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Administrative data

acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
equivalent or similar to guideline
OECD Guideline 403 (Acute Inhalation Toxicity)
Principles of method if other than guideline:
The acute inhalation toxicity of the test substance was assessed by exposing groups each of 10 rats, for a period of 4 hours, to two concentrations of an aerosol of the test substance.
GLP compliance:
Test type:
traditional method
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
Nickel bis(dibutyldithiocarbamate)
EC Number:
EC Name:
Nickel bis(dibutyldithiocarbamate)
Cas Number:
Molecular formula:
Nickel(II) Dibutyldithiocarbamate
Test material form:
solid: particulate/powder
Specific details on test material used for the study:
- Name of the test item (as cited in study report): Nickel dibutyldithiocarbamate
- Batch No.: C 0131100 NF
- Appearance: Dark green, powder

Test animals

Details on test animals or test system and environmental conditions:
- Source: Charles River (UK) Ltd., Manston Road, Margate, Kent, England, obtained on 1 November 1985 and 20 November 1985
- Age at study initiation: 8-9 weeks
- Weight at study initiation: 143-211 g
- Housing: before exposure animals were housed in polypropylene cage (size 38 x 56 cm x 18 cm height) per 10 rats (5 males and 5 females) before exposure; following exposure animals were housed in stainless steel mesh cage (30.5 x 19 x 20 cm height) per rat
- Diet: Labsure LAD 1, ad libitum
- Water: tap water, ad libitum

- Temperature: 19.2 - 21.3 °C
- Humidity: 42-51%

Administration / exposure

Route of administration:
inhalation: dust
Type of inhalation exposure:
whole body
clean air
Mass median aerodynamic diameter (MMAD):
<= 5.5 µm
Details on inhalation exposure:
A Wright dust generator was used to produce a test atmosphere containing the dust of the test substance. The generator was designed to produce and maintain test atmospheres containing dust by suspending material scraped from the surface of a compressed powder in a stream of dry air. The concentration of dust in the air may be altered by changing the gear ratio of the mechanism.

The whole-body exposure chambers used were the square section an were fitted with pyramidal tops. The chambers were made of perspex and had an internal volume of approximately 0.13 m3. For exposure the animals were held in cages of stainless steel mesh partitioned to provide 10 individual animal compartments.
The test atmosphere entered the chamber through a port in the top for Group 2 (Test 1) or in the base centre for Group 3 (Test 2) and passed out through small holes in the lower edge of the square section. The neutraliser was not used for Groups 3 (Test 2) as it was found that higher concentration was achieved by introducing the material directly into the chamber.

The test atmoshere produced by the generator for Group 2 (Test 1) only was passed through a Thermo Systemc Inc., Model 3054, aerosol neutraliser to attempt to minimise electrostatic charge effects.

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 0.5 tons weight. The packed container was weighed.
For Group 2 (Test 1) the dust generator was positioned on a stand at the side of the exposure chamber and the output connected to an inlet port in the top centre of the chamber by the aerosol neutraliser.
For Group 3 (Test 2) the dust generator was positioned on a stand below the chamber and was connected to the inlet port of the chamber. The gear ratio of the generator mechanism was set to give the highest possible concentration of dust (1).
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 rats were placed into separate compartments of the exposure chamber.
The powder container of the Wright dust generator was advanced manually until a trace of suspended dust was in the chamber. The gearing on the generator was then engaged and the generator motor switched on to start the exposure. After a 12-minute equilibration period (2), the exposure was timed for 4 hours (2). The generator was then switched off and the chamber allowed to clear before the rats were removed for examination.
The rats were placed into individual cages and returned to the holding room for the remainder of the observation period. The rack containing the cages was placed in a ventilated cabinet drawing its air supply from the holding room.
The control group was treated similarly but received clean air only for 4 hours.

(1) The performance of the dust generators was assessed prior to scheduling the animal exposures. The gear ratio of 8:1 (increased speed) used in this study was the highest consistent with reliable operation of the dust feed with this material.
(2) 12 minutes is the theoretical time for the chamber concentration to reach 90% of the final concentration under the conditions described.
(3) Operation of the dust generator was interrupted briefly to change the canister on 1 occasion.

Eight air samples were taken from a sampling port in the chamber during exposure and weighed to determine the concentration of the test substance in the chamber air. A further 4 samples were taken from'a second sampling port in a different wall of the chamber to check the spatial distribution of the test material.
The samples were drawn through a weighed Whatman GF/A glass fibre filter, mounted in an open face filter holder, at a rate of 4 litres per minute. The volume of the air sample was measured with a wet type gas meter.
Four further air samples were taken using an Andersen mini sampler (Andersen 2000 Inc.) and the collected material was weighed to determine the particle size distribution of the test substance.
At a sampling rate of 1.4 litres per minute the collection characteristics of the Andersen sampler are:
Stage 1 - Particles larger than 5.5 µm aerodynamic diameter (a.d.)
Stage 2 - Particles between 3.5 µm and 5.5 µm a.d.
Stage 3 - Particles between 2.0 µm and 3.5 µm a.d.
Stage 4 - Particles between 0.3 µm and 2.0 µm a.d.
Filter - Particles smaller than 0.3 µm a.d.

The air temperature in the exposure chamber was measured with a mercury-in-glass thermometer and recorded at the start of the exposure and then at 60-minute intervals during the 4-hour exposure.

The concentration of water vapour in the chamber air was monitored using an Analytical Development Co. Ltd., water vapour analyser, model 225, and recorded at the start of exposure and then at 60-minute intervals.
The relative humidity was calculated from the recorded data for the water vapour content and temperature of the chamber air.
Analytical verification of test atmosphere concentrations:
Duration of exposure:
4 h
Group 2 (Test 1): 0.090 mg/L (37% respirable)
Group 3 (Test 2) 0.416 mg/L (14% respirable)
0.416 mg/L was the highest concentration that could be generated.
No. of animals per sex per dose:
Control animals:
Details on study design:
- Duration of observation period following administration: 14 days post exposure
- Frequency of observations and weighing: The rats were observed continuously during exposure and twice daily throughout the observation period. All rats were weighed on Days 1 (before exposure), 2, 3, 5, 8, 11 and 15.
- Necropsy of survivors performed: Yes. The lungs were infused with, and preserved in, buffered 10% formalin together with samples of the liver and kidneys for possible future microscopic examination.

Results and discussion

Effect levels
Key result
Dose descriptor:
Effect level:
> 0.416 mg/L air
Based on:
test mat.
Exp. duration:
4 h
There were no deaths during the study.
Clinical signs:
other: During exposure: closing or partial closing of the eyes, abnormal breathing and abnormal body posture were observed in all rats exposed to the test substance in group 3. The signs were considered to be consistent with a non-specific response to dust expos
Body weight:
In group 2 (Test 1) body weight gain was not affected by exposure to the test substance.
In group 3 (Test 2) there were slight reductions or reductions in the rate of gain overnight following exposure but subsequently weight gain was similar to that of the control rats.
Gross pathology:
There were no treatment-related macroscopic abnormalitites.

Any other information on results incl. tables

Nominal concentration

The nominal concentrations determined by dividing the total test substance used by the total airflow were 9.84 and 10.32 mg/L for Groups 2 and 3 respectively.

Particle size distribution

The, results show that, on average, 37% for Group 2 and 14% for Group 3 by weight, of the test substance in the chamber air was 5.5 µm or less in aerodynamic diameter and therefore of respirable size. The lower respirable fraction for Group 3 than for Group 2 was due to the equipment configuration. For Group 2 a greater proportion of nonrespirable particles would be lost in the aerosol neutraliser which would also act as an elutriation column.

Chamber air

The chamber mean air temperatures were between 23.1 and 23.3 °C.

Relative humidity

The mean relative humidity of the chamber air was between 35 and 47%.

Applicant's summary and conclusion

Interpretation of results:
study cannot be used for classification
The study determined a LC50 of > 0.416 mg/L, which was the highest concentration that could be generated. In order to achieve applicability of animal experiments to human exposure, the mean mass aerodynamic diameter (MMAD) should be low enough to ensure that the test substance will deposit in all regions of the rats respiratory tract of the appropriate test animal. According to OECD TG 403, the primary goal should be to achieve a MMAD of 1 - 4 µm when testing aerosols. In the study, particle size distribution analysis showed that the majority of the test substance exceeds a particle size of 5.5 µm during exposure. Because of the low efficiency of generation (measured concentration was only 0.9 - 4% of the nominal concentration) and the relative large particle size, data cannot be used for classification of acute inhalation toxicity. As sufficient data are available on the other two routes of exposure, the study is not warranted.