SEQ CHAPTER \h \r 1 United States			Prevention, Pesticides		EPA
738-R-06-007

Environmental Protection		and Toxic Substances		August 2006

Agency				(7510P)

Reregistration

Eligibility Decision

(RED) for Chlorine Dioxide and Sodium Chlorite (Case 4023)

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

CERTIFIED MAIL

Dear Registrant:

	This is to inform you that the Environmental Protection Agency
(hereafter referred to as EPA or the Agency) has completed its review of
the available data and public comments received related to the draft
risk assessments for the antimicrobials, chlorine dioxide and sodium
chlorite.   SEQ CHAPTER \h \r 1  The enclosed Reregistration Eligibility
Decision (RED) document was approved on August 3, 2006.  Public comments
and additional data received were considered in this decision.

Based on its review, EPA is now publishing its Reregistration
Eligibility Decision (RED) and risk management decision for chlorine
dioxide and sodium chlorite and the associated human health and
environmental risks.  A Notice of Availability will be published in the
Federal Register announcing the publication of the RED.

The RED and supporting risk assessments for chlorine dioxide are
available to the public in EPA’s Pesticide Docket EPA-HQ-OPP-2006-0328
at:   HYPERLINK "http://www.regulations.gov"  http://www.regulations.gov
.

The chlorine dioxide and sodium chlorite RED was developed through
EPA’s public participation process, published in the Federal Register
on April 26, 2006, which provides opportunities for public involvement
in the Agency’s pesticide tolerance reassessment and reregistration
programs.  Developed in partnership with USDA and with input from
EPA’s advisory committees and others, the public participation process
encourages robust public involvement starting early and continuing
throughout the pesticide risk assessment and risk mitigation
decision-making process.  The public participation process encompasses
full, modified, and streamlined versions that enable the Agency to
tailor the level of review to the level of refinement of the risk
assessments, as well as to the amount of use, risk, public concern, and
complexity associated with each pesticide.  Using the public
participation process, EPA is attaining its strong commitment to both
involve the public and meet statutory deadlines.

Please note that the chlorine dioxide and sodium chlorite risk
assessment and the attached RED document concern only these particular
pesticides.  This RED presents the Agency’s conclusions on the
dietary, drinking water, residential, occupational and ecological risks
posed by exposure to chlorine dioxide and sodium chlorite alone.  This
document also contains both generic and product-specific data that the
Agency intends to require in Data Call-Ins (DCIs).  Note that DCIs, with
all pertinent instructions, will be sent to registrants at a later date.
 Additionally, for product-specific DCIs, the first set of required
responses will be due 90 days from the receipt of the DCI letter.  The
second set of required responses will be due eight months from the
receipt of the DCI letter.

As part of the RED, the Agency has determined that chlorine dioxide and
sodium chlorite will be eligible for reregistration provided that all
the conditions identified in this document are satisfied, including
implementation of the risk mitigation measures outlined in Section IV of
the document.  Sections IV and V of this RED document describe labeling
amendments for end-use products and data requirements necessary to
implement these mitigation measures.  Instructions for registrants on
submitting the revised labeling can be found in the set of instructions
for product-specific data that accompanies this document.

Should a registrant fail to implement any of the risk mitigation
measures outlined in this document, the Agency will continue to have
concerns about the risks posed by chlorine dioxide and sodium chlorite.
Where the Agency has identified any unreasonable adverse effect to human
health and the environment, the Agency may at any time initiate
appropriate regulatory action to address this concern.  At that time,
any affected person(s) may challenge the Agency’s action.

If you have questions on this document or the label changes necessary
for reregistration, please contact the Chemical Review Manager, ShaRon
Carlisle,<PHONE_NUMBER>.  For questions about product reregistration
and/or the Product DCI that will follow this document, please contact
Emily Mitchell at<PHONE_NUMBER>.

						Sincerely,

						Frank Sanders, Director

						Antimicrobials Division (7510C)

REREGISTRATION ELIGIBILITY

DECISION

for

Chlorine Dioxide and Sodium Chlorite

Case Number 4023

Approved by:

______________________

Frank T. Sanders, Director

Antimicrobials Division

________________________

Date

TABLE OF CONTENTS

Glossary of Terms and
Abbreviations……………………………………………..	ix

Chlorine Dioxide Reregistration
Team…………………………………………….	viii

Executive
Summary………………………………………………………
………....	xi

	I.
Introduction……………………………………………………
…………………..	1

II. Chemical
Overview………………………………………………………
…….	..

3

	A. Regulatory
History……………………………………………………..		3

	B. Chemical Identification
………………………………………………..	3

	C. Use
Profile………………………………………………………
………...	4

III. Summary of Chlorine Dioxide Risk
Assessments……………………………….

6

	A. Human Health Risk
Assessment………………………………………	6

		1. Toxicity of Chlorine
Dioxide…………………………………….	6

		2. FQPA Safety
………………………………………………………	10

		3. Population Adjusted Dose
(PAD)………………………………...	10

			a. Acute PAD…………………………………………………
11

			b. Chronic PAD……………………………………………		11

		4. Exposure
Assumptions……………………………………………	12

		5. Dietary (Food) Risk
Assessment………………………………….	13

			a. Acute Dietary Risk………………………………………..
13

			b. Chronic (Non-Cancer) Dietary Risk……………………..	16

		6. Dietary Risks from Drinking
Water……………………………..	16

			a. Drinking Water Exposure………………………………..	17

			b. Acute Dietary Risk (Drinking Water)…….……………..	18

			c. Chronic Dietary Risk (Drinking Water)………………..	18

		7. Residential
Exposure...……………………………………………	19

			a.
Toxicity…………………………………………………….	19

			b. Residential Handler…...…………………………………..
21

		i. Exposure Scenarios, Data and Assumptions……..	21

			ii. Residential Handler Risk Estimates……………..	22

			c. Residential Post-application ….………………………….
23

			i. Exposure Scenarios, Data and Assumptions……..	23

ii. Residential Post-Application Risk Estimates….	23

		8. Aggregate
Risk……………………………………………………	25

			a. Acute Aggregate Risk …………………………. ....……..
26

			b. Short and Intermediate Acute Aggregate Risk ………..	26

			c. Chronic Aggregate Risk……………………………..	27

		9. Occupational
Risk………………………………………………...	28

			a. Occupational Toxicity…………………………………….
28

			b. Occupational Handler Exposure…………………………	29

			c. Occupational Handler Risk Summary…………………...	33

			d. Occupational Post-Application Risk Summary…………	36

			e. Human Incident Data……………………………………..	37

	B. Environmental Risk
Assessment………………………………………..	37

		1. Environmental Fate and
Transport……………………………...	38

		2. Ecological
Risk……………………………………………………	38

		3. Listed Species Consideration
…………………………………….	39

			a. The Endangered Species Act…….……………………….	39

IV. Risk Management, Reregistration, and Tolerance Reassessment
Decision…

41

	A. Determination of Reregistration
Eligibility……………………………	41

	B. Public Comments and
Responses……………………………………….	41

	C. Regulatory
Position………………………………………………………
42

		1. Food Quality Protection Act Considerations…………………...
42

			a. "Risk Cup" Determination……………………………….	 42

			b. Determination of Safety to U.S. Population…………….	43

			c. Determination of Safety to Infants and Children………	43

			d. Endocrine Disruptor Effects……………………………..	43

			e. Cumulative Risks………………………………………….
44

		2. Tolerance
Summary……………………………………………	44

			a. Tolerances Currently Listed and Tolerance
Reassessment…………………………………………	45

			b. Codex Harmonization……………………………………	45

	D. Regulatory
Rationale……………………………………………………..
45

		1. Human Health Risk Management……………………………….
45

			a. Dietary (Food) Risk Mitigation………………………….	45

b. Safety Drinking Water Act ……………………………..	45

			c. Drinking Water Risk Mitigation………………………..	48

			d. Residential Risk Mitigation………………………………	49

e. Aggregate Risk Mitigation ……………………………….	50

			f. Occupational Risk Mitigation……………………………	50

				i. Occupational Handler…………………………….	50

		2. Environmental Risk Management…………………………..	52

		3. Other Labeling
Requirements……………………………………	52

		4. Threatened and Endangered Species Considerations…………..	52

			a. The Endangered Species Program……………………….	52

			b. General Risk Mitigation………………………………..	53

V. What Registrants Need to
Do…………………………………………………..

54

	A. Manufacturing
Use-Products……………………………………………	55

		1. Additional Generic Data Requirements………………………..
55

		2. Labeling for Technical and Manufacturing-Use Products……..	56

	B. End-Use
Products……………………………………………………..
56

		1. Additional Product Specific Data Requirements…………..........
56

		2. Labeling for End-Use
Products…………………………………..	56

			a. Label Changes Summary Table………………………….	58

VI.
Appendices……………………………………………………
………………….	62

	A. Table of Use Patterns for Chlorine
Dioxide……………………………	63

	 Table of Use Patterns for  Sodium Chlorite…………………….	74

	B. Table of Generic Data Requirements and Studies Use to Make the
Reregistration
Decision…………………………………………….

90

	C. Technical Support
Documents…………………………………………	95

	D. Bibliography
Citations………………………………………………….	96

	E. Generic Data
Call-In…………………………………………………….	107

	F. Product Specific Data
Call-In……………………………………………	108

	G. Batching of End-Use
Products………………………………………….	109

	H. List of All Registrants Sent the Data
Call-In…………………………..	110

	I. List of Available
Forms…………………………………………………..	111

Chlorine Dioxide Reregistration Team

Antimicrobials Division

Science Team

Melba Morrow (Science Coordinator)

Timothy McMahon

Timothy Leighton

Najm Shamim

Genevieve Angle

Jonathan Chen

Risk Management

ShaRon Carlisle

Diane Isbell

Jennifer Slotnick

Registration Support

Emily Mitchell

Wanda Henson

Office of General Counsel

Erin Koch

Michele Knorr

Glossary of Terms and Abbreviations

a.i.		Active Ingredient

aPAD		Acute Population Adjusted Dose

APHIS		Animal and Plant Health Inspection Service

ARTF		Agricultural Re-entry Task Force

BCF		Bioconcentration Factor

CDC		Centers for Disease Control

CDPR		California Department of Pesticide Regulation

CFR		Code of Federal Regulations

ChEI		Cholinesterase Inhibition

CMBS		Carbamate Market Basket Survey

cPAD		Chronic Population Adjusted Dose

CSFII		USDA Continuing Surveys for Food Intake by Individuals

CWS		Community Water System

DCI		Data Call-In

DEEM		Dietary Exposure Evaluation Model

DL		Double layer clothing {i.e., coveralls over SL}

DWLOC	Drinking Water Level of Comparison

EC		Emulsifiable Concentrate Formulation

EDSP		Endocrine Disruptor Screening Program

EDSTAC	Endocrine Disruptor Screening and Testing Advisory Committee

EEC		Estimated Environmental Concentration.  The estimated pesticide
concentration in an environment, such as a terrestrial ecosystem.

EP		End-Use Product

EPA		U.S. Environmental Protection Agency

EXAMS		Tier II Surface Water Computer Model

FDA		Food and Drug Administration

FFDCA		Federal Food, Drug, and Cosmetic Act

FIFRA		Federal Insecticide, Fungicide, and Rodenticide Act

FOB		Functional Observation Battery

FQPA		Food Quality Protection Act

FR		Federal Register

GL		With gloves

GPS		Global Positioning System

HIARC		Hazard Identification Assessment Review Committee

IDFS		Incident Data System

IGR		Insect Growth Regulator

IPM		Integrated Pest Management

RED		Reregistration Eligibility Decision

LADD		Lifetime Average Daily Dose

LC50		Median Lethal Concentration.  Statistically derived concentration
of a substance expected to cause death in 50% of test animals, usually
expressed as the weight of substance per weight or volume of water, air
or feed, e.g., mg/l, mg/kg or ppm.

LCO		Lawn Care Operator

LD50		Median Lethal Dose.  Statistically derived single dose causing
death in 50% of the test animals when administered by the route
indicated (oral, dermal, inhalation), expressed as a weight of substance
per unit weight of animal, e.g., mg/kg.

LOAEC		Lowest Observed Adverse Effect Concentration

LOAEL		Lowest Observed Adverse Effect Level

LOC		Level of Concern

LOEC		Lowest Observed Effect Concentration

mg/kg/day	Milligram Per Kilogram Per Day

MOE		Margin of Exposure

MP		Manufacturing-Use Product

MRID		Master Record Identification (number).  EPA's system of recording
and tracking studies submitted.

MRL		Maximum Residue Level

N/A		Not Applicable

NASS		National Agricultural Statistical Service

NAWQA	USGS National Water Quality Assessment

NG 		No Gloves

NMFS		National Marine Fisheries Service

NOAEC		No Observed Adverse Effect Concentration

NOAEL		No Observed Adverse Effect Level

NPIC		National Pesticide Information Center

NTP		National Toxicology Program

NR		No respirator

OP		Organophosphorus

OPP		EPA Office of Pesticide Programs

ORETF		Outdoor Residential Exposure Task Force

PAD		Population Adjusted Dose

PCA		Percent Crop Area

PDCI		Product Specific Data Call-In

PDP		USDA Pesticide Data Program

PF10		Protections factor 10 respirator

PF5		Protection factor 5 respirator

PHED		Pesticide Handler's Exposure Data

PHI		Preharvest Interval

ppb		Parts Per Billion

PPE		Personal Protective Equipment

PRZM		Pesticide Root Zone Model

RBC		Red Blood Cell

RAC		Raw Agricultural Commodity

RED		Reregistration Eligibility Decision

REI		Restricted Entry Interval

RfD		Reference Dose

RPA		Reasonable and Prudent Alternatives

RPM		Reasonable and Prudent Measures

RQ		Risk Quotient

RTU		(Ready-to-use)

RUP		Restricted Use Pesticide

SCI-GROW	Tier I Ground Water Computer Model

SF		Safety Factor

SL		Single layer clothing

SLN		Special Local Need (Registrations Under Section 24(c) of FIFRA)

STORET	Storage and Retrieval

TEP		Typical End-Use Product

TGAI		Technical Grade Active Ingredient

TRAC 		Tolerance Reassessment Advisory Committee

TTRS		Transferable Turf Residues

UF		Uncertainty Factor

USDA		United States Department of Agriculture

USFWS		United States Fish and Wildlife Service

USGS		United States Geological Survey

WPS		Worker Protection Standard

Abstract tc "EXECUTIVE SUMMARY"

	The Environmental Protection Agency (EPA or the Agency) has completed
the human health and environmental risk assessments for Chlorine Dioxide
and Sodium Chlorite and is issuing its risk management decision and
tolerance reassessment.  The risk assessments, which are summarized
below, are based on the review of the required target database
supporting the use patterns of currently registered products and
additional information received through the public docket.  After
considering the risks identified in the revised risk assessments,
comments received, and mitigation suggestions from interested parties,
the Agency developed its risk management decision for uses of chlorine
dioxide and sodium chlorite that pose risks of concern.  As a result of
this review, EPA has determined that chlorine dioxide and sodium
chlorite containing products are eligible for reregistration, provided
that risk mitigation measures are adopted and labels are amended
accordingly.  That decision is discussed fully in this document.  The
Inorganic Chlorates Reregistration Eligibility Decision (RED) (PC code
073301), determined that sodium chlorate tolerances were safe provided a
safety finding could be made for chlorine dioxide and sodium chlorite.
This decision fulfills that condition.

I.  	Introduction  XE "I. Introduction"

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) was
amended in 1988 to accelerate the reregistration of products with active
ingredients registered prior to November 1, 1984 and amended again by
the Pesticide Registration Improvement Act of 2003 to set time frames
for the issuance of Reregistration Eligibility Decisions.  The amended
Act calls for the development and submission of data to support the
reregistration of an active ingredient, as well as a review of all
submitted data by the U.S. Environmental Protection Agency (EPA or the
Agency).  Reregistration involves a thorough review of the scientific
database underlying a pesticide’s registration.  The purpose of the
Agency’s review is to reassess the potential hazards arising from the
currently registered uses of the pesticide; to determine the need for
additional data on health and environmental effects; and to determine
whether or not the pesticide meets the “no unreasonable adverse
effects” criteria of FIFRA.

On August 3, 1996, the Food Quality Protection Act of 1996 (FQPA) was
signed into law.  This Act amends FIFRA to require reregistration
assessments of the prior to 1984 chemicals.  The Agency has decided
that, for those chemicals that have tolerances and are undergoing
reregistration, the tolerance reassessment will be initiated through
this reregistration process.  The Act also requires that by 2006, EPA
must review all tolerances in effect on the day before the date of the
enactment of the FQPA.  FQPA also amends the Federal Food, Drug, and
Cosmetic Act (FFDCA) to require a safety finding in tolerance
reassessment based on factors including consideration of cumulative
effects of chemicals with a common mechanism of toxicity.  This document
presents the Agency’s revised human health and ecological risk
assessments; and the Reregistration Eligibility Decision (RED) for
chlorine dioxide and sodium chlorite.

	Chlorine dioxide and sodium chlorite are active ingredients in numerous
products used in the control of bacteria, fungi, and algal slimes.  In
addition, chlorine dioxide and sodium chlorite are used as material
preservatives and as disinfectants.  At this time, products containing
chlorine dioxide and sodium chlorite are intended for agricultural,
commercial, industrial, medical and residential use.  The agricultural
premises and equipment uses include the disinfection of hard surfaces
and equipment (such as hatching facilities and mushroom houses) and
water systems (such as chiller water and humidification water in poultry
houses).  Commercial, industrial, and medical uses include disinfection
of ventilation systems, hard surfaces (e.g., floors, walls, and
laboratory equipment), water systems, pulp/paper mills, and food rinses.
 Residential uses include disinfection of hard surfaces (e.g., floors,
bathrooms), heating ventilating and air-conditioning (HVAC) systems, and
treatment of pool & spa water circulation systems.  In addition, there
is a continuous release gas product (sachet) for the home to control
odors.

	The Agency has concluded that the FQPA Safety Factor for chlorine
dioxide should be removed (equivalent to 1X) based on: (1) the existence
of a complete developmental and reproductive toxicity database; (2) the
endpoint selected for assessment of risk from dietary and non-dietary
exposure to chlorine dioxide is protective of potentially susceptible
populations including children and (3) the risk assessment does not
underestimate the potential exposure for infants and children.

Risks summarized in this document are those that result only from the
use of the active ingredients chlorine dioxide and sodium chlorite.  The
FFDCA requires that the Agency consider available information concerning
the cumulative effects of a particular pesticide’s residues and other
substances that have a common mechanism of toxicity.  The reason for
consideration of other substances is due to the possibility that
low-level exposures to multiple chemical substances that cause a common
toxic effect by a common toxic mechanism could lead to the same adverse
health effect that would occur at a higher level of exposure to any of
the substances individually.  Unlike other pesticides for which EPA has
followed a cumulative risk approach based on a common mechanism of
toxicity, EPA has not made a common mechanism of toxicity finding for
chlorine dioxide and sodium chlorite and any other substances.
Chlorine dioxide and sodium chlorite do not appear to produce a toxic
metabolite produced by other substances.  For the purposes of this
action, therefore, EPA has not assumed that chlorine dioxide and sodium
chlorite has a common mechanism of toxicity with other substances.  For
information regarding EPA’s efforts to determine which chemicals have
a common mechanism of toxicity and to evaluate the cumulative effects of
such chemicals, see the policy statements released by EPA’s Office of
Pesticide Programs concerning common mechanism determinations and
procedures for cumulating effects from substances found to have a common
mechanism on EPA’s website at   HYPERLINK
"http://www.epa.gov/pesticides/cumulative"
http://www.epa.gov/pesticides/cumulative  .

This document presents the Agency’s decision regarding the
reregistration eligibility of the registered uses of chlorine dioxide
and sodium chlorite.  In an effort to simplify the RED, the information
presented herein is summarized from more detailed information which can
be found in the technical supporting documents for chlorine dioxide and
sodium chlorite referenced in this RED.  The revised risk assessments
and related addenda are not included in this document, but are available
in the Public Docket at     HYPERLINK "http://www.epa.gov/edocket"
http://www.epa.gov/edocket  (EPA-HQ-OPP-2006-0328).

This document consists of six sections.  Section I is the introduction.
Section II provides a chemical overview, a profile of the use and usage
of chlorine dioxide and sodium chlorite and its regulatory history.
Section III, Summary of Chlorine Dioxide and Sodium Chlorite Risk
Assessment, gives an overview of the human health and environmental
assessments, based on the data available to the Agency.  Section IV,
Risk Management, Reregistration, and Tolerance Reassessment Decision,
presents the reregistration eligibility and risk management decisions.
Section V, What Registrants Need to Do, summarizes the necessary label
changes based on the risk mitigation measures outlined in Section IV.
Finally, the Appendices list all use patterns eligible for
reregistration, bibliographic information, related documents and how to
access them, and Data Call-In (DCI) information.

II.	Chemical Overview

	A.	Regulatory History

EPA first registered the aqueous form of chlorine dioxide for use as a
disinfectant and a sanitizer in 1967.  In industrial processes, chlorine
dioxide is used as a disinfectant in water treatment, ammonia plants,
pulp mills, oil fields, scrubbing systems, odor control systems, and the
electronics industry.  In 1988, EPA registered chlorine dioxide gas as a
sterilant.  Chlorine dioxide gas is registered for sterilizing
manufacturing and laboratory equipment, environmental surfaces, tools,
and clean rooms.  One of the major antimicrobial uses of chlorine
dioxide is to treat drinking water.  In addition, the largest use of
chlorine dioxide is the non-pesticidal bleaching use in the pulp and
paper industry.

Both sodium chlorite and the active ingredient sodium chlorate are used
as a precursor in the generation of chlorine dioxide.  Sodium chlorite
is a strong oxidizing agent that under oxidizing conditions is readily
reduced to chlorite, another strong oxidizing agent, and to a lesser
extent, chlorate.  Sodium chlorate (included in the group of inorganic
chlorates) is predominantly used in the pulp and paper manufacturing
process and as a herbicide in agriculture.  The antimicrobial uses of
sodium chlorate are a minor part of the use pattern.  The uses of sodium
chlorate were assessed separately in the Inorganic Chlorates
Reregistration Eligibility Decision (RED) (PC code 073301).  The RED for
the inorganic chlorates is available in the public docket at   HYPERLINK
"http://www.regulations.gov"  www.regulations.gov  in docket number
EPA-HQ-OPP-2005-0507.  This RED will focus on the uses of chlorine
dioxide/sodium chlorite.

	B.	Chemical Identification

CHLORINE DIOXIDE: PHYSICAL/CHEMICAL CHARACTERISTICS

Chemical Name:		Chlorine dioxide, Chlorine (IV) oxide

Chemical Formula:		ClO2

CAS#:				10049-04-4

Molecular Weight:		67.45 g/mol

Color:                                      Gas phase- Yellow green to
orange

                                                 Liquid phase- reddish
brown

Melting Point:			-59 o C

Boiling Point:			11 o C

Odor:				Strongly pungent, chlorine-like

Physical State:			Gas at room temperature

Density:			1.64 g/ml at 0 o C (liquid)

				1.614 g/ml at 10 o C (liquid)

Vapor Pressure:		490 mm Hg (0o C)

				>760 mm Hg (25 o C)

Stability:			Unstable, estimated half life in water ~ 25 minutes*

Solubility (water):		3.01 g/L at 25 o C and 34. 5 mm Hg**

Chlorine dioxide is explosive at > -40 o C, and its explosive velocity
in air is 50 m/s.  It is highly miscible in water up to 60 g/L and is
highly unstable in sunlight.

In aqueous solutions at pH>10, chlorine dioxide will hydrolyze to form
chlorate and chlorite ions.  In neutral or near neutral solutions (4< pH
<10) chlorine dioxide is relatively stable and exists as a free radical
in water.  The rate of the hydrolysis reaction between water and
chlorine dioxide is about ten million times slower than that of chlorine
at neutral pH.

SODIUM CHLORITE: PHYSICAL/CHEMICAL CHARACTERISTICS

Chemical Name:		Sodium chlorite

Synonyms(s):			Chlorous acid, sodium salt

Chemical Formula:		NaClO2

CAS#:				7758-19-2

Molecular Weight:		90.45 g/mol

Color:				White

Melting Point:			180-200 o C (decomposes)

Boiling Point:			n/a

Physical State:			Solid

Density:			2.468 g/ml (as a solid)

Vapor Pressure:		n/a

Stability:			Stable at Room Temperature

Solubility (water):		390 g/L at 30 o C

Compatibility:	Incompatible with organic matter, sulfur, powdered coal,
and is a powerful oxidizer.

	C.	Use Profile

	The following is information on the currently registered uses of
chlorine dioxide and sodium chlorite, including an overview of use sites
and application methods.  A detailed table of the uses of sodium
chlorate eligible for reregistration is available in Appendix A.

Type of Pesticide: 			Antimicrobial

Target Pests:			Bacteria, fungi, and algal slimes.

Use Site:

Agricultural uses:	The agricultural premises and equipment uses include
the disinfection of hard surfaces and equipment (such as hatching
facilities and mushroom houses) and water systems (such as chiller water
and humidification water in poultry houses).

Non-agricultural uses:	Commercial, industrial, and medical uses include
disinfection of ventilation systems, hard surfaces (e.g., floors, walls,
and laboratory equipment), water systems, pulp/paper mills, and food
rinses

Residential:	Residential uses include disinfection of hard surfaces
(e.g., floors, bathrooms), heating ventilating and air-conditioning
(HVAC) systems, and treatment of pool & spa circulation systems.  In
addition, there is a continuous release gas product (sachet) for the
home to control odors.

Use Classification:	General Use

Method and Rates of Application:

Equipment:	Foaming wand, sprayer, injector systems, mist and fogger, dip
carcass, mop, pump, cloth and add to systems

Application Rates:	Concentrations of chlorine dioxide and sodium
chlorite range from 5ppm to 5000ppm

Formulation Types:			Soluble concentrates and ready-to-use liquid
solutions

III.	Summary of Chlorine Dioxide and Sodium Chlorite Risk Assessments

The purpose of this summary is to assist the reader by identifying the
key features and findings of these risk assessments, and to help the
reader better understand the conclusions reached in the assessments.
The human health and ecological risk assessment documents and supporting
information listed in Appendix C were used to formulate the safety
finding and regulatory decision for chlorine dioxide and sodium
chlorite.  While the risk assessments and related addenda are not
included in this document, they are available from the OPP Public
Docket, located at   HYPERLINK "http://www.regulations.gov"
http://www.regulations.gov , under docket number EPA-HQ-OPP-2006-0328.
Hard copies of these documents may be found in the OPP public docket
under this same docket number.  The OPP public docket is located in Room
S-4400, One Potomac Yard (South Building), 2777 South Crystal Drive,
Arlington, VA, 22202 and is open Monday through Friday, excluding
Federal holidays, from 8:30 a.m. to 4:00 p.m.

	A.	Human Health Risk Assessment

	The human health risk assessment for chlorine dioxide and sodium
chlorite incorporates potential exposure and risks from all sources,
which include food, drinking water, residential (if applicable), and
occupational scenarios.  Aggregate assessments combine food, drinking
water, and any residential or other non-occupational (if applicable)
exposures to determine potential exposures to the U.S. population.  The
Agency’s human health assessment is protective of all U.S.
populations, including infants and young children.  For more information
on the chlorine dioxide and sodium chlorite human health risk
assessment, see Revised Chlorine Dioxide Risk Assessment, dated July 27,
2006, available at   HYPERLINK "http://www.regulations.gov"
www.regulations.gov  (EPA-HQ-OPP-2006-0328).

	The Agency’s use of human studies in the sodium chlorite risk
assessment is in accordance with the Agency's Final Rule promulgated on
January 26, 2006, related to Protections for Subjects in Human Research,
which is codified in 40 CFR Part 26.

		1.	Toxicity of Chlorine Dioxide and Sodium Chlorite

	A brief overview of the toxicity studies used for determining endpoints
in the dietary risk assessments are outlined in Table 2.  The Agency has
reviewed all toxicity studies submitted for chlorine dioxide and has
determined that the toxicological database is complete, reliable, and
sufficient for reregistration.  For more details on the toxicity and
carcinogenicity of the chlorine dioxide and sodium chlorite, see the
Chlorine Dioxide Toxicology Disciplinary Chapter, Case 4023, dated
April, 5, 2006, which is available under docket number
EPA-HQ-OPP-2006-0328.

Major features of the toxicology profile are presented below. The acute
toxicity of chlorine dioxide is moderate by the oral route (toxicity
category II).  The acute toxicity of chlorine dioxide using sodium
chlorite as the test material is considered minimal by the dermal route
(toxicity category III).  By the inhalation route using sodium chlorite
as the test material, chlorine dioxide was moderately toxic. For primary
eye irritation, chlorine dioxide was a mild irritant (toxicity category
III), but the technical test material was not used.  For primary dermal
irritation, sodium chlorite was a primary irritant (toxicity category
II).  For dermal sensitization, there are no acceptable studies for
chlorine dioxide or sodium chlorite.  The acute toxicity profile for
chlorine dioxide is summarized in Table 1 below.

Table 1.  Acute Toxicity Profile for Chlorine Dioxide/ Sodium Chlorite

Guideline Number	Study Typea / Test substance (% a.i.)	MRID Number/
Citation	Results	Toxicity Category

870.1100

(§81-1)	Acute oral

(79% chlorine dioxide)	43558601	LD50 = 292 mg/kg (males)

LD50 = 340 mg/kg (females)	II

870.1200

(§81-2)	Acute dermal

(80% sodium chlorite)	40168704	LD50 > 2000 mg/kg	III

870.1300

(§81-3)	Acute inhalation

(80.6% sodium chlorite)	42484101	LC50 = 0.29 mg/L	II

870.2400

(§81-4)	Primary eye irritation

(2% chlorine dioxide)	43441903	Mild irritant	III

870.2500

(§81-5)	Primary dermal irritation

(80% sodium chlorite)	40168704	Primary irritant	II

870.2600

(§81-6)	Dermal sensitization	No acceptable sensitization study
available.

a The available acute studies are all graded as acceptable.  An
acceptable dermal sensitization study is not available in the database.

The doses and toxicological endpoints selected for the dietary exposure
scenarios are summarized in Table 2 below.

Table 2: Summary of Toxicological Doses and Endpoint Selection for

Chlorine Dioxide/ Sodium Chlorite

Exposure Scenario	Dose Used in Risk Assessment (mg/kg/day)	UF/MOE for
Risk Assessment	Study and Toxicological Effects

Acute Dietary	  SEQ CHAPTER \h \r 1 An acute dietary endpoint was not
identified in the database for chlorine dioxide.  This risk assessment
is not required.

Chronic Dietary	NOAEL = 3 mg/kg/day	UF = 100 (10x inter-species
extrapolation, 10x intra-species variation)

Chronic  PAD = 0.03 mg/kg/day	Two-generation reproduction toxicity study
(CMA, 1996) - decreases in absolute brain and liver weight, and lowered
auditory startle amplitude at LOAEL of 6 mg/kg/day

Developmental Toxicity - Rat (Orme et al., 1985)- neurobehavioral and
exploratory deficits in rat pups

Carcinogenicity	No cancer data is available for chlorine dioxide.

General Toxicity Observations

Subchronic

Subchronic oral toxicity studies conducted with chlorine dioxide showed
significant reductions in body weight increases and decreases in food
consumption at 200 mg/L, the highest dose tested.  Significant
reductions in water consumption were observed in males and in females.
Absolute liver weights were decreased in males at ( 50 mg/L, and
absolute spleen weights were decreased in females at ( 25 mg/L.   The
LOAEL is 25 mg/L, based on a significant increase in the incidence of
nasal lesions.  No exposure-related deaths were reported in this study.

Subchronic oral toxicity studies conducted with sodium chlorite showed
increased salivation, significantly decreased erythrocyte counts, and
decreased total serum protein levels, and effects in the blood.  During
this study four animals died during treatment.  It should be noted that
one exposure-related death was observed in a range-finding study for the
subchronic oral toxicity study each sex in the 200 mg/kg/day group on
treatment days 2 and 3.

Dietary

	An acute dietary endpoint was not identified in the database for
chlorine dioxide; this risk assessment is not required for chlorine
dioxide/sodium chlorite.  The chronic dietary endpoint is 3 mg/kg/day,
based on decreases in absolute brain and liver weight, and lowered
auditory startle amplitude at LOAEL of 6 mg/kg/day in a two-generation
reproduction toxicity study and is supported by a developmental toxicity
study in rats.  The target MOE is 100 for all dietary exposures.

Incidental Oral

	The short-and intermediate-term oral endpoint is 3 mg/kg/day, based on
decreases in absolute brain and liver weight, and lowered auditory
startle amplitude at LOAEL of 6 mg/kg/day in a two-generation
reproduction toxicity study and is supported by a developmental toxicity
study in rats.  The target MOE is 100 for all incidental oral exposures.

Dermal

	The short-, intermediate-, and chronic-term dermal endpoint is based on
decreases in absolute brain and liver weight, and lowered auditory
startle amplitude at LOAEL of 6 mg/kg/day in a two-generation
reproduction toxicity study and is supported by a developmental toxicity
study in rats.  The target MOE is 100 for all dermal exposures.

Inhalation

The inhalation route of exposure to chlorine dioxide is assessed for
three distinct subpopulations:  (1) occupational exposures (8 hours/day,
5 days/week), (2) one-time exposures for residential uses (e.g., HVAC
systems, mopping floors, etc), and (3) long-term exposure for continuous
release products in the home (24 hours/day, 7 days/week).  Several
animal studies were used to develop reference concentrations (RfCs).
The effects seen at various concentrations include rhinorrhea, altered
respiration, respiratory infection, bronchial inflammation, alveolar
congestion and hemorrhage, vascular congestion, and peribronchiolar
edema.  Readers are referred to USEPA (2000a) for a detailed review of
the effects seen at specific concentrations and exposure durations along
with the derivation of the RfC.  In summary, the occupational RfC is
determined to be 0.003 ppm and represents an 8-hour time weighted
average (TWA).  The one-time residential exposure scenario is
represented by the RfC of 0.05 ppm and the RfC for long-term, continuous
exposure is 0.00007 ppm.  The RfC methodology incorporates the
uncertainty factors into the concentration.  For inhalation, the RfC is
compared directly to the air concentration of interest.  Inhalation
risks are of concern if the air concentrations people are exposed to
exceed the RfC.

Carcinogenicity

Chlorine dioxide has not been assessed for carcinogenic   SEQ CHAPTER \h
\r 1 potential.  The available dermal carcinogenicity studies do not
definitively characterize the carcinogenicity of chlorine dioxide, and
additional studies are required, and will be included in a data call-in
(DCI) to follow this RED.  One subchronic rat study, examined the
effects of administration of chlorine dioxide at dose levels of 0, 25,
50, 100, or 200 mg/L for 90 days in drinking water.  In this subchronic
rat study, a significant increase in the incidence of nasal lesions was
found at all dose levels tested.  The significance of these findings is
uncertain, as they have not been observed in other long-term studies of
chlorine dioxide.

Mutagenicity

The Agency reviewed data from submitted studies as well as open
literature.  Data on the mutagenicity of chlorine dioxide indicate that
negative effects were reported in one study from a 400-fold drinking
water concentrate of chlorine dioxide, whereas a 4000-fold concentrate
was mutagenic only in the absence of metabolic activation.  In another
study, chlorine dioxide was positive for forward mutations under
non-activated conditions.  Chlorine dioxide was positive for structural
chromosome aberrations under non-activated and activated conditions and
was negative for increased transformed foci up to cytotoxic levels.  In
one mouse study on chlorine dioxide, In vivo micronucleus and bone
marrow chromosomal aberration assays were negative, as was a sperm-head
abnormality assay.

Developmental/Reproductive

One developmental toxicity study conducted using rats was conducted for
chlorine dioxide and sodium chlorite.  In this study, a NOAEL of 20 mg/L
was established based on decreased exploratory and locomotor activities
in the offspring of rats exposed to chlorine dioxide in drinking water.
Another developmental toxicity study conducted in rabbits using sodium
chlorite established a NOAEL for developmental and maternal toxicity at
200 ppm, based on a dose-related increase of does with reduced fecal
output during the dosing period, consistent with decreased food
consumption.

A two-generational reproductive toxicity study was performed using
sodium chlorite.  The NOAEL for this study is 35 ppm (2.9 mg/kg-day) and
the LOAEL is 70 ppm (5.9 mg/kg-day chlorite) based on lowered auditory
startle amplitude and absolute brain weights in two generations.  There
were no significant effects of chlorine dioxide on body weight of dams
or pups at any dose level tested.

Endocrine Disruption Potential

EPA is required under the FFDCA, as amended by FQPA, to develop a
screening program to determine whether certain substances (including all
pesticide active and other ingredients) “may have an effect in humans
that is similar to an effect produced by a naturally occurring estrogen,
or other such endocrine effects as the Administrator may designate.”
 Following recommendations of its Endocrine Disruptor and Testing
Advisory Committee (EDSTAC), EPA determined that there was a scientific
basis for including, as part of the program, the androgen and thyroid
hormone systems, in addition to the estrogen hormone system.  EPA also
adopted EDSTAC’s recommendation that the Program include evaluations
of potential effects in wildlife.  For pesticide chemicals, EPA will
use FIFRA and, to the extent that effects in wildlife may help determine
whether a substance may have an effect in humans, FFDCA authority to
require the wildlife evaluations.  As the science develops and
resources allow, screening of additional hormone systems may be added to
the Endocrine Disruptor Screening Program (EDSP).

FQPA Safety Factor Considerations

The FQPA Safety Factor (as required by FQPA) is intended to provide an
additional 10-fold safety factor (10X), to protect for special
sensitivity in infants and children to specific pesticide residues in
food, drinking water, or residential exposures, or to compensate for an
incomplete database.  For chlorine dioxide and sodium chlorite, the FQPA
Safety Factor has been removed (i.e., reduced to 1X).  This safety
factor has been removed because the endpoint selected for both dietary
and non-dietary exposures was based upon adverse effects observed in
offspring from developmental and reproductive toxicity data.  This
approach is consistent with that used by the EPA’s Office of Water for
use of chlorine dioxide as a drinking water disinfectant (Federal
Register Vol. 63, No. 61, pages 15673-15692, March 31, 1998) and the
updated guidance on selection of a safety factor under FQPA.  The
endpoint selected for assessment of risk from dietary and non-dietary
exposure to chlorine dioxide and sodium chlorite is believed to be
protective of potentially susceptible populations, including children,
based upon the selection of an endpoint and effects observed in
offspring and the use of a NOAEL value based on those effects.
Therefore, it was concluded that an additional safety factor under FQPA
is not necessary in this case.  Further, the risk assessment does not
underestimate the potential exposure for infants and children.

3.	Population Adjusted Dose (PAD)

Dietary risk is characterized in terms of the Population Adjusted Dose
(PAD), which reflects the reference dose (RfD), either acute or chronic,
that has been adjusted to account for the FQPA Safety Factor (SF).  This
calculation is performed for each population subgroup.  A risk estimate
that is less than 100% of the acute or chronic PAD is not of concern.

a.	Acute PAD  XE "III. Summary of 2,4-DB Risk Assessments:A. Human
Health Risk Assessment: 3. Population Adjusted Dose (PAD): a. Acute PAD"

Acute dietary risk is assessed by comparing acute dietary exposure
estimates (in mg/kg/day) to the acute Population Adjusted Dose (aPAD).
Acute dietary risk is expressed as a percent of the aPAD.  The aPAD is
the acute reference dose, modified by the FQPA safety factor. Although
several studies were considered, an acute reference dose (aRfD) was not
identified for chlorine dioxide.  None of the available studies provided
an endpoint of toxicity attributable to a single exposure. Therefore, no
acute dietary endpoint for chlorine dioxide and sodium chlorite was
selected.

b.	Chronic PAD  XE "III. Summary of 2,4-DB Risk Assessments:A. Human
Health Risk Assessment: 3. Population Adjusted Dose (PAD): a. Acute PAD"

	Chronic dietary risk for chlorine dioxide is assessed by comparing
chronic dietary exposure estimates (in mg/kg/day) to the chronic
Population Adjusted Dose (cPAD).  Chronic dietary risk is expressed as a
percent of the cPAD.  The cPAD is the chronic reference dose modified by
the FQPA safety factor.  The cPAD was derived from a two-generation
reproduction toxicity study and a developmental toxicity study in which
the NOAEL (3 mg/kg/day) and LOAEL (6 mg/kg/day) were determined. The
chlorine dioxide and sodium chlorite cPAD is 0.03 mg/kg/day based on a
reference does of 0.03 mg/kg/day, which incorporates the FQPA safety
factor (1X) for the overall U.S. population and all population
subgroups.

Metabolites and Degradates

Sodium chlorite is a strong oxidizing agent and under proper reducing
conditions is readily reduced to chloride, and to a lesser extent,
chlorate.  In strong acidic conditions, chlorite can change into
chlorine dioxide.  The main source of chlorite ion exposure in the soil,
water, or indirect food contacts is through the disinfectant
applications.  However, it is likely that some chlorate in these media
is formed through use of antimicrobial applications (disinfectant) of
chlorine dioxide, sodium chlorite, and sodium/calcium hypochlorites.

In aqueous media, these oxyanions (chlorite, chlorate, and hypochlorite)
exist because of the unique chemistry of chlorine, that has a tendency
to change its oxidation states (charges).  Thus, in chlorate, chlorine
has a +5 charge, in chlorite it bears a +3 charge, in hypochlorite a + 1
charge, while in chloride a net -1 charge exists.  These variations in
charges (hence the speciations) are dependent on factors such as:  pH of
the medium, temperature, redox potential of the medium, presence of
oxidizing or reducing species, etc.  Similarly, chlorate itself can
undergo redox reactions, depending on the pH of the aqueous medium to
form, chloride, chlorine, hypochlorite, chlorous acid, chlorine dioxide.

The Agency lacks data that would quantify the interconversions between
chlorate, chlorine dioxide, sodium chlorite, and sodium/calcium
hypochlorite.  Simultaneous conversions of these species are not likely
to occur as these factors (mentioned above) do not work in tandem.  Thus
at this time, any additional dietary risks from interconversions in
drinking water (non-cancer risks), and food (non-cancer risks) cannot be
estimated.  The Agency has included the highest possible dietary
contribution of chlorite ion from use of sodium chlorate from the most
sensitive subpopulation in the dietary risk estimates of sodium
chlorite.  Therefore, the Agency has conservatively determined that
there are no additional risks other than the ones that have been
estimated in chlorine dioxide/sodium chlorite Risk Assessment and sodium
chlorate RED.

	The inorganic chlorates were evaluated in the Inorganic Chlorates
Reregistration Eligibility Decision (case number 4049) (hereinafter
referred to as the “Inorganic Chlorates RED”).  That assessment
considered the contribution of chlorate ion from the use of chlorine
dioxide and sodium chlorate.  Please see Revised Sodium Chlorite Risk
Assessment, dated July 27, 2006, for additional details.

4.     Exposure Assumptions  XE "III. Summary of 2,4-DB Risk
Assessments:A. Human Health Risk Assessment: 3. Population Adjusted Dose
(PAD)"

	The use of chlorine dioxide and sodium chlorite on food or feed contact
surfaces, agricultural commodities, in animal premises and poultry
premises including hatcheries and application to food-grade eggs may
result in pesticide residues in human food.  No residue chemistry data
were required to support these uses in the past; therefore, no residue
data was available for the assessment of these uses

To estimate chlorine dioxide residues on food due to migration of this
chemical from sanitizing and/or disinfecting hard non-porous surfaces,
the Agency has used the US Food and Drug Administration (FDA) model to
determine the Estimated Daily Intake (EDI).  Potential use sites
include: (1) poultry hatcheries, (2) food handling establishments, (3)
post-harvest potato treatments, (4) poultry house disinfection, poultry
chiller water/carcass spray or dip, (5) food processing plants (meat and
fish), (6) dairies, breweries, and bottling plants, and (7) pulp/paper,
polymer slurries, paper adhesive, and paper coating.  The EDI
calculations presented in this assessment assumes that food can contact
2,000 cm2 or 4,000 cm2 (50% and 100% respectively of the FDA worst case
scenario) of treated surfaces, and that 10% of the pesticide would
migrate to food.  The use of the 10% transfer rate, instead of the 100%
transfer rate was used for all indirect food contact surfaces except for
food bottling and packaging surfaces.  The 10% migration rate is based
on Agency Residential Standard Operation Procedures.  These daily
estimates were conservatively used to assess both acute (i.e. percent
acute population adjusted dose or %aPAD) and chronic dietary risks (i.e.
percent chronic population adjusted dose or %cPAD).  The maximum
application rate of 1000 ppm for chlorine dioxide from the various
labeled products was used.  Additional details about the dietary
assessment can be found in “Dietary Risk Assessment for Chlorine
Dioxide and Sodium Chlorite Indoor Uses as Disinfectants/Sanitizers,”
dated July 22, 2006.

	The Agency has conservatively added the highest chronic dietary
exposure to chlorite ion from consumption of food treated with inorganic
chlorates to the total chronic dietary exposure from chlorine
dioxide/sodium chlorite.  This assumes that all residues on food
resulting from the use of inorganic chlorates are sodium chlorite.  The
Agency has decided to include these exposures as part of the chlorine
dioxide/sodium chlorite dietary assessment in order to ensure that the
most conservative dietary assumptions are used.  The inclusion of these
exposures is considered to be highly conservative because it is unlikely
that significant chlorite residues will result from the use of inorganic
chlorates on food crops.  As mentioned previously, the inorganic
chlorates have been reassessed separately from chlorine dioxide.

There is no evidence that there will be residues of chlorine dioxide or
sodium chlorite in mushrooms following its use as a mushroom house
disinfectant.  Further, if dietary exposures from mushroom house uses
occurred they would be expected to be much lower than the dietary
exposures resulting from the surface disinfectant and sanitizing uses.
The labels associated with mushroom house use state that the product is
not to be applied to the mushroom crop, compost or casing and that
treated surfaces are to be rinsed with potable water before contact with
the crop, compost or casing.  Because any potential exposures would not
likely pose risks of concern and the sanitizing uses represent a
worst-case scenario, these uses were not assessed.

5.    Dietary (Food) Risk Assessment

The Agency conducted a dietary exposure/risk assessment for chlorine
dioxide and sodium chlorite.  Generally, a dietary risk estimate that is
less than 100% of the acute or chronic PAD does not exceed the
Agency’s risk concerns.  A summary of acute and chronic risk estimates
are shown in Table 3.

			a.  	Acute Dietary Risk   XE "III. Summary of 2,4-DB Risk
Assessments:5. Dietary (Food) Risk Assessment: a. Acute Dietary Risk"

No acute dietary endpoint was selected because effects attributable to a
single dose were not seen in the available data; therefore, an acute
dietary risk assessment was not conducted.

b.  	Chronic Dietary Risk

A chronic dietary risk assessment was conducted for chlorine
dioxide/sodium chlorite direct and indirect application to food.  For
indirect food applications, the highest individual subpopulation percent
cPAD calculated is 4.2% for children’s consumption of milk.  For
direct food uses, the chronic risk from the post-harvest use of fruit
and vegetable washes is 42% of the cPAD for children.  For the chlorite
exposure resulting from the use of inorganic chlorate application to
agricultural crops, exposure to children (most highly exposed
subpopulation) resulted in risk estimate of 28 % of the cPAD.  As a
conservative measure, the dietary risk estimates of sodium chlorite
include the highest dietary risk estimate for sodium chlorate for the
most sensitive subpopulation.

Although there is not a concern for chronic dietary risk estimates
alone, it is important to note that the individual exposure received
from the post-harvest application of sodium chlorite to fruits and
vegetables is an extremely high-end estimate.  This assessment was
conducted with the most conservative assumptions and resulted in an
estimate of 42% of the cPAD for children ages 1-2.   For example, this
assessment assumed that all fruits and vegetables in the U.S. had a
chlorine dioxide solution applied and that these commodities were not
washed, cooked or processed prior to consumption.  However, the Chlorine
Dioxide Panel has agreed to limit the residual concentration of chlorine
dioxide to 3 ppm for post-harvest application to fruits and vegetables
that are not Raw Agricultural Commodities.  In order to get to this
residual, the panel has agreed to label restrictions that require that
fruits and vegetables treated with chlorine dioxide must be blanched,
cooked, or canned before consumption or distribution in commerce.
Although the Agency cannot quantify the reduction of chlorine dioxide
dietary exposure resulting from this mitigation measure at this time, it
is believed that this measure would significantly reduce the percent of
chlorine dioxide cPAD resulting from this use.

	The dietary risks for adult and children from food uses are shown in
Table 3.  As there is no acute dietary endpoint for chlorine dioxide,
only chronic dietary risk is presented.  For adults, the total chronic
dietary risk is 9.1% of the cPAD and is not of concern.  For children
(1–2 years), and infants less than 1 year old, the total dietary
exposure is 76%, and 32% of the cPAD, respectively.  These risks are
below the Agency’s level of concern, less than 100% of the cPAD.  As
stated above, this risk scenario is very conservative.  For example, the
Agency does not believe that 100% treatment of fruits and vegetables is
a realistic scenario.  If 50% of this food is treated, which we think is
still unrealistic, the cPad for children (1-2 years) would be
approximately 54%.  The Agency will issue a DCI requiring data be
submitted on how much food is washed with these pesticides.

Table 3.  Summary of Dietary Exposure and Risk for Chlorine Dioxide

Use Site	Food Type	Population Subgroup	EDI (mg/person/day)	Chronic
Dietary

Dietary Exposurea (mg/kg/day)	% cPAD b

Indirect Food Use

Food handling establishments/ kitchens	NA	Adult	2.00 x 10-1	9.5E-07
0.00316

Child

8.8E-06	0.0293

Dairies, Breweries, Bottling Plants, Food Contact Surfaces/Food
Processing Plants for Meats and Fishd	Beverages, alcoholic, beer	Adult
1.2 x 10-3	1.70E-05	0.56

	Beverages, non-alcoholic	Adult	1.6 x 10-3	2.40E-05	0.08

Child

1.00E-04	0.33

	Egg Products, Mayonnaise	Adult	1.4 x 10-4	2.00E-06	0.0086

Child

9.33E-06	0.031

	Milk	Adult	1.9 x 10-2	2.70E-04	0.66

Child

1.30E-03	4.2

Pulp/Paper, Polymer Slurries, Paper Adhesive, Paper Coating	NA	Adult	1.1
x 10-1	9.8E-05	0.326

Child

2.3E-04	0.766

Total Indirect Food-Contact Exposure	Adult	3.3 x 10-1	4.12E-04	1.64

	Child

1-2 years	2.7 x 10-1	1.65E-03	5.35

	Infant

<1

	<5.35 f

Direct Food Use

Post Harvest Application 	Fruit and Vegetable Wash	Adult	 	2.24E-03c,
e	7.5

Child	 	1.27E-02 c, e	42.3

Total Direct Food-Contact Exposure	Adult	 	2.24E-03	7.5

	Child

1-2 years 	 	1.27E-02	42.3g

	Infant

<1

3.49E-03	11.6 f

Inorganic Chlorate Use

Highest Exposure from

Agricultural Use	Child

1 – 2 years

	 	8.38E-03c	28

	Infant

<1 year

4.511E-03	15 f

Total Dietary Exposure

Total Direct and Indirect Food-Contact Exposure	Adult	 	2.65E-03	9.1

	Child

1-2 years	 	2.27E-02	75.7

	Infant

<1 year

	<31.95 f

a-- For adults, acute and chronic exposure analysis is based on a body
weight of 70 kg.  For adult females, the body weight is 60 kg.  For
children, exposure is based on a body weight of 15 kg.

b--%PAD = dietary exposure (mg/kg/day) * 100 / cPAD, where cPAD for
adults and children = 0.03 mg/kg/day;

c--children 1-2 years of age, adults 20-49 years of age

d--food processing plants for meats/fish have exposures which are
similar to other food contact surfaces, exposure numbers not included
for this scenario.

e-- includes all fruits and vegetables and apple and orange juices;
assumes 100% of fruit is washed with chlorine dioxide.

f--Infants (<1 year) are included in this table for comparison purposes
and were not added to the total dietary exposure as it was not the most
highly exposed subpopulation.

g--Assuming 50% of fruits/vegetables are treated, the dietary risk for
children (1 – 6) would represent 21% of the cPAD.

6.	Dietary Risk from Drinking Water

  XE "III. Summary of 2,4-DB Risk Assessments:5. Dietary (Food) Risk
Assessment: c. Dietary Risk from Drinking Water"

Chronic dietary (water only) risk assessments were conducted using
DEEM-FCID™ Version 2.03 and drinking water consumption data from the
USDA’s CSFII from 1994-1996 and 1998.  Exposures were single point
estimates; no residue decline was utilized.

	Chlorine dioxide is commonly used as an antimicrobial material
preservative and for disinfecting non-porous surfaces indoors.  These
use patterns are not expected to result in surface or groundwater
contamination.  However, chlorine dioxide is commonly used for drinking
water treatment.  Therefore, the drinking water discussion will focus on
the dietary risks that result from drinking water treatment.

	In the U.S., there are two primary methods of drinking water treatment
that do not involve filtration.  The first method is the generation of
chlorine dioxide.  In the second method, either gaseous chlorine or
hypochlorite is used to produce free chlorine.  Except when gaseous
chlorine is used, these methods produce chlorate as a disinfection
byproduct (DBP).  The American Water Works Association (AWWA)
Disinfection Systems Committee tracks disinfection practices in US
community water systems.  AWWA’s most recent comprehensive survey
(completed in 1998) estimated that, of all community water systems
(CWS), approximately 20% of CWSs serving populations greater than 10,000
use sodium hypochlorite (2% generated it on-site), 8% use chlorine
dioxide, and <1% use calcium hypochlorite.  For CWSs using groundwater
and serving populations less than 10,000, the survey estimated that
approximately 34% use sodium hypochlorite, none use chlorine dioxide,
and at least 4.5% use calcium hypochlorite.  For CWSs using surface
water and serving less than 10,000, the survey estimated that 17% use
sodium hypochlorite, 6% use chlorine dioxide, and 9% use calcium
hypochlorite.

	For chlorine dioxide generation, both sodium chlorate and sodium
chlorite are used as precursor materials in the water disinfection
process.  Sodium chlorite is more commonly used than sodium chlorate.
The free chlorine disinfection process involves the use of either
gaseous chlorine, or sodium or calcium hypochlorite, as precursor
materials.  Historically, gaseous chlorine has been far more widely used
than hypochlorite to produce free chlorine.  In recent years, primarily
as a result of various homeland security measures, many drinking water
systems are switching from gaseous chlorine to hypochlorite.  These
processes (except for the use of gaseous chlorine) result in chlorate
byproduct in finished drinking water, exposure to which was considered
in the Inorganic Chlorates RED.

The chlorite ion (ClO2-) is a major degradation product resulting from
the reaction of chlorine dioxide with inorganic and organic constituents
in the water.  When free chlorine is used after the application of
chlorine dioxide in the treatment process, chlorite is oxidized to
chlorate.  This conversion will continue over time as the water travels
through the distribution system.  Chlorate ion is also formed by
photodecomposition of chlorine dioxide when treated water is exposed to
bright sunlight in open basins.  The rate at which chlorate forms
affects the amount of chlorine dioxide or chlorite that remain in the
finished drinking water.  Formation of chlorate from chlorite and
chlorine dioxide was considered in the Inorganic Chlorates RED.

Drinking Water Exposure

Data on the occurrence of sodium chlorite in drinking water were
available from the Information Collection Rule (ICR) Auxiliary 1
Database, Version 5.0.  The water systems represented in the ICR
database serve 60% of the total U.S. population.  The EPA Office of
Water (OW) issued the ICR in order to collect data to support future
regulation of microbial contaminants, disinfectants, and disinfection
byproducts.  Monitoring for sodium chlorite was included in the ICR.
Source water and drinking water were monitored for sodium chlorite ion
between July 1997 and December 1998.  Water systems serving a population
of at least 100,000 were required to monitor for chlorite ion at
treatment plants using chlorine dioxide or hypochlorite solutions in the
treatment process.  Plants using chlorine dioxide collected monthly
samples of the source water entering the plant, the finished water
leaving the plant, and at three sample points in the distribution system
(near the first customer, an average residence time, and a maximum
residence time).  Plants using hypochlorite solutions were required to
collect quarterly samples of the water entering and leaving the plant.
If chlorine dioxide or hypochlorite solutions were used intermittently
at a plant, chlorite ion samples were only required in sample periods in
which they were in use.

Monitoring data were collected from 29 water treatment plants using
chlorine dioxide treatment.  The minimum reporting level (MRL) was
established at 20 µg/L, all samples below this value were considered
zero.  Data from 418 samples (point of entry to the distribution) showed
chlorite ion concentration ranged from 20 µg/L to 2,029 µg/L. Data
from 1,115 samples (collected from within the distribution system)
showed the concentration of chlorite ion between 20 µg/L to 1,850
µg/L.  The average concentration of chlorite ion from 27 out of 29
treatment plants when averaged from the three distribution system sample
points ranged from 20µg/L to 801 µg/L.

Based on the results of this monitoring data, the Agency established a
maximum contaminant level goal (MCLG) and a maximum contaminant level
(MCL) for chlorite ions.  The MCLG and MCL are 0.8mg/L and 1.0 mg/L,
respectively.  In the original ICR monitoring data a number of samples
and distribution systems showed large exceedences based on the MCL and
MCLG.  Currently, water systems have indicated that treatment is
generally designed to meet a level of at least 20% below the MCL in
order to ensure compliance. Based on this assumption, the Agency has
readjusted all reported concentrations over 1000µg/L to 800 µg/L and
recalculated the data.  Table 4 below shows the adjusted values for
chlorite concentrations.

	Based on the values obtained from the monitoring data, the Agency
conducted a drinking water assessment using chlorite concentrations at
the maximum, 90th percentile, and median annual averages of chlorite
concentrations of 0.7, 0.63, and 0.39 mg/L, respectively.  The 90th
percentile exposure values will be used in the aggregate risk
assessments, with children represented by the 1-6 year old age category.

Table 4.  Chlorine Dioxide Water Monitoring Data (g/L) – ICR Dataa

	Distribution System Entry Point	Near First Customer	Average Residence
Time	Maximum Residence Time	Distribution System Average2

10th Percentile	60	52	58	30	45

20th Percentile	99	79	87	81	84

50th Percentile	440	380	360	310	390

80th Percentile	590	580	600	510	550

90th Percentile	660	660	640	650	630

Maximum	800	740	680	680	700

Number of Water Treatment Plants	29	27	27	27	27

Number of Public Water Systems	22	21	21	21	21

	aICR Data Adjusted for MCL Compliance

			b.	Acute Dietary Risk (Drinking Water)

No acute dietary endpoint was selected because effects attributable to a
single dose were not seen in the available data; therefore, an acute
dietary risk assessment was not conducted.

Chronic Dietary Risk (Drinking Water)

The chronic dietary (water only) risk assessment for sodium chlorite in
drinking water estimated at 49 % of the cPAD for the general U.S.
population and is below 100% of the cPAD, and therefore, is below the
Agency’s level of concern.  All risks for the U.S. population
subgroups are below 100 % of the cPAD except infants (<1 year of age).
The highest exposed subgroup, infants, was 161% of the cPAD, based on
the highest annual average concentration of sodium chlorite, and
therefore, above the Agency’s level of concern.  The 90th percentile
exposure values will be used in the aggregate risk assessments, with
children represented by the 1-6 year old age category.  See Table 5
below for details.

Table 5. Chlorite Exposure by Population Group

Population subgroup	Maximum Concentration	90th Percentile Concentration
Median Concentration

	Total exposure

(mg/kg/day)	% cPAD	Total exposure

(mg/kg/day)	% cPAD	Total exposure (mg/kg/day)	% cPAD

U.S. Population	0.014754	49	0.013279	  44	0.008220	27

Infants < 1 year	0.048372	161	0.043535	145	0.026950	90

Children 1-6 years	0.020613	69	0.018552	  62	0.011485	38

Children 7 -12 years	0.013402	45	0.012062	  40	0.007467	25

Females 13-50	0.014274	48	0.012846	  43	0.007952	27

Residential Exposure

Residential exposure assessment considers all potential pesticide
exposure, other than exposure due to residues in food or in drinking
water.  Residential exposure may occur during cleaning or mopping of
hard surfaces, application of chlorine dioxide to swimming pools and
spas and through application to HVAC systems.  Each route of exposure
(oral, dermal, inhalation) is assessed, where appropriate, and risk is
expressed as a Margin of Exposure (MOE), which is the ratio of estimated
exposure to an appropriate NOAEL.  Based on its use pattern, the
residential handler assessment evaluated application of chlorine
dioxide-containing products by homeowners to control mold and mildew.
The post-application assessment evaluated risks from dermal, inhalation
and incidental oral exposure for children due to hand-to-mouth exchange.

Toxicity

The toxicological endpoints and associated uncertainty factors used for
assessing the non-dietary risks for chlorine dioxide and sodium chlorite
are listed in Table 6.

A MOE greater than or equal to 100 is considered adequately protective
for the residential exposure assessment for the dermal, incidental oral
and inhalation routes of exposure. The MOE of 100 includes 10x for
inter-species extrapolation, 10x for intra-species variation.

Table 6.  Summary of Toxicological Doses and Endpoint Selection for the

Chlorine Dioxide/ Sodium Chlorite Residential Assessment

Exposure Scenario	Dose Used in Risk Assessment (mg/kg/day)	UF/MOE for
Risk Assessment	Study and Toxicological Effects

Incidental Oral

(short and intermediate term)	NOAEL = 3 mg/kg/day	MOE  = 100
Two-generation reproduction toxicity study (CMA, 1996) - decreases in
absolute brain and liver weight, and lowered auditory startle amplitude
at LOAEL of 6 mg/kg/day

Developmental Toxicity - Rat (Orme et al., 1985)- neurobehavioral and
exploratory deficits in rat pups at LOAEL of 14 mg/kg/day

Dermal

All Durations (1-30 days)	NOAEL = 3 mg/kg/day	MOE = 100	Two-generation
reproduction toxicity study (CMA, 1996) - decreases in absolute brain
and liver weight, and lowered auditory startle amplitude at LOAEL of 6
mg/kg/day

Developmental Toxicity - Rat (Orme et al., 1985)- neurobehavioral and
exploratory deficits in rat pups at LOAEL of 14 mg/kg/day

Inhalation

(occupational and homeowner short-term)	Homeowner

short-term:

LOAEL = 28 mg/m3 (10 ppm)

Occupational exposure:

LOAEL  = 2.8 mg/m3 (1.0 ppm)

NOAEL = 0.28 mg/m3 (0.1 ppm).	Homeowner short-term ‘RfC’ = 0.14
mg/m3 (0.05 ppm)

Occupational ‘RfC’ = 0.009 mg/m3 (0.003 ppm)	Inhalation toxicity
studies- Rat

Dalhamn, 1957; Paulet and Debrousses, 1970, 1972.

Inhalation (homeowner long-term)	Agency RfC methodology used to derive
an RfC value of 2 x 10-4 mg/m3 (USEPA, 2000a)	(Paulet and Desbrousses,
1970, 1972) selected as co-critical studies (USEPA, 2000a)

Residential Handler

Exposure Scenarios, Data and Assumptions

Residential exposure to chlorine dioxide can occur through mopping,
spraying, and applying products to pools and spas.  A number of
assumptions, or estimates, such as adult body weight and area treated
per application, are made by the Agency for residential risk assessment.
 Also, note that residential handlers are addressed somewhat differently
than occupational handlers in that homeowners are assumed to complete
all elements of an application (mix/load/apply) without the use of
personal protective equipment.  In addition, for residential handlers it
is assumed that all exposures are short-term.

The residential handler risk assessment based on these scenarios:

	(1)	Mopping: 1 gal/use

	(2)	Trigger-pump sprayers: 0.5 liters or 0.13 gal/day

	(3)	Swimming pools:  160 g ai/20,000 gallons of water

Chlorine dioxide and sodium chlorite products are widely used and have a
large number of use patterns that are difficult to completely capture in
the risk assessment.  As such, the Agency has selected representative
scenarios for each use site that are believed to be high-end estimates
for the vast majority of chlorine dioxide uses, based on end-use product
application methods and use amounts.

For the residential handler risk assessment, dermal unit exposure values
were taken from the proprietary Chemical Manufacturers Association (CMA)
antimicrobial exposure study, 1999, (MRID 42587501) or from the
Pesticide Handler Exposure Database (PHED, 1998).  The scenarios
evaluated for dermal and inhalation risks in the residential handler
assessment are as listed below:

Mopping floors;

Applying trigger-pump sprays to hard surfaces; and

Placing solid tablets in swimming pools or spas

Off-gassing during application of the aqueous solution.

The potential exposures from mopping and cleaning are expected to be
best represented by the short-term duration.  Dermal and inhalation
exposures were assessed for all residential handler scenarios.  For the
mopping application and application of tablets to swimming pools and
spas, values from the Chemical Manufacturers Association (CMA)
antimicrobial study (U.S. EPA, 1999) were used.  For the application of
chlorine dioxide products with a trigger-pump spray, the Pesticide
Handler Exposure Database (PHED, 1998) was used to determine exposure.

To determine the potential inhalation handler exposure resulting from
the vapor of chlorine dioxide as a general purpose cleaner, the model
EFAST (Exposure and Fate Assessment Screening Tool) was used to estimate
the chlorine dioxide air concentrations.  For additional information,
please refer to “Chlorine Dioxide Occupational and Residential
Exposure Assessment,” dated August 2, 2006.

Residential Handler Risk Estimates

Based on toxicological criteria and potential for exposure, the Agency
has conducted dermal and inhalation exposure assessments.  A summary of
the residential handler exposures and risk are presented on Table 7.
The exposure duration of most homeowner applications of cleaning
products and pools are believed to be best represented by the short-term
duration.  The toxicological endpoint is based on an oral study and no
dermal absorption value is available.  Therefore 100% dermal absorption
was assumed for chlorine dioxide or chlorite ion residues.  While there
is some evidence that chlorine dioxide is readily absorbed in skin, this
assessment is very conservative.  The dermal MOEs for the floor mopping,
and application to hard surfaces, are above the target MOE of 100, and
therefore, are not of concern.  The short-term dermal MOE for pool or
spa treatments is 46 without the use of gloves and is of concern to the
Agency; therefore, the labels must be amended to require gloves.  Based
on the average daily air concentration, the handler inhalation exposures
of chlorine dioxide are not of concern (i.e., the average air
concentration estimated by EFAST of 0.003 ppm is below the RfC of 0.05
ppm).

Table 7. Calculation of Short-term Dermal MOEs for Residential Handlers

Exposure Scenario	Application Ratea

(lb ai/gal)	Amount Handled/ Treated Dailyb

(gal)	Baseline Dermal Unit Exposurec (mg/lb ai)	Baseline Dermal Dosed,e

(mg/kg/day)	Baseline Dermal MOEf

(Target MOE = 100)

Mopping

(CMA data)	Hard Surfaces	0.002	1	71.6	0.0024	1300

Trigger-pump sprayer (Aerosol can

PHED data used as surrogate)	Hard Surfaces	0.002	0.13	220	0.00095	3200

Solid Place

(Tablets)

	Pools & Spa water Circulation Systems	1.8E-5

(4 tablets /10,000 gal.  Pool tablet is 100 g x 4 tablets x 20%ai = 80 g
ai/10,000 gal = 1.8E-5 lb ai/gal)	20,000 gal	10.8

(no gloves)	0.065

(no gloves)	46

(no gloves)

0.412

(with gloves)	0.006

(with gloves)	500

(with gloves)

Residential Post-Application

Exposure Scenarios, Data and Assumptions

Residential post-application exposures result when bystanders (adults
and children) come in contact with chlorine dioxide in areas where
pesticide end-use products have recently been applied (e.g., treated
hard surfaces/floors), or when children incidentally ingest the
pesticide residues through hand-to-mouth contact of the treated surface.
The residential post-application scenarios considered in this assessment
are exposure to residues from hard surfaces (i.e., floors) that have
been mopped or cleaned with a product containing chlorine dioxide, the
use of continuous release air deodorizers, and a single treatment of
HVAC systems with chlorine dioxide.

	Chlorine dioxide and/or sodium chlorite can be applied as an aqueous
solution to hard surfaces such as floors and potentially result in
inhalation exposure.  The Agency assessed these risks based on dilution
and ventilation along with the half-life of chlorine dioxide.  This
assessment estimated an 8-hour time weighted average air concentration
starting immediately after application.

	Typically, most products used in a residential setting result in
exposures occurring over short-term time duration (1 – 30 days).  For
the purposes of this screening-level assessment, post application
scenarios have been developed that encompass multiple products, but
still represent a high-end scenario for all products represented.

Four scenarios have been evaluated in the residential post-application
assessment.

Exposure to residue from hard floors that have been cleaned with a
solution containing chlorine dioxide;

Exposure to chlorine dioxide used to clean residential HVAC systems;

Exposure to a continuous release (gas) deodorizer; and

Swimming in treated pools or spas.

Residential Post-Application Risk Estimates

Based on toxicological criteria and potential for exposure, the Agency
has conducted dermal, incidental oral and inhalation exposure
assessments.  As noted previously, MOEs greater than or equal to 100 are
considered adequately protective for the residential exposure
assessment.

  SEQ CHAPTER \h \r 1  A summary of the residential handler exposures
and risk are presented on Table 8. The risks from dermal and incidental
oral exposures for all scenarios are below the Agency’s level of
concern.

	  SEQ CHAPTER \h \r 1 For children, the short- and intermediate-term
oral and dermal MOEs for contact of hard surfaces following disinfection
are above the target MOE of 100 for applications in residential and
daycare settings.  Therefore, the risks from these uses are not of
concern.

	Inhalation exposures due to post application activities could occur for
children after the treatment of floors; adults and children after the
treatment of HVAC systems; and adults and children after the use of
continuous release (gas) deodorizers.  Chlorine dioxide/sodium chlorite
can be applied as an aqueous solution to hard surfaces such as floors
and potentially result in inhalation exposure.  For this assessment, the
Agency estimated the air concentration to be 0.003 ppm, which is below
the short-term RfC of 0.05 ppm, and therefore not of concern.  For
application to HVAC systems, this use is not of concern.  For the
continuous release deodorizer, the estimated constant air concentration
was 0.52 ppm, assuming no air exchange and no build up of chlorine
dioxide over time because of the short half-life.  This risk is of
concern to the Agency.  The RfC for long-term continuous exposure is
0.00007 ppm; therefore this risk is of concern to the Agency.  The
registrant has agreed to delete residential uses of these products.

	The application of chlorine dioxide to swimming pools or spas, is not
assessed quantitatively.  Based on use directions on current labels,
dermal, incidental oral, and inhalation exposures to chlorine dioxide
residual levels after the dilution in the water, and cleaning of the
circulation systems are expected to be minimal.  Table 8 shows a
representative sample of the short- and intermediate-term residential
post-application risks.

	There is also the potential for inhalation exposure as a result of the
use of chlorine dioxide as a dust on carpets.  The registrant has agreed
to mitigate any potential risk from this use by limiting it to
professional carpet applicators, packaging only in containers that are
large enough to discourage retail sale and requiring an REI of one hour
prior to entry into a treated room.

Table 8.  Summary of Short- and Intermediate-Term

Residential Post-application Exposures and Risks

Scenario	Dose a

(mg/kg/day) 	MOEb

Dermal Exposure

Hard surface Disinfection	Residential Setting and

Daycare Center	0.017 a	280

Incidental Oral Exposure

Hard surface Disinfection	Residential Setting and

Daycare Center	0.0013a	2,300

Inhalation Exposure

Scenario	Estimated Air Concentration	RfC (level of concern)

Application to

HVAC Systems	Residential Setting and

Daycare Center	<0.01 ppm	0.05 ppm c

Continuous Release Deodorizer	Residential Setting and

Daycare Center	<0.52 ppm	0.00007 ppm d

a	Dose calculations for each scenario above are outlined in the attached
Occupational/Residential Assessment.

b	MOE= NOAEL (mg/kg/day) / Dose (mg/kg/day). Oral and dermal NOAEL is 3
mg/kg/day.

c RfC  - short-term target is 0.05 ppm.

d RfC  - long-term target is  0.00007 ppm.

8.	Aggregate Risk  XE "III. Summary of 2,4-DB Risk Assessments:A. Human
Health Risk Assessment: 5. Dietary (Food) Risk Assessment"

The FQPA amendments to the Federal Food, Drug, and Cosmetic Act (FFDCA,
Section 408(b)(2)(A)(ii)) require “that there is a reasonable
certainty that no harm will result from aggregate exposure to the
pesticide chemical residue, including all anticipated dietary exposures
and other exposures for which there is reliable information.”
Aggregate exposure will typically include exposures from food, drinking
water, residential uses of a pesticide, and other non-occupational
sources of exposure.

	In accordance with FQPA, the Agency must consider and aggregate
pesticide exposures and risks from three major sources: food, drinking
water, and if applicable, residential or other non-occupational
exposures.  In an aggregate assessment, exposures from relevant sources
are added together and compared to quantitative estimates of hazard
(e.g., a NOAEL), or the risks themselves can be aggregated.  When
aggregating exposures and risks from various sources, the Agency
considers both the route and duration of exposure.  Aggregate exposure
and risk assessments for sodium chlorite include the following: food +
water + residential handler.  For the aggregate of the inhalation route
of exposure, only use of the continuous release air deodorizer product
is assumed to co-occur with the other uses.  In addition, the HVAC
applications will not occur frequently (single exposure); therefore it
was not included in the aggregate assessment.  The inhalation risk for
the continuous release is of concern by itself.  Because we have
agreement that the residential application of the continuous release
deodorizer will be canceled, it has been removed from consideration in
the aggregate assessment.  However, the continuous release air
deodorizer will be allowed in spaces where extended exposure is not
likely, e.g., dumpsters.  This mitigation will result in aggregate risks
that are no longer a concern.  Results of the aggregate risk assessment
are summarized here, and are discussed more extensively in the document:
 Revised Chlorine Dioxide Risk Assessment, dated July 27, 2006, which is
available in the public docket.

Acute Aggregate Risk

	For chlorine dioxide, the acute and chronic aggregate risk assessments
include only dietary, drinking water, and residential exposures.  An
acute dietary risk assessment was not conducted for chlorine dioxide
because there were no acute dietary endpoints of concern.

Short- and Intermediate -Term Aggregate Risk

	The short- and intermediate-term aggregate assessments were conducted
for adults and children.  Table 9 shows the exposure scenarios that were
included in the aggregate assessment for chlorine dioxide.  Use patterns
involving exposure by inhalation (continuous use deodorizer) were not
aggregated because these use patterns were above the Agency’s level of
concern on their own and the Agency has agreement that the use will be
voluntarily cancelled, therefore these aggregate risks are no longer a
concern.

Table 9. Exposure Scenarios Included in the Aggregate Assessments

	Short-term Aggregate	Intermediate-Term Aggregate

Adults	chronic dietary (direct and indirect)

handling cleaning products – spray (dermal only)

handling cleaning products – mopping (dermal only)

chronic drinking water	Not Assessed

Children	chronic dietary – (direct and indirect)

post-app to cleaning product (dermal and oral)

chronic drinking water	chronic dietary – (direct and indirect)

post application to cleaning product (dermal and oral)

chronic drinking water

a Dietary (indirect + direct food contact) exposures = sum of dietary
exposures presented in Table 3.

b Aggregate Dietary Exposures = sum of both dietary (direct and indirect
food contact) exposures and drinking water exposures.

	The toxicity endpoints for the oral and dermal routes of exposure are
based on the same study and same toxic effect; therefore, these two
routes of exposure are aggregated together.  Table 10 presents a summary
of these exposures, including the aggregate dietary exposure (all direct
and indirect food contact exposures) as well as a total dietary
aggregate exposure value (drinking water plus direct/indirect dietary
exposures).  Table 10 presents a summary of the short- and
intermediate-term aggregate exposures and the corresponding aggregate
risks.

	The short-term and immediate-term aggregate risks are not of concern
for adults (total MOE=130).   The short-term and immediate-term
aggregate risks are of concern for children (MOE=44) and infants
(MOE=41).  The primary driver for these risks is dietary exposures.

Table 10. Short- and Intermediate-term Aggregate Risks (MOEs)

Exposure Routes	Aggregate Dietary Risks	Dermal Risks (MOE)	Aggregate
Risks

(MOE)

Hard Surface Cleaning

	Applicator	Post-Application

	Mop	Spray

Adults

Oral Ingestion MOEs	150	NA	NA	NA	150

Dermal MOEs	NA	1300	3200	NA	900

Total MOE	150	1300	3200	NA	130

Children (age 1 – 6)

Oral Ingestion MOEs	60	NA	NA	2300	58

Dermal MOEs	NA	NA	NA	180	180

Total MOE	60	NA	NA	160	44

Infants < 1

Oral Ingestion	55	NA	NA	2300	55

Dermal MOEs	NA	NA	NA	180	180

Total MOE	55	NA	NA	160	41

MOE = NOAEL/dose

Aggregate MOE = 1/((1/MOEdietary) + (1/MOEdrinking water) +
(1/MOEdermal)

All NOAELs = 3 mg/kg/day

Target MOE oral = 100

Target MOE dermal = 100

Chronic Aggregate Risk

	The chronic aggregate risk estimates associated with chlorine dioxide
from dietary uses are below the Agency’s level of concern for adults
at 53% of the cPAD.  However the dietary risks are above the level of
concern for children aged 1 to 6 (133% of the cPAD).

	The chronic aggregate risks are not of concern for adults, as the total
aggregate of the cPAD is 53% (excluding the continuous use deodorizer),
below the target of 100%.  For children, the aggregate risk estimates
are above 100% (133% cPAD) and thus are of concern.  Table 11 presents
the chronic aggregate exposures and risks.

Table 11.  Chlorine Dioxide Chronic Aggregate Exposures and Risks

Exposure Routes	Chronic Dietary Exposures (mg/kg/day)

	Dietary (indirect + direct food contact+ chlorate) Exposuresa	Drinking
water exposures 	Aggregate Dietary Exposuresb	Aggregate Dietary Risks
(%cPAD)

Adults

Oral Ingestion	2.65E-03	1.33E-02	1.6E-02	53.3%

Children (age 1 – 6)

Oral Ingestion	2.27E-02	1.86E-02	4.13e-02	133%

a Dietary (indirect + direct food contact) exposures = sum of dietary
exposures presented in Table 6.

b Aggregate Dietary Exposures = sum of both dietary (direct and indirect
food contact) exposures and drinking water exposures.

		9.	Occupational Exposure and Risk

Workers can be exposed to a pesticide through mixing, loading, and/or
applying a pesticide, or re-entering treated sites.  Occupational
handlers of chlorine dioxide and sodium chlorite include workers in a
variety of occupational settings.  Additionally, post-application
exposures are likely to occur in these settings.  The representative
scenarios selected for assessment were evaluated using maximum
application rates as recommended on the product labels for chlorine
dioxide and sodium chlorite.

Occupational risk is assessed for exposure at the time of application
(termed “handler” exposure) and is assessed for exposure following
application, or post-application exposure.  Application parameters are
generally defined by the physical nature of the formulation (e.g.,
formula and packaging), by the equipment required to deliver the
chemical to the use site, and by the application rate required to
achieve an efficacious dose.

Occupational risk for all of these potentially exposed populations is
measured by a Margin of Exposure (MOE), which determines how close the
occupational exposure comes to a No Observed Adverse Effect Level
(NOAEL) from toxicological studies.  In the case of chlorine dioxide and
sodium chlorite, MOEs greater than 100 for dermal exposures and
inhalation exposures are not of concern to the Agency.  For workers
entering a treated site, MOEs are calculated for each day after
application to determine the minimum length of time required before
workers can safely re-enter.

For more information on the assumptions and calculations of potential
risk of chlorine dioxide to workers, see the Occupational Exposure
Assessment section in the “Chlorine Dioxide Risk Assessment,” dated
July 27, 2006.

a.  	Occupational Toxicity   XE "III. Summary of 2,4-DB Risk
Assessments:7. Occupational Risk:a. Occupational Toxicity"

	Table 6 provides a listing of the toxicological endpoints used in the
occupational risk assessment for chlorine dioxide and sodium chlorite.

Occupational Handler Exposure

  XE "III. Summary of 2,4-DB Risk Assessments:7. Occupational Risk:b.
Occupational Handler Exposure"

Potential occupational handler exposure can occur at various use sites,
including agricultural, food handling, commercial and institutional, and
medical premises; human drinking water systems; industrial processes and
water systems; application to materials as preservatives; and swimming
pools and other aquatic areas.

The Agency has assessed the handler risks from the use of chlorine
dioxide using unit exposure data from both the proprietary Chemical
Manufacturers Association (CMA) antimicrobial exposure study and the
Pesticide Handlers Exposure Database (PHED). Table 12 lists the handler
exposure scenarios assessed for chlorine dioxide.  These scenarios are
considered representative of high-end exposures for the industrial
applications.

Table 12. Exposure Scenarios Associated with

Occupational Exposure Assessed in this Document

Representative Use	Application Method	EPA Registration Number (chemical
associated with use)	Application Rate (lb ai/gal)	Exposure Scenario
Assessed

Use Site Category I (Agricultural Premises and Equipment)a

Application to Hard Surfaces and Equipment	low-pressure hand wand
74602-2

(Sodium Chlorite)	(Application rate from label, 2.5 fl oz/gal)*(1
gal/128 oz)*(0.75 lb ai/gal) = 0.015	Short- and Intermediate-term (ST
and IT) Adult Handler (dermal and inhalation) and Adult Bystander and
Post Application (dermal and inhalation)

	trigger-pump sprayer

fogger (1 hour REI after fogging)	74602-2

(Sodium Chlorite)	(Application rate from label, 2.5 fl oz/gal)*(1
gal/128 oz)*(0.75 lb ai/gal) = 0.015

mop	9150-2

(Chlorine Dioxide)	(Application rate from label, 3.25 fl oz/gal)*(1
gal/128 oz)*(0.69 lb ai/gal) = 0.018

foaming wand	9150-11

(Chlorine Dioxide)	(Application rate from label, 0.25 gal of
product*0.10 lb ai/gal) = 0.025 lb ai/gal.)  Apply at rate of 4 to 6
gallons/minute to inside/outside of animal trucks/equipment.

ULV fogger (e.g., Dramm fogger)	74602-2

(Sodium Chlorite)	( Egg house label rate, 1 gal product x 5% ClO2) per
50 gal = 0.0083)

	Use Site Categories II (Food Handling), III (Commercial/Institutional),
and V (Medical)

Application to Hard Surfaces and Equipment Without Food Contact

	mop 	9150-10 active

(10589-3 transferred)

(Chlorine Dioxide)	(Application rate from label, 5 oz/gal)*(1 gal/128
oz)*(0.49 lb ai/gal) = 0.019	ST/IT Adult Handler (dermal and inhalation)
and Adult Post Application/Bystander (dermal and inhalation)

	trigger-pump sprayer	21164-3

(Sodium Chlorite)

	(Application rate from label, 12 fl oz/gal)*(1 gal/128 oz)*(0.86 lb
ai/gal) = 0.08

	Application to foods (Fruit/Vegetable Rinse) 	dip	74602-2

(Sodium Chlorite)	(Application rate from label, 1.9 oz/gal)*(1 gal/128
oz)*(0.75 lb ai/gal) = 0.011

	Use Site Category VI (Human Drinking Water Systems)

Application to Water Systems (Water Treatment and Water Storage Systems)
metering pump	9804-1

(Chlorine Dioxide)

	(Application rate from label, 3.25 fl oz/gal)*(1 gal/128 oz)*(0.27 lb
ai/gal) = 0.007	ST/IT Adult Handler; Potential for inhalation exposure
unknown at this time.

Use Site Category VII (Material Preservatives)

Applications to Metal Working Fluids	liquid pour	9150-2

(Chlorine Dioxide)	batch method: 0.0001

(per week)

continuous method:

8E-7 (per day)

badly contaminated systems:  4E-6 (slug dose)	ST/IT Adult Handler
(dermal and inhalation) and Long-term Dermal and Inhalation for
Machinists.

Use Site Category VIII (Industrial Processes and Water Systems)

Application to Pulp and Paper White Water Systems	metering pump	74602-3

(Sodium Chlorite)

	(Application rate from label, 15 gal/100,000 gal white water to be
treated or 4 gal/100 tons paper produced)*(0.86 lb ai/gal) = 0.0001 lb
ai/gal white water or 3.44 lb ai/100 ton paper produced	ST/IT Adult
Handler (dermal and inhalation) and Adult Bystander (inhalation)

Application to Oil Systems (oil Wells During Secondary

Recovery Operations)

	liquid pour	9150-2

(Chlorine Dioxide)

	(Application rate from label, 1 gal/10 gal)*(0.69 lb ai/gal) = 0.069.

Label indicates to portion 1 part of this solution to 150 parts
reinjection water.	ST/IT Adult Handler (dermal and inhalation) and Adult
Bystander (inhalation)

Use Site Category XI (Swimming Pools)

Application to Public Swimming Pool Circulation Water Systems (Swimming
Pools)	solid place (tablets)	70060-20

(Sodium chlorite)

	4 tablet /10,000 gal

(Pool tablet is 100 g x 4 tablets x 20%ai = 80 g ai/10,000 gal = 1.8E-5
lb ai/gal)	Short-term Adult Handler (dermal and inhalation)

Use Site Category XII ( Aquatic Areas)

Non-potable Water Systems (e.g., retention basins and ponds, decorative
pools and fountains)	liquid pour	9150-11

(Chlorine Dioxide)	0.00001

(18 fl oz x 0.72% ai per 100 gallons water)	ST/IT Adult Handler (dermal
and inhalation)

Use Site Category XIII (HVAC)

Application to Ventilation Systems

(HVAC)	airless sprayer

fogger  (1hour REI after fogging)	9804-1

(Chlorine Dioxide)	(Application rate from label, 3.25 fl oz/gal)*(1
gal/128 oz)*(0.27 lb ai/gal) = 0.007	ST/IT Adult Handler (dermal and
inhalation) and Short-term Child and Adult Post Application (inhalation)

Occupational Handler Risk Summary

i. 	Dermal Risks

For the occupational handler dermal risk assessment, the short- and
intermediate- term risks calculated at baseline exposure (no gloves and
no respirators) were above target MOEs for all scenarios (i.e., dermal
MOEs were >100), except for the following:

Agricultural premises and equipment:

application to hard surfaces: low pressure handwand (MOE=31);

application to hard surfaces: mopping (MOE=70); and

application to hard surfaces: foam applicator equipment (MOE=8).

Food Handling, Commercial/Institutional, and Medical Premises and
Equipment:

application to hard surfaces:

mopping (MOE=66 commercial; 3 medical).

Swimming pools:

placement of tablets (MOE=5)

A summary of the occupational handler assessment is provided in Table
13.

Table 13.  Short-, Intermediate-Term Dermal Risks for Occupational
Handlers

Exposure Scenario	Method of Application	Application Rate

(lb ai/ gallon)	Quantity Handled/

Treated per day (gallons)	Dermal MOEc

Baseline Dermala

(Target MOE>100)	PPE Gloves Dermalb

(Target MOE>100)

1Agricultural Premises and Equipment

Application to Hard Surfaces	Low pressure handwand	0.015	2	31	No data

	Liquid Pour

0.188	1,300	6,300

	Trigger-pump sprayer

0.26	240	570

	Mopping	0.018	2	70	No data

	Foam applicator equipment	0.025 	60	3	8

Food Handling, Commercial/Institutional, and Medical Premises and
Equipment

Application to Hard Surfaces	Mopping (general)	0.019	2	66	No data

	Trigger-pump sprayer	0.08	0.26	46	110

	Mopping

(medical)	0.019	45	3	No data

Human Drinking Water Systems

Water and Storage Systems	Metering pump	0.007	34,000	No data	120

Material Preservatives

Metal Working Fluid	Liquid pour	0.0001	300	No data	33,000

Industrial Processes and Water Systems

Paper and Pulp White Water Systems	Metering pump	0.0344 lb ai/ton paper
500 tons paper	No data	2,300

Oil Systems	Open pour	0.069	2.8	NA	6,900

	5.6

3,500

Swimming Pools and Aquatic Areas

Retention Ponds/ Fountain	Liquid pour	0.00001	10,000 gal	No data	670

Swimming Pools (public)	Solid place	1.8E-5	200,000 gal	5	120

HVAC Systems

HVAC	Airless sprayer	0.007	5	140	NA

	Fogger

(liquid pour)

0.25	2,000	NA

a	Baseline Dermal:  Long-sleeve shirt, long pants, no gloves.

b	PPE Dermal with gloves: baseline dermal plus chemical-resistant
gloves.

c	MOE = NOAEL  (mg/kg/day) / Daily Dose [Where short-and
intermediate-term NOAEL = 3 mg/kg/day for dermal exposure]. Target MOE
is 100 for dermal exposure.

			ii.	Inhalation Risks

Inhalation exposures and risks were not assessed separately for the
handlers.  Instead, the occupational inhalation handler exposures are
combined as part of the full work-day for handler/bystanders to be
comparable to EPA’s inhalation toxicological endpoint which is based
on an 8-hour time-weighted average.  For the peak, short-term exposures
to chlorine dioxide gas experienced during mixing/loading and/or system
leaks/failures, EPA will rely on the American Conference of Governmental
Industrial Hygienists (ACGIH) Short-term Exposure Limit (STEL) and
Immediately Dangerous to Life or Health (IDLH) standards to mitigate
risks.

For most of the bystander/post application occupational scenarios, the
inhalation risks for the bystander/post application occupational
exposures are of concern using the EPA’s selected inhalation
toxicological endpoint (RfC).  The occupational RfC, 0.003 ppm, is below
the limit of detection for chlorine dioxide.  Based on OSHA’s
Integrated Management Information System (IMIS) data available for
chlorine dioxide, all air concentration measurements, even those that
were undetectable, are above the RfC.  EPA is aware of the discrepancy
between the EPA risk-based RfC and current OSHA standards,
reconciliation will occur at a later date.

d.	Occupational Post-application

					i.	Dermal Post-Application Exposure

	No information is available to assess post application/bystander dermal
exposure to uses in agricultural premises as well as food handling,
commercial/institutional and medical premises; human drinking water
facilities; industrial processes; and retention ponds.  However, dermal
post application exposure to chlorine dioxide is expected to be less
than that of the dermal contact of children playing on treated floor
surfaces.  Therefore, the dermal exposure route is not believed to be of
concern in these industries.

					ii.	Inhalation Post-Application Exposure

Non-Fogging Uses

Post-application/bystander inhalation exposures were assessed by
obtaining air concentration measurements from the Occupational Safety
and Health Administration (OSHA) for the non-fogging uses. The data
selected for this analysis include only those samples that are reported
as 8-hour time-weighted average (TWA) measurements from personal air
samplers.  Other samples, such as peak concentrations and/or area
monitors, have been omitted.  The inhalation endpoint selected by EPA is
0.003 ppm, just below the OSHA LOD for an 8-hour TWA air sample.  The
summary results of the 33 observations taken from 8-hour TWA personal
air samplers for chlorine dioxide are above the EPA selected inhalation
reference concentration (RfC) of 0.003 ppm, and therefore, are of
concern.

Fogging Uses

The fogging use of chlorine dioxide is unique such that no persons are
present during the actual application/fogging.  There is also a greater
potential for chlorine dioxide gas formation from fogging than an
aqueous-based application such as mopping.  Therefore, a separate
assessment was developed for foggers that indicate potential inhalation
exposure and reentry recommendations.  The air concentration in a fogged
area should be below the occupational RfC of 0.003 ppm before the room
is entered by persons not wearing respiratory protection.

One scenario based on labeled application rates allows chlorine dioxide
fogging and misting applications while workers are in the room if the
level of chlorine dioxide does not exceed the TLV-TWA of 0.1 ppm.  The
occupational RfC of 0.003 ppm could be exceeded based on these use
directions (i.e., workers do not need to leave treatment area unless the
TLV-TWA of 0.1 ppm is exceeded).  This scenario is of potential concern
to the Agency.  To mitigate this risk, labels must be changed to
prohibit re-entry into treated areas for one hour after treatment.

EPA’s Risk-based RfC versus OSHA PEL

It is also important to note that the OSHA Permissible Exposure Limit
(PEL) for chlorine dioxide is 0.1 ppm.  Air concentrations above the PEL
are assumed to be mitigated at each facility.  Facilities using chlorine
dioxide are not required to mitigate inhalation exposures until the air
concentration reaches 0.1 ppm.  Based on the occupational inhalation
toxicological endpoint selected for chlorine dioxide (i.e., RfC of 0.003
ppm), levels at or near the PEL are of concern.  In fact, the capability
(i.e., LOD) of the OSHA sampling method is insufficient for the
occupational RfC presented in this document.  Reconciliation of the EPA
risk-based RfC and the current OSHA standards will be made at a later
date.

					e.  	Human Incident Data   XE "III. Summary of 2,4-DB Risk
Assessments:7. Occupational Risk:e. Human Incident Data"

  XE "III. Summary of 2,4-DB Risk Assessments:7. Occupational Risk:e.
Human Incident Data"

The Agency reviewed available sources of human incident data for
incidents relevant to chlorine dioxide/sodium chlorite.    tc "8.0
INCIDENTS"   SEQ CHAPTER \h \r 1 EPA consulted the following sources of
information for human poisoning incidents related to TCMTB use:  (1) OPP
Incident Data System (IDS) - The Office of Pesticide Programs (OPP)
Incident Data System contains reports of incidents from various sources,
including registrants, other federal and state health and environmental
agencies and individual consumers, submitted to OPP since 1992;  (2)
SEQ CHAPTER \h \r 1 California Department of Pesticide Regulation
(1982-2004) – The California Department of Pesticide Regulation
pesticide poisoning surveillance program consists of reports from
physicians of  illness suspected of being related to pesticide exposure
since 1982.  (3)   SEQ CHAPTER \h \r 1 National Pesticide Information
Center (NPIC) - NPIC is a toll-free information service supported by OPP
that provides a ranking of the top 200 active ingredients for which
telephone calls were received during calendar years 1984-1991.

There are some reported incidents associated with exposure to end-use
products containing chlorine dioxide.  Inhalation is the primary route
of exposure.  Most of the incidents are related to irritation type
reactions to bronchial and nasal passages, and the eyes.

The most common symptoms reported for cases of inhalation exposure were
respiratory irritation/burning, irritation to mouth/throat/nose,
coughing/choking, shortness of breath, dizziness, flu-like symptoms, and
headache.

B.  	Environmental Risk Assessment   XE "III. Summary of 2,4-DB Risk
Assessments:B. Environmental Risk Assessment"

A summary of the Agency’s environmental risk assessment is presented
below.  The following risk characterization is intended to describe the
magnitude of the estimated environmental risks for chlorine dioxide and
sodium chlorite use sites and any associated uncertainties.

For a detailed discussion of all aspects of the environmental risk
assessment, see the document “Environmental Hazard and Risk
Assessment,” dated July 13, 2006.

Environmental Fate and Transport

In the environment, chlorine dioxide and sodium chlorite are assessed
together because chlorine dioxide is produced by a reaction of sodium
chlorite (and sometime sodium chlorate) and hypochlorite/acid. In
addition, chlorite is a breakdown product of chlorine dioxide.

Chlorine dioxide has a short half-life and in the presence of sunlight
will break down into chloride and chlorate ions (between pH 4 and 7).
At pH lower than 4, its breakdown products are chlorite and chlorate.
Chlorite is the dominant breakdown product.

Chlorate and chlorite ions tend to only undergo biodegradation only
under anaerobic conditions.  Biodegradation of chlorate and chlorite has
been observed in anoxic groundwater, sediments and some soils. The end
products are the chloride and oxygen.  No adsorption/desorption
constants (Kds) have been measured or reported in published literature
for either chlorite or chlorate.  These ions are likely to be mobile and
may travel from surface to groundwater easily.  The estimated log Kow of
chlorine dioxide is -3.22 and for sodium chlorite is -7.17.  It is not
expected that either would bioaccumulate in aquatic organisms.

Ecological Exposure and Risk

Chlorine dioxide and sodium chlorite are used as antimicrobial
pesticides at numerous use sites.  Sodium chlorite is used as a
precursor in the generation of chlorine dioxide.  The antimicrobial
registered uses of chlorine dioxide/sodium chlorite fall into several
major categories including use in the treatment of human drinking water
systems; in industrial process and water systems; as a materials
preservative; and as a general disinfectant in medical, residential,
agricultural, commercial and industrial settings.  The indoor uses of
sodium chlorite will not result in exposure to the environment.

The use of chlorine dioxide in cooling towers was modeled because it
represents the worst-case scenario for the chlorine dioxide uses.  For
terrestrial animals, the results of studies show that toxicity of
chlorine dioxide/sodium chlorite to birds ranges from highly to slightly
toxic to birds on an acute oral basis and from slightly toxic to
practically non-toxic on a subacute dietary basis.

For freshwater aquatic animals, the results of studies examining the
toxicity of chlorine dioxide/sodium chlorite to freshwater fish indicate
these chemicals range from slightly toxic to practically non-toxic on an
acute basis.  For aquatic invertebrates, the studies indicate that
chlorine dioxide and sodium chlorite range from very highly toxic for
technical grade sodium chlorite to practically non-toxic for the
formulated product on an acute basis.  Results of toxicity studies
indicate that chlorine dioxide/sodium chlorite are slightly toxic to
estuarine/marine fish on an acute basis and range from highly toxic to
slightly toxic to estuarine/marine invertebrates on an acute basis.

For terrestrial plants, results of toxicity studies indicate that
chlorine dioxide/sodium chlorite are moderately toxic to terrestrial
plants.  For aquatic plants, toxicity study results indicate chlorine
dioxide/sodium chlorite are moderately toxic to aquatic plants.

 For aquatic organisms, acute risk is anticipated from the use of
chlorine dioxide/sodium chlorite in once-through cooling towers based on
the modeling conducted.  At the highest doses, there is risk to
freshwater and marine/estuarine fish and invertebrates and aquatic
plants, and at the lowest doses there is risk only to freshwater
invertebrates.  Chronic risk to aquatic organisms cannot be assessed at
this time due to the lack of chronic toxicity endpoints for fish and
aquatic invertebrates.  When the required aquatic chronic toxicity
testing described above is submitted, chronic risk to these organisms
will be assessed.

The once-through cooling tower use of chlorine dioxide/sodium chlorite
has been selected for risk assessment because out of all the uses of
these chemicals, it is the one expected to have the most potential for
environmental exposure.  The environmental risk assessment was conducted
using sodium chlorite endpoints because under environmental conditions,
chlorine dioxide converts mostly into chlorite ions.

Listed Species Consideration

			a.	The Endangered Species Act   XE "IV. Risk Management,
Reregistration, and Tolerance Reassessment Decision:D. Regulatory
Rationale: 4. Threatened and Endnagered Species Considerations: a. The
Endangered Species Program"

Section 7 of the Endangered Species Act, 16 U.S.C. Section 1536(a)(2),
requires all federal agencies to consult with the National Marine
Fisheries Service (NMFS) for marine and anadromous listed species, or
the United States Fish and Wildlife Services (FWS) for listed wildlife
and freshwater organisms, if they are proposing an “action” that may
affect listed species or their designated habitat.  Each federal agency
is required under the Act to insure that any action they authorize,
fund, or carry out is not likely to jeopardize the continued existence
of a listed species or result in the destruction or adverse modification
of designated critical habitat.  To jeopardize the continued existence
of a listed species means “to engage in an action that reasonably
would be expected, directly or indirectly, to reduce appreciably the
likelihood of both the survival and recovery of a listed species in the
wild by reducing the reproduction, numbers, or distribution of the
species.” 50 C.F.R. § 402.02.

To facilitate compliance with the requirements of the Endangered Species
Act subsection (a)(2) the Environmental Protection Agency, Office of
Pesticide Programs has established procedures to evaluate whether a
proposed registration action may directly or indirectly reduce
appreciably the likelihood of both the survival and recovery of a listed
species in the wild by reducing the reproduction, numbers, or
distribution of any listed species (U.S. EPA, 2004).  After the
Agency’s screening-level risk assessment is performed, if any of the
Agency’s Listed Species LOC Criteria are exceeded for either direct or
indirect effects, a determination is made to identify if any listed or
candidate species may co-occur in the area of the proposed pesticide
use.  If determined that listed or candidate species may be present in
the proposed use areas, further biological assessment is undertaken.
The extent to which listed species may be at risk then determines the
need for the development of a more comprehensive consultation package as
required by the Endangered Species Act.

Acute risk to listed birds and mammals is not anticipated from the use
of chlorine dioxide and sodium chlorite products due to low exposure and
low toxicity.  Further evaluation is needed before it can be determined
if there are risks to listed aquatic organisms from the once through
cooling tower use of chlorine dioxide/sodium chlorite.  Chronic risks to
listed aquatic organisms cannot be assessed at this time; this risk will
be assessed when required chronic toxicity data are submitted to and
evaluated by the Agency.  These conclusions are based solely on EPA’s
screening-level assessment and do not constitute “may effect”
findings under the Endangered Species Act for any listed species.

IV.  	Risk Management, Reregistration, and Tolerance Reassessment
Decision  XE "IV. Risk Management, Reregistration, and Tolerance
Reassessment Decision"

	A.  	Determination of Reregistration Eligibility   XE "IV. Risk
Management, Reregistration, and Tolerance Reassessment Decision: A.
Determination of Reregistration Eligibility" \i

	Section 4(g)(2)(A) of FIFRA calls for the Agency to determine, after
submission of relevant data concerning an active ingredient, whether or
not products containing the active ingredient are eligible for
reregistration.  The Agency has previously identified and required the
submission of the generic (i.e., active ingredient-specific) data
required to support reregistration of products containing chlorine
dioxide and sodium chlorite as an active ingredient.  The Agency has
completed its review of these generic data, and has determined that the
data are sufficient to support reregistration of all supported products
containing chlorine dioxide and sodium chlorite.

	The Agency has completed its assessment of the dietary, occupational,
drinking water, and ecological risks associated with the use of
pesticide products containing the active ingredient chlorine dioxide and
sodium chlorite.  Based on a review of these data and on public comments
on the Agency’s assessments for the active ingredient chlorine dioxide
and sodium chlorite, the Agency has sufficient information on the human
health and ecological effects of chlorine dioxide and sodium chlorite to
make decisions as part of the tolerance reassessment process under FFDCA
and reregistration process under FIFRA, as amended by FQPA.  The Agency
has determined that all chlorine dioxide and sodium chlorite
pesticide-containing products are eligible for reregistration provided
that: (i) current data gaps and confirmatory data needs are addressed;
(ii) the risk mitigation measures outlined in this document are adopted;
and (iii) label amendments are made to reflect these measures.  Label
changes are described in Section V.  Appendix A summarizes the uses of
chlorine dioxide and sodium chlorite that are eligible for
reregistration.  Appendix B identifies the generic data requirements
that the Agency reviewed as part of its determination of reregistration
eligibility of chlorine dioxide and sodium chlorite, and lists the
submitted studies that the Agency found acceptable.  Data gaps are
identified as generic data requirements that have not been satisfied
with acceptable data.

	Based on its evaluation of chlorine dioxide and sodium chlorite, the
Agency has determined that chlorine dioxide and sodium chlorite
products, unless labeled and used as specified in this document, would
present risks inconsistent with FIFRA.  Accordingly, should a registrant
fail to implement any of the risk mitigation measures identified in this
document, the Agency may take regulatory action to address the risk
concerns from the use of chlorine dioxide and sodium chlorite.  If all
changes outlined in this document are incorporated into the product
labels, then all current risks for chlorine dioxide and sodium chlorite
will be substantially mitigated for the purposes of this determination.
Once an Endangered Species assessment is completed, further changes to
these registrations may be necessary as explained in Section III of this
document.

B.  	Public Comments and Responses   XE "IV. Risk Management,
Reregistration, and Tolerance Reassessment Decision: B. Public Comments
and Responses" \i

	Through the Agency’s public participation process, EPA worked with
stakeholders and the public to reach the regulatory decisions for
chlorine dioxide and sodium chlorite.  During the public comment period
on the risk assessments, which closed on June 26 ,2006, the Agency
received comments from the registrants, Chlorine Dioxide Panel and other
interested parties.  These comments in their entirety, as well as the
risk assessments for chlorine dioxide, are available in the public
docket (EPA-HQ-OPP-2006-0328) at   HYPERLINK
"http://www.regulations.gov/"  http://www.regulations.gov/ .   The
Agency’s responses to these comments are incorporated into the risk
assessment and revised chapters, which are also available in the public
docket.

	C.  	Regulatory Position   XE "IV. Risk Management, Reregistration, and
Tolerance Reassessment Decision:C. Regulatory Posistion" \i

		1.	Food Quality Protection Act Findings   XE "IV. Risk Management,
Reregistration, and Tolerance Reassessment Decision: C. Regulatory
Position: 1. Food Quality Protection Act Findings"

			a.  	“Risk Cup” Determination   XE "IV. Risk Management,
Reregistration, and Tolerance Reassessment Decision: C. Regulatory
Position: 1. Food Quality Protection Act Findings: a. "Risk Cup"
Determination"

As part of the FQPA tolerance reassessment process, EPA assessed the
risks associated with this pesticide.  The Agency has determined that,
if the mitigation described in this document is adopted and labels are
amended, human health risks as a result of exposures to sodium chlorite
are within acceptable levels.  In other words, EPA has concluded that
the exemptions from tolerances for sodium chlorite meet FQPA safety
standards.  In reaching this determination, EPA has considered the
available information on the special sensitivity of infants and
children, as well as exposures to sodium chlorite from all possible
sources.

b.	Determination of Safety to U.S. Population

  SEQ CHAPTER \h \r 1 	As part of the FQPA tolerance reassessment
process, EPA assessed the risks associated with chlorine dioxide and
sodium chlorite. The Agency has determined that, taking into
consideration that a safety finding was made for sodium chlorate in the
Inorganic Chlorates RED, the established tolerance exemptions for
chlorine dioxide and sodium chlorite, with amendments and changes as
specified in this document, meet the safety standards under the FQPA
amendments to section 408(b)(2)(D) of the FFDCA, and that there is a
reasonable certainty no harm will result to the general population or
any subgroup from the use of chlorine dioxide and sodium chlorite.  In
reaching this conclusion, the Agency has considered all available
information on the toxicity, use practices and exposure scenarios, and
the environmental behavior of chlorine dioxide and sodium chlorite.  As
discussed in Section III, the acute, and chronic dietary (food and
drinking water) risks from chlorine dioxide and sodium chlorite are
below the Agency’s level of concern, provided that mitigation measures
outlined in this document and the and the Inorganic Chlorates RED are
adopted and labels are amended.

		c.  	Determination of Safety to Infants and Children   XE "IV. Risk
Management, Reregistration, and Tolerance Reassessment Decision:C.
Regulatory Position: 1. Food Quality Protection Act Findings: c.
Determination of Safety to Infants and Children "

	EPA has determined that the tolerance exemptions for chlorine dioxide
and sodium chlorite, with amendments and changes as specified in this
document, meet the safety standards under the FQPA amendments to section
408(b)(2)(C) of the FFDCA, that there is a reasonable certainty of no
harm for infants and children.  The safety determination for infants and
children considers factors of the toxicity, use practices, and
environmental behavior noted above for the general population, but also
takes into account the possibility of increased dietary exposure due to
the specific consumption patterns of infants and children, as well as
the possibility of increased susceptibility to the toxic effects of
chlorine dioxide and sodium chlorite residues in this population
subgroup.

In determining whether or not infants and children are particularly
susceptible to toxic effects from exposure to residues of chlorine
dioxide/sodium chlorite, the Agency considered the completeness of the
hazard database for developmental and reproductive effects, the nature
of the effects observed, and other information.  On the basis of this
information, the FQPA safety factor has been reduced to 1X for chlorine
dioxide/sodium chlorite.  The rational for the decisions are based on:
(1) the existence of a complete developmental and reproductive toxicity
database; (2) the endpoint selected for assessment of risk from dietary
and non-dietary exposure to chlorine dioxide is protective of
potentially susceptible populations including children and (3) the risk
assessment does not underestimate the potential exposure for infants and
children.

			d.  	Endocrine Disruptor Effects   XE "IV. Risk Management,
Reregistration, and Tolerance Reassessment Decision:C. Regulatory
Position: 1. Food Quality Protection Act Findings: d. Endocrine
Disruptor Effects"

EPA is required under the Federal Food Drug and Cosmetic Act (FFDCA), as
amended by FQPA, to develop a screening program to determine whether
certain substances (including all pesticide active and other
ingredients) “may have an effect in humans that is similar to an
effect produced by a naturally occurring estrogen, or other such
endocrine effects as the Administrator may designate.”  Following
recommendations of its Endocrine Disruptor and Testing Advisory
Committee (EDSTAC), EPA determined that there was a scientific basis for
including, as part of the program, the androgen and thyroid hormone
systems, in addition to the estrogen hormone system.  EPA also adopted
EDSTAC’s recommendation that the Program include evaluations of
potential effects in wildlife.  For pesticide chemicals, EPA will use
FIFRA and, to the extent that effects in wildlife may help determine
whether a substance may have an effect in humans, FFDCA authority to
require the wildlife evaluations.  As the science develops and
resources allow, screening of additional hormone systems may be added to
the Endocrine Disruptor Screening Program (EDSP).

			e.  	Cumulative Risks   XE "IV. Risk Management, Reregistration, and
Tolerance Reassessment Decision:C. Regulatory Position: 1. Food Quality
Protection Act Findings: e. Cumulative Risks"

	Risks summarized in this document are those that result only from the
use of chlorine dioxide and sodium chlorite.  The Food Quality
Protection Act (FQPA) requires that the Agency consider “available
information” concerning the cumulative effects of a particular
pesticide’s residues and “other substances that have a common
mechanism of toxicity.”  The reason for consideration of other
substances is due to the possibility that low-level exposures to
multiple chemical substances that cause a common toxic effect by a
common toxic mechanism could lead to the same adverse health effect as
would a higher level of exposure to any of the substances individually.
Unlike other pesticides for which EPA has followed a cumulative risk
approach based on a common mechanism of toxicity, EPA has not made a
common mechanism of toxicity finding for chlorine dioxide and sodium
chlorite.  For information regarding EPA’s efforts to determine which
chemicals have a common mechanism of toxicity and to evaluate the
cumulative effects of such chemicals, see the policy statements released
by EPA’s Office of Pesticide Programs concerning common mechanism
determinations and procedures for cumulating effects from substances
found to have a common mechanism on EPA’s website at     HYPERLINK
"http://www.epa.gov/pesticides/cumulative/"
http://www.epa.gov/pesticides/cumulative/ .

2.	Tolerance Reassessment Summary

Table 12 summarizes the reassessment of the chlorine dioxide tolerance
exemptions

for sodium chlorite.

	In order to support the use of chlorine dioxide/sodium chlorite as a
fruit and vegetable wash for Raw Agricultural Commodities that will not
be processed, a petition to establish a tolerance exemption must be
submitted.

Tolerances Currently Listed Under 40 CFR §180.940(b)(c) and
Tolerance Reassessment

  XE "IV. Risk Management, Reregistration, and Tolerance Reassessment
Decision:C. Regulatory Position: 2. Tolerance Reassessment: a.
Tolerances Currently listed and Tolerance Reassessment"

Table 12.  Tolerance Information Listed Under 40 CFR 180.1070

Expression	Commodity	Current Tolerance	Tolerance Reassessment	Use

Sodium chlorite 	 Brassica (cole) leafy vegetables 	Exempt

	Exempt 1	seed soak treatment in the growing of the raw agricultural
commodities crop group Brassica (cole) leafy vegetables and radishes

Sodium chlorite	Radishes	Exempt

	Exempt 1	seed soak treatment in the growing of the raw agricultural
commodities crop group Brassica (cole) leafy vegetables and radishes

Tolerance Exemption Expression	CAS No.	40 CFR

	Use Pattern	Limits

Oxychloro species(including chlorine dioxide) generated by acidification
of an aqueous solution of sodium chlorite	N/A	180.940 (b)2(c)3
Food-contact surface sanitizing solution 	When ready for use, the
end-use concentration is not to exceed 200 ppm chlorine dioxide

Tolerance Exemption Expression	CAS No.	40 CFR

	Use Pattern	Limits

Oxychloro species (predominately chlorite, chlorate and chlorine dioxide
in an equilibrium mixture) generate either  (i) by directly metering a
concentrated chlorine dioxide solution prepared just prior to use, into
potable water, or (ii) by acidification of an aqueous alkaline solution
of oxychloro species (predominately chlorite and chlorate) followed by
dilution with potable water	N/A	180.940 (c)3	Food-contact surface
sanitizing solution 	When ready for use, the end-use concentration is
not to exceed 200 ppm chlorine dioxide

Residues listed under 40 CFR §180.1070 are exempted from the
requirement of a tolerance  when used as a  seed soak treatment in the
growing of the raw agricultural commodities group listed

Under 40 CFR §180.940(b), chemical substances when use as ingredients
in an antimicrobial pesticide formulation may be applied to dairy
processing equipment, and food-processing equipment and utensils.

Under 40 CFR §180.940 (c), chemical substances when used as ingredients
in an antimicrobial pesticide formulation may be applied to
food-processing equipment and utensils.

b.	Codex/International Harmonization

There are no Codex maximum residue limits (MRLs) for sodium chlorite.

D.	Regulatory Rationale   XE "IV. Risk Management, Reregistration, and
Tolerance Reassessment Decision:D. Regulatory Rationale"

	The Agency has determined that chlorine dioxide and sodium chlorite are
eligible for reregistration provided that additional required data
confirm this decision and that the risk mitigation measures outlined in
this document are adopted, and label amendments are made to reflect
these measures.

	The following is a summary of the rationale for managing risks
associated with the use of chlorine dioxide and sodium chlorite.  Where
labeling revisions are warranted, specific language is set forth in the
Table 13 of Section V of this document.

		1.	Human Health Risk Management   XE "IV. Risk Management,
Reregistration, and Tolerance Reassessment Decision: D. Regulatory
Rationale: 1. Human Health Risk Management"

			a.	Dietary (Food) Risk Mitigation   XE "IV. Risk Management,
Reregistration, and Tolerance Reassessment Decision:D. Regulatory
Rationale:1. Human Health Risk Management: a. Dietary (Food) Risk
Mitigation"

Acute Dietary (Food) Risk

No acute dietary endpoint was selected because effects attributable to a
single dose were not seen in the available data; therefore, an acute
dietary risk assessment was not conducted.

Chronic Dietary (Food) Risk

Although there is not a concern for chronic dietary risk estimates for
all populations.  Dietary exposure from food did have an impact of the
aggregate assessment for children which is of concern (MOE = 44).  The
individual exposure received from the post-harvest application of sodium
chlorite to fruits and vegetables is an extremely high-end estimate.
This assessment was conducted with the most conservative assumptions and
resulted in an estimate of 42% of the cPAD for children.  For example,
this assessment assumed that all fruits and vegetables in the U.S. had a
chlorine dioxide solution applied and that these commodities were not
washed, cooked or processed prior to consumption.  Additionally, the
Chlorine Dioxide Panel has agreed to limit the residual concentration of
chlorine dioxide to 3 ppm for post-harvest application to fruits and
vegetables that are not raw agricultural commodities.  Therefore, fruits
and vegetables treated with chlorine dioxide must be followed by
blanching, cooking or canning.  Although the Agency cannot quantify the
reduction of chlorine dioxide dietary exposure at this time, it is
believed that this measure would significantly reduce the percent of
chlorine dioxide cPAD resulting from this use.  No additional dietary
risk mitigation measures are required to address exposure to chlorine
dioxide and sodium chlorite residues in food.  Further, these
conservatisms and label changes also mitigate the aggregate risks to
children so that they are no longer of concern.

		b.	Safe Drinking Water Act

When determining whether a pesticide tolerance is safe, EPA must
consider the factors listed in section 408(d) of the FFDCA.  One of
these factors is the consideration of other non-occupational pesticidal
exposures.  For chlorine dioxide and sodium chlorite, exposures occur
through drinking water from treatment plant disinfection.  These
exposures need to be considered when reassessing the tolerances
associated with the registered uses of these pesticides.

Chlorine dioxide and sodium chlorite are used to disinfect water in
treatment plants in order to meet the Safe Drinking Water Act’s (SDWA)
requirements to protect drinking water.  In addition to the statute, 40
C.F.R. section 141.72 states, “A public water system that uses a
surface water source and does not provide filtration treatment must
provide the disinfection treatment  . . . .” The required residual of
the disinfectant chlorine dioxide is specified in 40 C.F.R. 141.74.

The SDWA was originally passed by Congress in 1974 to protect public
health by regulating the nation's public drinking water supply. The law
was amended in 1986 and 1996 and requires many actions to protect
drinking water and its sources: rivers, lakes, reservoirs, springs, and
ground water wells. (SDWA does not regulate water systems, which serve
fewer than 25 individuals.) SDWA authorizes the EPA to set national
health-based standards for drinking water to protect against both
naturally-occurring and man-made contaminants that may be found in
drinking water. EPA, states, and water systems then work together to
make sure that these standards are met.

Drinking water that is not properly treated or disinfected, or which
travels through an improperly maintained distribution system, may pose a
health risk.  SDWA applies to every public water system in the United