Hexachlorocyclopentadiene

Endpoint summary

Description of key information

A Harmonised Classification as Acute Tox 4, H302 (oral route), Acute Tox 2, H330 (inhalation) and Acute Tox. 3; H311 (dermal route) is currently attributed to Hexachlorocyclopentadiene for acute toxicity. This Harmonised Classification was translated from Directive 67/548/EEC and should therefore be considered as a minimum classification unless there is evidence showing that the substance should be classified more severely according to Annex VI Section 1.2 of Regulation (EC) N° 1272/2008.

The acute toxicity via oral route of Hexachlorocyclopentadiene was determined by Huntingdon Research Centre (1986) using a procedure similar to the OECD Testing Guideline 401. This study was selected as a key study due to the lack of information on necropsy or clinical information in the other studies available for this endpoint. Mortality was observed following ingestion of the substance, along with a reduction of the bodyweight gain and clinical signs of adverse effects in surviving animals from the highest dose groups. These effects were fully reversible by the end of the observation period (14 days). The LD50 for male and female rats was found to be 1,400 mg/kg bw. The substance meets the criteria for classification as Acute Tox 4, H302 according to Regulation (EC) N° 1272/2008. It is consistent with the current Harmonised Classification of the substance.

 

The acute toxicity via inhalation of Hexachlorocyclopentadiene was determined by Rand et al. (1982) using a procedure equivalent to the OECD Testing Guideline 403. This study was selected as a key study; the other available studies for this endpoint showed to have significant methodological deficiencies and were used as weight of evidence. In the Rand et al. (1982) study mortality was observed with the majority of the deaths occurring within the first day following exposure to the substance. The mortality rate was the highest in male rats. Clinical signs of adverse effects and weight loss were observed in surviving animals from the highest dose groups. These effects did not revert by the end of the observation period (14 days). At necropsy significant pulmonary abnormalities in the surviving animals from the highest dose groups were identified. The LC50 was 1.6 ppm for male rats and 3.5 ppm for female rats. The substance meets the criteria for classification as Acute Tox 1, H330 according to Regulation (EC) N° 1272/2008. This classification is more severe than the current Harmonised Classification, in accordance with Annex VI Section 1.2 of Regulation (EC) N° 1272/2008.

No reliable study was identified to be used as a key study to assess the acute toxicity of Hexachlorocyclopentadiene via the dermal route. Therefore a weight-of-evidence approach was used based on available information on the acute dermal toxicity of the substance. No evidence was found indicating that Hexachlorocyclopentadiene should receive a more severe classification than the current Harmonised Classification as Acute Tox. 3; H311 for the dermal route.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 20 August 1986 to 3 September 1986

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

yes

Remarks:

doses different from the ones currently recommended

Qualifier:

according to guideline

Guideline:

EPA OTS 798.1175 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

no

Limit test:

no

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Stored at ambient temperature in the original containers
- Stability under test conditions: Stability and absorption of the test substance were not determined

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: Hexachlorocyclopentadiene was prepared at various (w/v) concentrations in corn oil and administered at a volume of 10.0 mL/kg

Species:

rat

Strain:

other: CFY (Sprague-Dawley)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Interfauna UK Ltd., Huntingdon, Cambridgeshire, England
- Age at study initiation: approximately 4-6 weeks
- Weight at study initiation: 103 - 137 g
- Fasting period before study: access to food prevented overnight prior to and approximately 4 hours after dosing
- Housing: housed in groups by sex in metal cages with wire mesh floors; accommodated with forced-ventilation whole-body inhalation chambers (40" x 36" x 37.5")
- Diet: standard laboratory rodent diet (Labsure LAD 1) provided ad libitum
- Water: ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature: mean daily minimum and maximum temperatures were 18 °C and 20 °C respectively
- Humidity: mean daily relative humidity was 63%
- Air changes: approximately 15 air changes per hour
- Photoperiod: 12 hours artificial light in each 24 hour period

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 12.6% (w/v); 16.0% (w/v); 20.0% (w/v)
- Amount of vehicle (if gavage): 10.0 mL/kg

Doses:

1,260 mg/kg; 1,600 g/kg; 2,000 g/kg

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: animals were observed soon after dosing, then at frequent intervals for the remainder of Day 1. On subsequent days the animals were observed once in the morning and again at the end of the experimental day.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs; body weight; approximate time of death; nature, severity, time of onset and duration of each toxic sign

Statistics:

Separate LD50 values for males and females were estimated by undertaking probit analysis on the mortality data by fitting two parallel lines on the data (males only and females only) using the technique described by Finney (1978, Statistical Method in Biological Assay, 3rd Edition, Charles Griffin, London). A chi-squared test was carried out to check that the data did not contain any evidence for non-parallelism.

Preliminary study:

A trial test was carried out to establish a dosing regimen, using groups of 2 males and 2 female rats, at dose levels of 50, 100, 200, 500, 1260, 2500 and 5000 mg/kg bw. Results of this preliminary study indicated that the acute median lethal oral dose was between 1.26 and 2.5 g/kg bodyweight

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

1 400 mg/kg bw

Based on:

test mat.

95% CL:

>= 1 200 - <= 1 500

Sex:

male

Dose descriptor:

LD50

Effect level:

1 500 mg/kg bw

Based on:

test mat.

95% CL:

>= 1 300 - <= 1 700

Sex:

female

Dose descriptor:

LD50

Effect level:

1 300 mg/kg bw

Based on:

test mat.

95% CL:

>= 1 000 - <= 1 500

Mortality:

Deaths among male/female rats given doses of 1.26 g/kg and above. Mortalities generally occurred on days 2 or 3 but additional single female rats dosed at 1.26 g/kg were found dead on Days 4 and 12.

Clinical signs:

Signs of reaction to treatment observed in all rats shortly after dosing were pilo-erection, abnormal body carriage (hunched posture), abnormal gait (waddling), lethargy, decreased respiration, ptosis, pallor of the extremities and diarrhoea. In addition a high-stepping gait was observed amond the female rats dose at 1.26 g/kg and two males dosed at 2.00 g/kg were prostate before their demise. Recovery of survivors, as judged by external appearance and behaviour, was completed at various times between Days 6 and 11.

Body weight:

Bodyweight losses or no change of bodyweight (in one case) were recorded for the rats that died. Low bodyweight gains were recorded on Day 8 for all rats that survived the effects of treatment. All rats achieved at least the anticipated bodyweight gain during the second week of the observation period.

Gross pathology:

Terminal autopsy findings were normal.

See attached background material for full results tables of mortality data and observations, including mortality response curve.

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

The study determined the LD50 of male and female rats to be 1400 mg/kg bw, which meets the GHS criteria for classification as acute toxicity hazard Category 4.

Executive summary:

The acute oral toxicity of hexachlorocyclopentadiene was determined according to EPA OTS 798.1175, and was equivalent to the OECD Guideline for Testing of Chemicals 401, with deviations. The study was non GLP compliant. The study was carried out on male and female CFY Sprague-Dawley rats, which were administered appropriate doses of the test substance via oral gavage. Rats were observed for 14 days after dosing and observations on mortality, clinical signs, bodyweight and terminal autopsy were recorded. The study determined the LD50 of male and female rats to be 1400 mg/kg bw, which meets the GHS criteria for classification as acute toxicity hazard Category 4.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

1 400 mg/kg bw

Quality of whole database:

The key study was considered as reliable as it is carried out using a procedure equivalent the OECD Guideline 403, and the results are supported by additional supporting studies reaching a similar conclusion.

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

5 February 1986 - 11 March 1986

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

yes

Remarks:

missing details on test animals; exposure of only 1 hour

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Wistar

Remarks:

Albino

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Diet and water: The amount of food and water consumed by each cage of rats was measured daily from the day following arrival, and the mean daily intake for each rat was calculated.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 22 °C
- Humidity (%): 30 - 31%
- Photoperiod (hrs dark / hrs light): fluorescent lamp for 12 hours each day (08:00 - 20:00)

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: See attached background material for diagram of exposure system. The generator was designed to produce and maintain an atmosphere containing HEX at a concentration that could be varied by changing the temperature of the oven or the water bath. All parts of the generator were made of PTFE, glass or stainless steel. The vaporiser consisted of a 1" pipe size stainless steel 'T' connector and a small glass cup, forming a reservoir for the liquid HEX, supported in a PTFE holder and located in the side arm of the 'T' connector.
- Source and rate of air: The HEX was vaporised from a sintered glass bulb, fused to the base of the cup, by passing air through the 'T' connector.
- Method of conditioning air: The air supply could be heated by passing it through a heat exchanger maintained at the required temperature in a water bath.
- Temperature, humidity, pressure in air chamber: 20 - 22 °C and 30 - 31% humidity

TEST ATMOSPHERE
- Brief description of analytical method used: Three air samples taken from chamber during each exposure and analysed to determine the concentration of HEX in the chamber atmosphere. Samples were drawn through a gas absorption trap, containing approx 20 mL ethanol chilled to -70 °C, at a rate if 2 L per min. Volume of air sample was measured with a wet-type gas meter. Temperature in the exposure chamber was measured with a mercury bulb thermometer and was recorded at the start of the exposure and at 30-minute intervals during the exposure.
- Samples taken from breathing zone: yes

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

1 h

Concentrations:

18.7 μg/L; 39.5 μg/L; 70.0 μg/L; 93.0 μg/L; 26.6 μg/L

No. of animals per sex per dose:

5

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 21 days
- Frequency of observations and weighing: rats were observed continuously during exposure for signs of reaction to the test formulation and at least twice daily during the observation period; all rats were weighed daily from day of delivery to Huntingdon Research Centre until the end of the observation period.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight, macroscopic pathology

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 3.69 ppm

Based on:

test mat.

95% CL:

0.467

Exp. duration:

1 h

Mortality:

See table below under 'Any other information on results incl tables'.

Clinical signs:

other: During exposure to HEX the signs were consistent with exposure to a mildly irritant vapour and included closure/partial closure of the eyes, abnormal respiratory pattern and adoption of an abnormal body posture. Excessive salivation in rats exposed at 70

Body weight:

The rats surviving exposure to HEX at 18.7 μg/L lost weight or gained at a reduced rate for up to 10 days following exposure but eventually achieved a rate of bodyweight gain similar to that of the control group. See attached background material for full results.

Gross pathology:

Abnormalities seen in the lungs of a proportion of rats exposed to HEX at any concentration included a swollen and sometimes pale appearance of the lungs, areas of congestion and a hepatised appearance of part or complete lobes of the lungs. Other changes seen in a proportion of rats exposed at 39.5 μg/L or higher concentrations were small or abnormal appearance of some internal organs and distended gas-filled stomachs. See attached background material for full results.

Table showing atmospheric concentrations of HEX and mortality:

Exposure level (ug/L)	Mortality on Day 14
	Males	Females	Total
18.7	0/5	1/5	1/10
39.5	2/5	2/5	4/10
70.0	3/5	4/5	7/10
93.0	5/5	5/5	10/10
26.6	2/5	0/5	2/10

Interpretation of results:

study cannot be used for classification

Conclusions:

This acute inhalation toxicity study determined the 1 hour LC50 of rats to hexachlororcyclopentadiene to be 3.69 ppm (standard error of 0.467 ppm). Due to the exposure duration this study cannot be used for classification.

Executive summary:

The acute inhalation toxicity of hexachlorocyclopentadiene to albino Wistar rats was determined in a GLP compliant study, using a procedure similar to the OECD Guideline for Testing of Chemicals. Deviations from the guideline include a exposure duration limited to one hour instead of the four hours currently recommended for this endpoint. The study was assessed as having a Klimisch score of 3 due this significant deviation. The acute inhalation toxicity was assessed by exposing groups of rats to different concentration of the test substance in air for 1 hour, then monitoring clinical signs and body weight throughout the 21 day observation period. Mortality was recorded on day 14. The study determined the 1 hour LC50 to be 3.69 ppm (standard error of 0.467 ppm). Due to the exposure duration this study cannot be used for classification.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LC50

Value:

17.87 mg/m³

Quality of whole database:

The key study was considered as reliable as it is carried out using a procedure equivalent the OECD Guideline 401, and the results are supported by additional supporting studies reaching a similar conclusion. The LC50 of 1.6 ppm observed on male rats was converted in mg/m3.

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

other: expert assessment

Adequacy of study:

weight of evidence

Study period:

6 March 2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: An assessment was performed based on the Harmonised Classification and data on the acute dermal toxicity of the substance.

Qualifier:

no guideline followed

Principles of method if other than guideline:

An assessment was performed based on the Harmonised Classification and data on the acute dermal toxicity of the substance.

GLP compliance:

no

Test type:

other: An assessment was performed based on the Harmonised Classification and data on the acute dermal toxicity of the substance.

Limit test:

no

Remarks on result:

other: An assessment was performed based on the Harmonised Classification and data on the acute dermal toxicity of the substance.

Mortality:

Hexachlorocyclopentadiene is to be considered as acute toxic by the dermal route and should be classified as Acute Tox. 3; H311.

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

Hexachlorocyclopentadiene is to be considered as acute toxic by the dermal route and should be classified as Acute Tox. 3; H311.

Executive summary:

A Harmonised Classification as Acute Tox. 3; H311 (toxic in contact with the skin) is currently attributed to Hexachlorocyclopentadiene for the acute toxicity by the dermal route. This Harmonised Classification was translated from the Directive 67/548/EEC and should therefore be considered as a minimum classification unless there is evidence showing that the substance should be classified more severely.

Data was provided by the Lead Registrant on the acute toxicity of the substance by the dermal route.

A study was performed on Sprague-Dawley rats and concluded that the substance was not acutely toxic under the conditions of the test. This study is considered as reliable but does not allow revision of the Harmonised Classification as it would represent a less severe classification.

A study was performed on albino rabbits and concluded that the LD50 was below 200 mg/kg bw. This study is not considered as reliable due to significant deviations from the current OECD Testing Guidelines expected to lead to aggravated adverse effects and should not be used for the classification of the substance for its acute toxicity by the dermal route.

Additional data was provided by the EU (2007) as a secondary source but could not be accessed and assessed for their reliability.

No reliable data were available suggesting that Hexachlorocyclopentadiene should receive a more severe classification than the current Harmonised Classification as Acute Tox. 3; H311. In conclusion Hexachlorocyclopentadiene is to be considered as acute toxic by the dermal route and should be classified as Acute Tox. 3; H311. It is not considered relevant to perform an acute toxicity study on the substance by the dermal route.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

300 mg/kg bw

Quality of whole database:

Hexachlorocyclopentadiene is classified as Acute Tox. 3; H311. In accordance with the CLP Regulation the converted acute toxicity estimate for substances classified as Acute Tox. 3; H311 is 300 mg/kg bw.

Justification for classification or non-classification

Oral route:

An acute toxicity study by the oral route was performed according to a method similar to the OECD Testing Guideline 401. The study determined the LC50 of male and female rats to be 1400 mg/kg bw. This substance meets the criteria for classification as Acute Tox 4, H302 according to Regulation (EC) No.1272/2008.

Inhalation route:

An acute toxicity study by inhalation was performed according to a method similar to the OECD Testing Guideline 403. The 4 hour LC50 and 95% confidence limits was found to be 1.6 ± 0.6 ppm for male rats and 3.5 ± 2.1 for female rats. This substance meets the criteria for classification as Acute Tox 1, H330 according to Regulation (EC) No.1272/2008.

Dermal route:

The substance received a Harmonised Classification as Acute Tox. 3; H311. No evidence was identified showing that the substance should receive a more severe classification according to Regulation (EC) No.1272/2008 on the Classification, Labelling and Packaging of Substances and Mixtures.