Document ID: EPA-HQ-OPP-2008-0343-0003
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2008-05-14T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

PC Code: 055801

DP Barcodes: DP 351119

MEMORANDUM					DATE: April 9, 2008

							

	

SUBJECT:	Revised Drinking Water Exposure Assessment for the Human Health
Risk Assessment for the Reregistration Decision Eligibility (RED) of
Naphthalene Incorporating the Registrant’s Error Correction Comments

FROM:	Mark Corbin, Senior Environmental Scientist

		Environmental Risk Branch 3

		Environmental Fate and Effects Division (7507P)

THRU:	Tom Bailey, Acting Branch Chief

Environmental Risk Branch 3

		Environmental Fate and Effects Division (7507P)

TO:		Molly Clayton

		Reregistration Branch 3

		Special Review and Reregistration Division (7508P)

This memorandum transmits the Environmental Fate and Effects
Division’s (EFED) drinking water exposure assessment for naphthalene. 
This revised memorandum incorporates the registrants (Landis
International, Inc.) error correction comments on the Drinking Water
Assessment dated April 25, 2007 (DP Barcode 339118).  No acceptable
environmental fate data have been submitted to support the registration
of naphthalene.  Several environmental fate studies (aerobic soil and
aqueous photolysis) were submitted but deemed to be unacceptable for
risk assessment purposes due to poor material balances, inadequate
sample intervals, and issues with volatile trapping and therefore have
not been used in this assessment.  A single overview of open literature
data (MRID 45346801) provided supplemental data on the
adsorption/desorption and aerobic soil metabolism properties of
naphthalene.

For sorption a total of 13 open literature studies were submitted and
summarized and indicated that the solubility of naphthalene ranged from
30 mg/L to 31.7 mg/L and that the Koc ranged from 200 to 1470 for a
variety of soils from North America, Europe and China.     The study
author concluded from this review that naphthalene was bound relatively
rapidly to soils with a sustained desorption over days to weeks.  For
biodegradation a total of 15 open literature studies were submitted and
reviewed and found that naphthalene degraded with aerobic soil
metabolism half lives between 3.5 and 40 days with no appreciable
degradation under anaerobic conditions.  Possible degradation processes
affecting naphthalene (and PAH’s in general) include volatilization,
photo-oxidation, bioaccumulation, adsorption, leaching, and microbial
degradation.  

As a check on these data the USEPA’s Estimation Programs Interface
(EPI) Suite, or EPISuite (version 3.2 available at   HYPERLINK
"http://www.epa.gov/oppt/exposure/pubs/episuitedl.htm" 
http://www.epa.gov/oppt/exposure/pubs/episuitedl.htm ) was used to
estimate values for aerobic soil metabolism half life and Koc.  The
estimated values derived were 75 days for aerobic soil metabolism (based
on the level III fugacity model) and 1837 for Koc.  These estimated
values are not used as model inputs but provide context to the values
from the open literature survey and suggest that these data are
reasonable approximations of naphthalene fate.  

A number of degradates were identified in the various open literature
studies.  The study author proposed a degradation pathway for
naphthalene which ultimately resulted in catechol.  Transitional
degradates included cis-1,2-dihydroxy-1,2-dihydronaphthalene,
1,2-dihydroxy-naphthalene, 2-hydroxchromene-2-carboxylate (HCCA),
trans-o-hydroxy-benzylidenpyruvate (tHBPA), salicyladehyde, and
salicylate.  However, there is no environmental fate data for these
degradates and therefore, exposure estimates are for parent only.  

Aquatic Exposure Modeling

Typically, EFED relies on an integrated approach for conducting exposure
assessments that relies on an analysis of both monitoring data and
modeling.  In the case of naphthalene, no monitoring data are available.
 Therefore, this assessment relies solely on modeling.     

EFED uses a tiered system of pesticide exposure modeling to assess risk
of a pesticide to the environment.  Each of the tiers is designed to
screen out pesticides by requiring higher, more complex levels of
investigation only for those that have not passed the next lower tier. 
In this case, EFED has conducted a Tier I aquatic exposure assessment
relying on FIRST.  FIRST (FQPA Index Reservoir Screening Tool, version
1) is a program to calculate acute as well as longer-term estimated
environmental concentration (EEC) values. It considers reduction in
dissolved pesticide concentration due to adsorption of pesticide to soil
or sediment, incorporation, degradation in soil before washoff to a
water body, direct deposition of spray drift into the water body, and
degradation of the pesticide within the water body. 

Given the limited use of this compound and the fact that it is applied
to in a band around ornamentals, planting beds and gardens as a
repellent, an adjustment to the modeled EEC was made assuming 4.1% of a
typical residential lot would be treated.  The 4.1%, or percent of lot
treated, was derived using data from the United States 2000 Census that
indicated that a typical lot size is represented by a ¼ acre lot
(10,890 square feet) with a typical house with a footprint of 1000
square feet.  Assuming this house is symmetrical yields a perimeter of
126.4 ft (31.6 ft on each side).  It is then assumed that the ornamental
beds will be present in a 10 foot band around the house yielding a
perimeter of 206.4 ft.  Assuming that a typical application band is 1
foot (12 inches) yields a typical treated area of 206.4 square feet.  In
addition, it is assumed that a garden will typically be present and thus
an additional calculation was made to account for the potential
treatment to the perimeter of the garden.  In this case, it is assumed
that a typical garden would be 20 feet by 100 feet for a perimeter of
240 feet.  Assuming a one foot band of naphthalene around this garden
yields a total treated area of 240 square feet.  Adding these together
and dividing by the total ¼ acre lot area yields a percent lot treated
of 4.1%.  The resultant FIRST EEC has been adjusted by this factor.  

  SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1 The appropriate FIRST input
parameters were selected from the environmental fate data submitted by
the registrant and in accordance with US EPA-OPP EFED water model
parameter selection guidelines, Guidance for Selecting Input Parameters
in Modeling the Environmental Fate and Transport of Pesticides, Version
2.3, February 28, 2002.  These parameters are summarized in Table II.1. 
Results of FIRST modeling are presented in Table II.2.  

Table II.1 Summary of GENEEC2 environmental fate data used for aquatic
exposure inputs for naphthalene

Fate Property	Value	MRID (or source)

Solubility in Water	31 ug/l	Product Chemistry

Photolysis in Water	stable	Assumed

Aerobic Soil Metabolism Half-lives	32.6 days (90th % of 9 values)	MRID
45346801

Hydrolysis	stable	Assumed

Aerobic Aquatic Metabolism (water column)	65.2 days 	Twice the aerobic
soil metabolism rate constant

Koc	131	MRID 45346801

Application Efficiency	100 % for granular1	default value

Spray Drift Fraction	0 % for granular	default value

1 – Although not specified on labels it is assumed that only ground
granular applications are allowed 

Two scenarios were modeled to represent a high naphthalene use scenario
and at low use scenarios.  The high use scenario was modeled at 10.8
lbs/acre with six applications per year, while the low use scenario was
modeled at 0.56 lbs/acre with six applications per year.  The
application method was modeled as ground application with a granular
formulation.  The results of the Tier I modeling is summarized in Table
II.2.  

Table II.2  Results of GENEEC2 Modeling for Naphthalene Use on
Ornamentals*

Use Site	Application Rate (lbs/acre)	Number of Applications

(interval)	Peak EEC (ppb)	Annual Average EEC (ppb)

Ornamentals for rabbit & dog repellent	10.8

	6

(2 months)	43.4	6.5

Ornamentals for snake repellent	0.56	6

(2 months)	2.2	0.3

* Note these EECs are adjusted by 4.1% to account for the fact that the
product is only applied in a band around ornamental, planting beds, and
gardens

Unaccounted for in this exposure assessment is the fact that naphthalene
is volatile.  No product chemistry data were available but an estimate
of the vapor pressure was made using EpiSuite.  EpiSuite reported an
experimentally derived value for vapor pressure of 8.5 x10-2 mm Hg
(which is consistent with the registrant reported value of 10.5 Pa, or
7.8 x 10-2 mm Hg) and a Henry’s Law Constant of 0.00044 atm-m3/mol
suggesting that naphthalene is volatile.  Given the potential volatility
of this compound and the fact that the Tier I model used to estimate
exposure does not account for volatility as a route of dissipation it is
likely that the exposure estimates derived above are over-predictions of
potential exposure.  It is unclear from the open literature data whether
degradation in the studies reported accounted for the fraction lost due
to volatility or not.  

Finally, Sci-Grow modeling was conducted for both use scenarios to
provide an estimate of the potential loading of naphthalene to
groundwater.  Sci-Grow modeling relied on similar model inputs with the
exception of aerobic soil metabolism which uses the average half life of
14 days.  The results are summarized in Table II.3.  



Table II.3.  Results of Sci-Grow modeling for naphthalene used on
ornamentals at the high and low application rates

Use Site	Application Rate (lbs/acre)	Number of Applications

(interval)	Annual Average EEC (ppb)

Ornamentals for rabbit & dog repellent	10.8	6

(2 months)	4.5

Ornamentals for snake repellent	0.56	6

(2 months)	0.2

 See   HYPERLINK "http://www.epa.gov/oppefed1/models/water/index.htm" 
http://www.epa.gov/oppefed1/models/water/index.htm  for more details.

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