Paraquat-dichloride

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Mar 1995 - Jul 1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Objective of study:

distribution

excretion

Qualifier:

according to guideline

Guideline:

EPA OPP 85-1 (Metabolism and Pharmacokinetics)

Qualifier:

according to guideline

Guideline:

other: Japanese MAFF regulations

Qualifier:

according to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Qualifier:

according to guideline

Guideline:

other: EU Council Directive 67/548/EEC

Qualifier:

according to guideline

Guideline:

other: Commission Directive 87/302/EEC

GLP compliance:

yes

Radiolabelling:

yes

Remarks:

[14C]-methyl at both N-methyl positions

Species:

rat

Strain:

other: Alpk:APfSD

Details on species / strain selection:

Laboratory rats were selected as standard for rodent species to comply with the corresponding toxicological studies.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Biological Services Section, Zeneca Pharmaceuticals, Macclesfield, Cheshire, UK
- Weight at study initiation: 176g - 206g
- Housing: stock cages for same sex groups during acclimation; then individual plastic metabolic cages
- Diet: Pelleted PCD rat diet (Special Diets Services Ltd, Stepfield, Witham, Essex, UK), ad libitum, except for 12h prior and 3h after dosing
- Water: ad libitum
- Acclimation period: 5 days in stock cages; 24h in metabolic cages

ENVIRONMENTAL CONDITIONS
- Temperature (°C): between 19 and 23
- Humidity (%): between 40 and 70
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

sterile, double deionised

Duration and frequency of treatment / exposure:

single oral, bodyweight dependent dose in dose vehicle

Dose / conc.:

1 mg/kg bw (total dose)

No. of animals per sex per dose / concentration:

5 male; 5 female

Control animals:

no

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Distribution, excretion)
- Tissues and body fluids sampled: urine and faeces collected separately, urine collected in cage washes of 5 mL water, blood and plasma, tissues (whole): brain, gonads, heart, kidneys, liver, lungs, spleen; parts of tissue: fat (abdominal), bone (femur), muscle
- Time and frequency of sampling: urine only - once, after 6h; urine (in cage washes) and faeces collected at 12, 24, 36, 48 and 72h after dosing; blood, plasma and tissues collected 3 days after dosing following killing of the rats
- All samples were taken by duplicate

Type:

excretion

Results:

Radioactivity in urine: males-17.9%, females-11.6% of administered dose. Radioactivity in faeces (first 24h after administration): males-63.1% and females-74.1% of the dose. Total radioactivity (including cage washings): males-92.5%, females-93.8%

Type:

distribution

Results:

Highest radioactivity tissue concentrations in males and females were found in lungs (0.023µg and 0.02µg equiv/g, respectively) and kidneys (0.01µg and 0.011µg equiv/g, respectively

Details on distribution in tissues:

Three days after dosing, highest radioactivity tissue concentrations in males and females were found in lungs (0.023µg and 0.020µg equiv/g, respectively) and kidneys (0.010µg and 0.011µg equiv/g, respectively). The residual carcasses of male and female rats contained 0.006µg and 0.005µg equiv/g respectively which corresponds to 0.64% and 0.54% of the dose. Remaining tissues showed concentrations equal to or less than that found in carcasses. Table 1 in "Any other information on results incl. tables" section presents a complete overview of tissue and residual carcass radioactivity measurements.

Details on excretion:

The rates and amounts of radioactivity excreted in urine were similar for both sexes. During the first 24h after the administration of the radiolabelled test substance, male rats excreted in urine a mean of 17.9% of administered dose and females a mean of 11.6%. The rates of excretion of radioactivity in faeces by males and females were also similar, however the total amount of radioactivity excreted by females was slightly higher. During the first 24h after administration males excreted a mean of 63.1% and females 74.1%. The total amounts of radioactivity excreted in urine and faeces (including cage washings) were 92.5% for male rats and 93.8% for female rats. The detailed results for excretion of radioactivity in urine and faeces expressed as percentages of the administered radioactivity dose, are presented as group mean results with standard deviations in Table 2 in "Any other information on results incl. tables" section.

Table 1. Tissue and residual carcass radioactivity measurements in male and female rats three days after dosing (values are expressed as percentages of administered radioactivity and as concentrations µg equivalents of substance/g of tissue)

 

Tissue		% of the dose – males			% of the dose - females		concentration – males			concentration - females
		mean		SD	mean	SD	mean		SD	mean	SD
brain		<0.01		<0.01	<0.01	<0.01	0.005	0.002		0.004		<0.001
heart		<0.01		<0.01	<0.01	<0.01	0.006	0.002		0.004		<0.001
kidney		0.01		<0.01	0.01	<0.01	0.010	0.003		0.011		<0.001
liver		0.02		<0.01	0.02	<0.01	0.003	0.001		0.003		<0.001
lungs		0.02		<0.01	0.01	<0.01	0.023	0.007		0.20		0.005
spleen		<0.01		<0.01	<0.01	<0.01	0.005	0.002		0.005		0.001
gonads		0.01		<0.01	<0.01	<0.01	0.003	0.001		0.004		0.002
abdominal fat		-		-	-	-	0.005	0.001		<0.004		<0.002
bone (femur)		-		-	-	-	0.004	0.001		0.005		0.001
muscle		-		-	-	-	0.005	0.001		0.003		0.001
blood		-		-	-	-	0.002	<0.001		0.002		<0.001
plasma		-		-	-	-	<0.001			0.001		<0.001
carcass		0.639		0.186	0.543	0.105	0.006	0.002		0.005		0.001
Total	0.697		0.196		0.591	0.112

Table 2. Excretion of radioactivity in urine and faeces, male and female rats (values are expressed as percentages of the administered radioactivity and each represents the mean of five rats with standard deviation)

 

Time after dosing [h]		urine – males		urine - females		faeces – males			faeces - females
		mean	SD	mean	SD	mean		SD	mean	SD
0 – 6		14.14	5.63	7.58	1.66	-	-		-		-
6 - 12		2.54	1.15	2.31	1.35	-	-		-		-
0 – 12		-	-	-	-	23.95	17.26		16.56		16.00
12 -24		1.25	0.62	1.68	0.69	39.13	11.96		57.51		14.83
24 - 36		0.37	0.22	0.39	0.12	3.49	3.40		3.34		2.10
36 - 48		0.39	0.53	0.31	0.13	3.65	2.35		0.83		0.40
48 - 72		0.37	0.45	0.28	0.05	2.14	1.12		1.63		0.72
0 - 72		19.07	7.86	12.55	1.78	72.36	5.95		79.86		4.00
	mean (males)			sd (males)		mean (females)			sd (females)
cage wash	1.07			0.86		1.40			0.16
total excreted	92.49			3.40		93.81			4.04

Conclusions:

Seventy two hours after administration of 1mg radiolabelled test substance/kg bw, low levels of radioactivity were present in the tissues and carcass. Following a single oral dose, radioactivity was rapidly eliminated in urine and faeces. The total amounts of radioactivity excreted in urine and faeces (including cage washings) were 92.5% for male rats and 93.8% for female rats.

Executive summary:

In a GLP compliant study performed according to EPA OPP 85-1 guideline, a single oral dose of the radiolabelled test substance was administrated at 1mg/kg body weight by gavage to one group of male and one group of female rats (strain: Alpk:APfSD).

Urine, faeces and cage washes were collected at different times. After 3 days post administration the rats were sacrificed and tissues were analysed for radiolabelled content. No test substance related or otherwise unusual behaviour of the animals were observed. The rates and amounts of radioactivity excreted in urine and faeces were similar for both sexes. During the first 24 hours after the administration of radiolabeled test substance, male rats excreted in urine a mean of 17.9% and female rats a mean of 11.6% of the radioactivity. During the same period males excreted a mean of 63.1% and females a mean of 74.1% of the dose in faeces. The total amount of radioactivity excreted in urine and faeces (including cage washings) was 92.5% for males and 93.8% for females. Three days after dosing the highest tissue concentrations of radioactivity in both male and female rats were present in lungs (0.023µg and 0.020µg equiv/g respectively) and kidneys (0.010µg and 0.011µg equiv/g) In male and female rats 0.64% and 0.54% of the dose remained in the carcass which corresponds to 0.006µg and 0.005 µg equiv/g respectively. The total mean percentage recoveries, including excreta and tissue residues, for male rats was 93.2% and for females was 94.4%. In conclusion, seventy two hours after dosing only low levels of radioactivity were present in the tissues and carcass. Following a single oral dose, radioactivity was rapidly excreted in faeces and urine.

Reference 2

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Feb 1995 - Jul 1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Objective of study:

distribution

excretion

Qualifier:

according to guideline

Guideline:

EPA OPP 85-1 (Metabolism and Pharmacokinetics)

Qualifier:

according to guideline

Guideline:

other: Japanese MAFF regulations

Qualifier:

according to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Qualifier:

according to guideline

Guideline:

other: EU Council Directive 67/548/EEC

Qualifier:

according to guideline

Guideline:

other: Commission Directive 87/302/EEC

GLP compliance:

yes

Radiolabelling:

yes

Remarks:

[14C]-methyl at both N-methyl positions

Species:

rat

Strain:

other: Alpk:APfSD

Details on species / strain selection:

Laboratory rats were selected as standard for rodent species to comply with the corresponding toxicological studies.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Biological Services Section, Zeneca Pharmaceuticals, Macclesfield, Cheshire, UK)
- Weight at study initiation: 183g-208g
- Housing: stock cages for same sex groups; later-individual plastic metabolic cages
- Diet: Pelleted PCD rat diet (Special Diets Services Ltd, Stepfield, Witham, Essex, UK), ad libitum, except for 12h prior and 3h after dosing
- Water: ad libitum
- Acclimation period: 5 days in stock cages; 24h in metabolic cages

ENVIRONMENTAL CONDITIONS
- Temperature (°C): between 19 and 23
- Humidity (%): between 40 and 70
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

sterile, double deionised

Duration and frequency of treatment / exposure:

single oral, bodyweight-dependent dose in dose vehicle

Dose / conc.:

50 mg/kg bw (total dose)

No. of animals per sex per dose / concentration:

5 male; 5 female

Control animals:

no

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Distribution, excretion)
- Tissues and body fluids sampled: urine and faeces collected separately, urine collected in cage washes of 5 mL water, blood and plasma, tissues (whole): brain, gonads, heart, kidneys, liver, lungs, spleen; parts of tissue: fat (abdominal), bone (femur), muscle
- Time and frequency of sampling: urine only - once, after 6h; urine (in cage washes) and faeces collected at 12, 24, 36, 48 and 72h after dosing; blood, plasma and tissues collected 3 days after dosing following killing of the rats

Type:

excretion

Results:

Radioactivity in urine: males-9.2%, females-11.6% of administered dose. Radioactivity in faeces (first 24h after administration): males-54.5% and females-49.6% of the dose. Total radioactivity (including cage washings): males-92.7%, females-91.7%

Type:

distribution

Results:

Highest radioactivity tissue concentrations in males and females were found in lungs (0.661µg and 1.077µg equiv/g, respectively) and carcass (0.401µg and 0.414µg equiv/g, respectively)

Details on distribution in tissues:

The results for the tissue measurements of radioactivity, expressed as percentages of the administered radioactivity and as µg equivalents radiolabelled test substance per g of sample (µg equiv/g), are presented as group mean results with standard deviations in Table 2 in "Any other information on results incl. tables" section. Three days after dosing the highest tissue concentrations of radioactivity in both male and female rats were present in lungs (0.661µg and 1.077µg equiv/g respectively) and carcass (0.401 and 0.414µg equiv/g). In all tissues analysed (with the exception of abdominal fat) there was a lower concentration of radioactivity in males than in females. In male and female rats 0.82% and 0.80% of the dose respectively remained in the carcass.

Details on excretion:

The results for the excretion of radioactivity in urine and faeces, expressed as percentages of the administered radioactivity, are presented as group mean results with standard deviations in Table 1 in "Any other information on results incl. tables" section. The rates and amounts of radioactivity excreted in urine and faeces were similar for both sexes. During the first 24 hours after the administration of radiolabelled test substance, male rats excreted in urine a mean of 9.2% and female rats a mean of 11.6% of the radioactivity. During the same period males excreted a mean of 54.5% and females a mean of 49.6% of the dose in faeces. The total amount of radioactivity excreted in urine and faeces (including cage washings) was 92.7% for males and 91.7% for females.

Table 1. Excretion of radioactivity in urine and faeces, male and female rats (values are expressed as percentages of the administered radioactivity and each represents the mean of five rats with standard deviation)

 

Time after dosing [h]		urine – males		urine - females		faeces – males			faeces - females
		mean	sd	mean	sd	mean		sd	mean	sd
0 – 6		6.03	0.33	8.14	3.38	-	-		-		-
6 - 12		1.50	0.20	1.70	1.00	-	-		-		-
0 – 12		-	-	-	-	6.05	6.32		7.55		9.69
12 -24		1.68	0.23	1.77	0.59	48.41	5.52		42.02		16.61
24 - 36		1.06	0.33	1.03	0.85	17.18	3.59		13.07		7.04
36 - 48		0.38	0.31	0.61	0.54	5.91	3.29		11.93		10.11
48 - 72		0.27	0.25	0.39	0.32	3.63	1.67		3.12		1.83
0 - 72		10.92	1.13	13.63	5.92	81.18	2.58		77.67		7.25
	mean (males)			sd (males)		mean (females)			sd (females)
cage wash	0.64			0.38		0.37			0.15
total excreted	92.73			2.00		91.67			2.18

Table 2. Tissue and residual carcass radioactivity measurements in male and female rats three days after dosing (values are expressed as percentages of administered radioactivity and as concentrations µg equivalents of substance/g of tissue)

tissue	% of the dose – males		% of the dose - females		concentration – males		concentration - females
	mean	sd	mean	sd	mean	sd	mean	sd
brain	<0.01	<0.01	<0.01	<0.01	0.112	0.006	0.150	0.049
heart	<0.01	<0.01	<0.01	<0.01	0.185	0.042	0.240	0.075
kidney	<0.01	<0.01	0.01	0.01	0.185	0.025	0.367	0.204
liver	0.02	0.01	0.02	0.01	0.159	0.069	0.194	0.083
lungs	0.01	<0.01	0.01	0.01	0.661	0.090	1.077	0.418
spleen	<0.01	<0.01	<0.01	<0.01	0.200	0.026	0.247	0.072
gonads	<0.01	<0.01	<0.01	<0.01	0.101	0.010	0.216	0.073
abdominal fat	-	-	-	-	<0.202	<0.088	<0.140	<0.140
bone (femur)	-	-	-	-	0.136	0.043	0.174	0.031
muscle	-	-	-	-	0.156	0.032	0.189	0.063
blood	-	-	-	-	0.078	<0.014	0.091	0.025
plasma	-	-	-	-	<0.085	<0.056	0.157	0.036
carcass	0.82	0.26	0.80	0.38	0.401	0.131	0.414	0.200
Total	0.86	0.27	0.85	0.39

Conclusions:

Following a single oral dose of 50mg radiolabelled test substance/kg, radioactivity was rapidly eliminated in faeces and urine. Seventy two hours after dosing only low levels of radioactivity were present in the tissues and carcass. No sex difference in excretion observed following administration of a single oral dose of radiolabelled test substance was found in this study.

Executive summary:

In this GLP compliant study performed according to EPA OPP 85-1 guideline, a single oral dose of the radiolabelled test substance was administrated at 50mg/kg body weight to one group of male and one group of female rats (strain: Alpk:APfSD).

Urine, faeces and cage washes were collected at different times. After 3 days post administration the rats were sacrificed and tissues were analysed for radiolabelled content.

No test substance related or otherwise unusual behaviour of the animals were observed.

The rates and amounts of radioactivity excreted in urine and faeces were similar for both sexes. During the first 24 hours after the administration of radiolabeled test substance, male rats excreted in urine a mean of 9.2% and female rats a mean of 11 .6% of the radioactivity. During the same period males excreted a mean of 54.5% and females a mean of 49.6% of the dose in faeces. The total amount of radioactivity excreted in urine and faeces (including cage washings) was 92.7% for males and 91.7% for females. Three days after dosing the highest tissue concentrations of radioactivity in both male and female rats were present in lungs (0.661µg and 1.077µg equiv/g respectively) and carcass (0.401µg and 0.414µg equiv/g). In all tissues analysed (with the exception of abdominal fat) there was a lower concentration of radioactivity in males than in females. In male and female rats 0.82% and 0.80% of the dose respectively remained in the carcass. The total mean percentage recoveries, including excreta and tissue residues, for male rats was 93.6% and for females was 92.5%.

Comparison of the results obtained in this study with those obtained following a single oral dose of 1 mg radiolabeled test substance/kg (Lythgoe 1995a) show that the pattern of excretion was similar at both dose levels with rapid faecal excretion predominating. The sex difference in excretion observed at the lower dose level was not found in this study. The difference found between tissue levels of radioactivity at the two dose levels is less than or approximately equal to the ratio of the dose levels studied.

In conclusion, seventy two hours after dosing only low levels of radioactivity were present in the tissues and carcass. Following a single oral dose, radioactivity was rapidly excreted in faeces and urine.

Reference 3

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Mar 1995 - Jul 1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Objective of study:

distribution

excretion

Qualifier:

according to guideline

Guideline:

EPA OPP 85-1 (Metabolism and Pharmacokinetics)

GLP compliance:

yes

Radiolabelling:

yes

Remarks:

[14C]-methyl at both N-methyl positions

Species:

rat

Strain:

other: Alpk:APfSD

Details on species / strain selection:

Laboratory rats were selected as standard for rodent species to comply with the corresponding toxicological studies.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Biological Services Section, Zeneca Pharmaceuticals, Macclesfield, Cheshire, UK)
- Weight at study initiation: 203g-246g
- Housing: stock cages for same sex groups; later-individual plastic metabolic cages
- Diet: Pelleted PCD rat diet (Special Diets Services Ltd, Stepfield, Witham, Essex, UK), ad libitum, except for 12h prior and 3h after dosing
- Water: ad libitum
- Acclimation period: 5 days in stock cages; 24h in metabolic cages

ENVIRONMENTAL CONDITIONS
- Temperature (°C): between 19 and 23
- Humidity (%): between 40 and 70
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

sterile, double deionised (CTL Y04517/015)

Duration and frequency of treatment / exposure:

14 daily oral doses of 1mg/kg bw of unlabelled test substance (8 males and 8 females) in vehicle;
a single, oral dose of 1 mg/kg bw of radiolabelled test substance in vehicle (5 males and 5 females)

Dose / conc.:

1 mg/kg bw (total dose)

Dose / conc.:

1 mg/kg bw (total dose)

Remarks:

radiolabelled

No. of animals per sex per dose / concentration:

8 males and 8 females received unlabelled test substance for 14 days; 5 males and 5 females received a single dose of labelled substance

Control animals:

no

Details on study design:

All subjects were given 14 daily 1mg/kg bw doses of unlabelled test substance. Approximately 24 hours after the fourteenth unlabeled dose, 5 males and 5 females were given a single 1mg/kg bw dose of radiolabelled test substance.

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, cage washes, blood, plasma, brain, gonads, heart, kidneys, liver, lungs, spleen, fat (abdominal), bone (femur), muscle
- Time and frequency of sampling: urine only - once, after 6h; urine (in cage washes) and faeces collected at 12, 24, 36, 48 and 72h after dosing; blood, plasma and tissues collected 3 days after dosing following killing of the rats

Type:

excretion

Results:

Radioactivity in urine (72h after administration): males-20%, females-11.2% of administered dose. Radioactivity in faeces: males-71.1% and females-81.4%. Total radioactivity excreted (including cage washings): males-92.5%, females-93.9%

Type:

distribution

Results:

Highest radioactivity tissue concentrations in males and females were found in lungs (0.037µg and 0.023µg equiv/g, respectively) and kidneys (0.020µg and 0.015µg equiv/g, respectively)

Details on distribution in tissues:

Three days after dosing, highest radioactivity tissue concentrations in males and females were found in lungs (0.037µg and 0.023µg equiv/g, respectively) and kidneys (0.020µg and 0.015µg equiv/g, respectively). The residual carcasses of male and female rats contained 0.007µg and 0.006µg equiv/g respectively which corresponds to 0.70% and 0.55% of the dose. Table 2 in "Any other information on results incl. tables" section presents a complete overview of tissue and residual carcass radioactivity measurements.

Details on excretion:

The combined rate of elimination of radioactivity in urine and faeces was similar for both sexes during the initial 12h after dosing with radiolabelled test substance. However, the proportions of the dose eliminated in urine and faeces were different. During the 0-12h period male rats excreted a greater percentage (17.1%) of the dose in urine than did females (8.9%). In the period 12 to 72h after dosing the rate of urinary excretion was much lower and was similar for both sexes. The initial higher rate of urinary excretion by males led to a significant difference in the proportion of administered radioactivity excreted over the 72h course of the study with males excreting a total of 20% of the dose and females 11.2%. The lower level of urinary excretion found in females was accompanied by a correspondingly higher level of faecal excretion with females excreting 81.4% of the dose via faeces over 72h. During the same period males excreted 71.1% of the dose in faeces. The total amounts of radioactivity excreted in both urine and faeces (including cage washings) over 72h were 92.5% for males and 93.9% for females. Table 1 in "Any other information on results incl. tables" section presents a complete overview of excretion of radioactivity in urine and faeces for male and female rats.

Table 1. Excretion of radioactivity in urine and faeces, male and female rats (values are expressed as percentages of the administered radioactivity and each represents the mean of five rats with standard deviation)

 

Time after dosing [h]		urine – males		urine - females		faeces – males			faeces - females
		mean	SD	mean	SD	mean		SD	mean	SD
0 – 6		15.66	5.99	8.10	2.92	-	-		-		-
6 - 12		1.44	0.72	0.85	0.33	-	-		-		-
0 – 12		-	-	-	-	4.25	5.82		15.72		18.40
12 -24		1.67	0.51	1.35	0.41	64.08	4.28		54.94		17.80
24 - 36		0.55	0.21	0.32	0.14	1.40	0.76		5.09		3.37
36 - 48		0.36	0.17	0.39	0.17	0.72	0.48		3.89		2.03
48 - 72		0.28	0.08	0.24	0.05	0.64	0.23		1.77		0.63
0 - 72		19.97	5.47	11.25	3.02	71.09	6.32		81.42		4.23
	mean (males)			sd (males)		mean (females)			sd (females)
cage wash	1.44			0.58		1.23			0.32
total excreted	92.50			6.53		93.89			1.61

 

Table 2. Tissue and residual carcass radioactivity measurements in male and female rats three days after dosing (values are expressed as percentages of administered radioactivity and as concentrations µg equivalents of substance/g of tissue)

 

tissue	% of the dose – males		% of the dose - females		concentration – males		concentration - females
	mean	sd	mean	sd	mean	sd	mean	sd
brain	<0.01	<0.01	<0.01	<0.01	0.008	0.001	0.006	0.001
heart	<0.01	<0.01	<0.01	<0.01	0.009	0.001	0.007	0.001
kidney	0.02	0.01	0.01	<0.01	0.020	0.007	0.015	0.004
liver	0.02	<0.01	0.01	<0.01	0.005	0.001	0.003	<0.001
lungs	0.02	0.01	0.01	<0.01	0.037	0.007	0.023	0.002
spleen	<0.01	<0.01	<0.01	<0.01	0.006	0.001	0.005	0.001
gonads	0.01	<0.01	<0.01		0.005	<0.001	0.003	0.001
abdominal fat	-	-	-	-	0.003	0.002	<0.001
bone (femur)	-	-	-	-	0.003	0.001	0.004	0.001
muscle	-	-	-	-	0.006	0.001	0.005	0.001
blood	-	-	-	-	0.002	<0.001	0.002	<0.001
plasma	-	-	-	-	0.001	<0.001	0.001	<0.001
carcass	0.70	0.11	0.55	0.06	0.007	0.001	0.006	0.001
Total	0.77	0.12	0.59	0.06

Conclusions:

Following fourteen, consecutive, daily oral doses of 1mg/kg bw unlabeled test substance and a single oral dose of 1 mg/kg bw radiolabeled test substance, radioactivity was rapidly excreted in faeces and urine. A sex difference was observed with male rats excreting a higher proportion of the dose in urine and a lower proportion in the faeces than female rats. The sex difference in excretion observed following repeat dosing was more pronounced than that observed following a single dose (Lythgoe 1995a).

Executive summary:

In this GLP compliant study performed according to EPA OPP 85-1 guideline, a single oral dose of the radiolabelled test substance was administrated at 1mg/kg body weight to one group of 5 male and one group of 5 female rats (strain: Alpk:APfSD). Prior to that, a larger group of rats (8 males and 8 females) encompassing these were orally dosed with 1mg/kg bw unlabelled test substance for 14 consecutive days.

Urine, faeces and cage washes were collected at different times. Three days post administration of radiolabelled test substance, the rats were sacrificed and tissues were analysed for radiolabelled content.

No test substance related or otherwise unusual behaviour of the animals were observed.

The rates and amounts of radioactivity excreted were similar for both sexes. During the first 24 hours after the administration of radiolabeled test substance, both male and female rats excreted 82% of the administered radioactivity dose and after 72h – around 92%. A sex difference was found with male rats excreting a higher proportion of the administered radioactivity in urine than did females, 20% and 11% respectively. This was accompanied by a corresponding difference in faecal excretion, 71% and 81% of the administered dose for males and females respectively. Three days after dosing the highest tissue concentrations of radioactivity in both male and female rats were present in lungs (0.037µg and 0.023µg equiv/g respectively) and kidneys (0.020µg and 0.015µg equiv/g).

In male and female rats 0.70% and 0.55% of the dose respectively remained in the carcass which corresponds to 0.007 µg equiv/g and 0.006 µg equiv/g. The total mean percentage recoveries, including excreta and tissue residues, for male rats was 93.3% and for females was 94.5%. Comparison of the results obtained in this study with those obtained following a single oral dose of 1mg radiolabeled test substance/kg (Lythgoe and Howard , 1995) show that the pattern of excretion was similar with rapid faecal excretion predominating. The sex difference in excretion observed following repeat dosing was more pronounced than that following a single dose. The tissue level of radioactivity found following repeat dosing were similar to those observed following a single dose. In conclusion, seventy two hours after dosing only low levels of radioactivity were present in the tissues and carcass. Following fourteen, consecutive, daily oral doses of 1mg/kg bw unlabeled test substance and a single oral dose of 1 mg/kg bw radiolabeled test substance, radioactivity was rapidly excreted in faeces and urine.

Reference 4

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 Nov 1999 - 8 Dec 1999

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Version / remarks:

draft OECD guidelines for in vitro percutaneous absorption measurement (OECD, 1996)

GLP compliance:

yes

Radiolabelling:

yes

Type of coverage:

open

Vehicle:

unchanged (no vehicle)

Duration of exposure:

54h

Doses:

- 207 g/L for concentrate formulation
- 2.07 g/L for 1:100 v/v spray strength dilutions and 1:100 v/v spray strength dilutions with wetting agent

Details on study design:

DOSE PREPARATION
- Method for preparation of dose suspensions: Three doses were prepared in total. The concentrate formulation was prepared by adding appropriate quantities of radiolabelled test substance to the formulation concentrate. Two further doses were similarly prepared by adding appropriate quantities radiolabelled test substance to the formulation concentrate and then diluting the mixture with distilled water such that the resultant preparation was equivalent to a nominal 1:100 v/v aqueous spray dilution of the concentrate. One of the preparations also had an amount of wetting agent added equivalent to 0.1 % v/v of the dose.

APPLICATION OF DOSE:
- Amount(s) applied (volume or weight with unit): 10 µL/cm2.

TEST SITE
- Area of exposure: 2.54 cm2
- Time intervals: 2, 4, 6, 8, 10, 12, 18, 24, 30, 36, 42, 48 and 54 h, 0.5 ml samples of the receptor fluid were taken for analysis.

REMOVAL OF TEST SUBSTANCE
- Washing procedures and type of cleansing agent: The epidermal surface of the skin was decontaminated by gently swabbing the application site with natural sponges pre-wetted with 3 % detergent, and with further sponges pre-wetted with water. Decontamination was shown to be complete following assessment of residual radioactivity levels on the skin surface with a Geiger counter. The sponges were combined, digested in a solvent and a sample taken for analysis. The remaining epidermis was carefully removed from the receptor chamber and digested in solvent and the whole digest analysed.
- Time after start of exposure: 54 h.

ANALYSIS
- Method type for identification: Liquid scintillation counting.
- Liquid scintillation counting period: 6 minutes or to a 1 % standard deviation of the count.

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: human whole skin samples obtained post mortem.
- Part of skin: epidermis
- Preparative technique: skin samples were immersed in water at 60 °C for 40-45 seconds and the epidermis teased away from the dermis.
- Membrane integrity check: measurement of their electrical resistance across the skin membrane. Membranes with a measured resistance <10 kQ were regarded as having a lower integrity than normal and not used for exposure to the test material.
- Storage conditions: frozen on aluminium foil.

PRINCIPLES OF ASSAY
- Receptor fluid: distilled water
- Solubility of test substance in receptor fluid: adequate
- Test temperature: 32 ± 1 °C
- Occlusion: unoccluded

Signs and symptoms of toxicity:

not examined

Dermal irritation:

not examined

Absorption in different matrices:

Detailed absorption rates and percentages are summarised in "Any other information on results incl. tables" section.

Total recovery:

- Total recovery:
- Recovery of applied dose acceptable:
For concentrated formulation - The total mean percent recovery from the mass balance was 103 %. Nearly all the dose was washed off the skin (92.9 %) after 54 hours exposure and a small amount of test substance (0.318 %) remained in the epidermis.

For 1:100 v/v spray dilution - The total mean percent recovery from the mass balance was 99.1 %. Most of the dose was washed off the skin (82.2 %) after 54 hours exposure and a small amount of test substance (1.79 %) remained in the epidermis.

For 1:100 v/v spray dilution with wetter - The total mean percent recovery from the mass balance was 101 %. Most of the dose was washed off the skin (89.7 %) after 54 hours exposure and a small amount of test substance (0.847 %) remained in the epidermis.

Key result

Time point:

54 h

Dose:

207g/L

Parameter:

rate

Remarks:

µg/cm2/h

Absorption:

0.241

Remarks on result:

other: concentrate formulation

Time point:

54 h

Dose:

2.07g/L

Parameter:

rate

Remarks:

µg/cm2/h

Absorption:

0.004

Remarks on result:

other: 1:100 v/v spray dilution

Time point:

54 h

Dose:

2.07g/L

Parameter:

rate

Remarks:

µg/cm2/h

Absorption:

0.002

Remarks on result:

other: 1:100 v/v spray dilution with wetting agent

Test substance mean absorption rates:

MEAN ABSORPTION RATES
Concentration	Time period (h)	Absorption rate (µg/cm^2/h ± SEM)
concentrate formulation	0-10	0.196	± 0.091
	0-54	0.241	± 0.109
1:100 v/v aqueous spray dilution	0-10	0.004	± 0.001
	0-54	0.004	± 0.001
1:100 v/v aqueous spray dilution with wetting agent	0-10	0.005	± 0.001
	0-54	0.002	± 0.000

Mean amount and percentage of test substance absorbed:

MEAN AMOUNT AND ABSORBED PERCENT OF DOSE
Concentration	Time (h)	Amount (µg/cm^2)	Percent absorbed
concentrate formulation	6	1.11	0.054
	8	1.54	0.074
	10	1.98	0.095
	24 54	5.20 13.24	0.251 0.639
1:100 v/v aqueous spray dilution	6	0.033	0.158
	8	0.039	0.190
	10	0.045	0.218
	24 54	0.093 0.193	0.448 0.929
1:100 v/v aqueous spray dilution with wetting agent	6	0.046	0.220
	8	0.048	0.230
	10	0.054	0.263
	24 54	0.079 0.132	0.380 0.636

Conclusions:

The amount absorbed at 24 hours was 5.20 µg/cm2 (concentrate; equivalent to 0.251 % of applied dose), 0.093 µg/cm2 (1:100 dilution without wetting agent; equivalent to 0.448 % of applied dose) and 0.079 µg/cm2 (1:100 dilution with wetting agent; equivalent to 0.380 % of applied dose). There was very little difference in the absorption and distribution of paraquat from the 1:100 v/v aqueous spray dilutions with or without wetting agent.
The mass balance and distribution data predict that the majority of test substance which contacts human skin would be washed off the surface during normal washing procedures.

Executive summary:

The absorption of test substance has been measured in vitro through human epidermis.

The formulation was applied as the concentrate formulation (actual content 207 g test substance ion/L) and as a 1:100 v/v spray strength dilution of the formulation in water with and without added wetting agent. The actual test substance ion content of the spray dilutions was 2.07 g/L. The absorption process was followed using¹⁴C-labelled test substance, which was added to the formulations prior to application. The concentrate formulation and the spray strength dilutions were applied to the epidermal membranes at a rate of 10 µL/cm². All applications were left unoccluded for an exposure period of 54 hours. These applications were designed to simulate potential human dermal exposure to the formulation during normal use.

The absorption of test substance from the concentrate formulation through human epidermis was slow during the first 10 hours of exposure, giving a mean absorption rate of 0.196 µg/cm²/h which was slightly higher at 0.241 µg/cm²/h between 0 and 54 hours. The amount of test substance absorbed during working day periods of 6, 8 and 10 hours was 1.11 µg/cm²,1.54 µg/cm²and 1.98 µg/cm², equivalent to less than 0.1 % of the applied dose for each exposure period. The amount absorbed at 24 hours was 5.20 µg/cm²(equivalent to 0.251 % of applied dose).

The total mean percent recovery from the mass balance was 103 %. Nearly all the dose was washed off the skin (92.9 %) after 54 hours exposure and a small amount of test substance (0.318 %) remained in the epidermis.

The absorption of test substance from the 1:100 v/v spray dilution without wetting agent was very slow during the first 10 hours of exposure, giving a mean absorption rate of 0.004 µg/cm²/h which was the same as the 0 to 54 hour period. The amount of test substance absorbed during working day periods of 6, 8 and 10 hours were 0.033 µg/cm², 0.039 µg/cm²and 0.045 µg/cm²,equivalent to 0.158 %, 0.190 % and 0.218 % of the applied dose, respectively. The amount absorbed at 24 hours was 0.093 µg/cm²(equivalent to 0.448 % of applied dose).

The total mean percent recovery from the mass balance was 99.1 %.Most of the dose was washed off the skin (82.2 %) after 54 hours exposure and a small amount of test substance (1.79 %) remained in the epidermis.

The absorption of test substance from the spray dilution with wetting agent was very slow during the first 10 hours of exposure, giving a mean absorption rate of 0.005 µg/cm²/h. The absorption rate during the 0 to 54 hour period was slightly lower at 0.002 µg/cm²/h. The amount of test substance absorbed during working day periods of 6, 8 and 10 hours were 0.046 µg/cm², 0.048 µg/cm²and 0.054 µg/cm²,equivalent to 0.220 %, 0.230 % and 0.263 % of the applied dose, respectively. The amount absorbed at 24 hours was 0.079 µg/cm²(equivalent to 0.380 % of applied dose).

The total mean percent recovery from the mass balance was101 %. Most of the dose was washed off the skin (89.7 %) after 54 hours exposure and a small amount of test substance (0.847 %) remained in the epidermis.

There was very little difference in the absorption and distribution of test substance from the 1:100 v/v aqueous spray dilutions with or without wetting agent.

Description of key information

Basic toxicokinetics - Lythgoe 1995a, b, c

Excretion

The total amounts of radioactivity excreted in urine and faeces (including cage washings) 72 h post administration were between 91% and 94% of the administered radioactivity dose for both sexes, all examined doses and dosing regimes.

Distribution and tissue retention

72 h after dosing only low levels of radioactivity were present in the tissues and carcass.

For a single dose of 1 mg/kg bw: lungs 0.023 µg and 0.02 µg equiv/g, and kidneys 0.01 µg and 0.011 µg equiv/g, for males and females respectively.

For a single dose of 50 mg/kg bw: lungs 0.661 µg and 1.077 µg equiv/g, and carcass 0.401 µg and 0.414 µg equiv/g, for males and females respectively.

For a repeated dose of 1 mg/kg bw/14 days: lungs 0.037 µg and 0.023 µg equiv/g, and kidneys 0.020 µg and 0.015 µg equiv/g, for males and females, respectively.

Dermal absorption - Clowes 2000

 

Absorption of the test substance by human epidermis

The concentrate formulation absorbed during 24 hours of exposure -  5.20 µg/cm² (0.251% of applied dose).

The total mean percent recovery from the mass balance was 103%. Nearly all the dose was washed off the skin (92.9%) after 54 hours exposure and a small amount of test substance (0.318%) remained in the epidermis.

The test substance from the 1:100 v/v spray dilution without wetter absorbed during 24 hours of exposure - 0.093 µg/cm² (0.448% of applied dose).

The total mean percent recovery from the mass balance was 99.1%. Most of the dose was washed off the skin (82.2%) after 54 hours exposure and a small amount of test substance (1.79%) remained in the epidermis.

The test substance from the spray dilution with wetter absorbed 24 hours of exposure - 0.079 µg/cm² (0.380% of applied dose).

The total mean percent recovery from the mass balance was101%. Most of the dose was washed off the skin (89.7%) after 54 hours exposure and a small amount of test substance (0.847%) remained in the epidermis.

 

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Basic toxicokinetics - Lythgoe 1995a

In this GLP compliant study performed according to EPA OPP 85-1 guideline, a single oral dose of the radiolabelled test substance was administrated at 1 mg/kg bw to one group of male and one group of female rats (strain: Alpk:APfSD).

Urine, faeces and cage washes were collected at different times. After 3 days post administration the rats were sacrificed and tissues were analysed for radiolabelled content.

No test substance related or otherwise unusual behaviour of the animals were observed.

The rates and amounts of radioactivity excreted in urine and faeces were similar for both sexes. During the first 24 hours after the administration of radiolabeled test substance, male rats excreted in urine a mean of 17.9% and female rats a mean of 11.6% of the radioactivity. During the same period males excreted a mean of 63.1% and females a mean of 74.1% of the dose in faeces. The total amount of radioactivity excreted in urine and faeces (including cage washings) was 92.5% for males and 93.8% for females. Three days after dosing the highest tissue concentrations of radioactivity in both male and female rats were present in lungs (0.023 µg and 0.020 µg equiv/g respectively) and kidneys (0.010 µg and 0.011 µg equiv/g). In male and female rats 0.64% and 0.54% of the dose remained in the carcass which corresponds to 0.006 µg and 0.005 µg equiv/g respectively. The total mean percentage recoveries, including excreta and tissue residues, for male rats was 93.2% and for females was 94.4%. In conclusion, seventy two hours after dosing only low levels of radioactivity were present in the tissues and carcass. Following a single oral dose, radioactivity was rapidly excreted in faeces and urine.

Basic toxicokinetics - Lythgoe 1995b

In this GLP compliant study performed according to EPA OPP 85-1 guideline, a single oral dose of the radiolabelled test substance was administrated at 50 mg/kg bw to one group of male and one group of female rats (strain: Alpk:APfSD).

Urine, faeces and cage washes were collected at different times. After 3 days post administration the rats were sacrificed and tissues were analysed for radiolabelled content.

No test substance related or otherwise unusual behaviour of the animals were observed.

The rates and amounts of radioactivity excreted in urine and faeces were similar for both sexes. During the first 24 hours after the administration of radiolabeled test substance, male rats excreted in urine a mean of 9.2% and female rats a mean of 11.6% of the radioactivity. During the same period males excreted a mean of 54.5% and females a mean of 49.6% of the dose in faeces. The total amount of radioactivity excreted in urine and faeces (including cage washings) was 92.7% for males and 91.7% for females. Three days after dosing the highest tissue concentrations of radioactivity in both male and female rats were present in lungs (0.661 µg and 1.077 µg equiv/g respectively) and carcass (0.401 µg and 0.414 µg equiv/g). In all tissues analysed (with the exception of abdominal fat) there was a lower concentration of radioactivity in males than in females. In male and female rats 0.82% and 0.80% of the dose respectively remained in the carcass. The total mean percentage recoveries, including excreta and tissue residues, for male rats was 93.6% and for females was 92.5%.

Comparison of the results obtained in this study with those obtained following a single oral dose of 1 mg/kg bw radiolabeled test substance (Lythgoe 1995a) show that the pattern of excretion was similar at both dose levels with rapid faecal excretion predominating. The sex difference in excretion observed at the lower dose level was not found in this study. The difference found between the levels of radioactivity in tissues at the two dose levels is less than or approximately equal to the ratio of the dose levels studied.

In conclusion, seventy two hours after dosing only low levels of radioactivity were present in the tissues and carcass. Following a single oral dose, radioactivity was rapidly excreted in faeces and urine.

Basic toxicokinetics - Lythgoe 1995c

In this GLP compliant study performed according to EPA OPP 85-1 guideline, a single oral dose of the radiolabelled test substance was administrated at 1 mg/kg body weight to one group of 5 male and one group of 5 female rats (strain: Alpk:APfSD). Prior to that, rats (8 males and 8 females) were orally dosed with 1 mg/kg bw unlabelled test substance for 14 consecutive days.

Urine, faeces and cage washes were collected at different times. Three days post administration of radiolabelled test substance, the rats were sacrificed and tissues were analysed for radiolabelled content.

No test substance related or otherwise unusual behaviour of the animals were observed.

The rates and amounts of radioactivity excreted were similar for both sexes. During the first 24 hours after the administration of radiolabeled test substance, both male and female rats excreted 82% of the administered radioactivity dose and after 72h – around 92%. A sex difference was found with male rats excreting a higher proportion of the administered radioactivity in urine than did females, 20% and 11% respectively. This was accompanied by a corresponding difference in faecal excretion, 71% and 81% of the administered dose for males and females respectively. Three days after dosing the highest tissue concentrations of radioactivity in both male and female rats were present in lungs (0.037 µg and 0.023 µg equiv/g respectively) and kidneys (0.020 µg and 0.015 µg equiv/g).

In male and female rats 0.70% and 0.55% of the dose respectively remained in the carcass which corresponds to 0.007 µg equiv/g and 0.006 µg equiv/g. The total mean percentage recoveries, including excreta and tissue residues, for male rats was 93.3% and for females was 94.5%. Comparison of the results obtained in this study with those obtained following a single oral dose of 1 mg/kg bw radiolabeled test substance (Lythgoe 1995a) show that the pattern of excretion was similar with rapid faecal excretion predominating. The sex difference in excretion observed following repeated dosing was more pronounced than that following a single dose. The tissue levels of radioactivity found following repeated dosing were similar to those observed following a single dose. In conclusion, seventy two hours after dosing only low levels of radioactivity were present in the tissues and carcass. Following fourteen consecutive, daily oral doses of 1 mg/kg bw unlabeled test substance and a single oral dose of 1 mg/kg bw radiolabeled test substance, radioactivity was rapidly excreted in faeces and urine.

Dermal absorption - Clowes 2000

The absorption of test substance has been measured in vitro through human epidermis.

The formulation was applied as the concentrate formulation (actual content 207 g test substance ion/L) and as a 1:100 v/v spray strength dilution of the formulation in water with and without added wetter. The actual test substance ion content of the spray dilutions was 2.07 g/L. The absorption process was followed using 14C-labelled test substance, which was added to the formulations prior to application. The concentrate formulation and the spray strength dilutions were applied to the epidermal membranes at a rate of 10 µL/cm2. All applications were left unoccluded for an exposure period of 54 hours. These applications were designed to simulate potential human dermal exposure to the formulation during normal use.

The absorption of test substance from the concentrate formulation through human epidermis was slow during the first 10 hours of exposure, giving a mean absorption rate of 0.196 µg/cm2/h, which was slightly higher at 0.241 µg/cm2/h between 0 and 54 hours. The amount of test substance absorbed during working day periods of 6, 8 and 10 hours was 1.11 µg/cm2, 1.54 µg/cm2 and 1.98 µg/cm2, equivalent to less than 0.1% of the applied dose for each exposure period. The amount absorbed at 24 hours was 5.20 µg/cm2 (equivalent to 0.251% of applied dose).

The total mean percent recovery from the mass balance was 103%. Nearly all the dose was washed off the skin (92.9%) after 54 hours exposure and a small amount of test substance (0.318%) remained in the epidermis.

The absorption of test substance from the 1:100 v/v spray dilution without wetter was very slow during the first 10 hours of exposure, giving a mean absorption rate of 0.004 µg/cm2/h, which was the same as during the 0 to 54 hour period. The amount of test substance absorbed during working day periods of 6, 8 and 10 hours were 0.033 µg/cm2, 0.039 µg/cm2 and 0.045 µg/cm2, equivalent to 0.158%, 0.190% and 0.218% of the applied dose, respectively. The amount absorbed at 24 hours was 0.093 µg/cm2 (equivalent to 0.448% of applied dose).

The total mean percent recovery from the mass balance was 99.1%. Most of the dose was washed off the skin (82.2%) after 54 hours exposure and a small amount of test substance (1.79%) remained in the epidermis.

The absorption of test substance from the spray dilution with wetter was very slow during the first 10 hours of exposure, giving a mean absorption rate of 0.005 µg/cm2/h. The absorption rate during the 0 to 54 hour period was slightly lower at 0.002 µg/cm2/h. The amount of test substance absorbed during working day periods of 6, 8 and 10 hours were 0.046 µg/cm2, 0.048 µg/cm2 and 0.054 µg/cm2, equivalent to 0.220%, 0.230% and 0.263% of the applied dose, respectively. The amount absorbed at 24 hours was 0.079 µg/cm2 (equivalent to 0.380% of applied dose).

The total mean percent recovery from the mass balance was101%. Most of the dose was washed off the skin (89.7%) after 54 hours exposure and a small amount of test substance (0.847%) remained in the epidermis.

There was very little difference in the absorption and distribution of test substance from the 1:100 v/v aqueous spray dilutions with or without wetter. The results obtained in this study demonstrate that the absorption of test substance through human epidermis is extremely slow when compared with the absorption rates of other penetrants measured using this in vitro technique (Dugard et al, 1984; Dugard and Scott, 1984). These data predict that the dermal absorption of test substance from potential exposure to this formulation and its spray strength dilutions with and without wetter, through human epidermis, would be very low.

The mass balance and distribution data predict that the majority of test substance which contacts human skin would be washed off the surface during normal washing procedures.