O-(4-bromo-2-chlorophenyl) O-ethyl S-propyl phosphorothioate

Neurotoxicity

Key value for chemical safety assessment

Effect on neurotoxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

neurotoxicity: sub-chronic oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 August 1992 to 20 November 1992

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

other: EPA-FIFRA guidelines (Pesticide Assessment Guidelines - Subdivision F, Hazard Evaluation, Addendum 10 - Neurotoxicity Series 81, 82 and 83)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Route of administration:

oral: feed

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

90 consecutive days / dietary

Frequency of treatment:

Continuous

Remarks:

Doses / Concentrations:0, 30, 135, 600 ppmBasis:nominal in diet

Remarks:

Doses / Concentrations:Males: 0, 1.7, 7.7, 36 mg/kg dietBasis:actual ingested

Remarks:

Doses / Concentrations:Females: 0, 1.84, 8.4, 37.9 mg/kg dietBasis:actual ingested

No. of animals per sex per dose:

15 animals/sex/gp, with 10 animals/sex/gp used for neurological tests and 5 animals/sex/gp used for cholinesterase measurements

Control animals:

yes, plain diet

Dose descriptor:

NOAEL

Remarks:

neurotoxicity

Effect level:

ca. 135 ppm (nominal)

Sex:

male/female

Basis for effect level:

other: (equvialent to 7.7 or 8.4 mg/kg diet in males and females respectively) based on brain cholinesterase inhibition (and reduction in bodywieght gain) observed at 600 ppm.

Remarks on result:

other:

Table 7.9.1 -7:%AChE inhibition

Dose (ppm)	Time (weeks)	Plasma				RBC				Brain
		Male	Sig	Female	Sig	Male	Sig	Female	Sig	Male	Sig	Female	Sig
0	3	-	-	-	-	-	-	-	-	-	-	-	-
30	3	29	**	58	**	54	**	56	**	-	-	-	-
135	3	65	**	78	**	76	**	75	**	-	-	-	-
600	3	80	**	91	**	76	**	78	**	-	-	-	-
0	7	-	-	-	-	-	-	-	-	-	-	-	-
30	7	28	**	60	**	74	**	56	**	-	-	-	-
135	7	64	**	83	**	82	**	57	**	-	-	-	-
600	7	81	**	94	**	84	**	79	**	-	-	-	-
0	12	-	-	-	-	-	-	-	-	-	-	-	-
30	12	31	**	61	**	64	**	51	**	0	NS	5	NS
135	12	63	**	83	**	75	**	72	**	2	NS	6	NS
600	12	79	**	93	**	74	**	77	**	12	**	20	**

 

Statistically significant reductions in both erthryocyte and plasma cholinesterase were observed from weeks 3 to 12 in both males and females, with the plasma derivative appearing to be more sensitive; however as brain cholinesterase activity was measured, this was seen as the prefential marker (JMPR, 2000). At terminaton (week 12) brain cholinesterase activity was significantly inhibited in both males and females at 600 ppm, however in accordance with the JMPR guidance this was only deemed biologically relevant in females where the level of inhibition was 20%. Whilst no clinical signs of toxicity, effects on the functional observational battery or motor effects suggestive of a relationship to treatment were observed at any dose level, a reduction in bodyweight gain was observed at 600 ppm. Therefore the NOAEL based on brain cholinesterase inhibition (and reduction in bodywieght gain) was deemed 135 ppm (equvialent to 7.7 or 8.4 mg/kg/day in males and females respectively), based on the effects observed at 600 ppm.

 

Reference:

JMPR (2000). Pesticide residues. Guidelines for the preparation of toxicological working papers for the WHO core assessment group of the Joint Meeting on Pesticide Residues. Geneva, Switzerland, December 2000. 

Conclusions:

The NOAEL based on brain cholinesterase inhibition (and reduction in bodywieght gain) was deemed 135 ppm (equvialent to 7.7 or 8.4 mg/kg/day in males and females respectively), based on the effects observed at 600 ppm.

Executive summary:

The potential subchronic effects of Profenofos were investigated in a rat dietary study where groups of rats (15/sex/gp) were fed Profenofos at dietary concentrations of 0, 30, 135 and 600 ppm for up to 13 weeks. The average daily dosages, based on nominal concentrations in the feed were 1.7, 7.7 and 36 mg/kg diet for males and 1.84, 8.4 and 37.9 mg/kg diet for females in the respectively 30, 135 and 600 ppm groups.

 

Statistically significant reductions in both erythrocyte and plasma cholinesterase were observed from weeks 3 to 12 in both males and females, with the plasma derivative appearing to be more sensitive; however as brain cholinesterase activity was measured, this was seen as the preferential marker (JMPR, 2000). At termination (week 12) brain cholinesterase activity was significantly inhibited in both males and females at 600 ppm, however in accordance with the JMPR guidance this was only deemed biologically relevant in females where the level of inhibition was 20%. Whilst no clinical signs of toxicity, effects on the functional observational battery or motor effects suggestive of a relationship to treatment were observed at any dose level, a reduction in bodyweight gain was observed at 600 ppm. Therefore the NOAEL based on brain cholinesterase inhibition (and reduction in bodyweight gain) was deemed 135 ppm (equivalent to 7.7 or 8.4 mg/kg diet in males and females respectively), based on the effects observed at 600 ppm.

Reference 2

Endpoint:

neurotoxicity: acute oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

3 May 2003 to 7 June 2003

Reliability:

1 (reliable without restriction)

Qualifier:

no guideline available

Principles of method if other than guideline:

No specific guidance for this study type although the United States Environmental Protection Agency have provided a guidance document 'Guidance on cholinesterase measures in developmental neurotoxicity and related studies' dated 29 October 2001.

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: Alpk:APfSD

Sex:

male/female

Route of administration:

oral: gavage

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

single oral admin

Frequency of treatment:

once

Remarks:

Doses / Concentrations:0, 1, 5, 25, 100 mg/kgBasis:nominal conc.

Remarks:

Doses / Concentrations:0, 1, 5, 25, 100 mg/kgBasis:analytical conc.

No. of animals per sex per dose:

25 males and 25 female/dose

Control animals:

yes, concurrent vehicle

Dose descriptor:

NOAEL

Remarks:

neurotoxicity

Effect level:

ca. 5 mg/kg bw (total dose)

Sex:

male/female

Basis for effect level:

other: based on statistically significant inhibition of brain cholinesterase at 25 mg/kg and greater in rats 12 days post partum

Remarks on result:

other: Generation: other: - pups (migrated information)

Dose descriptor:

NOAEL

Remarks:

neurotoxicity

Effect level:

ca. 25 mg/kg bw (total dose)

Sex:

male/female

Basis for effect level:

other: based on statistically significant inhibition of brain cholinesterase at 100 mg/kg and greater in rats 22 and 42 days post partum

Remarks on result:

other: Generation: other: - young adults (migrated information)

Table 7.9.1 -4: AChE %inhibition

Dose	Time	Plasma				RBC				Brain
(mg/kg)	(weeks)	Male	Sig	Female	Sig	Male	Sig	Female	Sig	Male	Sig	Female	Sig
Post Partum Day 12
0	Day 12	-	-	-	-	-	-	-	-	-	-	-	-
1	Day 12	3	NS	5	NS	10	NS	-2	NS	-3	NS	2	NS
5	Day 12	28	**	33	**	8	NS	19	NS	1	NS	2	NS
25	Day 12	67	**	61	**	33	**	22	NS	24	**	19	**
100	Day 12	88	**	88	**	55	**	54	**	65	**	65	**
Post Partum Day 22
0	Day 22	-	-	-	-	-	-	-	-	-	-	-	-
1	Day 22	2	NS	7	*	9	NS	-14	NS	-2	NS	-13	NS
5	Day 22	17	**	25	**	4	NS	-15	NS	0	NS	-12	NS
25	Day 22	56	**	60	**	92	*	89	NS	4	NS	-4	NS
100	Day 22	81	**	80	**	45	**	45	**	39	**	22	*
Post Partum Day 42
0	Day 42	-	-	-	-	-	-	-	-	-	-	-	-
1	Day 42	32	NS	11	*	11	NS	4	NS	-6	NS	-31	NS
5	Day 42	56	**	11	**	11	*	9	NS	-1	NS	-42	NS
25	Day 42	74	**	27	**	27	**	44	**	-17	NS	-46	NS
100	Day 42	87	**	55	**	55	**	47	**	-22	*	0	N

There were no treatment related effects on clinical observations or bodyweight

 

Statistically significant reductions in both erythrocyte and plasma cholinesterase were observed on post partum days 12, 22 and 42 in both males and females, however as brain cholinesterase activity was measured, this was seen as the preferential marker (JMPR, 2000). At post partum day 12, brain cholinesterase activity was inhibited at 25 and 100 mg/kg, with levels of inhibition ranging from 19 -65% for both males and females. At post partum day 22 and 42, statistically significant increases in inhibition were only observed at 100 mg/kg in males and/or females. The difference in brain cholinesterase inhibition in young rats was considered a result of increased exposure to profenofos due to incomplete blood brain barrier formation rather than increased sensitivity, as blood brain barrier development in the rat is completed post-natally. No inhibition of brain cholinesterase activity was seen at dose levels of 1 or 5 mg/kg. Therefore the NOAEL based on brain cholinesterase inhibition was deemed 5 mg/kg or 25 mg/kg in pups and young adult rats respectively.

 

Reference:

JMPR (2000). Pesticide residues. Guidelines for the preparation of toxicological working papers for the WHO core assessment group of the Joint Meeting on Pesticide Residues. Geneva, Switzerland, December 2000. 

Conclusions:

The NOAEL based on brain cholinesterase inhibition was deemed 5 mg/kg or 25 mg/kg in pups and young adult rats respectively.

Executive summary:

Cholinesterase activity was investigated in rats which were 12, 22 and 42 days old. Groups of five male and five female rats of each age were given a single dose of 0, 1, 5, 25 or 100 mg/kg profenofos (CGA 15324) in 1% (w/v) CMC. Approximately 3 -4hrs post dosing samples were taken for brain, erythrocyte and plasma cholinesterase.

 

Statistically significant reductions in both erythrocyte and plasma cholinesterase were observed on post partum days 12, 22 and 42 in both males and females, however as brain cholinesterase activity was measured, this was seen as the preferential marker (JMPR, 2000). At post partum day 12, brain cholinesterase activity was inhibited at 25 and 100 mg/kg, with levels of inhibition ranging from 19 -65% for both males and females. At post partum day 22 and 42, statistically significant increases in inhibition were only observed at 100 mg/kg in males and/or females. The difference in brain cholinesterase inhibition in young rats was considered a result of increased exposure to profenofos due to incomplete blood brain barrier formation rather than increased sensitivity, as blood brain barrier development in the rat is completed post-natally. No inhibition of brain cholinesterase activity was seen at dose levels of 1 or 5 mg/kg. Therefore the NOAEL based on brain cholinesterase inhibition was deemed 5 mg/kg or 25 mg/kg in pups and young adult rats respectively.

Reference 3

Endpoint:

neurotoxicity: oral

Remarks:

developmental

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 June 2002 to 6 March 2003

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.6300 (Developmental Neurotoxicity Study)

Deviations:

no

Limit test:

no

Species:

rat

Strain:

other: Alpk:APfSD

Sex:

male/female

Route of administration:

oral: feed

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

Day 7 of GD through to Day 23 post partum / dietary

Frequency of treatment:

continuous

Remarks:

Doses / Concentrations:0, 3, 60, 600 ppmBasis:nominal in diet

Remarks:

Doses / Concentrations:0, 0.3, 5.1, 50.6 mg/kg diet (during gestation)Basis:other: calculated

Remarks:

Doses / Concentrations:0, 10.5, 10.7, 103.4 mg/kg diet (post partum)Basis:other: calculated

No. of animals per sex per dose:

30 time mated females/group + additional 10 time mated females/gp for cholinesterase assessment

Control animals:

yes, plain diet

Dose descriptor:

NOAEL

Remarks:

neurotoxicity

Effect level:

ca. 60 ppm (nominal)

Sex:

female

Basis for effect level:

other: (equivalent to 5.1 mg/kg diet). Based on brain cholinesterase inhibition inexcess of 20% during gestation and post partum at 600 ppm

Remarks on result:

other: Generation: maternal (migrated information)

Dose descriptor:

NOAEL

Remarks:

neuro-developmental

Effect level:

ca. 600 ppm (nominal)

Sex:

male/female

Basis for effect level:

other: (equivalent to 103.4 mg/kg diet). No effect on brain cholinesterase activity observed.

Remarks on result:

other: Generation: offspring (migrated information)

Dose descriptor:

NOAEL

Remarks:

toxicity

Effect level:

ca. 60 ppm (nominal)

Sex:

male/female

Basis for effect level:

other: (equivalent to 10.7 mg/kg diet). Due to a reduction in bodyweight gain at 600 ppm.

Remarks on result:

other: Generation: offspring (migrated information)

Table 7.9.1 -2: Maternal AChE activity - %inhibition

Dose	Time	Plasma		RBC		Brain
(ppm)	(weeks)	Female	Sig	Female	Sig	Female	Sig
Gestation Day 22
0	GD22	-	-	-	-	-	-
3	GD22	-6	NS	5	NS	9	NS
60	GD22	60	**	50	**	13	NS
600	GD22	84	**	59	**	44	**
Post Partum Day 22
0	PPD22	-	-	-	-	-	-
3	PPD22	13	**	7	NS	-24	NS
60	PPD22	59	**	55	**	-38	NS
600	PPD22	78	**	57	**	26	NS

 

Table 7.9.1 -3: Pup AChE activity - %inhibition

Dose	Time	Plasma				RBC				Brain
(ppm)	(weeks)	Male	Sig	Female	Sig	Male	Sig	Female	Sig	Male	Sig	Female	Sig
Gestation Day 22
0	GD22	-	-	-	-	-	-	-	-	-	-	-	-
3	GD22	-3	NS	6	NS	-24	NS	-2	NS	-1	NS	3	NS
60	GD22	-10	NS	2	NS	-11	NS	-28	NS	-7	NS	5	NS
600	GD22	2	NS	8	NS	3	NS	-6	NS	-1	NS	7	NS
Post Partum Day 22
0	PPD5	-	-	-	-	-	-	-	-	-	-	-	-
3	PPD5	8	NS	8	NS	-2	NS	3	NS	-2	NS	-5	NS
60	PPD5	6	NS	8	NS	3	NS	-1	NS	0	NS	-3	NS
600	PPD5	10	NS	13	NS	4	NS	9	NS	-14	NS	11	*

PPD - Post partum day 22; GD22 - Gestation day 22

 

There were no treatment related effects on clinical observations, functional observation battery, reproductive parameters, litter losses or pup survival.

 

On gestation day 22 and post partum day 22 a significant reduction in plasma cholinesterase of between 60 -80% was observed in paternal females recieving 60 and 600 ppm. A similar effect was observed with the erythrocyte cholinesterase acitivty over the same period. In accordance with the JMPR (2000) guidance, brain cholinesterase activity is the prefential endpoint of concern. In paternal females, a statistically significant decrease in brain cholinesterase activity (44%) was observed in animals on GD 22 recieving 600 ppm. A similar reduction, although not statistically significant (26%) was observed PPD 22 at the same dose. Therefore the NOAEL for maternal toxicity was considered to be 60 ppm (5.1 mg/kg/day) based on significant reductions in brain cholinesterase activity during gestation and post partum.

 

There were no treatment related effects in the F₁ animals on motor activity, auditory startle response, learning and memory or neurohistopathology. Statistically significant decreases in cholinesterase acitivty was limited to brain activity on PP day 22 in females recieving 600 ppm (11%), however inaccordance with the guidance from the JMPR, as this did not achieve 20% or more, the level of inhibition was deemed not biologically relevant. Therefore the NOAEL for developmental toxicity was considered to be 600 ppm (103.4 mg/kg/day). Due to a reduction in bodyweight gain, the NOAEL for offspring toxicity was 60 ppm (10.7 mg/kg/day).

 

Reference:

JMPR (2000). Pesticide residues. Guidelines for the preparation of toxicological working papers for the WHO core assessment group of the Joint Meeting on Pesticide Residues. Geneva, Switzerland, December 2000. 

Conclusions:

The NOAEL for maternal toxicity was considered to be 60 ppm (5.1 mg/kg/day) based on significant reductions in brain cholinesterase activity during gestation and post partum.  The NOAEL for developmental toxicity was considered to be 600 ppm (103.4 mg/kg/day, the maximum dose tested). Due to a reduction in bodyweight gain, the NOAEL for offspring toxicity was 60 ppm (10.7 mg/kg/day).

Executive summary:

Groups of 30 time mated female rats were fed diets containing 0, 3, 60 and 600 ppm profenofos from gestation day 7. These dietary dose levels corresponded to daily doses of 0, 0.3, 5.1 and 50.6 mg/kg diet during gestaion and 0, 0.5, 10.7 and 103.4 mg/kg diet during lactation and weaning. Pups were selected on day 5 post partum to 8 pups/litter with equal sexes for the F₁ generation; they were separated on day 29 and allowed to grow to adulthood. Rats were killed on post partum day 63 and tissues removed for neuropathology investigations. Additional animals were used to determined plasma, erythrocyte and brain cholinesterase in dams on GD 22 and post partum day 22, in foetuses on GD 22 and in pups on days 5, 12 and 22 post partum.

 

There were no treatment related effects on clinical observations, functional observation battery, reproductive parameters, litter losses or pup survival.

 

On gestation day 22 and post partum day 22 a significant reduction in plasma cholinesterase of between 60 -80% was observed in paternal females recieving 60 and 600 ppm. A similar effect was observed with the erythrocyte cholinesterase activity over the same period. In accordance with the JMPR (2000) guidance, brain cholinesterase activity is the prefential endpoint of concern. In paternal females, a statistically significant decrease in brain cholinesterase activity (44%) was observed in animals on GD 22 recieving 600 ppm. A similar reduction, although not statistically significant (26%) was observed PPD 22 at the same dose. Therefore the NOAEL for maternal toxicity was considered to be 60 ppm (5.1 mg/kg/day) based on significant reductions in brain cholinesterase activity during gestation and post partum.

 

There were no treatment related effects in the F₁ animals on motor activity, auditory startle response, learning and memory or neurohistopathology. Statistically significant decreases in cholinesterase activity was limited to brain activity on PP day 22 in females receiving 600 ppm (11%), however in accordance with the guidance from the JMPR, as this did not achieve 20% or more, the level of inhibition was deemed not biologically relevant. Therefore the NOAEL for developmental toxicity was considered to be 600 ppm (103.4 mg/kg diet). Due to a reduction in bodyweight gain, the NOAEL for offspring toxicity was 60 ppm (10.7 mg/kg diet).

Reference 4

Endpoint:

neurotoxicity: short-term oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 May 2002 to 20 June 2002

Reliability:

1 (reliable without restriction)

Qualifier:

no guideline available

Principles of method if other than guideline:

No specific guidance for this study type although the United States Environmental Protection Agency have provided a guidance document 'Guidance on cholinesterase measures in developmental neurotoxicity and related studies' dated 29 October 2001

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: Alpk:APfSD

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

CMC (carboxymethyl cellulose)

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

10 consecutive days / oral gavage

Frequency of treatment:

once daily

Remarks:

Doses / Concentrations:0, 0.5, 5, 50 mg/kg/dayBasis:nominal conc.

Remarks:

Doses / Concentrations:0, 0.5, 5, 50 mg/kg/dayBasis:analytical conc.

No. of animals per sex per dose:

5 male and 5 females/gp

Control animals:

yes, concurrent vehicle

Dose descriptor:

NOAEL

Remarks:

neurotoxicity

Effect level:

ca. 1 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: based on statistically significant inhibition of brain cholinesterase at 5 mg/kg and greater in rats 21 days post partum

Remarks on result:

other: Generation: other: - pre-weaning (migrated information)

Dose descriptor:

NOAEL

Remarks:

neurotoxicity

Effect level:

ca. 5 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: based on statistically significant inhibition of brain cholinesterase at 50 mg/kg and greater in rats 51 days post partum

Remarks on result:

other: Generation: other: - young adults (migrated information)

Table 7.9.1 -5: %AChE inhibition

Dose (mg/kg)	Time (weeks)	Plasma				RBC				Brain
		Male	Sig	Female	Sig	Male	Sig	Female	Sig	Male	Sig	Female	Sig
Post Partum Day 21
0	Day 21	-	-	-	-	-	-	-	-	-	-	-	-
0.5	Day 21	19	**	9	**	5	NS	15	*	22	NS	9	NS
5	Day 21	42	**	41	**	44	**	49	**	33	*	15	**
50	Day 21	77	**	75	**	60	**	59	**	68	**	59	**
Post Partum Day 51
0	Day 51	-	-	-	-	-	-	-	-	-	-	-	-
0.5	Day 51	4	NS	5	NS	-10	NS	15	NS	0	NS	2	NS
5	Day 51	48	**	58	**	37	**	48	**	-7	NS	18	NS
50	Day 51	82	**	88	**	44	**	54	**	18	**	25	**

Statistically significant reductions in both erythrocyte and plasma cholinesterase were observed on post partum days 21 and 51 in both males and females, with the plasma derivative appearing to be more sensitive; however as brain cholinesterase activity was measured, this was seen as the preferential marker (JMPR, 2000). At post partum day 21, brain cholinesterase activity was inhibited at 5 and 50 mg/kg, with levels of inhibition ranging from 15 -68% for both males and females. At post partum day 51, statistically significant increases in inhibition were only observed at 50 mg/kg in males and females. The difference in brain cholinesterase inhibition in young rats was considered a result of increased exposure to profenofos due to incomplete blood brain barrier formation rather than increased sensitivity. No inhibition of brain cholinesterase activity was seen at dose levels of 0.5 or 5 mg/kg. Therefore the NOAEL based on brain cholinesterase inhibition was deemed 0.5 mg/kg/day and 5 mg/kg/day for pre-weaning and young adult rats respectively

 

Reference:

JMPR (2000). Pesticide residues. Guidelines for the preparation of toxicological working papers for the WHO core assessment group of the Joint Meeting on Pesticide Residues. Geneva, Switzerland, December 2000. 

Conclusions:

The NOAEL based on brain cholinesterase inhibition was deemed 1 mg/kg/day and 5 mg/kg/day for pre-weaning and young adult rats respectively. 

Executive summary:

Groups of rats were dosed orally by gavage with 0, 0.5, 5 or 50 mk/kg/day profenofos . For each group one litter of 5 male and 5 female pups were dosed once daily for 10 consecutive days, i.e. 12 -21 post partum inclusive. Furthermore, a further 5 male and 5 female young adult rats were dosed also, using the same dosing regimen as previously detailed. Animals were killed 3 -4 hours post the final dose, with brain, erythrocyte and plasma cholinesterase activity determined.

 

Statistically significant reductions in both erythrocyte and plasma cholinesterase were observed on post partum days 21 and 51 in both males and females, with the plasma derivative appearing to be more sensitive; however as brain cholinesterase activity was measured, this was seen as the preferential marker (JMPR, 2000). At post partum day 21, brain cholinesterase activity was inhibited at 5 and 50 mg/kg, with levels of inhibition ranging from 15 -68% for both males and females. At post partum day 51, statistically significant increases in inhibition were only observed at 50 mg/kg in males and females. The difference in brain cholinesterase inhibition in young rats was considered a result of increased exposure to profenofos due to incomplete blood brain barrier formation rather than increased sensitivity. No inhibition of brain cholinesterase activity was seen at dose levels of 1 or 5 mg/kg. Therefore the NOAEL based on brain cholinesterase inhibition was deemed 1 mg/kg/day and 5 mg/kg/day for pre-weaning and young adult rats respectively.

Reference 5

Endpoint:

neurotoxicity: sub-chronic oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: IBTL study, non-GLP, non-guideline compliant. Study not validated by EPA, therefore data considered not reliable

Qualifier:

no guideline followed

Principles of method if other than guideline:

Hens administered 2 doses of profenofos 21 days apart, and then examined for a further 21 days. No cholinesterase activity determined, only gross and histopathological analysis of neural tissue performed.

GLP compliance:

no

Limit test:

no

Species:

hen

Strain:

other: White Leghorn

Sex:

female

Route of administration:

oral: gavage

Vehicle:

corn oil

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

42 days / oral gavage

Frequency of treatment:

Dosing on day 0 followed by a further dose on day 21

Remarks:

Doses / Concentrations:0, 30, 45.7 mg/kgBasis:nominal conc.Dosing on day 0

Remarks:

Doses / Concentrations:0, 17.1 mg/kgBasis:nominal conc.Due to increased mortality observed in the treated groups, all suriviving birds were redosed at 17.1 mg/kg

No. of animals per sex per dose:

Untreated control: 10 hensDose gp 30 mg/kg: 40 hensDose gp 45.7 mg/k: 50 hensPositive control: 15 birds

Control animals:

other: Yes, untreated control

Dose descriptor:

other:

Sex:

female

Basis for effect level:

other: This study confirmed that Profenofos did not cause delayed neurotoxic effects in adult hens when treated up to sub-lethal doses.

Remarks on result:

not measured/tested

Remarks:

Effect level not specified

Conclusions:

This study confirmed that Profenofos did not cause delayed neurotoxic effects in adult hens when treated up to sub-lethal doses.

Executive summary:

A delayed neurotoxicity study was conducted in White Leghorn hens at dose levels of 30 and 45.7 mg/kg. The dose levels were based on an initial assessment of the acute toxicity of Profenofos which showed the LD50 to be 45.7 mg/kg. Surviving birds were administered a second dose 21 days after the initial dose, but due to unexpectantly high mortality after the first administration the second dose was reduced to 17.1 mg/kg (which was the revised LD50 based on mortality after the first dose). A positive control group was administered tri-orthocresyl phosphate. The birds were observed daily for mortality and possible neurotoxic signs for up to 21 days after the second dose. At the end of the study the sciatic nerves, brain and spinal cord were examined.

 

41/50 hens administered 45.7 mg/kg and 28/40 birds administered 30 mg/kg Profenofos died within 21 days of dosing (mostly within 24 hours). Only one further mortality was observed when animals were redosed 21 days after the first administration, even with atropine treatment. Clinical signs of toxicity included salivation and lethargy post the first dose, with slight lethargy present for 24 -48hrs post the second dose. There were no behavioral signs of delayed neurotoxicity or locomotor disturbances. Bodyweight gain and food consumption was reduced in treated birds, particularly post the first dose. Gross and histopathological studies of neural tissues from treated birds did not reveal any treatment related findings. This study confirmed that Profenofos did not cause delayed neurotoxic effects in adult hens when treated up to sub-lethal doses.

Reference 6

Endpoint:

neurotoxicity: acute oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 June 1992 to 11 July 1992

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

other: EPA-FIFRA guidelines (Pesticide Assessment Guidelines - Subdivision F, Hazard Evaluation, Addendum 10 - Neurotoxicity Series 81, 82 and 83)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

corn oil

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

Single / oral gavage

Frequency of treatment:

Once

Remarks:

Doses / Concentrations:0, 95, 1990, 380 mg/kgBasis:nominal conc.

No. of animals per sex per dose:

15 animals/sex/gp, with 10 animals/sex/gp used for neurological tests and 5 animals/sex/gp used for cholinesterase measurements

Control animals:

yes, concurrent vehicle

Dose descriptor:

NOAEL

Remarks:

neurotoxicity

Effect level:

ca. 190 mg/kg bw (total dose)

Sex:

male/female

Basis for effect level:

other: The high dose group (380 mg/kg) was toxic with autonomic and functional changes consistent with inhibition of cholinesterase activity.

Remarks on result:

other:

Table 7.9.1 -6:%AChE inhibition

Dose (mg/kg)	Time (weeks)	Plasma				RBC				Brain
		Male	Sig	Female	Sig	Male	Sig	Female	Sig	Male	Sig	Female	Sig
0	4hrs	-	-	-	-	-	-	-	-	-	-	-	-
95	4hrs	84	**	94	**	74	**	68	**	-	-	-	-
190	4hrs	92	**	94	**	93	**	72	**	-	-	-	-
380	4hrs	92	**	97	**	96	**	87	**	-	-	-	-
0	14	-	-	-	-	-	-	-	-	-	-	-	-
95	14	-3	NS	5	NS	25	NS	46	**	3	NS	1	NS
190	14	8	NS	5	NS	45	**	59	**	5	NS	5	NS
380	14	1	NS	3	NS	47	**	53	**	7	NS	8	NS

Statistically significant reductions in both erthryocyte and plasma cholinesterase activites were observed across all dose levels when sampled 4hrs post dosing for both genders. At termination (Day 14), plasma cholinesterase was more resilient to the effects of Profenofos, with no significant inhbition in activity observed. Erythrocyte cholinesterase activity was again significantly inhibited at all levels in both genders but the extent of inhibition was not as great (25 -59%) when compared to sampling 4hrs post dosing (68 -96%). As brain cholinesterase activity was measured this was seen as the prefential marker (JMPR, 2000). Whilst no significant inhibition was observed across all dose levels for both genders (1 -8%), FOB effects occurred on the day of dosing primarily at 380 mg/kg. Effects on the autonomic nervous (diarrhoea, lacrimation, slight impairment of respiration and miosis), bizarre behavioural effects, neuromuscular (ataxia, abormal gait, impaired reflexes etc.) and CNS effects (tremors, altered posture, ease of handling) were only observed in animals of the 380 mg/kg dose group at the time of peak effect. Motor activity of these animals was reduced at this time point. At the peak effect in the high dose group no effects on the FOB and motor activity tests were observed in the two lower dose groups.

 

All necropsy observations as well as all microscopic findings were interpreted as incidental. There was no evidence of neuropathological alterations attributable to the treatment with Profenofos in any of the examined tissues.

 

The high dose group (380 mg/kg) was toxic with autonomic and functional changes consistent with inhibition of cholinesterase activity. The dose level of 190 mg/kg was deemed the NOAEL for neurotoxic effects.

 

Reference:

JMPR (2000). Pesticide residues. Guidelines for the preparation of toxicological working papers for the WHO core assessment group of the Joint Meeting on Pesticide Residues. Geneva, Switzerland, December 2000. 

Conclusions:

The high dose group (380 mg/kg) was toxic with autonomic and functional changes consistent with inhibition of cholinesterase activity. The dose level of 190 mg/kg was deemed the NOAEL for neurotoxic effects.

Executive summary:

Profenofos was administered once via oral gavage to 15 rats/sex at dose levels 0, 95, 190 and 380 mg/kg. Positive control animals were given a single dose of either Propoxut (6 mg/kg) or triademifon (!50 mg/kg). FOB, motor activity, plasma and erythrocyte cholinesterase levels were determined 4hr post dosing and at day 14. Brain cholinesterase activity was determined on day 14.

 

Statistically significant reductions in both erythrocyte and plasma cholinesterase activities were observed across all dose levels when sampled 4hrs post dosing for both genders. At termination (Day 14), plasma cholinesterase was more resilient to the effects of Profenofos, with no significant inhibition in activity observed. Erythrocyte cholinesterase activity was again significantly inhibited at all levels in both genders but the extent of inhibition was not as great (25 -59%) when compared to sampling 4hrs post dosing (68 -96%). As brain cholinesterase activity was measured this was seen as the preferential marker (JMPR, 2000). Whilst no significant inhibition was observed across all dose levels for both genders (1 -8%), FOB effects occurred on the day of dosing primarily at 380 mg/kg. Effects on the autonomic nervous (diarrhoea, lacrimation, slight impairment of respiration and miosis), bizarre behavioural effects, neuromuscular (ataxia, abnormal gait, impaired reflexes etc.) and CNS effects (tremors, altered posture, ease of handling) were only observed in animals of the 380 mg/kg dose group at the time of peak effect. Motor activity of these animals was reduced at this time point. At the peak effect in the high dose group no effects on the FOB and motor activity tests were observed in the two lower dose groups.

 

All necropsy observations as well as all microscopic findings were interpreted as incidental. There was no evidence of neuropathological alterations attributable to the treatment with Profenofos in any of the examined tissues.

 

The high dose group (380 mg/kg) was toxic with autonomic and functional changes consistent with inhibition of cholinesterase activity. The dose level of 190 mg/kg was deemed the NOAEL for neurotoxic effects.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

5.1 mg/kg bw/day

Effect on neurotoxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Effect on neurotoxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Several studies have been conducted to address the potential neurotoxic effect of Profenofos. These studies range from: i) developmental studies where gravid female rats were fed Profenofos throughout gestation (from day 7) through lactation and weaning, with the F₁ generation then fed the diet until post partum day 22; ii) acute and repeat dose studies where pre-weaning and young adults were administered the test material either by oral gavage or through the diet (respectively) in order to assess effects on cholinesterase activity; ii) Acute and repeat dose neurotoxicity studies in young adult rats and; iii) Delayed neurotoxicity testing in hens.

 

Both erythrocyte and plasma acetylcholinesterase activity was found to be significantly more sensitive to Profenofos than brain cholinesterase activity (where measured). In no species were there any signs of toxicity seen at doses that did not also produce significant inhibition of brain cholinesterase. The conclusion from the JMPR review on Profenofos (2007) and in accordance with the guidance published by the JMPR (2000) was that inhibition of brain acetylcholinesterase activity was the more appropriate end-point for risk assessment of Profenofos. This is further supported by the endpoint specific guidance published by ECHA.

 

Developmental neurotoxicity studies:

Following exposure to Profenofos during gestation in gravid female rats through to post partum day (PPD) 22 in the F₁ offspring, significant reductions in plasma cholinesterase of between 60-80% were observed in paternal females receiving 60 and 600 ppm. A similar effect was observed with erythrocyte cholinesterase activity over the same period. In accordance with the JMPR guidance, brain cholinesterase activity is the preferential endpoint of concern. In paternal females, a statistically significant decrease in brain cholinesterase activity (44%) was observed in animals on GD 22 receiving 600 ppm. A similar reduction, although not statistically significant (26%) was observed PPD 22 at the same dose. Therefore the NOAEL for maternal toxicity was considered to be 60 ppm (5.1 mg/kg/day) based on significant reductions in brain cholinesterase activity during gestation and post partum.

 

There were no treatment related effects in the F₁animals on motor activity, auditory startle response, learning and memory or neurohistopathology. Statistically significant decreases in cholinesterase activity was limited to brain activity on PPD 22 in females receiving 600 ppm (11%), however in accordance with the guidance from the JMPR, as this did not achieve 20% or more, the level of inhibition was deemed not biologically relevant. Therefore the NOAEL for developmental neurotoxicity was considered to be 600 ppm (103.4 mg/kg diet). Due to a reduction in bodyweight gain, the NOAEL for offspring toxicity was 60 ppm (10.7 mg/kg diet).

 

Acute dose pre-weaning neurotoxicity study:

Cholinesterase activity was investigated in rats which were 12, 22 and 42 days old. Groups of five male and five female rats of each age were given a single dose of 0, 1, 5, 25 or 100 mg/kg Profenofos (CGA 15324) in 1% (w/v) CMC. Approximately 3 -4hrs post dosing samples were taken for brain, erythrocyte and plasma cholinesterase activity determination.

 

Statistically significant reductions in both erythrocyte and plasma cholinesterase were observed onpost partumdays 12, 22 and 42 in both males and females, however as brain cholinesterase activity was measured, this was seen as the preferential marker (JMPR). At post partum day 12, brain cholinesterase activity was inhibited at 25 and 100 mg/kg, with levels of inhibition ranging from 19 -65% for both males and females. At post partum day 22 and 42, statistically significant increases in inhibition were only observed at 100 mg/kg in males and/or females. The difference in brain cholinesterase inhibition in young rats was considered a result of increased exposure to Profenofos due to incomplete blood brain barrier (BBB) formation rather than increased sensitivity, as BBB development in the rat is completedpost-natally. No inhibition of brain cholinesterase activity was seen at dose levels of 1 or 5 mg/kg. Therefore the NOAEL based on brain cholinesterase inhibition was deemed 5 mg/kg or 25 mg/kg in pups and young adult rats respectively.

 

Repeat dose pre-weaning neurotoxicity study:

Groups of rats were dosed orally by gavage with 0, 0.5, 5 or 50 mg/kg/day Profenofos. For each group one litter of 5 male and 5 female pups were dosed once daily for 10 consecutive days, i.e. 12 -21post partuminclusive. Furthermore, a further 5 male and 5 female young adult rats were also dosed using the same dosing regimen as previously detailed. Animals were killed 3 -4 hours post the final dose, with brain, erythrocyte and plasma cholinesterase activity determined.

 

Statistically significant reductions in both erythrocyte and plasma cholinesterase were observed on post partum days 21 and 51 in both males and females, with the plasma derivative appearing to be more sensitive; however as brain cholinesterase activity was measured, this was seen as the preferential marker (JMPR). At post partum day 21, brain cholinesterase activity was inhibited at 5 and 50 mg/kg/day, with levels of inhibition ranging from 15 -68% for both males and females. At post partum day 51, statistically significant increases in inhibition were only observed at 50 mg/kg in males and females. As for the acute dose pre-weaning study, the difference in brain cholinesterase inhibition was due to incomplete formation of the BBB. No inhibition of brain cholinesterase activity was seen at dose levels of 1 or 5 mg/kg. Therefore the NOAEL based on brain cholinesterase inhibition was deemed 0.5 mg/kg/day and 5 mg/kg/day for pre-weaning and young adult rats respectively.

 

Delayed neurotoxicity study:

A delayed neurotoxicity study was conducted in White Leghorn hens at dose levels of 30 and 45.7 mg/kg. The dose levels were based on an initial assessment of the acute toxicity of Profenofos which showed the LD₅₀ to be 45.7 mg/kg. Surviving birds were administered a second dose 21 days after the initial dose, but due to unexpectantly high mortality after the first administration the second dose was reduced to 17.1 mg/kg (which was the revised LD₅₀ based on mortality after the first dose). A positive control group was administered tri-orthocresyl phosphate. The birds were observed daily for mortality and possible neurotoxic signs for up to 21 days after the second dose. At the end of the study the sciatic nerves, brain and spinal cord were examined.

 

41/50 hens administered 45.7 mg/kg and 28/40 birds administered 30 mg/kg Profenofos died within 21 days of dosing (mostly within 24 hours). Only one further mortality was observed when animals were re-dosed 21 days after the first administration, even with atropine treatment. Clinical signs of toxicity included salivation and lethargy post the first dose, with slight lethargy present for 24 -48hrs post the second dose. There were no behavioural signs of delayed neurotoxicity or locomotor disturbances. Bodyweight gain and food consumption was reduced in treated birds, particularly post the first dose. Gross and histopathological studies of neural tissues from treated birds did not reveal any treatment related findings. This study confirmed that Profenofos did not cause delayed neurotoxic effects in adult hens when treated up to sub-lethal doses.

 

Acute neurotoxicity:

Profenofos was administered onceviaoral gavage to 15 rats/sex at dose levels 0, 95, 190 and 380 mg/kg. Positive control animals were given a single dose of either Propoxur (6 mg/kg) or triademifon (150 mg/kg). FOB, motor activity, plasma and erythrocyte cholinesterase levels were determined 4hr post dosing and at day 14. Brain cholinesterase activity was determined on day 14.

 

Statistically significant reductions in both erythrocyte and plasma cholinesterase activities were observed across all dose levels when sampled 4hrs post dosing for both genders. At termination (Day 14), plasma cholinesterase was more resilient to the effects of Profenofos, with no significant inhibition in activity observed. Erythrocyte cholinesterase activity was again significantly inhibited at all levels in both genders but the extent of inhibition was not as great (25 -59%) when compared to sampling 4hrs post dosing (68 -96%). As brain cholinesterase activity was measured this was seen as the preferential marker (JMPR). Whilst no significant inhibition was observed at any dose levels for both genders (1 -8%), FOB effects occurred on the day of dosing primarily at 380 mg/kg. Effects on the autonomic nervous system (diarrhoea, lacrimation, slight impairment of respiration and miosis), bizarre behavioural effects, neuromuscular (ataxia, abnormal gait, impaired reflexes etc.) and CNS effects (tremors, altered posture, ease of handling) were only observed in animals of the 380 mg/kg dose group at the time of peak effect. Motor activity of these animals was reduced at this time point. At the peak effect in the high dose group no effects on the FOB and motor activity tests were observed in the two lower dose groups.

All necropsy observations as well as all microscopic findings were interpreted as incidental. There was no evidence of neuropathological alterations attributable to the treatment with Profenofos in any of the examined tissues.

 

The high dose group (380 mg/kg) was toxic with autonomic and functional changes consistent with inhibition of cholinesterase activity. The dose level of 190 mg/kg was deemed the NOAEL for neurotoxic effects.

 

Repeat neurotoxicity:

The potential subchronic effects of Profenofos were investigated in a rat dietary study where groups of rats (15/sex/group) were fed Profenofos at dietary concentrations of 0, 30, 135 and 600 ppm for up to 13 weeks. The average daily dosages, based on nominal concentrations in the feed were 1.7, 7.7 and 36 mg/kg diet for males and 1.84, 8.4 and 37.9 mg/kg diet for females in the respectively 30, 135 and 600 ppm groups.

Statistically significant reductions in both erythrocyte and plasma cholinesterase were observed from weeks 3 to 12 in both males and females, with the plasma derivative appearing to be more sensitive; however as brain cholinesterase activity was measured, this was seen as the preferential marker (JMPR). At termination (week 12) brain cholinesterase activity was significantly inhibited in both males and females at 600 ppm, however in accordance with the JMPR guidance this was only deemed biologically relevant in females where the level of inhibition was 20%. Whilst no clinical signs of toxicity, effects on the functional observational battery or motor effects suggestive of a relationship to treatment were observed at any dose level, a reduction in bodyweight gain was observed at 600 ppm. Therefore the NOAEL based on brain cholinesterase inhibition (and reduction in bodyweight gain) was deemed 135 ppm (equivalent to 7.7 or 8.4 mg/kg diet in males and females respectively), based on the effects observed at 600 ppm.

 

Table Summary of neurotoxicity data

Species	Study	Effect	NOAEL	LOAEL
Rat	Developmental toxicity (dietary)	Maternal toxicity	5.1 mg/kg diet (due on inhibition of brain AChE)	50.6 mg/kg diet (highest maternal dose)
		Offspring toxicity	10.7 mg/kg/day (due to bodyweight loss. No effect on brain AChE)	103.4 mg/kg/day (highest offspring dose)
Rat	Acute dose pre-weaning toxicity (gavage)^a	Pup toxicity	5 mg/kg (due on inhibition of brain AChE)	25 mg/kg
		Young adult toxicity	25 mg/kg (due on inhibition of brain AChE)	100 mg/kg (highest dose)
Rat	Repeat dose pre-weaning toxicity (gavage)^a	Pup toxicity	1 mg/kg/day (due on inhibition of brain AChE)	5 mg/kg/day
		Young adult toxicity	5 mg/kg/day (due on inhibition of brain AChE)	50 mg/kg/day (highest dose)
Hen	42 day delayed neurotoxicity (gavage)	Delayed neurotoxicity	No delayed neurotoxic effects
Rat	Acute dose neurotoxicity (gavage)	Male / female neurotoxicity	190 mg/kg (due to autonomic and functional changes consistent with inhibition of AChE)	380 mg/kg (highest dose)
Rat	Repeat (90 day) dose neurotoxicity (dietary)	Male neurotoxicity	7.7 mg/kg diet (due to bodyweight loss and inhibition of brain AChE)	36 mg/kg diet
		Females neurotoxicity	8.4 mg/kg diet (due to bodyweight loss and inhibition of brain AChE)	37.9 mg/kg diet

a – Studies designed to assess cholinesterase inhibition only

 

Summary

As only one key value for chemical safety assessment can be taken forward, the effect level considered most appropriate is the developmental toxicity NOAEL for maternal toxicity (5.1 mg/kg diet). The data indicate that there is no apparent sex difference in acute neurotoxicity of Profenofos, there is no evidence of developmental effects which would be produced by a single low dose. Even at a dose of up to 190 mg/kg there were no signs of neurotoxicity. Therefore selection of the maternal NOAEL value from the developmental neurotoxicity study is considered a conservative endpoint descriptor which is considered to provide protection against any clinical signs of acetyllcholinesterase inhibition seen in studies of both acute and repeat oral toxicity.

 

Reference:

ECHA (2008). Guidance on information requirements and chemical safety assessment. Chapter R.7a: Endpoint specific guidance. R.7.5 Repeat dose toxicity. Pg 349.

 

JMPR (2000). Pesticide residues. Guidelines for the preparation of toxicological working papers for the WHO core assessment group of the Joint Meeting on Pesticide Residues. Geneva, Switzerland, December 2000.

 

JMPR (2007). Pesticide residues in food. Joint FAO/WHO meeting on pesticide residues. Report of the Joint Meeting of the FAO Panel of Experts on Pesticide Residues in Food and the Environment and the WHO Core Assessment Group on Pesticide Residues. Geneva, Switzerland, 18 -27 September 2007.

Justification for classification or non-classification

Prodenofos is not classified for Neurotoxicity.