Chlorpyrifos

Endocrine disrupter testing in aquatic vertebrates – in vivo

Administrative data

Endpoint:

amphibian Xenopus laevis, juvenile: (sub)lethal effects

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD TG 231 (The Amphibian Metamorphosis Assay)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: EPA Endocrine Disruptor Screening Program Test Guidelines OPPTS 890.1100: Amphibian Metamorphosis (Frog). EPA 740-C-09-002

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Chlorpyrifos

EC Number:

220-864-4

EC Name:

Chlorpyrifos

Cas Number:

2921-88-2

Molecular formula:

C9H11Cl3NO3PS

IUPAC Name:

O,O-diethyl O-3,5,6-trichloropyridin-2-yl phosphorothioate

Test material form:

solid

Specific details on test material used for the study:

Substance ID: TSN101285
Lot Number: KC28161419
Purity: 99.8%

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

yes

Remarks:

acetone or dimethylformamide (DMF)

Test organisms

Aquatic vertebrate type:

frog

Test organisms (species):

Xenopus laevis

Study design

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Test conditions

Hardness:

54-70 mg/L as CaCO3 in the control water and 46-78 mg/L as CaCO3 in the highest treatment level

Test temperature:

21.4-22.6°C

pH:

7.0-7.6

Dissolved oxygen:

6.0-8.4 mg/L (remained ≥40 % air saturation)

Conductivity:

184.5-199.8 μmhos/cm in the control water and 174.9-196.6 μmhos/cm in the highest treatment level.

Nominal and measured concentrations:

Nominal: 0 (water control), 0 (solvent control) 0.3, 1.25, 5.00, and 20.0 μg/L
Measured:

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.881 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: Based on reduced cholinesterase activity in tail and hind limb tissues and reductions in tadpole growth

Effect concentrations 2

Key result

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

3.68 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: Based on reduced cholinesterase activity in tail and hind limb tissues and reductions in tadpole growth

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

NOEC (Frog): 0.881 μg/L
LOEC (Frog): 3.68 μg/L

Executive summary:

This study was conducted to ascertain whether or not the test substance has thyroid activity in the amphibian metamorphosis assay (AMA) in Xenopus laevis, following OECD guideline 231 and EPA OPPTS 890.1100.

The tadpoles were exposed for 21 days under flow-through conditions at nominal concentrations of 0.3, 1.25, 5.0, 20.0 µg/L. The measured concentrations were 0.215, 0.881, 3.68, and 13.6 μg/L. Water control and solvent control were included along with the test concentrations.

Throughout the entire exposure period, five tadpole mortalities were noted: one in the solvent control, one in the 0.215 μg/L treatment, one in the 0.881 μg/L treatment, and two in 13.6 μg/L test substance treatment (one of which was due to a handling error and was not counted as a mortality in the statistical analysis), indicating that concentrations of test substance used in the present study were not lethal to X. laevis tadpoles over the course of the exposure. Signs of generalized toxicity were apparent at day 7 and day 21. At day 7, there was a significant reduction in tadpole snout-vent length in the 13.6 μg/L test substance treatment compared to controls. By day 21, snout-vent length, wet weight, developmental stage and normalized hind limb length were all significantly reduced in the 13.6 μg/L treatment compared to controls, and snout-vent length and weight were also significantly reduced in the 3.68 μg/L treatment compared to controls. Additionally at day 21, tadpoles exposed to either 3.68 or 13.6 μg/L had significantly reduced cholinesterase activity in both the tail and hind limb tissues compared to controls. However, histopathological investigation of the hind limb and tail tissues of exposed tadpoles revealed no significant histopathological findings relative to controls despite reduced cholinesterase activity at the two higher treatment levels. Finally, compared to thyroid glands from controls, there were no treatment-related histopathological effects observed in the thyroid glands from test substance exposed tadpoles. Because there were no signs of advanced development (as measured by increased developmental stage and hind limb length) or asynchronous development among test substance exposed tadpoles relative to control tadpoles on either day 7 or day 21 of the exposure, and since there were no significant histopathological effects observed among thyroid glands from test substance-exposed tadpoles, test substance was considered “likely thyroid inactive” in the amphibian metamorphosis assay. The No-Observable-Effect Concentration in this study was 0.881 μg/L based on both reduced cholinesterase activity in tail and hind limb tissues and reductions in tadpole growth. The Low-Observable-Effect Concentration in this study was 3.68 μg/L based on both reduced cholinesterase activity in tail and hind limb tissues and reductions in tadpole growth.