Paraquat-dichloride

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 Mar 1985 to 10 Apr 1985

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1985

Report date:

1985

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

traditional method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Paraquat-dichloride

EC Number:

217-615-7

EC Name:

Paraquat-dichloride

Cas Number:

1910-42-5

Molecular formula:

C12H14N2.2Cl

IUPAC Name:

1,1’-dimethyl-4,4’-bipyridyldiylium dichloride

Test animals

Species:

rat

Strain:

Wistar

Remarks:

Alpk:AP

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: ~7 weeks
- Weight at study initiation: males average 230 g (range: 208 to 244 g), females average 206 g (range: 192 to 223 g)
- Housing: Rats were housed five to a cage (sexes separately). Each cage had the following internal measurements: length 38.0 cm, width 32.5 cm and height 21.0 cm, and was suspended over a collecting tray lined with absorbent paper. The cages were contained in a single-sided mobile rat rack, and each cage was labelled with a stock card prior to exposure, and during the study by an experimental card, identifying the study, species, sex, animals and Home Office licensee.
- Diet: The animals were provided with food (pelleted Parton Combined Diet), ad libitum except during exposure.
- Water: water (via an automatic water system), ad libitum except during exposure.
- Acclimation period: 7 days prior to exposure.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 2
- Humidity (%): 40 to 60
- Photoperiod (hours dark / hours light): 12 / 12

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

clean air

Mass median aerodynamic diameter (MMAD):

< 0.3 µm

Remark on MMAD/GSD:

>90% of the test aerosol for each treatment group had an aerodynamic equivalent diameter <0.3 µm

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: nose-only exposure using restraining tubes
- Exposure chamber volume: 18.4 L
- Source and rate of air: the flow rates, converted to normal temperature and pressure, were as follows:
* target concentration 0.2 mg/m3: 12.0 L/min generating air plus 15 L/min diluting air
* target 0.7 mg/m3: 16.5 L/min generating air plus 10 L/min diluting air
* target 1.5 mg/m3: 15.0 L/min generating air plus 10 L/min diluting air
*The control chamber was supplied with air at a rate of 12 L/min throughout exposure
- Method of conditioning air: dried and filtered through an atomiser and cyclone
- System of generating aerosols: Aerosols of the paraquat formulation were generated by passing clean, dry air through an atomiser and cyclone. For the 0.7 and 1.5 mg/m3 concentrations a 1% substance dilution was used. For the 0.2 mg/m3 a 0.1% substance dilution was used.
- Method of particle size determination: The aerodynamic particle size was measured once for each test group during the exposure period by means of a mini sampler which aerodynamically separates airborne particles into pre-determined size ranges. The major proportion (>84.5%) of the substance is present on stage 5 (aerodynamic equivalent diameter <0.3 µm).
- Temperature, humidity, pressure in air chamber: The temperature was 18 °C in all exposure chambers. Except for the top dose where it was 19 °C. The relative humidity was 27, 37, 38 and 41% in the control, 0.2, 0.7 and 1.5 mg/m3 groups, respectively.

TEST ATMOSPHERE
- Brief description of analytical method used: Nominal atmospheric concentration of active ingredient was calculated from the following formula after measuring, by weight loss, the amount of formulation used:


weight loss (mg) x % strength of final formulation x 1000
concentration (mg/m3) = -----------------------------------------------------------------------
Time (min) x Airflow (L/min) x 100


- Samples taken from breathing zone: yes

VEHICLE
- Composition of vehicle: clean, dry air

Analytical verification of test atmosphere concentrations:

yes

Remarks:

The concentrations of active ingredient were calculated based on the weight loss of the formulation.

Duration of exposure:

4 h

Concentrations:

The concentrations of active ingredient from the weight loss of the formulation, were calculated to be as follows:
- theoretical concentration 0.2 mg/m3 test ion -> analytical concentration 0.20 ± 0.04 mg/m3 test ion
- theoretical concentration 0.7 mg/m3 test ion -> analytical concentration 0.60 ± 012 mg/m3 test ion
- theoretical concentration 1.5 mg/m3 test ion -> analytical concentration 1.4 ± 0.2 mg/m3 test ion

No. of animals per sex per dose:

5

Control animals:

yes

Remarks:

Clean dry air

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: All rats were weighed on day -1 (defined as the day before exposure), prior to exposure on day 1 and then on days 2-8 and 15. The animals were also subjected to a detailed clinical examination on each day of the observation period and prior to post-mortem examination on day 15.
- Necropsy of survivors performed: yes, on day 15
- Other examinations performed: food consumption, gross pathology, organ weights (lungs, liver, kidneys and testes). Animals that died were also subjected to a post mortem examination.

Statistics:

Where appropriate, test and control data were compared statistically using a two-sided Student's t-test.

Results and discussion

Effect levels

Effect levels 1

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 0.6 - < 1.4 mg/m³ air

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: original value presented in study.

Effect levels 2

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 0.8 - < 1.9 mg/m³ air

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: recalculated value, expressed as pure test substance, see ‘Any other information on results incl. tables’ for respective calculation.

Mortality:

- There were no deaths in controls or test animals in the 0.20 or 0.60 mg/m3 groups during the exposure or observation periods.
- All animals in the 1.4 mg/m3 group survived the 4-hour exposure period, but the following deaths occurred during the observation period: 1 male (day 3); 2 males and 3 females (day 4); 1 female (day 5). The remaining 3 animals (2 males, 1 female) in this group were killed in extremis on day 6.

Clinical signs:

other: - During exposure: abnormalities normally associated with restraint (stains around the snout, chromodacryorrhea and wet fur) were seen in test and control groups. The severity of these effects was similar across the groups. - Immediately after exposure: a

Body weight:

Animals in all test and control groups lost weight following exposure. The effect was greatest in the top dose animals which continued to lose weight rapidly up to day 6 at which point the animals had either died or were killed in extremis. After the initial weight loss, the rate of weight gain in the 0.20 and 0.60 mg/m3 groups was similar to or greater than controls.

Gross pathology:

One male rat in the 0.20 mg/m3 group had dark red spots on the surfaces of all lobes of the lungs (this effect reduced after inflation with fixative) and froth exuded from the trachea during excision. No treatment related abnormalities were seen in any other animal in this group or in the 0.60 mg/m3 animals. Top dose animals had dark red, mottled lungs which were not fully deflated and several animals had froth exuding from the trachea.

Other findings:

- Organ weights: there were no statistically significant differences in the group mean organ weights or organ to last body weight ratios between animals in the 0.20 and 0.60 mg/m3 groups compared with controls. However, one male rat in the 0.2 mg/m3 group had a high lung weight (approximately 40% increase over the control value). The rats in the 1.4 mg/m3 group died or were killed in extremis before day 7 of the observation period and have therefore not been compared statistically with the controls. However, the data shows that there was a considerable increase in the lung weight of these animals (ratios increased by approximately 200-400%). There is also an apparent effect on the kidney with a low absolute value but high ratio to body weight. The apparently low liver-to-body weight-ratio and high testes-to-body weight-ratio are considered to result from the decreased body weight of these animals although glycogen depletion may have been a contributory factor in the liver.
- Other observations: There was a slight reduction in the food consumption of animals exposed to 1.4 mg/m3 between day 1 to 2 of the observation period with a pronounced reduction between day 2-6, i.e. after an apparent delayed effect of one day these animals ate very little food and then subsequently died or were killed in extremis before day 7. Food consumption of the controls and other test animals was similar throughout the study.

Any other information on results incl. tables

Calculation of key result

The doses of the test substance were expressed in test subtstance cation, which relates to the cation species in an aqueous solution of the registered substance. The effect levels are already corrected for the amount of water. The key effect levels are calculated by inclusion of the anion species:

(100/72.4) x 0.6 mg test substance cation / kg bw = 0.8 mg pure test substance/ kg bw.

(100/72.4) x 1.4 mg test substance cation / kg bw = 1.9 mg pure test substance/ kg bw.

Applicant's summary and conclusion

Interpretation of results:

Category 1 based on GHS criteria

Conclusions:

Based upon the results obtained in this study the LC50 for the pure test substance (recalculated value) was determined to be between 0.8 and 1.9 mg/m3. This calculation was based on original effect levels of 0.6 and 1.4 mg/m3.

Executive summary:

The acute inhalation toxicity of the substance was assessed in a study design similar to OECD 403 and following GLP. In this study groups of five male and five female rats/ dose/ sex were exposed by nose-only exposure of to test atmosphere containing 0.20, 0.60 and 1.4 mg/m3 aerosol for a single 4-hour period. After exposure, the rats were kept for a 14-day observation period. 

Dose-related irritation of the respiratory tract and death at the top dose were observed. All animals in this top dose group survived the exposure period but died or were killed in extremis before day 7 of the observation period. There were no deaths at the lower dose levels. The clinical abnormalities seen indicated irritation of the respiratory tract at all dose levels with some indications of a dose-related increase in severity and general debility at the top dose level. There were significant associated reductions in body weight gain and food consumption only at the top dose level. Irritation of the respiratory tract persisted in a high proportion of test animals in the 0.20 and 0.60 mg/m3 groups during the first 7-10 days of the observation period but was not evident by day 15. In addition, there was a considerable increase in the lung weight of the top dose animals and macroscopic evidence of acute lung damage seen at post mortem examination of these animals.

The 4-hour LC50 of the formulation as tested was therefore between 0.60 and 1.4 mg/m3, which corresponds to a recalculated value of 0.8 to 1.4 mg/m3 pure substance.