AGENDA

FIFRA SCIENTIFIC ADVISORY PANEL (SAP)

	OPEN MEETING

	

July 23, 2010

FIFRA SAP WEB SITE http://www.epa.gov/scipoly/sap/

OPP Docket Telephone: (703) 305-5805

Docket Number: EPA-HQ- OPP-2009-0378

U.S. Environmental Protection Agency

Conference Center - Lobby Level

One Potomac Yard (South Bldg.)

2777 S. Crystal Drive, Arlington, VA 22202 

Scientific Issues related to the Comparative Adult and Juvenile
Sensitivity Toxicity Protocols for Pyrethroids

Please note that all times are approximate 

(See note at the end of the Agenda)

		Friday, July 23, 2010

8:30 A.M.	Opening of Meeting and Administrative Procedures by Designated
Federal Official – Sharlene Matten, Ph.D., Designated Federal
Official, Office of Science Coordination and Policy, EPA

8:35 A.M.	Introduction and Identification of Panel Members – 

	Steven Heeringa, Ph.D., Chair, FIFRA Scientific Advisory Panel

8:40 A.M.	Welcome and Opening Remarks – Tina Levine, Ph.D., Director,
Health Effects Division, Office of Pesticide Programs, EPA 

9:00 A.M.	Regulatory Overview and Objectives – Edward Scollon, Ph.D.,

	Health Effect Division, Office of Pesticide Programs, EPA

10:00  A.M.	BREAK

10:15  A.M.	PUBLIC COMMENTS 

11:15  A.M.	Charge Question 1

Auditory Startle Response or Acoustic Startle Reflex (ASR)

1.1      The auditory startle is a commonly used technique to assess
neurobehavioral effects in rats.  Auditory startle reflex is a motor
reflex characterized by a sequence of reflexive muscle movements
elicited by sudden and intense acoustic stimuli measured by a change in
motor output. The proposed reflex path is short, consisting of the
auditory nerve, posteroventral cochlear nucleus, the nucleus reticularis
pontis caudalis, and motor neurons in the spinal cord   ADDIN EN.CITE
<EndNote><Cite><Author>Davis</Author><Year>1982</Year><RecNum>306</RecNu
m><DisplayText>(Davis et al.
1982)</DisplayText><record><rec-number>306</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">306</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>M
Davis</author><author>DS Gendelman</author><author>MD
Tischler</author><author>PM
Gendelman</author></authors></contributors><titles><title>a primary
acoustic startle circuit; lesion and stimulation
studies</title><secondary-title>J
Neurosci</secondary-title></titles><periodical><full-title>J
Neurosci</full-title></periodical><pages>791-805</pages><volume>6</volum
e><dates><year>1982</year></dates><urls></urls></record></Cite></EndNote
> (Davis et al. 1982) .  This mechanism is susceptible to a variety of
drugs and toxicants making the reflex a useful model of sensorimotor
reactivity across animal taxa, including rat and human   ADDIN EN.CITE
<EndNote><Cite><Author>Lee</Author><Year>1996</Year><RecNum>307</RecNum>
<DisplayText>(Lee et al.
1996)</DisplayText><record><rec-number>307</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">307</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Lee,
Younglim</author><author>Lopez, Dolores E.</author><author>Meloni,
Edward G.</author><author>Davis,
Michael</author></authors></contributors><titles><title>A Primary
Acoustic Startle Pathway: Obligatory Role of Cochlear Root Neurons and
the Nucleus Reticularis Pontis Caudalis</title><secondary-title>J.
Neurosci.</secondary-title></titles><periodical><full-title>J.
Neurosci.</full-title></periodical><pages>3775-3789</pages><volume>16</v
olume><number>11</number><dates><year>1996</year><pub-dates><date>June
1,
1996</date></pub-dates></dates><urls><related-urls><url>http://www.jneur
osci.org/cgi/content/abstract/16/11/3775</url></related-urls></urls></re
cord></Cite></EndNote> (Lee et al. 1996) .  With regard to pyrethroids,
auditory startle data in adult rats have demonstrated differing response
patterns related to pyrethroid structure   ADDIN EN.CITE   ADDIN
EN.CITE.DATA   (Crofton and Reiter 1984; Tilson et al. 1985; Crofton and
Reiter 1988; Hijzen et al. 1988; Hijzen and Slangen 1988) ; Type I
pyrethroids produced an increase in startle amplitude and Type II
pyrethroids produced a decrease in startle amplitude.  In addition, ASR
has been used to demonstrate age-dependent toxicity in rats following
high oral doses of pyrethroids   ADDIN EN.CITE
<EndNote><Cite><Author>Sheets</Author><Year>2000</Year><RecNum>343</RecN
um><DisplayText>(Sheets et al. 1994; Sheets
2000)</DisplayText><record><rec-number>343</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">343</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>LP
Sheets</author></authors></contributors><titles><title>A consideration
of age-dependent differences in susceptability to organophosphorus and
pyrethroid
insecticides</title><secondary-title>Neurotoxicology</secondary-title></
titles><periodical><full-title>NeuroToxicology</full-title></periodical>
<pages>57-63</pages><volume>21</volume><dates><year>2000</year></dates><
urls></urls></record></Cite><Cite><Author>Sheets</Author><Year>1994</Yea
r><RecNum>133</RecNum><record><rec-number>133</rec-number><foreign-keys>
<key app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">133</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Sheets, L.
P.</author><author>Doherty, J. D.</author><author>Law, M.
W.</author><author>Reiter, L. W.</author><author>Crofton, K.
M.</author></authors></contributors><titles><title>Age-Dependent
Differences in the Susceptibility of Rats to
Deltamethrin</title><secondary-title>Toxicology and Applied
Pharmacology</secondary-title></titles><pages>186-190</pages><volume>126
</volume><number>1</number><dates><year>1994</year></dates><isbn>0041-00
8X</isbn><urls><related-urls><url>http://www.sciencedirect.com/science/a
rticle/B6WXH-45PVPD7-1M/2/3fc364aacc860e51234f16417c460620</url></relate
d-urls></urls></record></Cite></EndNote> (Sheets et al. 1994; Sheets
2000) .  Therefore, ASR is a potentially sensitive measure to evaluate
differences in neurobehavioral effects between adults and pups.  

Since ASR is a behavioral measurement, it is important to consider
development, dose-response and variability during interpretation of the
results.  In rats, the onset of ASR response corresponds to the
development of the external auditory meatus.  In the rat, this usually
occurs between 13 and 16 days of age.  Sheets et al.   ADDIN EN.CITE
<EndNote><Cite
ExcludeAuth="1"><Year>1988</Year><RecNum>556</RecNum><DisplayText>(1988)
</DisplayText><record><rec-number>556</rec-number><foreign-keys><key
app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">556</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>LP
Sheets</author><author>KF Dean</author><author>LW
Reiter</author></authors></contributors><titles><title>Ontogeny of the
acoustic startle response and sensitization to background noise in the
rat</title><secondary-title>Behavioral
Neuroscience</secondary-title></titles><periodical><full-title>Behaviora
l
Neuroscience</full-title></periodical><pages>706-13</pages><volume>102</
volume><number>5</number><dates><year>1988</year></dates><urls></urls></
record></Cite></EndNote> (1988)  have shown the ability of rats to
respond to ASR as early as PND 13, however, the amplitude of response
continued to increase through PND 21.  Pyrethroids modify the voltage
gated sodium channels in the central nervous system and therefore the
brain is considered the major target organ for toxicity.  Kim et al.  
ADDIN EN.CITE <EndNote><Cite
ExcludeAuth="1"><Year>2010</Year><RecNum>548</RecNum><DisplayText>(2010)
</DisplayText><record><rec-number>548</rec-number><foreign-keys><key
app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">548</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Kim, K.
B.</author><author>Anand, S. S.</author><author>Kim, H.
J.</author><author>White, C. A.</author><author>Fisher, J.
W.</author><author>Tornero-Velez, R.</author><author>Bruckner, J.
V.</author></authors></contributors><auth-address>Department of
Pharmaceutical Engineering, Inje University, Gimhae, Gyongam 621-749,
Korea.</auth-address><titles><title>Age, dose, and time-dependency of
plasma and tissue distribution of deltamethrin in immature
rats</title><secondary-title>Toxicol
Sci</secondary-title></titles><periodical><full-title>Toxicol
Sci</full-title></periodical><pages>354-68</pages><volume>115</volume><n
umber>2</number><edition>2010/03/10</edition><dates><year>2010</year><pu
b-dates><date>Jun</date></pub-dates></dates><isbn>1096-0929
(Electronic)&#xD;1094-2025
(Linking)</isbn><accession-num>20211939</accession-num><urls><related-ur
ls><url>http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&amp;d
b=PubMed&amp;dopt=Citation&amp;list_uids=20211939</url></related-urls></
urls><electronic-resource-num>kfq074
[pii]&#xD;10.1093/toxsci/kfq074</electronic-resource-num><language>eng</
language></record></Cite></EndNote> (2010)  determined the distribution
of deltamethrin, a Type II pyrethroid, in brain, fat, liver, plasma, and
muscle in PND 10, 21, 40, and 90 rats for up to 510 hours.  Brain
concentrations in PND 10 pups were elevated for a longer time relative
to the adults.  This suggests that pyrethroid kinetics in the brain of
pups may not mirror those of adult rats.  The Kim et al.   ADDIN EN.CITE
<EndNote><Cite
ExcludeAuth="1"><Year>2010</Year><RecNum>548</RecNum><DisplayText>(2010)
</DisplayText><record><rec-number>548</rec-number><foreign-keys><key
app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">548</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Kim, K.
B.</author><author>Anand, S. S.</author><author>Kim, H.
J.</author><author>White, C. A.</author><author>Fisher, J.
W.</author><author>Tornero-Velez, R.</author><author>Bruckner, J.
V.</author></authors></contributors><auth-address>Department of
Pharmaceutical Engineering, Inje University, Gimhae, Gyongam 621-749,
Korea.</auth-address><titles><title>Age, dose, and time-dependency of
plasma and tissue distribution of deltamethrin in immature
rats</title><secondary-title>Toxicol
Sci</secondary-title></titles><periodical><full-title>Toxicol
Sci</full-title></periodical><pages>354-68</pages><volume>115</volume><n
umber>2</number><edition>2010/03/10</edition><dates><year>2010</year><pu
b-dates><date>Jun</date></pub-dates></dates><isbn>1096-0929
(Electronic)&#xD;1094-2025
(Linking)</isbn><accession-num>20211939</accession-num><urls><related-ur
ls><url>http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&amp;d
b=PubMed&amp;dopt=Citation&amp;list_uids=20211939</url></related-urls></
urls><electronic-resource-num>kfq074
[pii]&#xD;10.1093/toxsci/kfq074</electronic-resource-num><language>eng</
language></record></Cite></EndNote> (2010)  study emphasizes the
importance of determining the appropriate time course of effects (i.e.,
time-to-peak-effect and/or time-to-tissue-recovery) in both adult and
non-adult lifestages prior to measuring ASR responses.  Additionally,
the standard deviation for peak amplitude, the ASR measure proposed by
the PPTWG, can vary greatly in guideline DNT studies (20-125%) and
literature reviews   ADDIN EN.CITE
<EndNote><Cite><Author>Raffaele</Author><Year>2004</Year><RecNum>545</Re
cNum><DisplayText>(Raffaele et al.
2004)</DisplayText><record><rec-number>545</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">545</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Raffaele, Kathleen
C.</author><author>Fisher Jr, J. Edward</author><author>Hancock,
Scott</author><author>Hazelden, Keith</author><author>Sobrian, Sonya
K.</author></authors></contributors><titles><title>Determining normal
variability in a developmental neurotoxicity test A report from the ILSI
Research Foundation/Risk Science Institute expert working group on
neurodevelopmental endpoints</title><secondary-title>Neurotoxicology and
Teratology</secondary-title></titles><periodical><full-title>Neurotoxico
logy and
Teratology</full-title></periodical><pages>288-325</pages><volume>30</vo
lume><number>4</number><keywords><keyword>Developmental neurotoxicity
testing</keyword><keyword>DNT</keyword><keyword>Variability in DNT
testing</keyword><keyword>Regulatory
testing</keyword></keywords><dates><year>2004</year><pub-dates><date>200
8/8//</date></pub-dates></dates><isbn>0892-0362</isbn><urls><related-url
s><url>http://www.sciencedirect.com/science/article/B6T9X-4RHWP06-1/2/81
993766065e550b9b791ec103e19127</url></related-urls></urls></record></Cit
e></EndNote> (Raffaele et al. 2004) .  However, this variability can be
reduced down to 20-30% if the studies are conducted in proven
laboratories   ADDIN EN.CITE
<EndNote><Cite><Author>Sette</Author><Year>2004</Year><RecNum>543</RecNu
m><DisplayText>(Sette et al.
2004)</DisplayText><record><rec-number>543</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">543</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>W.F.
Sette</author><author>K.M. Crofton</author><author>S.L.
Makris</author><author>J.D. Doherty</author><author>K.C.
Raffaele</author></authors></contributors><titles><title>Auditory
startle reflex habituation in developmental neurotxicity testing; a
cross-laboroatory comparison of control data</title><secondary-title>The
Toxicologist</secondary-title></titles><periodical><full-title>The
Toxicologist</full-title></periodical><pages>275</pages><volume>78</volu
me><dates><year>2004</year></dates><urls></urls></record></Cite></EndNot
e> (Sette et al. 2004) .

The PPTWG is proposing that the ASR provides a robust and sensitive
measure of neurotoxicity and is well suited to assess age-dependent
sensitivity to pyrethroids.  Please comment on the appropriateness of
the ASR technique as a measure of pyrethroid induced toxicity, including
suggestions to assure quality of the study design (i.e., appropriate
time-to-peak response, variability of peak response, etc.) and resulting
data.

Age-dependent toxicity has been observed in rat studies following high
doses (i.e., LD50 studies resulting in 50% mortality of test subjects)
of Type II pyrethroids   ADDIN EN.CITE   ADDIN EN.CITE.DATA  
(Cantalamessa 1993; Sheets et al. 1994; Sheets 2000) .  However, in
sublethal studies using the ASR as a measure of toxicity, ED50 (dose at
which 50% of the test subjects are affected) values were similar between
postnatal day (PND) 21 and adult rats.  These findings suggest that
age-dependent toxicity may only be observed at high doses.  Based on in
vivo   ADDIN EN.CITE
<EndNote><Cite><Author>Cantalamessa</Author><Year>1993</Year><RecNum>342
</RecNum><DisplayText>(Cantalamessa
1993)</DisplayText><record><rec-number>342</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">342</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>F
Cantalamessa</author></authors></contributors><titles><title>Acute
toxicity of two pyrethroids, permethrin and cypermethrin, in neonatal
and adult rats</title><secondary-title>Archives of
Toxicology</secondary-title></titles><pages>510-3</pages><volume>67</vol
ume><dates><year>1993</year></dates><urls></urls></record></Cite></EndNo
te> (Cantalamessa 1993)  and in vitro   ADDIN EN.CITE
<EndNote><Cite><Author>Anand</Author><Year>2006</Year><RecNum>147</RecNu
m><DisplayText>(Anand et al.
2006)</DisplayText><record><rec-number>147</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">147</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Anand, Sathanandam
S.</author><author>Bruckner, James V.</author><author>Haines, Wendy
T.</author><author>Muralidhara, Srinivasa</author><author>Fisher,
Jeffrey W.</author><author>Padilla,
Stephanie</author></authors></contributors><titles><title>Characterizati
on of deltamethrin metabolism by rat plasma and liver
microsomes</title><secondary-title>Toxicology and Applied
Pharmacology</secondary-title></titles><pages>156-166</pages><volume>212
</volume><number>2</number><keywords><keyword>Carboxylesterases</keyword
><keyword>CYP450s</keyword><keyword>Deltamethrin</keyword><keyword>Pyret
hroid metabolism</keyword><keyword>Liver
microsomes</keyword><keyword>Plasma</keyword><keyword>Vmax and
Km</keyword><keyword>Rat</keyword></keywords><dates><year>2006</year></d
ates><isbn>0041-008X</isbn><urls><related-urls><url>http://www.sciencedi
rect.com/science/article/B6WXH-4H45GTM-1/2/ef2038f2560398715f630d868e5a8
9f5</url></related-urls></urls></record></Cite></EndNote> (Anand et al.
2006)  studies, the apparent discrepancy between high- and low-dose
age-dependent toxicity is likely attributable to incomplete maturation
of the enzymes that detoxify pyrethroids in immature animals,
particularly the carboxylesterases and cytochrome P450s.  These
clearance mechanisms are overwhelmed in younger animals given LD50
doses, leading to increased accumulation of the pyrethroids in nervous
tissue and ultimately increased toxicity.  

Carboxylesterases and P450 enzymes are the two major enzyme families
responsible for metabolism of pyrethroids.  In the rat, it has been
shown that carboxylesterase activities are below adult levels at weaning
  ADDIN EN.CITE   ADDIN EN.CITE.DATA   (Moser et al. 1998; Karanth and
Pope 2000; Anand et al. 2006; de Zwart et al. 2008; Yang et al. 2009) . 
Information on the ontogeny of carboxylesterase development in the human
is more limited.  However, increased plasma esterase activity during
postnatal maturation has been reported   ADDIN EN.CITE
<EndNote><Cite><Author>Ecobichon</Author><Year>1973</Year><RecNum>557</R
ecNum><DisplayText>(Ecobichon and Stephens
1973)</DisplayText><record><rec-number>557</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">557</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>DJ
Ecobichon</author><author>DS
Stephens</author></authors></contributors><titles><title>Perinatal
development of human blood esterases</title><secondary-title>Clinical
Pharmacology and
Therapeutics</secondary-title></titles><periodical><full-title>Clinical
Pharmacology and
Therapeutics</full-title></periodical><pages>41-7</pages><volume>14</vol
ume><number>1</number><dates><year>1973</year></dates><urls></urls></rec
ord></Cite></EndNote> (Ecobichon and Stephens 1973) .  In contrast, Pope
et al.   ADDIN EN.CITE <EndNote><Cite
ExcludeAuth="1"><Year>2005</Year><RecNum>404</RecNum><DisplayText>(2005)
</DisplayText><record><rec-number>404</rec-number><foreign-keys><key
app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">404</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Pope, Carey
N.</author><author>Karanth, Subramanya</author><author>Liu,
Jing</author><author>Yan,
Bingfang</author></authors></contributors><titles><title>Comparative
carboxylesterase activities in infant and adult liver and their in vitro
sensitivity to chlorpyrifos oxon</title><secondary-title>Regulatory
Toxicology and
Pharmacology</secondary-title></titles><pages>64-69</pages><volume>42</v
olume><number>1</number><keywords><keyword>Age-related
sensitivity</keyword><keyword>Risk
assessment</keyword><keyword>Organophosphates</keyword><keyword>Detoxifi
cation</keyword></keywords><dates><year>2005</year></dates><isbn>0273-23
00</isbn><urls><related-urls><url>http://www.sciencedirect.com/science/a
rticle/B6WPT-4FJTP9Y-3/2/a80156cc0bd89f6c5c5ea3679101e704</url></related
-urls></urls></record></Cite></EndNote> (2005)  found carboxylesterase
activity in hepatic tissues were similar for humans ranging in age from
2 months to 36 years, however, the sample sizes were small and
variability among the age groups was high.  Maturation of the P450
enzymes shows a similar trend.  2C19, a P450 enzyme which has shown high
pyrethroid metabolic activity   ADDIN EN.CITE
<EndNote><Cite><Author>Godin</Author><Year>2006</Year><RecNum>402</RecNu
m><DisplayText>(Godin et al.
2006)</DisplayText><record><rec-number>402</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">402</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Godin, Stephen
J.</author><author>Scollon, Edward J.</author><author>Hughes, Michael
F.</author><author>Potter, Philip M.</author><author>DeVito, Michael
J.</author><author>Ross, Matthew
K.</author></authors></contributors><titles><title>Species Differences
in the in Vitro Metabolism of Deltamethrin and Esfenvalerate:
Differential Oxidative and Hydrolytic Metabolism by Humans and
Rats</title><secondary-title>Drug Metab
Dispos</secondary-title></titles><pages>1764-1771</pages><volume>34</vol
ume><number>10</number><dates><year>2006</year><pub-dates><date>October
1,
2006</date></pub-dates></dates><urls><related-urls><url>http://dmd.aspet
journals.org/cgi/content/abstract/34/10/1764</url></related-urls></urls>
<electronic-resource-num>10.1124/dmd.106.010058</electronic-resource-num
></record></Cite></EndNote> (Godin et al. 2006) , increases rapidly in
the human during first 2 years of life, whereas numerous P450s examined
in the rat have minimal expression levels through gestation and do not
approach adult levels of expression until PND10 days or later   ADDIN
EN.CITE <EndNote><Cite><Author>de
Zwart</Author><Year>2008</Year><RecNum>403</RecNum><DisplayText>(de
Zwart et al.
2008)</DisplayText><record><rec-number>403</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">403</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>de Zwart,
Loeckie</author><author>Scholten, Martijn</author><author>Monbaliu,
Johan G.</author><author>Annaert, Pieter P.</author><author>Van Houdt,
Jos M.</author><author>Van den Wyngaert, Ilse</author><author>De
Schaepdrijver, Luc M.</author><author>Bailey, Graham
P.</author><author>Coogan, Timothy P.</author><author>Coussement, Werner
C.</author><author>Mannens, Geert
S.</author></authors></contributors><titles><title>The ontogeny of drug
metabolizing enzymes and transporters in the
rat</title><secondary-title>Reproductive
Toxicology</secondary-title></titles><pages>220-230</pages><volume>26</v
olume><number>3-4</number><keywords><keyword>Juvenile
animals</keyword><keyword>Ontogeny</keyword><keyword>Metabolizing
enzymes</keyword><keyword>Transporters</keyword></keywords><dates><year>
2008</year><pub-dates><date>2008/12//</date></pub-dates></dates><isbn>08
90-6238</isbn><urls><related-urls><url>http://www.sciencedirect.com/scie
nce/article/B6TC0-4TMBPSC-3/2/9d9dc93a5df5eb40242776111c859516</url></re
lated-urls></urls></record></Cite></EndNote> (de Zwart et al. 2008) .  

Comparisons between lifestages in the rat and human are difficult
because of the ontogeny of the brain development and metabolizing
enzymes are not an exact match.  However, PND 11 rats are considered to
be close in development to newborn humans and PND 17 rats are believed
to be closer developmentally to human toddlers   ADDIN EN.CITE   ADDIN
EN.CITE.DATA   (Davision and Dobbing 1966; Dobbing and Smart 1974;
Benjamins and McKhann 1981) .  From the aspect of exposure, previous
experience with developing cumulative risk assessments for other
insecticide groups, ongoing work on HED's Standard Operating Procedures
for Residential Pesticide Exposure Assessment, and the Agency's Guidance
on Selecting Age Groups for Monitoring and Assessing Childhood Exposures
for Environmental Contaminants  HYPERLINK
"http://www.epa.gov/raf/publications/guidance-on-selecting-age-groups.ht
m"
http://www.epa.gov/raf/publications/guidance-on-selecting-age-groups.htm
, the Agency believes that children three years old and younger,
particularly those who are mobile (crawling, walking) and who exhibit
hand-to-mouth behavior, have the potential for the greatest exposure to
pyrethroids.  Based on 1) the current understanding that the two major
enzyme families responsible for the metabolism of pyrethroids are below
adult activity levels at weaning (i.e., PND 21); 2) PND 17 rats are
approximately comparable to human toddlers in terms of development; and
3) children younger than 3 years of age are expected to have the
greatest exposures to pyrethroids, the Agency is concerned with the
PPTWG’s proposal to conduct ASR studies in PND 21 rats.  Instead, PND
15 to 17 rats, which have been shown to respond to ASR stimuli   ADDIN
EN.CITE
<EndNote><Cite><Author>Sheets</Author><Year>1988</Year><RecNum>556</RecN
um><DisplayText>(Sheets et al.
1988)</DisplayText><record><rec-number>556</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">556</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>LP
Sheets</author><author>KF Dean</author><author>LW
Reiter</author></authors></contributors><titles><title>Ontogeny of the
acoustic startle response and sensitization to background noise in the
rat</title><secondary-title>Behavioral
Neuroscience</secondary-title></titles><periodical><full-title>Behaviora
l
Neuroscience</full-title></periodical><pages>706-13</pages><volume>102</
volume><number>5</number><dates><year>1988</year></dates><urls></urls></
record></Cite></EndNote> (Sheets et al. 1988) , may better represent the
most susceptible human lifestage.

The PPTWG has proposed to use conduct ASR studies on 21-day old rats. 
Please comment on the appropriateness of this age group in regards to i)
assessing age-dependent toxicity and ii) assessing whether the 21-day
old rat will adequately inform the Agency regarding toxicity as it
relates to children three years of age and younger.   

12:00  P.M.	LUNCH

1:00 P.M. 	Charge Question 1 cont’d

2:00 P.M.	Charge Question 2

Physiologically-Based Pharmacokinetic (PBPK) Modeling

The PPTWG is proposing to use a model developed collaboratively by
EPA’s Office of Research and Development (ORD) and the University of
Georgia as a starting point in their modeling effort.  EPA’s ORD has
published a series of papers that describe the development and
enhancement of pyrethroid PBPK models starting with a deltamethrin model
in rats by Mirfazaelian et al.   ADDIN EN.CITE <EndNote><Cite
ExcludeAuth="1"><Year>2006</Year><RecNum>477</RecNum><DisplayText>(2006)
</DisplayText><record><rec-number>477</rec-number><foreign-keys><key
app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">477</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Mirfazaelian,
A</author><author>Kim, KB</author><author>Anand, SS</author><author>Kim,
HJ</author><author>Tornero-Velez, R</author><author>Bruckner,
JV</author><author>Fisher,
JW</author></authors></contributors><titles><title>Development of a
physiologically based pharmacokinetic model for deltamethrin in the
adult male Sprague-Dawley rat</title><secondary-title>Toxicol
Sci</secondary-title></titles><periodical><full-title>Toxicol
Sci</full-title></periodical><pages>432 -
442</pages><volume>93</volume><number>2</number><dates><year>2006</year>
</dates><urls></urls></record></Cite></EndNote> (2006)  , improved by
Godin et al.  ADDIN EN.CITE <EndNote><Cite
ExcludeAuth="1"><Year>2010</Year><RecNum>542</RecNum><DisplayText>(2010)
</DisplayText><record><rec-number>542</rec-number><foreign-keys><key
app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">542</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Godin, Stephen
J.</author><author>DeVito, Michael J.</author><author>Hughes, Michael
F.</author><author>Ross, David G.</author><author>Scollon, Edward
J.</author><author>Starr, James M.</author><author>Setzer, R.
Woodrow</author><author>Conolly, Rory B.</author><author>Tornero-Velez,
Rogelio</author></authors></contributors><titles><title>Physiologically
Based Pharmacokinetic Modeling of Deltamethrin: Development of a Rat and
Human Diffusion-Limited Model</title><secondary-title>Toxicol.
Sci.</secondary-title></titles><periodical><full-title>Toxicol.
Sci.</full-title></periodical><pages>330-343</pages><volume>115</volume>
<number>2</number><dates><year>2010</year><pub-dates><date>June 1,
2010</date></pub-dates></dates><urls><related-urls><url>http://toxsci.ox
fordjournals.org/cgi/content/abstract/115/2/330</url></related-urls></ur
ls><electronic-resource-num>10.1093/toxsci/kfq051</electronic-resource-n
um></record></Cite></EndNote> (2010) , modified for permethrin by
Tornero-Velez et al. (in prep.), and finally expanded to include age-
and chemical-dependent parameters by Tornero-Velez et al.   ADDIN
EN.CITE <EndNote><Cite
ExcludeAuth="1"><Year>2010</Year><RecNum>541</RecNum><DisplayText>(2010)
</DisplayText><record><rec-number>541</rec-number><foreign-keys><key
app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">541</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Rogelio
Tornero-Velez</author><author>Ahmad
Mirfazaelian</author><author>Kyu-Bong Kim</author><author>Sathanandam S.
Anand</author><author>Hyo J. Kim</author><author>Wendy T.
Haines</author><author>James V, Bruckner</author><author>Jeffrey W.
Fisher</author></authors></contributors><titles><title>Evaluation of
deltamethrin kinetics and dosimetry in the maturing rat using a PBPK
model</title><secondary-title>Toxicol Appl
Pharmacol</secondary-title></titles><periodical><full-title>Toxicol Appl
Pharmacol</full-title></periodical><pages>208-17</pages><volume>244</vol
ume><dates><year>2010</year></dates><urls></urls></record></Cite></EndNo
te> (2010) .  In 2007, ORD and OPP jointly presented an issue paper to
the SAP   ADDIN EN.CITE
<EndNote><Cite><Author>USEPA</Author><Year>2007</Year><RecNum>561</RecNu
m><DisplayText>(USEPA
2007)</DisplayText><record><rec-number>561</rec-number><foreign-keys><ke
y app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">561</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>USEPA</author></aut
hors></contributors><titles><title>Assessing Approaches for the
Development of PBPK Models of Pyrethroid Pesticides.
www.epa.gov/scipoly/sap/meetings/2007/august/pyrethroidpbpk_sap_2007_fin
alv1.pdf</title></titles><dates><year>2007</year></dates><urls></urls></
record></Cite></EndNote> (USEPA 2007)  which described an approach for
using a generic model structure with chemical specific parameters for
pyrethroids.  The “family modeling” approach was endorsed by the SAP
and has been successfully applied in the above PBPK efforts.  The Agency
believes that it is both reasonable and scientifically sound to use the
Tornero-Velez et al.   ADDIN EN.CITE <EndNote><Cite
ExcludeAuth="1"><Year>2010</Year><RecNum>541</RecNum><DisplayText>(2010)
</DisplayText><record><rec-number>541</rec-number><foreign-keys><key
app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">541</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Rogelio
Tornero-Velez</author><author>Ahmad
Mirfazaelian</author><author>Kyu-Bong Kim</author><author>Sathanandam S.
Anand</author><author>Hyo J. Kim</author><author>Wendy T.
Haines</author><author>James V, Bruckner</author><author>Jeffrey W.
Fisher</author></authors></contributors><titles><title>Evaluation of
deltamethrin kinetics and dosimetry in the maturing rat using a PBPK
model</title><secondary-title>Toxicol Appl
Pharmacol</secondary-title></titles><periodical><full-title>Toxicol Appl
Pharmacol</full-title></periodical><pages>208-17</pages><volume>244</vol
ume><dates><year>2010</year></dates><urls></urls></record></Cite></EndNo
te> (2010)  PBPK model as the starting point for the PPTWG effort to
build PBPK models for pyrethroids to assess young children. 
Furthermore, the PPTWG is proposing to develop PBPK models using in
vitro and in vivo rat data, and then using human in vitro data to inform
model to predict human internal dosimetry, similar to the approach which
was previously supported by the 2007 SAP.

  

The PPTWG proposes to increase the complexity of the Tornero-Velez et
al.   ADDIN EN.CITE <EndNote><Cite
ExcludeAuth="1"><Year>2010</Year><RecNum>541</RecNum><DisplayText>(2010)
</DisplayText><record><rec-number>541</rec-number><foreign-keys><key
app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">541</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Rogelio
Tornero-Velez</author><author>Ahmad
Mirfazaelian</author><author>Kyu-Bong Kim</author><author>Sathanandam S.
Anand</author><author>Hyo J. Kim</author><author>Wendy T.
Haines</author><author>James V, Bruckner</author><author>Jeffrey W.
Fisher</author></authors></contributors><titles><title>Evaluation of
deltamethrin kinetics and dosimetry in the maturing rat using a PBPK
model</title><secondary-title>Toxicol Appl
Pharmacol</secondary-title></titles><periodical><full-title>Toxicol Appl
Pharmacol</full-title></periodical><pages>208-17</pages><volume>244</vol
ume><dates><year>2010</year></dates><urls></urls></record></Cite></EndNo
te> (2010)  PBPK model by modifying some aspects.  For example, the
PPTWG is proposing to:

Predict intestinal permeability through the use of Ussing Chamber
technique with rat cells and human Caco-2 cells, with the potential to
increase the number of compartments within the intestinal tract

In vitro determination of partition coefficients

Obtain estimates of protein binding

Please comment on the proposed modifications to the Tornero-Velez et al.
  ADDIN EN.CITE <EndNote><Cite
ExcludeAuth="1"><Year>2010</Year><RecNum>541</RecNum><DisplayText>(2010)
</DisplayText><record><rec-number>541</rec-number><foreign-keys><key
app="EN"
db-id="zdpes0tpafsdwre0ssb5w9si25trr2fsa9wr">541</key></foreign-keys><re
f-type name="Journal
Article">17</ref-type><contributors><authors><author>Rogelio
Tornero-Velez</author><author>Ahmad
Mirfazaelian</author><author>Kyu-Bong Kim</author><author>Sathanandam S.
Anand</author><author>Hyo J. Kim</author><author>Wendy T.
Haines</author><author>James V, Bruckner</author><author>Jeffrey W.
Fisher</author></authors></contributors><titles><title>Evaluation of
deltamethrin kinetics and dosimetry in the maturing rat using a PBPK
model</title><secondary-title>Toxicol Appl
Pharmacol</secondary-title></titles><periodical><full-title>Toxicol Appl
Pharmacol</full-title></periodical><pages>208-17</pages><volume>244</vol
ume><dates><year>2010</year></dates><urls></urls></record></Cite></EndNo
te> (2010)  model as described in sections 4.3 of the PPTWG proposal. 
Please include in 

your comments consideration for balancing potentially improved
performance resulting from the increased complexity with model
parsimony. 

2.2   	Microsomal incubation studies have been used to inform the
pyrethroid PBPK models developed by ORD (Mirfazaelian et al. 2006;
Scollon et al. 2009; Godin et al. 2010; Tornero-Velez et al. 2010;
Tornero-Velez in prep.). The PPTWG has proposed to use intact
hepatocytes instead because they may provide a better prediction of
metabolism compared to microcellular fractions (Hewitt et al. 2007).
Additionally, the PPTWG is proposing to compare the clearance activity
of human hepatocytes and microsomal fractions for several age groups.
However, the Agency notes that there are a limited number of human
hepatocyte samples available to inform the PBPK model. Pooled human
microsomes are available representing larger segments of the population
relative to hepatocyte availability. The Working Group suggests
characterization of the hepatocytes (i.e., cypP450 and esterase
composition) and establishing a relationship between hepatocytes and
microsomal fraction activities may reduce model uncertainty in light of
limited data. 

Please comment on the strengths and weaknesses of the PPTWG proposal to
use hepatocytes in the PBPK effort, including the potential for
hepatocytes to decrease uncertainty of model predictions in light of
limited data.

3:15 P.M.	BREAK

3:30 P.M.	Charge Question 3

Alternative Study Design(s) For Evaluating Age Differences in
Pharmacokinetics

The Agency gives special consideration to the potential pre- and
postnatal lifestages regarding potential exposure to pesticides. 
Pre-natal exposure to pyrethroids has been evaluated extensively in over
80 developmental toxicity, reproductive toxicity, and DNT test guideline
studies and no sensitivity from in utero exposure has been observed.  As
previously described, there are gaps in knowledge surrounding the
potential for post-natal sensitivity and, as described in Question 1.2,
the Agency considers children less than 3 years of age to be the most
susceptible population.  The PPTWG has proposed a robust PBPK model
development effort to describe pyrethroid dosimetry across several
lifestages; however, these models will not be ready for use by the
Agency until approximately 2013.  

Are there alternative approaches using empirical or data generation
techniques potentially requiring less time than the PBPK effort proposed
by the PPTWG for evaluating the potential for post-natal sensitivity,
particularly with respect to differences in pharmacokinetic profiles,
that could be used by the Agency?

5:00 P.M.	Adjourn

Please be advised that agenda times are approximate; when the discussion
for one topic is completed, discussions for the next topic will begin. 
For further information, please contact the Designated Federal Official
for this meeting, Dr. Sharlene Matten, via telephone: (202)-564-0130;
fax: (202) 564-8382; or email:   HYPERLINK
"mailto:matten.sharlene@epa.gov"  matten.sharlene@epa.gov .

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