Chlorothalonil

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 Jul 1992 to 12 Aug 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1993

Report date:

1993

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OPP 81-3 (Acute inhalation toxicity)

GLP compliance:

yes

Test type:

traditional method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Chlorothalonil

EC Number:

217-588-1

EC Name:

Chlorothalonil

Cas Number:

1897-45-6

Molecular formula:

C8Cl4N2

IUPAC Name:

tetrachlorobenzene-1,3-dicarbonitrile

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: Males about 6 weeks old; females about 8 weeks old
- Weight at study initiation: circa 200 g
- Housing: The holding cages (size 31 cm x 19 cm x 20 cm height) were made of stainless steel sheet and wire mesh and were suspended on a movable rack.
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25
- Humidity (%): 40 to 70
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 15 Jul 1992 To: 12 Aug 1992

Administration / exposure

Route of administration:

inhalation: dust

Type of inhalation exposure:

whole body

Vehicle:

clean air

Mass median aerodynamic diameter (MMAD):

>= 2.5 - <= 3.6 µm

Geometric standard deviation (GSD):

>= 2.45 - <= 2.49

Remark on MMAD/GSD:

Respirable fraction (<6µm) 71.0 to 83.5%

Details on inhalation exposure:

A sample of the test substance was packed into the container of the Wright dust generator using a hydraulic bench press to assist packing. Even density of the powder was achieved by packing the container in stages and applying a force of 0.8 tons weight. The packed container was weighed. The dust generator was positioned on a stand beside the exposure chamber and the output connected to an inlet port in the top centre of the chamber by the elutriation column. The speed controller of the generator mechanism was set to give a concentration of dust that was expected to produce some deaths.

A supply of clean dried compressed air was connected to the dust generator and the supply pressure was adjusted to give a flow rate of 25 litres per minute measured at the generator outlet nozzle. The total chamber air supply was derived from the air flow through the dust generator. The first group of rats (5 per sex) to be exposed were placed into separate compartments of the exposure chamber so that male and female rats were at alternate positions. The powder container of the Wright dust generator was advanced manually until a trace of suspended dust was seen in the chamber. The gearing on the generator was then engaged and the generator motor switched on to start the exposure. After an 11-minute equilibration period, the exposure was timed for 4 hours. The generator was then switched off and the chamber allowed to clear before the rats were removed for examination.

The procedure was repeated, with appropriate settings of the speed controller, for each of the other test groups. Following exposure, the rats were returned to the holding cages and food and water supplies were restored. The test rats were kept in a ventilated cabinet overnight and then returned to the holding room for the remainder of the observation period. The control group was treated similarly but exposed to air only for 4 hours. The control rats were returned to the holding room at the end of the exposure procedure.

Five air samples were taken from the chamber during each exposure to determine the concentration of the test substance in the chamber air. Each air sample was withdrawn, at 4 litres per minute, through a weighed glass fibre filter mounted in an open face filter holder. The filters were removed and re-weighed. The volume of the air sample was measured with a wet-type gas meter. Four additional air samples were taken during each exposure using a Marple cascade impactor. The material collected on the stages of the sampler was weighed to determine the particle size distribution of the test substance in the test atmospheres. The nominal concentration of test substance in the exposure chamber was calculated from the amount of test substance dispersed in the generator and the total air flow through the generator.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

0.14, 0.08 and 0.21 mg/L

No. of animals per sex per dose:

5

Control animals:

yes

Details on study design:

Clinical signs
The rats were observed continuously for signs of reaction to the test substance during exposure and at least twice daily throughout the observation period. The clinical signs were recorded at the end of the chamber equilibration period, at 0.25, 0.5 and 1.0 hours and then at hourly intervals during the exposure and for 2 hours post exposure. During the observation period, the clinical signs were recorded once in the morning and then as necessary following a later check for clinical signs.

Body weight
All rats were weighed daily from the day of delivery until the day of exposure and then on Day 7 and Day 14 of the observation period or following death.

Terminal studies
At the end of the 14-day observation period, the surviving rats were anaesthetised by intraperitoneal injection of pentobarbitone sodium and killed by exsanguination. All rats that died as a result of exposure and those killed at the end of the observation period were subjected to a detailed macroscopic examination. The lungs were removed, dissected clear of surrounding tissue and weighed in order to calculate the lung weight to body weight ratio. The lungs were infused with, and preserved in, buffered 10% formalin together with samples of the liver and kidneys for possible microscopic examination.

Statistics:

The concentration of the test substance likely to cause death in 50% of exposed rats following a single 4-hour exposure was calculated by the log probit method of Miller and Tainter.

Results and discussion

Effect levels

Effect levels 1

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

0.1 mg/L air (analytical)

Based on:

test mat.

95% CL:

>= 0.07 - <= 0.14

Exp. duration:

4 h

Effect levels 2

Sex:

male

Dose descriptor:

LC50

Effect level:

0.1 mg/L air (analytical)

Based on:

test mat.

95% CL:

>= 0.03 - <= 0.18

Exp. duration:

4 h

Effect levels 3

Sex:

female

Dose descriptor:

LC50

Effect level:

0.1 mg/L air (analytical)

Based on:

test mat.

95% CL:

>= 0.05 - <= 0.15

Exp. duration:

4 h

Mortality:

In Group 2 (0.14 mg/L), one female rat died 10 minutes post exposure. Two male rats died overnight following exposure. One male rat and 2 female rats were found dead on Day 2 (a.m.) of observation period.
In Group 3 (0.08 mg/L), one male rat and one female rat died overnight following exposure and were found dead on Day 1 (a.m.). One female rat died on Day 1 (p.m.). One male rat was found dead on Day 2 (a.m.) of the observation period.
In Group 4 (0.21 mg/L) two female rats died on Day 1 (a.m.) and two male rats and two female rats died on Day 1 (p.m.). One male rat and one female rat were found dead on Day 2 (a.m.) and one male rat died on Day 2 (p.m.) of the observation period.

Clinical signs:

other: See description in "Any other information on results incl. tables'.

Body weight:

There were moderate reductions in the rate of body weight gain during the first week following exposure. Subsequently, weight gain for rats that survived exposure to the test substance was similar to that of the control rats.

Gross pathology:

The findings for rats that died as a result of exposure to te test substance were typified by congestion of the lungs. The stomachs of a number of decedents were found to be gas-filled and a white frothy fluid was found in the trachea. There were no abnormalities in rats that survived exposure to the test substance.

Any other information on results incl. tables

Verification of test atmosphere concentrations

The nominal concentrations were calculated from the amounts of the test substance dispersed and the total volumes of air supplied to the exposure system. The measured concentrations were between 9 and 21% of nominal.

Clinical signs

- During the exposure: The signs seen during exposure were considered to be consistent with inhalation of an irritant aerosol and included partial closing of the eyes, wetness around the eyes, exaggerated respiratory movements and restless behaviour. Gasping was seen in rats exposed at 0.14 mg/L or 0.21 mg/L.

 

- During the observation period: Clinical signs evident during the 2-hour period included exaggerated respiratory movements, wet fur, gasping and a discharge from the eyes. Most of these signs and also brown staining were seen on Day 1. Exaggerated respiratory movements persisted or recurred for several days. Deaths as a result of exposure occurred on Days 0 - 2 of observation. Recovery from the effects of exposure was evident from Day 4 and the majority of rats surviving exposure to the test substance were normal by Day 9 of the observation period.

Table 1. Mortality

Group	Mean measured concentration (mg/L)	Mortality (males)	Mortality (females)
1	Control	0/5	0/5
2	0.14	3/5	3/5
3	0.8	2/5	2/5
4	0.21	4/5	5/5

Applicant's summary and conclusion

Interpretation of results:

Category 1 based on GHS criteria

Remarks:

Including STOT-SE Cat. 3 for respiratory irritation

Conclusions:

Based on the mortality data for all groups and sexes from this study (EPA FIFRA 81-3 guideline and GLP), the LC50 estimate and corresponding 95% confidence limits (CL) were calculated from the actual (measured) concentrations: 0.10 mg/L air (0.07 – 0.14 mg/L).

Executive summary:

The acute inhalation toxicity of the test substance was assessed by exposing 3 groups of rats, each for a period of 4 hours, to aerosols produced from the test substance following the EPA FIFRA 81-3 guideline and GLP. A fourth group was exposed to air only. The animals were exposure using whole-body exposure. The observation period was 14 days post exposure.

During exposure: signs consistent with exposure to an irritant aerosol, including partial closing of the eyes, wetness around the eyes, exaggerated respiratory movements and restless behaviour. During observation period: signs seen in rats exposed to the test substance included abnormal respiration, wet fur, brown staining around the snout and jaws, discharges from the eyes and deaths. Recovery from the effects of exposure was evident from Day 4 and the majority of surviving rats were normal by Day 9 of observation. Reduced rate of body weight gain during the first week following exposure. Subsequently weight gain was generally similar to that for control rats. The lungs of the majority of rats that died as a result of exposure were congested and the stomachs were gas-filled. A white frothy fluid was found in the trachea of a number of rats. There were no macroscopic abnormalities in rats surviving exposure to the test substance.

In conclusion, from the mortality data for all groups and sexes, the LC50 estimate and 95% confidence limits (CL) were calculated from the actual (measured) concentrations: 0.10 mg/L air (0.07 – 0.14 mg/L).