Document ID: EPA-HQ-OPP-2005-0058-0004
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2006-09-27T04:00Z

FQPA Company Notice of Filings for Pesticide Petitions

Ethaboxam

LG Life Sciences, Ltd.

 PP [4E6863]

-cyano-2-thenyl)-4-ethyl-2-(ethylamino)-1,3-thiazole-5-carboxamide,
in or on grapes, raisins, grape juice, and wine.  The tolerances are set
at the following value: grapes at 3.5 ppm, grape juice at 3.3 ppm,
raisins at 5.8 ppm and wine at 2.5 ppm. EPA has determined that the
petition contains data or information regarding the elements set forth
in section 408(d)(2) of the FDCA; however, EPA has not fully evaluated
the sufficiency of the submitted data at this time or whether the data
supports granting of the petition.  Additional data may be needed before
EPA rules on the petition.

A.	Residue Chemistry                                        

1. 	Plant metabolism.   

The primary metabolic pathways of ethaboxam in plants were established
in grapes, tomatoes, and potatoes.  Extensive metabolism occurred in the
grape.  The proposed bio-transformation pathway for ethaboxam in grapes
is the formation of LGC-35523 from ethaboxam (by photolytic degradation)
and incorporation of LGC-35523 into natural products (sugars).  In the
potato, most of the parent compound was metabolized and incorporated
into starch.  Following acid hydrolysis of the starch fraction to
glucose, a substantial proportion of the radiolabel was converted to
glucosazone.  It was therefore concluded that the radiolabel was
incorporated into the starch backbone and formed part of the
carbohydrate pool.  In the tomato, fruit taken at harvest showed that
the major component at harvest was unchanged ethaboxam, accounting for
49-57% total radioactive residues.

2. 	Analytical method.

LG Life Sciences, Ltd., has submitted validated analytical methodology
for the determination of residues in grapes and grape processed
fractions (juice, raisins, and wine).  Samples were extracted with
acetonitrile: water.  Extracts were cleaned-up by a liquid-liquid
partition with hexane before liquid-liquid extraction into ethyl
acetate.  The organic phase was removed and the samples reconstituted in
methanol: water (50:50 v:v) before quantitation by liquid chromatography
with mass spectrometric detection (LC-MS).

No significant interferences were found when the method was applied to
untreated samples, thus assuring the specificity of the method.  The
methodology was validated at 0.01 and 1.00 mg/kg for the detection of
ethaboxam in each matrix.

μg/ml (equivalent to 0.005 mg/kg in grapes).

3.	 Magnitude of residues.

A program of nineteen residue trials was conducted in both Northern and
Southern Europe over a two year period (2001-2002) on vines.  In
Northern Europe trials were conducted in France and Germany, while in
Southern Europe the trials were in France, Italy, and Spain. 
Applications of ethaboxam 10% SC were made at the proposed GAP of 5 x
200 g a.s./ha with a 21 day PHI.  Of the 19 trials, 8 were conducted as
decline studies, with5 in Southern Europe and 3 in Northern Europe. 
Residue levels in grapes ranged from less than the limit of detection
(<0.005 ppm) to 3.4 ppm with a mean value of 1.07 ppm.  The proposed EU
MRL for grapes is 3.5 ppm and the MRLs for grape processed commodities
based on the concentration/dilution factors determined in the processing
study are 2.5 ppm for young wine, 1.3 ppm for wine, 2.3 ppm for juice,
and 5.8 ppm for raisins.  

These proposed MRLs were combined with a program of seven trials
conducted in 2004.  This program was conducted in Chile (3 trials),
Australia (2 trials), Argentina (1 trial), and Mexico (1 trial). 
Residues were analyzed resulting from 5 applications of ethaboxam 10% SC
at 2 or 4 L/ha, sampled at 21 days following the final application.  No
residues of ethaboxam were detected above the limit of detection of
0.002 ppm in any non-treated samples from any of the trials.  Residues
of ethaboxam detected in grapes ranged from 0.183 to 1.827 ppm in
samples sprayed at a rate of 2 L/ha and from 1.121 to 7.072 ppm for
grapes sprayed at a rate of 4 L/ha.  Residues detected in juice (must)
samples were between 0.64 and 3.24 ppm (2 L/ha rate); in raisins
residues were between 0.39 and 1.68 ppm (2 L/ha rate); in wine residues
were between 0.11 and 0.49 ppm (2 L/ha rate).  Combining the residues
from the two programs the following tolerances are proposed; grapes at
3.5 ppm, grape juice at 3.3 ppm, raisins at 5.8 ppm, and wine at 2.5
ppm.  

Neither livestock feeding studies or livestock metabolism, distribution
and expression of residue studies are required, as vines will not be
utilized for feeding.  

The storage stability of ethaboxam was assessed in grape homogenates
during freezer storage (-18C).  The results of the analysis show that
ethaboxam was stable for a minimum of 17 months.

B.	 Toxicological Profile

1. 	Acute toxicity.  

Ethaboxam has low acute toxicity.  The oral LD50 in rats is >5000 mg/kg
for males and females, combined.  The rat dermal LD50 is >5000 mg/kg and
the rat inhalation LC50 is >4.89 mg/L air.  Ethaboxam is not a skin
sensitizer in guinea pigs and does not produce dermal or eye irritation
in rabbits.  End-use formulations of ethaboxam have similar low acute
toxicity profiles.

2. 	Genotoxicity. 

There was no evidence of mutagenic activity in the bacterial in vitro
reverse mutation test and in the in vitro mammalian cell mutation assay.
 An in vivo micronucleus test did not show any evidence of causing
chromosome damage or bone marrow cell toxicity.  These studies show that
ethaboxam is not genotoxic.

3. 	Reproductive and developmental toxicity.

In a 2-generation study, a dietary concentration of 200 ppm (equivalent
to an average exposure of between 16-19 mg/kg/day for rats in the
10-week maturation period before breeding) is the NOAEL for somatic
growth and reproductive performance in the rat.  There was no
macroscopic or microscopic evidence of any change in the female
reproductive organs and the oestrous cycles were unaffected by
treatment.  Fertility was unaffected at the lower dietary
concentrations.  Treatments with diets containing 650 ppm was associated
with reduced body weight and food consumption, particularly of the
males, in both generations.  The most marked effects on body weight were
seen on the offspring before weaning (both sexes, both generations) and
this corresponds to the time of maximum chemical intake, whether it be
by the mother during lactation when food consumption is high, or by the
offspring.  Lower dietary concentrations (65 and 200 ppm) had no effects
upon food consumption or growth.  Fertility was unaffected in the first
generation but was adversely affected at 650 ppm in the second
generation and this effect could clearly be linked to the male.  At 650
ppm there was reduced male fertility (F1 generation), reduced sperm
mobility (F0 and F1 generations), reduced desire to mate (F1
generation), testicular (F1 generation) and epididmyal lesions (F0 and
F1 generations), and an increase in incidence of abnormal spermatozoa
(F0 and F1 generations).

 

Three studies were conducted to assess the embryo foetal toxicity of
ethaboxam in rats and rabbits.  Two studies were required in the rat as
the first study failed to establish an unequivocal no-effect level for
the foetus.  In comparing the two rat embryo foetal studies, 1000
mg/kg/day was established as a maternally toxic level with clear effects
on maternal body weight, food consumption, and water consumption.
Considering data from both studies 30 mg/kg/day is identified as a clear
NOEL for the developing foetus with the probability that 300 mg/kg/day
could be considered as the NOAEL.  The NOEL for the dam is also
established at 30 mg/kg/day.  The assessment of ethaboxam on the
pregnancy and embryo-foetal development in the rabbit was conducted at
0, 25, 75, and 125 mg/kg/day.  Dosage-related maternal responses to
treatment at 75 and 125 mg/kg/day were based upon an adverse effect on
food consumption.  At the highest dosage only, the severity of this
effect was reflected in the maternal bodyweight and by the necessity to
sacrifice two animals in poor condition.  Despite this maternal
toxicity, both dosages were considered to be without adverse
embryo-foetal effect.  The NOEL for the dam was 25 mg/kg/day and for
embryo foetal development was 125 mg/kg/day.

4. 	Subchronic toxicity. 

Ethaboxam was evaluated in 13-week subchronic oral toxicity studies in
rats, mice, and dogs.  In the rat study a NOEL of 16.3 mg/kg/day was
established.  The main adverse effects were growth retardation
attributed to toxicity rather than food intake at 2000 ppm in both sexes
and at 650 ppm in males, and severe testicular atrophy at 2000 ppm.  In
mice, results showed reduced body weight gain in males receiving 1000 or
2500 ppm and reduced food consumption in both sexes at 1000 ppm and
females receiving 450 and 2500 ppm.  Post mortem examinations showed
(dosage related in incidence and/or degree) increased liver weights for
both sexes at 1000 or 2500 ppm and males at 450 ppm, which appeared
microscopically as Centrilobular hepatocytes hypertrophy.  Microscopic
examination of the testes did not reveal any treatment related changes. 
All other microscopic findings were considered to be incidental and of
no toxicological significance.  The NOEL was established at 200 ppm (33
mg/kg/day).  In the-90 day dog toxicity study a NOAEL was not determined
due to slightly lower body weight gain in females in the lowest
treatment level.

5. 	Neurotoxicity.

No neurotoxicity findings were observed in the Functional Observational
Battery and motor activity assessments conducted in the 2-year combined
toxicity and carcinogenicity study in the rat.  In addition, ethaboxam
is unlikely to cause delayed neurotoxicity based on the chemical nature
of the compound.

6. 	Chronic toxicity. 

Chronic toxicity studies with ethaboxam have been conducted in rats,
mice, and dogs. In the 52-week dog study a NOAEL of 10 mg/kg/day was
established based on bodyweight impairment observed at 30 mg/kg/day.  In
the 78-week mouse study a NOAEL of 35 mg/kg/day for males and 44
mg/kg/day for females was established based on reduction in body weight
gain.  In the 104-week rat study a NOAEL of 5.5 / 21 mg/kg/day for males
/ females was established due to non-neoplastic lesions observed in the
testes and epididymides. 

7. 	Dermal toxicity. 

Ethaboxam was evaluated in 28-day dermal toxicity study in rats that
showed general dosage related signs of systemic toxicity at 300 and 1000
mg/kg/day.  Reduced food consumption and retarded body weight gain were
noted during the early phase of the study for both sexes receiving 1000
mg/kg/day and for females at 300 mg/kg/day.  Two females at 1000
mg/kg/day showed lower ATTP values.  Dermal reactions were not seen
clinically or macroscopically, but subsequent microscopic examination of
treated skin revealed epithelial hyperplasia, sometimes with
hyperkeratosis among males at these dosages.  Ulceration of treated skin
was also noted at histological examination for some males at 1000
mg/kg/day.  The NOEL was 100 mg/kg/day.

 

8. 	Carcinogenicity. 

The carcinogenic potential of ethaboxam has been evaluated in rats and
mice.  In a 78 week carcinogenicity study on mice, dietary
administration showed no treatment related neoplastic or toxicologically
significant non-neoplastic microscopic findings.  At the highest dose
(900 ppm) there was a 20% reduction in body weight gain in both sexes. 
The NOEL in the mouse was established at 35 mg/kg/day in males and 44
mg/kg/day in females.

A 104-week dietary and carcinogenicity study in the rat showed a slight
increase in the number of interstitial (Leydig) cell adenomas in the
testes of male rats at 300 and 650 ppm and a reduction in testosterone
levels.  After 13 weeks the circulating testosterone returned to normal
levels in response to elevated luteinising hormone.  Prolonged exposure
to elevated luteinising hormone would result in Leydig cell hyperplasia
and adenoma.  The occurrence of Leydig cell adenomas was therefore
considered to be secondary to the other effects in the testes.  Other
effects in the testes included reduced sperm mobility, reduced male
fertility, testicular and epididmyal lesions, and increase in incidence
of abnormal spermatozoa.  These findings were considered to be of no
toxicological significance to humans.  The NOAEL was established at
5.5/21 mg/kg/day for males/females.  

9. 	Animal metabolism. 

Studies of the absorption, distribution, metabolism and excretion of
ethaboxam (LGC-30473) were carried out using [14C]-LGC-30473
([14C-thiophene] LGC-30473 and [14C-thiazole] LGC-30473 dosed
separately.  Studies were performed in rats of the same strain used for
toxicity assessments at dose levels of 10 or 150 mg/kg and oral gavage
dosing in a 1%methylcellulose, 0.1% Tween 80 vehicle.

Excretion of radioactivity following either a single dose of
[14C-thiophene or 14C-thiazole] LGC-30473 or 14 consecutive doses of
[14C-thiazole] LGC-30473 was rapid with >90% of radioactivity eliminated
in urine or faeces within 48 hours.  Faecal excretion (66-92% of dose in
120 h) substantially exceeded urinary excretion (13-30% of dose in 120
h) with the percentage excreted in the urine higher at the lower dose. 
These factors suggest capacity limited absorption.  This was supported
by the pharmacokinetic data which showed a slightly less than dose
proportional increase in Cmax and AUC between the 10 and 150 mg/kg doses
(dose ratio 15, AUC ratio 11).  Substantial radioactivity was detected
in bile suggesting first-pass metabolism was significant.  Tmax was
around three times longer at the high dose level (3-6 h at 150 mg/kg
versus 1-2 h at 10 mg/kg).  The plasma elimination half-life of 31-41 h
was similar for both doses.  The blood cell elimination half-life was
considerably longer at 69-162 hours for both doses.  AUC120 was higher
in blood plasma following 14 doses at 10 mg/kg/day than following one
dose (~2 fold) but more notably higher in blood cells (~5 fold).

Distribution of radioactivity after a single dose at 10 or 150 mg/kg or
14 consecutive doses at 10 mg/kg was similar at both dose levels and was
highest in thyroid (thiazole label only), liver and blood cells. 
Concentrations 120 hours after the 14th dose were 5-15 fold higher than
after the single dose, but all tissue accumulation was low.

There were no substantial differences in distribution or excretion
pattern between sexes.  Extent of absorption, assessed in biliary
excretion experiments, was similar between the sexes at 10 mg/kg (71-72%
dose) but higher in females at 150 mg/kg (males, 48% dose; females 61%
dose).

All elements of this study indicate similar results for both labels and
there was little evidence of cleavage of the intact molecule.  Five
major metabolites were identified each accounting for >5% dose: 
LGC-32794, LGC-32800, LGC-32801, LGC-32802, and LGC-32803.  In one
pathway ethaboxam was N-de-ethylated to LGC-32794 followed by oxidation
of the thiazole sulphur to LGC-32800.  Ethaboxam also underwent
enolization.  In a second pathway the enol form underwent hydrolysis to
the amide LGC-32801.  In a third pathway the enol underwent sulphate
conjugation to LGC-32802 and hydroxylation/sulphate conjugation to
LGC-32803.  Ethaboxam was detected as a major component of faecal
extracts at both dose levels.  Destructive catabolism of the molecule
appeared to be negligible. 

10. 	Metabolite toxicology. 

From the grape metabolism study the proposed bio-transformation pathway
for ethaboxam (LGC-30473) in grapes is the formation of LGC-35523 from
LGC-30473 (by photolytic degradation) and incorporation of LGC-35523
into natural products (sugars).  The toxicological significance of
LGC-35523 (a non-mammalian metabolite) has been investigated in four
standard laboratory toxicity studies (acute oral toxicity, reverse
mutation test using bacteria, in vitro mammalian chromosome aberration
test and 28 day repeated oral toxicity) which show it to be of no
toxicological concern.  It is therefore proposed the definition of
residue of concern is ethaboxam (LGC-30473) only.

11. 	Endocrine disruption. 

Ethaboxam does not belong to a class of chemicals known or suspected of
having adverse effects on the endocrine system.  However, there were
some reproductive and developmental effects in the 104-week rat
chronic/carcinogenicity combination study.  Testosterone levels were
reduced in rats and there a slight increase in incidence of interstitial
(Leydig) cell adenomas in the testes of male rats at 300 and 650 ppm.

C.	 Aggregate Exposure

1. 	Dietary exposure. 

Acute dietary exposure assessments were conducted using a Tier I
approach.  This Tier I assessment incorporated tolerance level residues
and 100% crop-treated in the DEEMTM (Dietary Exposure Evaluation Model;
Exponent, Inc., 2003) software system.  DEEMTM utilized the food
consumption data derived from the 1994-1998 USDA Continuing Surveys of
Food Intake by Individuals (CSFII).  The resulting exposures were
compared to an aRfD of 0.10 mg/kg/day, which was based on the NOAEL of
10 mg/kg/day from the 52-week dog study and a 100-fold uncertainty
factor.  Acute dietary exposure estimates for the overall US population
and 25 population subgroups are below the acute RfD.  Results of these
analyses are summarized below.

ACUTE Dietary risk (DEEMTM) Analyses of Ethaboxam

Population Subgroup	%RfD

US population	9.02

All infants	1.42

Non-Nursing infants (<1 yr old)	3.14

Children (1-6 yrs)	37.88

Females 20+ 	7.63

Chronic dietary exposure assessments were also conducted using the same
Tier 1 approach as used in the acute assessments.  The DEEMTM software
was used to determine the estimates for chronic exposure based on an ADI
(acceptable daily intake) of 0.055 mg/kg/day.  The ADI is based on the
NOAEL of 5.5 mg/kg in males from the 104-week combined rat
chronic/carcinogenicity study.  A safety factor of 100 was applied, 10
for intraspecies variability and 10 for interspecies difference.  All
estimates are well below the ADI, the highest estimate was the children
1-2 years group with an estimate of 0.17%.  The overall population and
subgroups are well below the ADI.  The results of the analyses are
summarized below.

CHRONIC Dietary risk (DEEMTM) Analyses of Ethaboxam

Population Subgroup	% NOAEL

US population	0.03

All infants	0.03

Non-Nursing infants	0.03

Children (1-2 yrs)	0.17

Children (1-6 yrs)	0.12

Females 20+ 	0.02

2. 	Non-dietary exposure. 

LG Life Sciences, Ltd. does not request registrations for uses of
ethaboxam that produce non-dietary exposure in the U.S. 

D.  	Cumulative Effects

The potential for cumulative effects of ethaboxam and other substances
that have a common mechanism of toxicity has also been considered. 
There is no reliable information to indicate that toxic effects produced
by ethaboxam would be cumulative with those of any other chemical
including another pesticide.  Therefore, LG Life Sciences believes it is
appropriate to consider only the potential risks of ethaboxam in an
aggregate risk assessment.

E.  	Safety Determinations

1.  	U.S. population.

Using the acute exposure assumptions and the proposed RfD described
above, the dietary exposure to ethaboxam for the U.S. population (48
states, all seasons) was calculated to be 9 % of the reference dose of
10 mg/kg/day. Therefore, taking into account the proposed use on grapes
it can be concluded with reasonable certainty that residues of ethaboxam
in raw agricultural commodities and processed commodities on grapes will
not result in unacceptable levels of human health risk.

2.  	Infants and children.

FFDCA Section 407 provides that EPA shall apply an additional safety
factor for infants and children to account for prenatal and postnatal
toxicity and the completeness of the database.  Only when there is no
indication of increased sensitivity of infants and children and when the
database is complete, may the extra safety factor be removed.  In the
case of ethaboxam, the toxicology database is complete.  There is no
indication of increased sensitivity in the database overall, and
specifically, there is no indication of increased sensitivity in the
developmental and multi-generation reproductive toxicity studies. 
Therefore, LG Life Science concludes that there is no need for an
additional safety factor; the RfD of 0.1mg/kg/day is protective of
infants and children.

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 n (1-6) was calculated to be 37% of the reference dose of 0.1 mg/kg
bw/day.  Using the chronic exposure assumptions and proposed ADI
described above, the dietary exposure for infants and children (1-6) was
calculated to be 0.12% of the ADI of 0.055 mg/kg/day.

F.	 International Tolerances

No Codex Maximum Residue Levels (MRLs) have been established for
residues of Ethaboxam on any crops at this time.  There are proposed
MRLs for EU (Europe) based on a program conducted in 2001-2002 in
France, Germany, Italy, and Spain.  The MRLs are as follows; grapes at
3.5 ppm, young wine at 2.5 ppm, wine at 1.3 ppm, grape juice at 2.3 ppm,
and raisins at 5.8 ppm.