

Dose descriptor:

NOEC

Effect conc.:

2.23 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

other: Effect concentration calculated with molecular mass of source and target substance

Basis for effect:

not specified

Reference 2

Endpoint:

fish, juvenile growth test

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 215 (Fish, Juvenile Growth Test)

GLP compliance:

no

Analytical monitoring:

yes

Details on sampling:

Water samples for the determination of SCN- were taken from each tank at least weekly.

Vehicle:

no

Test organisms (species):

Pimephales promelas

Details on test organisms:

Juvenile fathead minnows were obtained from the lab breeding culture, University of Waterloo (Ontario). Each brood tank contained two male and four female fish, and received a continuous flow of well water at 23 to 25°C. The photoperiod was maintained at 16:8 h light:dark, with 15-min periods of simulated dusk and dawn. Routine practices for culture maintenance were based on those of the U.S. Environmental Protection Agency (EPA). Hardness, alkalinity, pH, and DO were monitored routinely and were essentially identical to those reported below for the subsequent experiment. A detailed characterization of the water supply is available elsewhere. Fish in the lab colony were fed three times daily, 7 d a week. Brood stock were fed frozen adult brine shrimp (Artemia salina) (Murex brand; Artemia Canada Ltd., Langley, British Columbia) (manufacturer's analysis: crude protein >=2.6%; fat >=0.7%; fibre <=0.18%; moisture <=95.7%).

Juvenile fish in the colony were fed a combination of frozen Artemia, tropical fish flake food TetraMin®, TetraWerke, Germany) and salmonid starter diet (Martin's Feed Mills, Elmira, Ontario) (manufacturer's analysis: protein >=52%; fat >=18%; fiber <=2.5%). Larval minnows were fed live Artemia nauplii three times per day; nauplii were incubated according to manufacturer's directions (Artemia Canada Ltd.) and rinsed with fresh water before feeding. During the actual experiment, adult and juvenile fish were fed frozen Artemia. Although the amount was not weighed, similar amounts were offered to each tank during feeding periods. Excess feed and faeces were siphoned from the tanks daily. Larval fathead minnows were fed live nauplii and gradually adapted to frozen brine shrimp.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

124 d

Hardness:

372 mg/L CaCO3

Test temperature:

24.6 °C

pH:

7.69 to 7.76

Dissolved oxygen:

6.41 mg/L

Nominal and measured concentrations:

nominal SCN- (mg/L) : 0; 1; 8; 18; 36

Key result

Duration:

124 d

Dose descriptor:

NOEC

Effect conc.:

1.84 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

other: decreased egg production, increased time to first spawn and development of overt goiter

Key result

Duration:

124 d

Dose descriptor:

LOEC

Effect conc.:

12.2 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

other: decreased egg production, increased time to first spawn and development of overt goiter

Reported statistics and error estimates:

Data were subjected to standard ANOVA procedures to determine significant treatment effects. Data normality and heterogeneity of variance were determined by residuals analysis . If these assumptions were violated, 1og10 or arcsine angular transformations were applied to the data before statistical analysis. Embryo and larval response parameters were analyzed as a split-plot ANOVA with subsampling, with the adult pre-exposure SCN- level as the whole plot and embryo exposure concentration as the split plot. In the event of a significant one-way ANOVA, multiple comparisons were conducted
using Tukey's (HSD) test (alpha = 0.05)

Growth, physiological, and reproductive responses of adult fathead minnows during 124-d exposure to SCN- 

Responses to various SCN- exposures
Parameter	omg/L	1.1 mg/L	7.3 mg/L	16.6 mg/L	2.6 mg/L	SE
Initial wt. (g)	1.42	1.32	1.31	1.34	1.28	0.129
Final wt. (g)	2.49	2.82	2.36	2.10	1.40	0.904
Mortalities%	0	0	3.3	30	63	13.11
Hematocrit	35.8	32	29.5	31.9	24.0	5.671
Plasma SCN-(mg/L)	ND	ND	0.25c	45.5	450	---
BCF	---	---	0.03	2.7	13.8	---
No. eggs produced	1,860	1,707	369	0	0	346.4
Time to first spawn (d)	5.7	2.3	25.7	---	---	4.726
Fertilization rates %	89.4	91.1	86.1	---	---	5.523
Larval deformities %	1.76	3.76	3.14	---	---	1.494
Reproductive index	3.87	4.0	3.23	2.30	1.33	0.498

Validity criteria fulfilled:

not applicable

Conclusions:

Although this study was not carried out under GLP or following a specific (inter)national guideline, the study itself is thorough and well described. Results from this study indicate that the major effects of chronic SCN- exposure in fathead minnow are on reproduction and thyroid histology. The most important results of interest from this study are:

Effects: Decreased egg production, increased time to first spawn, and development of overt goiter
NOEC = 1.1 mg/L SCN-, equivalent to 1.84 mg/L KSCN
LOEC = 7.3 mg/L SCN-, equivalent to 12.21 mg/L KSCN

Decreased growth and haematocrit
LOEC = 32.6 mg/L SCN-

Executive summary:

 

Juvenile fathead minnows(Pimephales promelas)were exposed to thiocyanate (SCN-) concentrations of 0, 1.1, 7.3, 16.6, or 32.6 mg/L for 124 d while monitoring growth, physiological, reproductive, and histological parameters. The NOEC for decreased egg production, increased time to first spawn, and development of overt goiter was 1.1 mg/L, whereas the LOEC for these parameters was 7.3 mg/L. Histological changes in thyroidal tissue were the most sensitive parameter observed, with an LOEC of 1.1 mg/L. Fish exposed to 16.6 or 32.6 mg SCN-/L neither completed development of secondary sexual characteristics nor spawned. The LOEC for decreased growth and hematocrit was 32.6 mg/L. SCN- accumulated in the plasma of fish exposed to 16.6 and 32.6 mg/L, with BCFs of 2.7 and 13.8, respectively. Development and mortality of embryos and larvae to 3 d post-hatch were also monitored in eggs spawned by adults exposed to 0 or 1.1 mg SCN-/L and subsequently incubated and hatched at 0, 1.1, 7.3, 16.6, or 32.6 mg/L. Eggs spawned by adults exposed to 1.1mg SCN-/L exhibited increased percentage of eyeup and hatch, while decreasing time to hatch and mortality. There were no effects of SCN- concentration during incubation on egg viability. After the 124-d exposure, adults were transferred to SCN- free water for 30 d. Insufficient numbers of adults were available from groups exposed to 32.6 mg/L to be included in the recovery study. Eggs were spawned by all groups during the recovery period, regardless of the SCN- pre-exposure level, although time to first spawn increased with pre-exposure concentration.

 

Description of key information

Read-across from Potassium thiocyanate.

NOEC corrected for molecular weight.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

NOEC

Effect concentration:

2.23 mg/L