"'"'~e.o sr,..~ ~~ ~~ i 8 t, UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

:S - 'ffi WASHINGTON D.C., 20460 

lJ (!) 

~ ~ 

" ~~ OFFICE OF CHEMICAL SAFETY 

~l, PRO"'{~V AND POLLUTLON PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

TO: 

September 27, 2012 

Revised Product Chemistry, Environmental Fate, and Ecological Effects 

Scoping Document in Support ofRegistration Review ofPerboric acid, 

sodium salt, monohydrate (PBSM) 

PC Code: 011105 DP Barcode: 394845 

Decision No.: 455962 Registration Nos.: See Table 1 

Petition No(s).: NA Regulatory Action: Ecological 

Environmental Scoping Document 

for Registration Review 

Risk Assessment Type: Single Case No.: 5007 

chemical 

TXRNo.:NA CAS No.: 10332-33-9 

MRID Nos.: See Page no. 4 40 CFR: None 

Srinivas 

Pat Jennings, 

Gowda, 

Environmenta

Microbiologist, 

l Engineer 

Coordinator 

tUc-

~cn\ ..... ~vaA 

~ 

~ 

David Bays, Microbiologist 

Risk Assessment and Science upport B 

Antimicrobials Division (751 OP) 

Steven Weiss, Acting Branch Chief %.. !/)~ Donna Randall, Ecological Risk Assessment Team Leader 

Risk Assessment and Science Support Branch (RASSB) 

Antimicrobials Division (7 51 OP) 

Seiichi Murasaki, Chemical Review Manager 

Regulatory Management Branch II 

Antimicrobials Division (751 OP) 

Page 1 of9 
Executive Summary 

Sodium perborate monohydrate (PBSM) is an inorganic, perboric acid salt, registered for 

use as a household laundry sanitizer. It was first registered in the United States on October 15, 

1998 as an active ingredient in Tide with Bleach, Tide with Bleach U, Gain with Bleach I, and 

Gain with Bleach II. A Reregistration Eligibility Decision (RED) has not been issued by the 

Agency for PBSM because the initial registration date was after the November 1984, federal 

mandated cutoff for initiation of the RED process. Currently there is one company with two 

registered products, both are end-use products formulated as soluble concentrates, and the active 

ingredient declarations are 4.74 and 5.28 percent. All product chemistry data requirements have 

been satisfied for this active ingredient. 

In response to a comment received during the 60-day public comment period, the Agency 

is revisiting its initial decision to forgo performing an ecological risk assessment on PBSM used 

as a laundry sanitizer. The Central Valley Regional Water Quality Control Board (Central 

Valley Water Board) identified impaired water bodies in California that exceed water quality 

standards for boron and sodium, two degradates of PBSM, and requested that the Agency 

conduct an environmental risk assessment for the following degradates of PBSM: hydrogen 

peroxide, borate, boric acid, and sodium. In response to these concerns, the Agency will perform 

an ecological risk assessment of PBSM degradates that are persistent enough to have the 

potential to enter surface water downstream of wastewater treatment plants as a result of PBSM' s 

use as a laundry sanitizer. The Agency has determined that under ambient conditions prevalent 

in most surface waters, the predominant persistent degradates of PBSM are expected to be boric 

acid and sodium. 

Since the environmental fate of PBSM and its degradates is well-documented and 

understood, the Agency does not anticipate the need to require additional environmental fate data 

for this registration review at this time. In addition, the Agency does not anticipate the need to 

require additional ecological effects data at this time. Since many studies on effects of PBSM 

degradates to aquatic organisms are available in the scientific literature, the Agency will review 

these studies during registration review to derive measurement endpoints that will be used in the 

ecological risk assessment. The Agency will, however, require information on the volume of 

PBSM produced as a laundry sanitizer so that it can perform a down-the-drain assessment of 

degradates that are persistent enough to have the potential to enter surface water downstream of 

domestic wastewater treatment plants as a result of PBSM's use as a laundry sanitizer. The 

Agency will use the down-the-drain module ofE-FAST, version 2.0 to perform this assessment. 

PBSM is highly reactive in aqueous solution under ambient conditions, instantly 

establishing equilibrium with two products: hydrogen peroxide and sodium metaborate. 

Hydrogen peroxide from this reaction degrades very rapidly to water and oxygen; this reaction is 

irreversible. The sodium metaborate from this reaction dissociates very rapidly in water to form 

sodium and boric acid. The pKa value of boric acid is 9.15, indicating that at pH=9 

approximately 50 percent of boric acid will be dissociated and 50 percent will remain in boric 

acid form. As the pH increases above 9, the percentage of boric acid that will dissociate will 

tend to increase and tetrahydroxyborate will tend to predominate rather than boric acid. Since 

the pH of many ambient waters is typically around 7, boric acid rather than tetrahydroxyborate is 

Page 2 of9 
expected to be the predominant degradate in surface water under ambient environmental 

conditions. 

Boron and sodium are present in the environment as a result of natural and anthropogenic 

sources. Sodium, boric acid, and boron-containing salts are ubiquitous in the environment. 

Sodium and boron occur naturally in soils, water, fruits, vegetables, and forage crops. Boron is 

an essential nutrient for plants as well as an essential element for many organisms; sodium is an 

essential element for animals. According to personal communications with Mr. Daniel J. 

McClure of California Water Board's TMDL Unit, 31 water bodies in California that are 

impaired due to high concentrations of boron and sodium are from natural origin, irrigation, and 

pumping, and not from pesticidal sources. Although the Agency currently has no information on 

the amount of PBSM used as a laundry sanitizer, the amount of boric acid and sodium ions 

introduced to the aquatic environment from this use ofPBSM is expected to be a fraction of the 

amounts introduced to the aquatic environment from natural origins and other non-pesticidal 

anthropogenic sources such as irrigation and pumping . PBSM that is used as a laundry sanitizer, 

however, can provide an additional source of boron and sodium to the aquatic environment 

downstream of wastewater treatment plants that receive persistent degradates of PBSM from this 

source. This additional source of boron and sodium can be a particular concern in water bodies 

that have been determined to be impaired as a result of high concentrations of boron and sodium. 

The Agency has not conducted a risk assessment that supports a complete endangered 

species determination for PBSM and its degradate, boric acid. The ecological risk assessment 

planned during registration review will allow the Agency to determine whether PBSM and its 

predominant persistent degradates, boric acid and sodium has "no effect" or "may affect" 

federally listed threatened or endangered species (listed species) or their designated critical 

habitats. When an assessment concludes that a pesticide's use "may affect" a listed species or its 

designated critical habitat, the Agency will consult with the U.S. Fish and Wildlife Service 

and/or National Marine Fisheries Service (the Services), as appropriate. 

Page 3 of9 
Introduction 

Perboric acid, sodium salt, monohydrate (PBSM) was first registered as an active 

ingredient with EPA on October 15, 1998. It's molecular formula NaB03·H20 is a 

representation of the average chemical composition but it's elementary structural unit is actually 

a dimer anion B20 4(0H)/ , in which two boron atoms are joined by two peroxo bridges. 

Presently, two end-use products (EPs) are registered for use as a household laundry sanitizer and 

these are listed in Table l . A Reregistration Eligibility Decision (RED) has not been issued by 

EPA for PBSM because the initial registration date was after November 1984, the federally 

mandated cutoff for initiation of the RED process. 

Table 1. Registered Products of PBSM 

Registration Registration Company Formulation %of Active 

# Name Name Type Ingredient 

The Procter & Gamble Soluble 

3573-56 Tide With Bleach II Company 

Concentrate 5.28 

EP 

The Procter & Gamble 

Soluble 

3573-58 Gain With Bleach II Concentrate 4.74 Company EP 

The Agency has conducted a review of the available product chemistry, environmental 

fate, and ecotoxicity data for PBSM. The findings are summarized below. 

A. Product Chemistry Summary of the Perboric acid, sodium salt, monohydrate (95% 

TGAI Powder) 

Common Name: 

Chemical N arne: 

OPP Chemical Code: 

CAS Registry Number: 

Molecular Formula: 

Molecular weight: 

Molecular Structure: 

Color: 

Physical State: 

Odor: 

Stability: 

pH: 

UV Nisible absorption: 

Melting point: 

Sodium Perborate Monohydrate 

Perboric acid, sodium salt, monohydrated (PBSM) 

011105 

10332-33-9 

NaB03.H20 which exists as a dimer B20 4(0H)4

2

-

99.81 g/mole 

White. 

Solid Granules. 

Odorless. 

The product is stable under ambient conditions. 

10 (concentration 15.2 gil) 

Not applicable: ionic salt. 

Melting point is 63°C at which point it decomposes. 

Page 4 of9 
Boiling Point: Not applicable, product is not a liquid. 

Density: 0.4-0.65 g/ml 

Dissociation Constant (pKa): Not applicable: ionic salt. 

Log Ko!w: Not applicable because product is an inorganic compound 

that decomposes in water. 

Solubilities: Water: 15-16 g/1 at 20 °C 

Vapor Pressure: This is not applicable because of the ionic hydrated 

structure. It is considered to have negligible vapor pressure. 

Enforcement Analytical 

Method: Titration for available oxygen. 

All product chemistry data requirements have been satisfied for the active ingredient 

PBSM (Source: MRIDs 43603601,44425602 and 45198501). 

B. Environmental Fate Summary 

For the laundry sanitizing use of PBSM, the Agency will not require any environmental fate data 

for PBSM or its degradates at this time. Fate and transport guidelines, while applicable for 

organic chemicals, are generally not applicable to inorganic chemicals and salts, such as PBSM 

and its degradates, and cannot be used to determine environmental fate, transport, and 

persistence of PBSM and its degradates. Since the environmental fate of PBSM and its 

degradates is well-understood and such information is available in the scientific literature, the 

Agency does not anticipate the need to require additional environmental fate data for this 

registration review at this time. 

PBSM is highly reactive in aqueous solution under ambient conditions, instantly establishing 

equilibrium with two products: hydrogen peroxide and sodium metaborate. Hydrogen peroxide 

from this reaction degrades very rapidly to water and oxygen; this reaction is irreversible. The 

sodium metaborate from this reaction dissociates very rapidly in water to form sodium and boric 

acid. The pKa value of boric acid is 9.15 indicating that at pH=9 approximately 50 percent of 

boric acid will be dissociated and 50 percent will remain in boric acid form. As the pH increases 

above 9, the percentage of boric acid that will dissociate will tend to increase and 

tetrahydroxyborate will tend to predominate rather than boric acid. Since the pH of many 

ambient waters is typically around 7, boric acid rather than tetrabydroxyborate or other 

polyborates is expected to be the predominant degradate in surface water under ambient 

environmental conditions. 

Boron and sodium are present in the environment as a result of natural and anthropogenic 

sources. Sodium, boric acid, borax, and boron-containing salts are ubiquitous in the 

environment. Sodium and boron occur naturally in soils, water, fruits, vegetables, and forage 

crops. Boron is an essential nutrient for plants as well as an essential element for many 

organisms; sodium is an essential element for animals. Humans ingest naturally occurring boron 

in the diet, and there is some data to suggest that trace levels are required in the human diet. 

PBSM is considered to be a hydrogen peroxide releaser that also releases boric acid, a degradate 

that does not contribute to the pesticidal activity of PBSM. In both terrestrial and aquatic 

systems, PBSM rapidly degrades to form hydrogen peroxide, water, oxygen, and a minor (<10 % 

of applied) amount of borate by both abiotic and biotic means. Available boron occurs in nature 

Page 5 of9 
in the form of a number of closely related compounds which differ chieflr in the water of 

hydration associated with the molecule and are not easily differentiated". 

Reaction of PBSM in Aqueous Solution 

PBSM hydrolyzes in aqueous solution to release hydrogen peroxide and sodium metaborate. 

The following are the appropriate conversion factors for expressing concentrations of PBSM 

(CposM) as equivalent concentrations of: 

• Boron: CB = CPBSM x 0.108; and 

• Hydrogen peroxide: CH2 o2 = CPBSM x 0.341 

In aqueous solutions at room temperature equilibrium between PBSM and hydrogen peroxide 

and sodium metaborate is instantly established (see reaction Equation I below). 

+ 2[NaB02 ] Equation I 

Sodium per borate monohydrate Hydrogen peroxide Sodium me tab orate water 

Further, the hydrogen peroxide is removed from the equilibrium-via degradation to active 

oxygen and water (reaction Equation H)-leading to an irreversible shift of the equilibrium given 

in Equation I to the degradation products sodium metaborate and water. The release of active 

oxygen also known as singlet oxygen (

1

0 2) from hydrogen peroxide is the basis of the pesticidal 

activity of sodium perborate monohydrate. 

+ Equation II 

Hydrogen peroxide water singlet oxygen 

The degradation product, sodium metaborate, dissociates in water and is present primarily as 

dissociated boric acid or as boron (reaction Equation ill and Equation IV). Boric acid and borates 

are naturally occurring compounds widely found in soils, water, and food. The bleaching activity 

of the perborates is associated with the hydrogen peroxide rather than the boric acid degradate. 

NaB02 + Z[H20J ~ Na+ + OH- + H3B03 

Sodium metaborate water Sodium ion Hyroxyl ion Boric acid 

Equation ill 

H3B03 + H2 0 ~ H+ + B(OH4 )-

Boric acid water Hydronium ion Tetrahydroxyborate 

Equation IV 

Reactions ofPBSM and NOBS inside the Washing Machine 

PBSM and sodium nonanoyloxvbenzenesulfonate (NOBS; PC Code: 089053; CAS#91125-43-8) 

are active ingredients in the currently registered laundry detergent products Tide With Bleach II 

1 U.S. Environmental Protection Agency. I 993. Reregistration Eligibility Decision for Boric Acid And Its Sodium 

Salts. Office of Prevention, Pesticides and Toxic Substances, Office ofPesticide Programs. September 1993. 

Page 6 of9 
(EPA Reg. No. 3573-56) and Gain With Bleach II (EPA Reg. No. 3573-58) by the Procter & 

Gamble Company. NOBS is a laundry bleach activator for hydrogen peroxide releasing 

chemicals such as PBSM. NOBS produces a highly active laundry bleach from the less reactive 

hydrogen peroxide. 

Detergent formulations containing NOBS are designed to help ensure rapid conversion of NOBS 

to the peroxy compound in the wash water. The peroxy compound itself is also short-lived due to 

rapid bleaching activity. To be effective in the wash cycle, the peracid precursor must be highly 

water-soluble, undergo rapid and total perhydrolysis, and produce a peracid bleach with surface 

activity. Bleach activators like NOBS essentially transfer active oxygen from the peroxide to the 

stain via the peracid. Reactions inside the washing machine are summarized below: 

• PBSM supplies alkalinity (pH 10). 

• PBSM hydrolyses, releasing hydrogen peroxide. 

• Hydrogen peroxide perhydrolyzes NOBS, producing pernonanoic acid. NOBS is referred 

to as a "bleach activator" since it produces a highly active laundry bleach pemonanoic 

acid from the less reactive hydrogen peroxide. These reactions are largely complete 

within the first two minutes of the wash. 

• Pemonaic acid bleaches laundry soils by additions of oxygen and sanitizes laundry. Most 

of the peracid bleach is consumed in the first eight minutes of the wash. 

q,p 

o r(Y8'o· Na• + ~ / H 

~0~ 0 - 0 

0 

OOH 

Sodium Nonanoyloxybenzens ulfonate (NOBS) Hydrogen pero~tide Pernonanoic acid laundry bleach 

Water Quality 

Pesticidal use of sodium perborate salt and its degradate boric acid are not identified as a cause 

of impairment for any water bodies listed as impaired under section 303(d) of the Clean Water 

Act, based on information provided at the Agency's National Pesticides Cause of Impairment of 

Waters website (searched September 20, 2012f In addition, no Total Maximum Daily Loads 

(TMDL) have been developed for sodium perborate salt and its degradate boric acid, based on 

information provided at the Agency's National Pesticide TMDL web site (searched September 

20, 2012)3

. More information on impaired water bodies and TMDLs can be found at 

http://www.epa.gov/owow/tmdll. The Agency invites submission of water quality data for this 

pesticide. To the extent possible, data should conform to the quality standards in Appendix A of 

the OPP Standard Operating Procedure: Inclusion of Impaired Water Body and Other Water 

Quality Data in OPP's Registration Review Risk Assessment and Management Process (see: 

http://www.epa.gov/oppfead 11cb/ppdc/2006/november06/session 1-sop.pdf ), in order to ensure 

they can be used quantitatively or qualitatively in pesticide risk assessments. 

2 • hup://iaspub.epa.gov/tmdl waters I 0/attains nation cy.cause detail 303d?p catt<ie group id-885 

3 

http://iaspub.epa.gov/lmdl waters I 0/attains nation.tmdl oollutant det.ail?p pollutant group id=885&p pollutant 

group name=PESTICIDES 

Page 7 of9 
TMDL Pollutant: Boron is identified as a cause of impairment, as defined under section 303(d) 

of the Clean Water Act, for three water bodies in California, eight water bodies in Colorado, six 

water bodies in Kansas, four water bodies in New Mexico, one water body in Nevada and one 

water body in Utah, based on information provided at 

http://iaspub.epa.gov/tmdl waterslO/attains impaired waters.tmdls?p pollutant id=230. 

Impaired Waters. Cause of Impairment: Boron: Boron is identified as a cause of impairment, as 

defined under section 303(d) of the Clean Water Act, for three water bodies in Arizona, nineteen 

water bodies in California, eleven water bodies in lllinois, one water body in Kansas, two water 

bodies in New Mexico, eight water bodies in Colorado, six water bodies in Kansas, four water 

bodies in New Mexico, sixteen water bodies in Nevada and one water body in Utah, based on 

information provided at 

http://ofmpub.epa.gov/tmdl waLerslO/attains impaired waters.control?p cause name=BORON 

According to California Water Boards, in California there are 31 water bodies that are impaired 

due to high concentrations of boron. The 2008-2010 Clean Water Act Section 303(d) list for 

California contains 15 stream segments in the Central Valley, 11 segments in the Central Coast 

region, 4 segments in the Los Angeles region, and 1 segment in the Lahontan region that exceed 

water quality standards for boron. Only 4 of the total 31 water bodies impaired for boron 

statewide currently have a total maximum daily load (TMDL) in place. 

http://www. waterboards.ca.gov/water issues/programs/tmdl/integrated20 1 O.shtml According to 

personal communications with Mr. Daniel J. McClure of California Water Board's TMDL Unit, 

31 water bodies in California that are impaired due to high concentrations of boron and sodium 

are from natural origin, irrigation, and pumping, and not from pesticidal sources. PBSM that is 

used as a laundry saniti zer, however, can provide an additional source of boron and sodium to 

the aquatic environment downstream of wastewater treatment plants that receive PBSM 

degradates from this source. This additional source of boron and sodium can be a particular 

concern in water bodies that have been determined to be impaired as a result of high 

concentrations of boron and sodium. During registration review of PBSM, the Agency will 

attempt to determine the contribution of PBSM used as a laundry sanitizer to boron and sodium 

concentrations in impaired water bodies. 

C. Ecological Effects Summary 

For the laundry sanitizing use of PBSM the Agency will not require any additional 

environmental effects toxicity data at this time for the persistent degradates of PBSM, boric acid 

and sodium. Because studies on effects of these PBSM degradates to aquatic organisms are 

available in the scientific literature, the Agency will review these studies during registration 

review to derive measurement endpoints that will be used in the ecological risk assessment and 

will not require any additional ecological effects data at this time. The Agency anticipates using 

a total toxic residue approach to assess ecological effects for the boron-containing degradates of 

PBSM, boric acid and borates. 

Page 8 of9 
Based on evidence obtained from an Activated Sludge Respiration Inhibition (ASRI) study on 

boric acid, this chemical appears to be unlikely to exhibit adverse effects on wastewater 

treatment plant microorganisms. The Agency reviewed an Activated Sludge Respiration 

Inhibition (ASRl) study of boric acid that was submitted by U.S. Borax Inc. for registration 

review of zinc borate which concluded that the ECso for boric acid was greater than 1001 mg/L 

(memorandum dated April 2, 2008 from Srinivas Gowda, Chemist, EPA Antimicrobials Division 

Risk Assessment and Science Support Branch to Mark Hartman, Chief, EPA Antimicrobials 

Division Regulatory Management Branch ll, DP341315). Since this concentration of boric acid 

would be expected to be highly unlikely to occur in wastewater treatment plant influents, boric 

acid would be very unlikely to reach levels in wastewater treatment plants that would inhibit the 

respiration of activated sludge microorganisms. 

Ecological Risk Assessment and Data Needs: 

Environmental Fate and Ecological Risk: 

The Agency has not conducted a risk assessment that supports a complete endangered species 

determination for PBSM and its degradate, boric acid. The ecological risk assessment planned 

during registration review will allow the Agency to determine whether PBSM and its degradate, 

boric acid has "no effect" or "may affect" federally listed threatened or endangered species 

(listed species) or their designated critical habitats. When an assessment concludes that a 

pesticide's use "may affect" a listed species or its designated critical habitat, the Agency will 

consult with the U.S. Fish and Wildlife Service and/or National Marine Fisheries Service (the 

Services), as appropriate. 

The Agency will conduct an ecological risk assessment for indoor use of PBSM (as a household 

laundry sanitizer inside the washing machine) and it's degradate boric acid for registration 

review, including a risk assessment that supports a complete endangered species determination. 

To support a complete endangered species assessment the Agency will evaluate risks to aquatic 

species from indoor uses of PBSM as a household laundry sanitizer inside the washing machine, 

specifically it's degradate, boric acid. 

Environmental Fate and Ecological Effects Data Gaps and Anticipated Work 

For the laundry sanitizing use of PBSM inside the washing machine the Agency will not require 

any additional environmental fate or ecological effects information to conduct environmental 

fate and ecological risk assessments planned during registration review. The Agency will, 

however, require information on volume ofPBSM produced as a laundry sanitizer. 

Page 9 of9