2-ethylhexyl (4-chloro-2-methylphenoxy)acetate

Repeated dose toxicity: dermal

Administrative data

Endpoint:

sub-chronic toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13.07.1999 - 19.08.1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Cross-reference

Reason / purpose for cross-reference:

read-across source

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

2009

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 410 (Repeated Dose Dermal Toxicity: 21/28-Day Study)

GLP compliance:

yes (incl. QA statement)

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

(4-chloro-2-methylphenoxy)acetic acid

EC Number:

202-360-6

EC Name:

(4-chloro-2-methylphenoxy)acetic acid

Cas Number:

94-74-6

Molecular formula:

C9H9ClO3

IUPAC Name:

(4-chloro-2-methylphenoxy)acetic acid

impurity 1

Reference substance name:

Water

EC Number:

231-791-2

EC Name:

Water

Cas Number:

7732-18-5

Molecular formula:

H2O

IUPAC Name:

water

Test material form:

solid

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

Wistar rats Imp-Wist (male and female) were used. The animals were obtained from the conventional breeding in Institute of Occupational Medicine in Łódź. Prior to the start of the study the animals were acclimated in the test conditions for 14 days. At the start of the test the animals were 2 months old. The average body weight was 253.9 g for males and 183.2 g for females.

Results and discussion

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

clinical biochemistry

haematology

organ weights and organ / body weight ratios

Target system / organ toxicity

Critical effects observed:

no

Any other information on results incl. tables

1.      Clinical observation

All the animals survived the experiment. The rats exposed to MCPA didn't vary from the rats from control group. The dressing put on the animals made moving difficult for the rats from both groups. From 3th day of the experiment slight blush and peeling of the cuticle were observed in the rats exposed to test substance in the place of its application. At the end of the experiment no dermal changes were noticed.

1.2. Body weight and fodder consumption

In the second half of the experiment body weight of males exposed to test substance was lower than body weight of control males — the difference was significant statistically

Table 1. MCPA: Repeated Dose Dermal Toxicity (21-day study) Body weight (g) - males

Day of experiment		Group
		0		1
1	254.4	± 12.5	253.4	± 8.7
4	263.2	± 11.0	257.0	± 10.1
8	275.6	± 9.6	266.0	± 11.1
11	284.6	± 12.4	268.8	± 10.6*
15	297.2	± 15.0	279.8	± 11.7*
18	304.4	± 18.8	290.6	± 8.2*
21	323.6	± 22.8	301.6	± 8.9*

* p≤0.05

 

No statistic differences were stated in the females

Table 2. MCPA: Repeated Dose Dermal Toxicity (21-day study) Body weight (g) – females

Day of experiment		Group
		0	1
1	183.2	± 12.9	183.2	± 11.6
4	187.6	± 16.3	182.6	± 10.5
8	196.0	± 21.9	189.8	± 8.3
11	200.0	± 19.7	196.4	± 7.6
15	205.8	± 20.3	200.4	± 7.9
18	211.2	± 26.1	208.8	± 8.1
21	223.2	± 26.8	216.2	± 8.9

 

In the second half of the experiment fodder consumption of males exposed to test substance was lower than fodder consumption of control males – the difference was significant statistically

Table 3. MCPA: Repeated Dose Dermal Toxicity (21-day study) Food intake (g/rat/day) - males

Week of experiment	Group
	0	1
1	25.3 ± 0.9	24.2 t 0.9
2	24.7 ± 1.8	22.2 ± 0.8*
3	27.6 ±2.2	26.4 ± 1.2

* p≤0.05

 

Fodder consumption of females exposed to the substance and from the control group was on the same level during entire experiment.

Table 4. MCPA: Repeated Dose Dermal Toxicity (21-day study) Food intake (g/rat/day) — females

Week of experiment		Group
		0		1
1	19.9	± 1.7	18.7	± 1.4
2	18.0	± 1.7	18.4	± 1.0
3	21.3	± 2.5	20.0	± 3.0

 

2. Hematology

The hematologic values are listed in the tables 5 and 6. No statistically significant differences were stated between rats exposed to the substance and control animals.

Table 5. MCPA: Repeated Dose Dermal Toxicity (21-day study) Hematologic examination after 21 days

Parameter		Group
		0	1
	Male
Hemoglobin	g/l	168.40 ± 12.80	167.00 ± 9.57
Hematocrit	l/l	0.38 ± 0.05	0.39 ± 0.04
Erythrocytes	x 10^12/l	7.48 ± 1.06	7.82 ± 0.89
Thrombocytes	x 10^12/l	0.85 ± 0.07	0.76 ± 0.12
Leukocytes	x 10^12/l	8.02 ± 0.69	9.40 ± 2.29
	Female
Hemoglobin	g/l	157,60 ± 7,50	158.60 ± 5.27
Hematocrit	l/l	0,35 ± 0,04	0.37 ± 0.03
Erythrocytes	x 10^12/l	6,93 ± 0,75	7.31 ± 0.53
Thrombocytes	x 10^12/l	0,88 ± 0,20	0.88 ± 0.17
Leukocytes	x 10^12/l	5,52 ± 1,26	5.68 ± 0.99

 

 

Table 6. MCPA: Repeated Dose Dermal Toxicity (21-day study) Hematologic examination after 21 days Leukogram

Parameter		Group
		0	1
	Male
Neutrocytes	l/l	0.13 ± 0.05	0,14 ± 0.06
Eosinocytes	l/l	0.01 ± 0.01	0,01 ± 0.01
Bazocytes	l/l	0.00 ± 0.00	0,00 ± 0.00
Limphocytes	l/l	0.86 ± 0.06	0,84 ± 0.06
Monocytes	l/l	0.01 ± 0.00	0,01 ± 0.01
Other cells	l/l	0.00 ± 0.00	0,00 ± 0.00
	Female
Neutrocytes	l/l	0.18 ± 0.03	0.15 ± 0.06
Eosinocytes	l/l	0.01 ± 0.01	0.02 ± 0.01
Bazocytes	l/l	0.00 ± 0.00	0.00 ± 0.00
Limphocytes	l/l	0.79 ± 0.03	0.81 ± 0.07
Monocytes	l/l ll	0,01 ± 0.01	0.01 ± 0.01
Other cells	l/l	0.00 ± 0.00	0.00 ± 0.00

 

3. Clinical biochemistry

The biochemical parameters are listed in the table 7.

Only one statistically significant difference was stated: the proportion of albumins to globulins was lower in the case of males exposed to MCPA than in case of males from the control group (table 7). No statistic differences were stated as far as females are concerned.

Table 7. MCPA: Repeated Dose Dermal Toxicity (21-day study) Clinical biochemistry after 21 days

Parameter	Group
	0	1
Male
Protein glob.                                   g/l	68.60 ± 1.02	69.94 ± 3.35
Albumin                                        g/l	45.14 ± 1.72	44.42 ± 2.10
Globulin                                        g/l	23.46 ± 1.60	25.52 ± 1.56
Ratio AJG	1.93 ± 0.20	1.74 ± 0.08*
Glucose                                mmol/l	8.38 ± 2.11	11.38 ± 2.99
Cholesterol                           mmol/l	1.61 ± 0.25	1.44 ± 0.48
Urea nitrogen                 mmo1/1	7.36 ± 1.07	6.82 ± 1.81
Creatynine                            mmol/l	42.92 ± 2.71	42.26 ± 4.61
Natrium                             mmo1/1	145.40 ± 1.82	143.60 ± 1.52
Callum                                    mmol/l	4.86 ± 0.38	5.44 ± 0.89
Female
Protein glob.                               g/l	69.36 ± 3.23	71.10 ± 4.87
Albumin                                      g/l	44.34 ± 1.59	44.10 ± 3.39
Globulin                                      g/l	25.02 ± 2.52	27.00 ± 4.25
Ratio AJG	1.79 ± 0.17	1.67 ± 0.31
Glucose                           mmol/l	5.78 ± 2.00	5.76 ± 1.12
Cholesterol                    mmol/l	1.75 ± 0.31	1.66 ± 0.28
Urea nitrogen               mmol/l	8.52 ± 0.79	8.90 ± 1.36
Creatynine                    mmol/l	40.94 ± 2.90	39.66 ± 3.55
Natrium                         mmol	144.00 ± 1.41	143.20 ± 2.17
Callum                              mmol/l	5.08 ± 0.72	5.18 ± 0.48

* p≤0.05

4. Enzyms

The enzymatic values are given in the table 8.

Table 8. MCPA: Repeated Dose Dermal Toxicity (21-day study) Enzymatic examination after 21 days

Parameter		Group
		0	1
	Male
Asp AT	IU	103.00 ± 28.31	117.80 ± 18.51
Al AT	IU	41.20 ± 4.32	59.00 ± 21.30
SDH	1U	2.50 ± 1.86	2.60 ± 0.88
AP	IU	177.00 ± 38.09	205.00 ± 43.03
LAP	IU	30.40 ± 3.71	32.60 ± 2.19
B-GR	IU	1.11 ±0.14	1.10 ± 0.08
CHE	mIU	0.51 ± 0.06	0.52 ± 0.05
	Female
Asp AT	IU	99.20 ± 20.54	88.40 ± 7.70
Al AT	IU	35.00 ± 9.03	37.40 ± 8.65
SDH	IU	2.52 ± 0.81	2.02 ± 1.04
AP	IU	102.40 ± 14.28	127.40 ± 23.94
LAP	IU	26.20 ± 3.90	30.00 ± 7.91
B-GR	IU	1.22 ± 0.16	1.03 ± 0.54
CHE	mIU	1.37 ± 0.23	1.19 ± 0.31

 

The activity of particular enzymes in the animals exposed to MCPA and the control animals showed considerable individual differences, but no statistically significant difference was stated in the mean values in both groups.

5. Pathology

In the macroscopic examination of skin and internal organs no pathologic changes were stated. In the absolute weight of internal organs a statistically significant decrease in the weight of adrenals was stated in case of females. In the relative weight of organs statistically significant increase in the weight of males' kidneys and fall in the weight of females' adrenals were observed (table 9 and 10).

Microscopic examination showed circulatory disturbances in the case of animals exposed to MCPA as well as control animals. The heart, liver, adrenals and hypophysis were congested.

Table 9. MCPA: Repeated Dose Dermal Toxicity (21-day study) Absolute organ weight (mg)

Organ	Number of rats	Sex	Group
			0	1
Liver	5	Male	9778.400 ± 596.798	9042.800 ± 580.195
	5	Female	6521.000 ± 996.234	6342.600 ± 253.917
Kidneys	5	Male	2183.800 ± 175.076	2208.600 ± 126.396
	5	Female	1477.800 ± 150.556	1462.800 ± 145.741
Adrenals	5	Male	77.600 ± 10.171	74.400 ± 10.092
	5	Female	93.600 ± 9.478	74.000 ± 2.828*
Testicles	5	Male	3464.200 ± 230.417	3187.800 ± 220.112

* p≤0.05

Table 10. MCPA: Repeated Dose Dermal Toxicity (21-day study) Relative organ weight (mg)

Organ	Number of rats	Sex	Group
			0	1
Liver	5	Male	3.024 ± 0.107	2.997 ± 0.151
	5	Female	2.910 ± 0.185	2.940 ± 0.204
Kidneys	5	Male	0.675 ± 0.041	0.732 ± 0.033*
	5	Female	0.663 ± 0.021	0.676 ± 0.055
Adrenals	5	Male	0.024 ± 0.003	0.025 ± 0.003
	5	Female	0.042 ± 0.003	0.034 ± 0.002*
Testicles	5	Male	1.072 ± 0.056	1.056 ± 0.056

* p≤0.05

 

6. Discussion

In the repeated dose dermal study (21 applications) of MCPA in a dose of 1000 mg/kg b.w./day in rats the test substance didn't cause any deaths in the tested group. On the skin in a place of application a temporary blush and slight peeling of the cuticle were observed. The rats from the exposed group didn't vary either in behavior or in appearance from control rats. Smaller discrease in body weight in case of males exposed to MCPA was probably caused by smaller fodder consumption of these animals.

In the hematologic parameters no statistically significant differences were stated between both groups.

In the biochemical parameters only one statistically significant difference was stated. It didn't concern examined biochemical parameters but only calculated proportion of albumins to globulins in case of males exposed to MCPA. Because obtained values of A/G indicator are contained in the range of values observed in the bigger historic control group, it should be accounted for accidental, resulting from low number of animals in a group.

The activity of examined enzymes was on the similar level in the group of animals exposed to MCPA and in the control group.

Some changes in the weight of internal organs (kidneys, adrenals) may be result of slight decrease in the body weight caused by temporary decrease in the fodder consumption.

The pathomorphologic examination didn't show any macroscopicall changes. Microscopically, some circulatory disturbances were observed, but the frequency was similar in the control and exposed group. They are not bound to the tested substance.

On the basis of the results of the clinical, hematologic, biochemical, enzymatic and pathomorphologic parameters it can be stated that MCPA in a dose of 1000 mg/kg b.w./day didn't have negative influence on rats' organism.

Applicant's summary and conclusion

Executive summary:

Conclusions:

1)           MCPA applied during 21 days on the skin of rats in a dose of 1000 mg/kg b.w./day didn't have negative impact on organism of rats.

2)           The no-observed-adverse-effect-level (NOAEL) is. 1000 mg/kg b.w./day.