diuron (ISO); 3-(3,4-dichlorophenyl)-1,1-dimethylurea

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 Oct 2006 to 07 Dec 2006

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP- Guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.2 (Acute Toxicity (Inhalation))

GLP compliance:

yes

Test type:

fixed concentration procedure

Test material

Test material information

Constituent 1

Reference substance name:

Diuron

EC Number:

206-354-4

EC Name:

Diuron

Cas Number:

330-54-1

Molecular formula:

C9H10Cl2N2O

IUPAC Name:

3-(3,4-dichlorophenyl)-1,1-dimethylurea

Details on test material:

- Name of test material (as cited in study report): Diuron Technical
- Substance type: Off white powder
- Physical state: Powder
- Analytical purity: > 98%
- Lot/batch No.: 0321205
- Storage condition of test material: Room temperature, in the dark

Test animals

Species:

rat

Strain:

other: Sprague-Dawley Crl:CD (SD) IGS BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River (UK) Ltd, Margate, Kent, UK.
- Age at study initiation: Approximately eight to twelve weeks old.
- Weight at study initiation: 200g to 350g
- Fasting period before study: No
- Housing: The animals were housed in groups of five by sex in solid-floor polypropylene cages with stainless steel lids, furnished with softwood flakes (Datesand Lts., Cheshire, UK) and provided with environmental enrichment items; wooden chew blocks (B & K Universal Ltd, Hull, UK) and cardboard ‘’fun tunnels’’ (Datesand Lts., Cheshire, Uk).
- Diet: Free access to food (EU Rodent Diet 5LF2, BCM IPS Linited, London, UK) was allowed throughout the study, except during the exposure period.
- Water: Free access to mains drinking water was allowed throughout the study, except during the exposure period.
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-25
- Humidity (%): 30-70
- Air changes (per hr): The rate of air exchange was at least fifteen changes per hour.
- Photoperiod : The lighting was controlled to give twelve hours continuous light and twelve hours darkness.

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: A cylindrical exposure chamber, SAG 410 solid aerosol generator and a metered compressed air supply.

- Exposure chamber volume: The cylindrical exposure chamber had a volume of approximately 30 litres (dimensions: 28 cm diameter x 50 cm high).

- Method of holding animals in test chamber: Each rat was individually held in a tapered, polycarbonate restraining tube fitted onto a single tier of the exposure chamber and sealed by means of a rubber ‘O’ ring. Only the nose of each animal was exposed to the test atmosphere.

- Source and rate of air: Compressed air was supplied by means of an oil free compressor and passed through a water trap and respiratory quality before it was introduced to the SAG 410.

- System of generating particulates/aerosols: A dust atmosphere was produced from the test material using a SAG 410 Solid Aerosol Generator (TOPAS GmbH, Dresden, Germany). The SAG 410 was connected to a metered compressed air supply.

- Method of particle size determination:
The particle size of the generated atmosphere inside the exposure chamber was determined three times during the exposure period using a Marple Personal Cascade Impactor (Westech IS Ltd, Beds., UK). This device consisted of six impactor stages (9.0, 6.5, 3.7, 1.6, 1.0 and 0.33 µm cut points) with stainless steel collection substrates and a back up glass fibre filter, housed in an aluminium sampler. The sampler was temporarily sealed in a sampling port in the animals’ breathing zone and a suitable; known of exposure air was drawn through it using a vacuum pump. The collection substrates and backup filter were weighed before and after sampling and the weight of test material, collected at each stage, calculated by difference. The mean amount for each stage was used to determine the cumulative amount below each cut-off point size. In this way, the proportion (%) of aerosol less than 9.0, 6.5, 3.7, 1.6, 1.0 and 0.33 µm was calculated. The mean values were converted to probits and plotted against Log10 cut-point size. From this plot, the Mass Median Aerodynamic (MMAD) was determined (as the 50% point) and the geometric standard deviation was calculated. In addition the proportion (%) of aerosol less than 4 µm (considered to be the inhalable fraction) was determined (See table 5)

- Treatment of exhaust air: The extract from the exposure chamber passed through a 'scrubber' trap and was connected with a high efficiency filter to a metered exhaust system.

- Temperature, humidity, pressure in air chamber: The temperature and relative humidity inside the exposure chamber were measured by an electronic thermometer/humidity meter (Hanna Instruments Ltd, Beds., UK) located in a vacent port in the animals' breathing zone of the chamber and was recorded every thirty minutes throughout the four- hour exposure period.

TEST ATMOSPHERE
- Brief description of analytical method used:
The actual chamber concentration was measured at regular intervals during the exposure period. The gravimetric method used glass fibre filter placed in a filter holder. The holder was temporarily sealed in a vacant port in the exposure chamber in the animals’ breathing zone and a suitable known volume of exposure chamber air was drawn through the filter using a vacuum pump. Each filter was weighed before and after sampling in order to calculate the weight of collected test material. The difference in the two weights, divided by the volume of atmosphere sampled, gave the actual chamber concentration (See table 4).
- Samples taken from breathing zone: yes

TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: 56.6% was less than 4µm (See table 5).
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): 3.59 µm/ 2.56

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

5.05 mg/L - Mean achieved concentration
14.5 mg/L -Nominal

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: All animals were observed for clinical signs at hourly intervals during exposure, immediately on removal from the restraining tubes at the end of exposure, one hour after termination of exposure and subsequently once daily for fourteen days. Any deaths or evidence of overt toxicity were recorded at each observation. Individual bodyweights were recorded prior to treatment on the day of exposure and on Day 7 and 14 or at death.
- Necropsy of survivors performed: yes

Results and discussion

Effect levels

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.05 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: Mean achieved Atmosphere Concentration.

Mortality:

Only one death occurred in a group of ten rats exposed to a mean achieved atmosphere concentration of 5.05 mg/L for four hours (See table 1).

Clinical signs:

other: Common abnormalities noted during the study included increased respiratory rate, hunched posture, pilo-erection and wet fur. All male animals appeared normal by day 6 post-exposure, whereas all surviving female animals appeared normal by day 11.

Body weight:

Male animals showed good bodyweight increases during both weeks of the recovery period, surviving female animals exhibited a reduced bodyweight gain or slight bodyweight loss during week 1. During week 2 three female animals showed good development whereas another animals remained at the same weight (See table 2)

Gross pathology:

Apart from one instance of abnormally dark lungs no macroscopic abnormalities were detected amongst surviving animals at necropsy. The following macroscopic abnormalities were detected in the animal that died during the course of the study at necropsy:
Lungs- abnormally dark;
Liver- accentuated lobular pattern (See table 3).

Any other information on results incl. tables

Table 1: Mortality Data

 

Mean Achieved Atmosphere Concentration (mg/L)	Sex	Deaths During Exposure	Deaths Post Exposure (1 hour)	Deaths During Day of Observation								Total Deaths
				1	2	3	4	5	6	7	8-14
5.05	M	0	0	0	0	0	0	0	0	0	0	1/10
	F	0	0	1	0	0	0	0	0	0	0

 

Table 2: Individual Bodyweights

 

Mean Achieved Atmosphere Concentration (mg/L)	Animal Number and Sex	Bodyweight (g) on Day:				Increment (g) During Week:
		0	7	14	At Death	1	2
5.05	1 Male	309	338	377		29	39
	2 Male	328	381	434		53	53
	3 Male	330	379	428		49	49
	4 Male	300	335	379		35	44
	5 Male	312	347	386		35	39
	6 Female	233	-	-	215	-	-
	7 Female	219	212	212		-7	0
	8 Female	244	251	278		7	27
	9 Female	224	222	232		-2	10
	10 Female	236	240	253		4	13

-      Animal dead 

 

Table 3: Individual Necropsy Findings

Mean Achieved Atmosphere Concentration (mg/L)	Macroscopic Observations	Animal Number and Sex
		1 Male	2 Male	3 Male	4 Male	5 Male	6* Female	7 Female	8 Female	9 Female	10 Female
5.05	Lungs: Abnormally Dark			P			P
	Liver: Accentuated Lobular Pattern						P
		N	N		N	N		N	N	N	N

 

P = Finding present

N =No abnormalities detected

*= Animal died during study

Table 4: Exposure Chamber Atmosphere Concentrations:

Duration of exposure (minutes)	Net Weight of sampling (mg)	Volume of Air Sampled (mg)	Chamber Flow Rate (L/min)	Atmosphere Concentration (mg/L)
1	12.29	2	55	6.15
7	10.30	2	55	5.15
17	11.71	2	55	5.86
24	11.22	2	55	5.56
38	11.43	2	55	5.72
46	8.93	2	55	4.47
55	5.14	2	55	2.57
63	9.14	2	55	4.57
77	12.25	2	55	6.13
85	11.29	2	55	5.65
101	9.70	2	55	4.85
116	10.56	2	55	5.28
135	10.30	2	55	5.15
150	10.09	2	55	3.82
168	7.63	2	55	4.29
176	8.57	2	55	4.29
194	9.50	2	55	4.75
206	11.45	2	55	5.73
223	9.41	2	55	4.71
234	10.80	2	55	5.40

 

Mean achieved atmosphere concentration (mg/L) = 5.05

Standard deviation = 0.85

Applicant's summary and conclusion

Executive summary:

In a reliable acute inhalation toxicity study performed according to OECD 403, five male and female Sprague-Dawley rats were noseonly exposed to 5.05 mg/L Diuron, the max. achievable atmosphere concentration (Griffith, 2007). One female rat died on day 1 post-exposure.Clinical signs noted during the study included increased respiratory rate, hunched posture, pilo-erection and wet fur. At necropsy, no macroscopic abnormalities were detected amonst surviving animals except for one instance of abnormally dark lungs. The animal that died showed abnormally dark lungs and an accentuated lobular pattern in the liver. Based on the results of this , the LC50 in the rat is considered to be > 5.05 mg/L Diuron.