1

UNITED STATES ENVIRONMENTAL PROTECTION 

AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

MEMORANDUM August 25, 2015

SUBJECT: Human Health and Ecological Risk Assessment for Cuprous Iodide

PC Code: 108301 DP Barcode No.: D408325, D408674, 

D408675, D408676, D408673

Decision No.: 468321 EPA File Nos.: 

Petition No.: NA Regulatory Action: New active ingredient 

Risk Assess Type: Single Chemical Case No.: NA

TXR No.: NA CAS No: 7681-65-4

MRID No(s).: NA 40 CFR: NA

FROM: Timothy Dole CIH, Industrial Hygienist

William Erikson, Biologist 

Pat Jennings, Senior Environmental Engineer 

Jonathan Leshin, Toxicologist

Siroos Mostaghimi, Senior Scientist 

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

TO: Jacqueline Hardy, Team leader, PM 34

Thomas Luminello, Jr. Risk Manager Reviewer

Regulatory Management Branch II (RMBII)

Antimicrobials Division (7510P)

THRU: Steven Weiss, Branch Chief

Laura Parsons, Associate Branch Chief

Timothy Leighton, Senior Scientist 

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)
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Table of Contents

1 INTRODUCTION................................................................................................................. 3

1.1 Risk Conclusions.............................................................................................................. 3

1.2 Proposed Uses.................................................................................................................. 3

2 HUMAN HEALTH RISK ASSESSMENT......................................................................... 4

2.1 Hazard Characterization and Endpoint Selection............................................................. 4

2.2 FQPA Considerations....................................................................................................... 6

2.3 Dietary and Drinking Water Exposure and Risks............................................................ 6

2.4 Occupational and Residential Exposure and Risk............................................................ 6

3 ENVIRONMENTAL RISK ASSESSMENT...................................................................... 8

3.1 Environmental Exposure Assessment .............................................................................. 8

3.2 Fabric Leaching Study Summary................................................................................... 10

3.3 Ecological Effects Data.................................................................................................. 10

3.4 Estimation of Risks to Aquatic Organism...................................................................... 12

4 REFERENCES.................................................................................................................... 17

List of Tables

Table 1 – Proposed Uses of Cuprous Iodide................................................................................... 3

Table 2 - Acute Toxicity of Cuprous Iodide Technical .................................................................. 4

Table 3 - Summary of Toxicological Endpoints for Cuprous Iodide. ............................................ 5

Table 4- Incidental Oral Iodine MOEs for Clothing Treated with Copper Iodide ......................... 7

Table 5 - Dermal Iodine MOEs for Clothing Treated with Copper Iodide .................................... 7

Table 6 - Combined MOEs for Clothing Treated with Copper Iodide ........................................... 8

Table 7 - Ecotoxicity Endpoints for Cuprous Iodide .................................................................... 11

Table 8 - Ecotoxicity Endpoints for Copper................................................................................. 11

Table 9 - Ecotoxicity Endpoints for Iodine................................................................................... 12

Table 10 - Screening-Level Estimates for Copper Ion (84.2 Percent WWTP Removal)............. 13

Table 11 - Screening-Level Estimates for Iodine (No WWTP Removal).................................... 14

Table 12 -Screening-Level Estimates for Cuprous Iodide (No WWTP Removal) ...................... 14
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1 INTRODUCTION

The registrant has applied to EPA to register three antimicrobial pesticide products containing 

the new active ingredient Cuprous Iodide proposed to be used as a material preservative. The 

manufacturing-use product (MP) is to contain 20% Cuprous Iodide and it is formulated as a 

master batch. This memorandum addresses both the human health and ecological risks 

associated with proposed uses of the new antimicrobial pesticide active ingredient, cuprous 

iodide. 

1.1 Risk Conclusions

The risk conclusions which are explained in the risk assessment can be summarized as follows:

 There are no inhalation or dermal risk concerns for handler exposures because the 

product is formulated as a master batch (plastic pellets).

 There are no dietary concerns from food or drinking water.

 There are no risks of concern for residential dermal, incidental oral or combined 

exposures to cuprous iodide in clothing or household items.

 There are no ecological concerns for non-listed aquatic species from the screening 

level ecological risk assessment.

1.2 Proposed Uses

Cuprous Iodide is proposed for use as a preservative to be incorporated into manufactured 

products at a rate of 0.2% to 5.0% by weight in the final article. The articles to be treated are 

listed in Table 1. 

Table 1 – Proposed Uses of Cuprous Iodide

Use Group Specific Uses

Fibers Household items (bedding, mattress cover pads, sheets, blankets, towels)

Upholstery

Carpet overlay and backing

Conveyor Belts (non-food contact)

Automotive and truck upholstery and carpeting truck liners, convertible tops and liners

Apparel including outwear, sportswear, sleepwear, undergarments, and socks

Floor Coverings Carpets, rugs, and mats

Plastics, coatings, 

films and laminates

Automotive and vehicular parts

Building materials and components

Wood and plastic composites (non-food contact)

Countertops (non-food contact)

Indoor furniture

Floor covering and flooring

Personal hygiene (combs, brushes, hairclips)

Fire system sprinkler pipe coatings (inside surfaces)

Adhesives and 

Sealants

Adhesives used in wood and plastic composites

Adhesives for ceramic tile, rubber, and plastic

Window glazing, grout
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2 HUMAN HEALTH RISK ASSESSMENT

2.1 Hazard Characterization and Endpoint Selection

The toxicology database for cuprous iodide is adequate to support the registered antimicrobial 

pesticidal uses of this chemical.

The acute toxicity study database for cuprous iodide (Table 2) indicates a moderate toxicity of a 

single oral dose (LD50 is 1030 mg/kg; Category III) and a low toxicity via the dermal route 

(LD50> 5,000 mg/kg; Category IV). Single dose toxicity by the inhalation route is also relatively 

low (0.52 < X < 2.12 mg/L; Category III). Cuprous iodide is a severe eye irritant (corneal 

opacity in 3/3 at 21 days; Category I) but does not appear to demonstrate dermal irritation 

(Category IV). Cuprous iodide does not demonstrate dermal sensitization potential. 

Table 2 - Acute Toxicity of Cuprous Iodide Technical

Guideline 

No.

Study Type MRID # Results Toxicity 

Category

870.1100 Acute Oral- Rats 49165101 1,030 (550-1750) mg/kg III

870.1200 Acute Dermal- Rats 49165102 5,000 mg/kg IV

870.1300 Acute Inhalation- Rats 49165104 0.52<X<2.12 mg/L III

870.2400 Primary Eye IrritationRabbits49165105 Corneal opacity in 3/3 at 21 

days. Extremely irritating

I

870.2500 Primary Skin IrritationRabbits49165106 No dermal irritation IV

870.2600 Dermal SensitizationGuinea pigs49165103 Not sensitizing --

The agency has determined that exposure to cuprous iodide via oral (water) or dermal route is 

primarily to copper and iodine ions, not cuprous iodide. Because cuprous iodide is formulated as 

a master batch, which consists of the a.i. imbedded in non-friable plastic pellets, there is 

negligible potential for inhalation exposure and thus an inhalation assessment is not needed. 

Therefore, the cuprous iodide human health risk assessment evaluates copper and iodine ions via 

the oral and dermal route only. 

The copper toxicity database is robust and, the agency has no concerns for systemic toxicity for 

human exposure to copper (Reregistration Eligibility Decision Document for Coppers, 2009).

Therefore, the agency is relying on the iodine toxicity database for the cuprous iodide risk 

assessment. There are three human studies from open literature examining oral and systemic 

toxicity of iodine. These studies were presented to the Human Studies Review Board in June 11, 

2014 for review of the ethics and science and were found acceptable for use in regulatory 

decisions. One repeated dose study (14 days) indicated that iodine was relatively nontoxic 

(changes in serum and free T4, changes in serum thyroid stimulating hormone (TSH) in response 

to thyrotropin releasing hormone (TRH), and changes in basal TSH starting at 1.5 mg/day with 

more significant effects at 4.5 mg/day, MRID 47358601). Another repeated dose study using 
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doses of 0.25, 0.5 and 1.5 mg/day (14 days) showed similar effects, with small decreases in T4

and T3 and compensatory increases in TSH and TRH induced TSH. These changes (at 1.5 

mg/day), while statistically significant, were within normal levels (MRID 47358603). A 90 day 

oral study of 32 mg/day, showed changes in thyroid size, which returned to normal on average 

within 7 months of stopping high dose iodine exposure. Additionally, TSH and TRH induced 

TRH increased during the study period, while T3 and T4 decreased initially, with T3 recovering 

by the end of the treatment period, indicating a compensatory response to the high dosing (MRID 

49318802). The data from these three studies indicate that the target organ for iodine toxicity in 

the human is the thyroid. Dermal absorption of iodine is estimated to be approximately 0.1% 

(MRID 49342401). Additional toxicity data for either copper or iodine are not warranted for the 

cuprous iodide risk assessment. Carcinogenicity, neurotoxicity, or immunotoxicity data are not 

needed for either copper or iodine since the cuprous iodide hazard assessment is based on effects 

observed in the human thyroid. Data demonstrate that the iodine component of cuprous iodide is 

not a developmental or reproductive toxicant (Reregistration Eligibility Decision Document for 

Iodine, 2006). The agency has granted waiver requests for a mutagenicity battery conducted with 

iodine for oral exposures to this chemical (Memorandum: from S. Diwan to J. Smith and M. 

Rice, 12/96).

Toxicity endpoints were selected for the iodine component of cuprous iodide to perform 

exposure and risk assessments for oral and dermal route of exposure. An incidental oral endpoint 

was selected for potential non-dietary exposure that may occur to cuprous iodide from treated 

article uses. Dermal endpoints were selected to assess exposures to cuprous iodide that may 

occur from dermal contact with materials treated with cuprous iodide. Because cuprous iodide is 

formulated as a master batch, which consists of the a.i. imbedded in non-friable plastic pellets, 

there is negligible potential for inhalation exposure and thus no inhalational endpoints were

selected. The endpoints are outlined in Table 3.

Table 3 - Summary of Toxicological Endpoints for Iodine

Exposure

Scenario

Dose Used in Risk

Assessment

UF and Target 

MOE 

Study and Toxicological 

Effects

Incidental Oral

Short-Term 

(1-30 days) and 

Intermediate-Term 

(1- 6 months)

NOAEL = 1.5 

mg/day

UF (i.e. target MOE)

Residential = 1

Occupational = N/A

Human Oral Study

(MRID 48358603)

LOAEL > 1.5 mg/day

Dermal

Short-Term

NOAEL = 1.5 

mg/day

Dermal absorption 

factor = 0.1%

UF (i.e. target MOE)

Occupational = 1

Residential = 1

Human Oral Study

(MRID 48358603)

LOAEL > 1.5 mg/day

Dermal absorption by 

miniature pigs (49342401)

UF = uncertainty factor, NOAEL = no observed adverse effect level, LOAEL = lowest observed adverse effect level, 

MOE = margin of exposure, RfC = reference concentration

A. An uncertainty factor of 10X is used to account for route to route extrapolation.
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2.2 FQPA Considerations

Under the Food Quality Protection Act (FQPA), P.L. 104-170, which was promulgated in 1996 

to amend the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Federal Food, 

Drug and Cosmetic Act (FFDCA), the Agency was directed to "ensure that there is a reasonable 

certainty that no harm will result to infants and children" from aggregate exposure to a pesticide 

chemical residue. The law further states that in the case of threshold effects, for purposes of 

providing this reasonable certainty of no harm, "an additional tenfold margin of safety for the 

pesticide chemical residue and other sources of exposure shall be applied for infants and children 

to take into account potential pre- and post-natal toxicity and completeness of the data with 

respect to exposure and toxicity to infants and children. Notwithstanding such requirement for an 

additional margin of safety, the Administrator may use a different margin of safety for the 

pesticide residue only if, on the basis of reliable data, such margin will be safe for infants and 

children."

There are no human health endpoints of concern from exposures to copper. The agency has 

adequate data on human health exposure to iodine to reduce the FQPA special sensitivity factor to 

1x.

2.3 Dietary and Drinking Water Exposure and Risks

Although, there could be exposure to copper and iodine as a result of residues in drinking water, 

this exposure is expected to be negligible from the use of this product as a materials preservative. 

Exposure is expected to be low based on limited leaching from textiles. There are no human 

health endpoints or risk concerns from exposure to copper from the proposed cuprous iodide 

uses. Iodine is an essential nutrient and has several pesticidal uses which may result in dietary 

exposures including drinking water disinfection. 

2.4 Occupational and Residential Exposure and Risk 

Occupational Exposure and Risk Assessment

Because the product is formulated as a master batch (plastic pellets) which does not release any 

significant amount of dust, occupational handler dermal or inhalation exposures during the 

pouring of cuprous iodide are anticipated to be negligible and do not need to be assessed. 

Residential Exposure and Risk Assessment 

A residential post application assessment addresses potential exposure and risk to humans who 

may be exposed to cuprous iodide fibers that are used to manufacture household items such as 
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blankets, towels, and apparel such as sleepwear. Given these uses, there is a potential for 

incidental oral exposure to children who chew on blankets, towels and clothing and there is a 

potential for dermal exposure to adults and children who wear treated clothing.

The incidental oral exposures were assessed for children (aged 1 to <2 years old) sucking on 

clothing that has been preserved with cuprous iodide as shown in Table 4. These exposure were 

assessed at the maximum labeled concentration of 5% using a saliva extraction rate of 0.025% 

based on the submitted leaching study (MRID 494859-01). The Margin of Exposure (MOE) is 

180, which is above the target MOE of 1, which means that the risks are not of concern.

Table 4- Incidental Oral Iodine MOEs for Clothing Treated with Cuprous Iodide

CuI 

Application 

RateA

CuI 

Application 

RateB

Iodine 

Application 

RateC

Area 

Mouthed

Saliva Extraction 

EfficiencyD

DoseE

(mg/day)

MOEF

(Target MOE = 1)

5% CuI in 

fabric 0.5 mg/cm2 0.34

mg/cm2 100 cm2

/day 0.025% 0.0085 180

A. Application Rate (% a.i. in fabric) = Amount a.i. in Product (% a.i.) * Product Application rate (% product in fabric) 

B. Application Rate (mg a.i./cm2of fabric) = Application Rate (% a.i. in fabric) * Fabric density (10 mg/cm2)

C. Iodine Application Rate = CuI application rate * [MW Iodine (126.9) /MW Cuprous Iodine (190.4)]

D. Based on the average of the 60 minute time point results from the submitted leaching study (MRID 494859-01).

E. Dose (mg/day) = Application Rate (mg/cm2) * Area Mouthed (100 cm

2

) * [Saliva Extraction Efficiency /100)]

F. MOE = NOAEL (mg/day) / Dose (mg/day) where the NOAEL = 1.5 mg/day

The dermal exposures were assessed for clothing preserved with cuprous iodide as shown in 

Table 5. These exposures were assessed at the maximum labeled concentration of 5% using a 

cloth to skin transfer factor of 0.025% based on the submitted leaching study. The MOE is 3,900

for children and 940 for adults. Both of these MOEs are above the target MOE of 1, which 

means that the risks are not of concern.

Table 5 - Dermal Iodine MOEs for Clothing Treated with Cuprous Iodide

Exposed 

Population

Iodine 

Application 

RateA

Skin Surface 

AreaB,C

Skin to Fabric 

Transfer 

EfficiencyD

ExposureE

(mg/day)

DoseF

(mg/day)

MOEG

(Target MOE = 1)

Children (1 to 

<2 years old)

0.34 mg/cm2 

4425 cm2

0.025%

0.38 0.00038 3,900

Adults 18,250 cm2 1.6 0.0016 940

A. Iodine Application Rate = Same as that calculated for incidental oral exposures (see Table 4)

B. Derived from US EPA, 2011. The total body surface area of 5300 cm2 minus 875 cm2for the head.

C. Derived from US EPA, 2011. The total body surface area of 19,500 cm2 minus 1250 cm2for the head.

D. Based on the average of the 60 minute time point results from the submitted leaching study (MRID 494859-01).

E. Exposure (mg/day) = Application Rate (mg/cm2) * Skin Surface Area (cm2) * [Transfer Efficiency /100)]

F. Dose (mg/day) = Exposure (mg/day) * Dermal Absorption (0.1%) 

G. MOE = NOAEL (mg/day) / Dose (mg/day) where the NOAEL = 1.5 mg/day
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The combined incidental oral and dermal exposures were assessed for children as shown in Table 

6. The combined MOE is 170 and is above the target MOE of 1, which means that the risks are 

not of concern.

Table 6 - Combined MOEs for Clothing Treated with Cuprous Iodide

Exposed 

Population

Iodine 

Application 

RateA

Incidental Oral 

ExposureB

(mg/day)

Dermal DoseC

(mg/day)

Combined 

DoseD

(mg/day)

MOEE

(Target MOE = 1)

Children (1 to 

<2 years old) 0.34 mg/cm2 0.0085 0.00038 0.0089 170

A. Iodine Application Rate = Same as that calculated for incidental oral exposures (see Table 4)

B. From Table 4.

C. From Table 5.

D. Combined Dose (mg/day) = Incidental Oral Dose (mg/day) + Dermal Dose (mg/day)

E. MOE = NOAEL (mg/day) / Dose (mg/day) where the NOAEL = 1.5 mg/day

Occupational and Residential Risk Conclusions

The proposed use in fibers that are used to manufacture household items such as blankets and 

towels and apparel such as sleepwear was assessed as incidental oral exposures for children,

dermal exposures for children and adults and combined incidental oral and dermal exposures for 

children. The Margin of Exposure (MOE) for incidental oral exposures to children is 180 and 

the MOE for dermal exposures is 3,900 for children and 940 for adults. The combined MOE is 

170 for children. All of these MOEs are above the target MOE of 1, which means that the risks 

are not of concern.

The MOEs were based on a submitted leaching study was only run for 60 minutes which yielded 

a leaching rate of 0.025 percent. Although it is probable that a longer time would have yielded a 

greater leaching rate, it is unlikely that this rate would have been 170 times greater (i.e. 4.25 

percent) which is the rate that would reduce the combined MOE of 170 to a combined MOE of 1. 

3 ENVIRONMENTAL RISK ASSESSMENT

3.1 Environmental Exposure Assessment

Cuprous iodide is proposed for use as a preservative to be incorporated into manufactured 

products at a rate of 0.2% to 5.0% by weight in the final article. The articles to which cuprous 

iodide will be applied include: fibers; floor coverings; plastics, coatings, films, and laminates; 

and adhesives and sealants. Cuprous iodide is expected to be present predominantly in the form 

of copper and iodine ions at concentrations below the solubility limit of cuprous iodide (i.e., Ksp 

= 1.27 x 10-12 moles/L, which corresponds to 0.43 mg/L (430 ug/L) of copper ions and of iodine 

ions). There are two predominant pathways by which copper and iodine would be expected to be 

released to the aquatic environment: (1) via process water that comes into contact with 
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manufactured products into which cuprous iodide is incorporated and (2) via leaching of cuprous 

iodide during in-service use of manufactured products. 

No information was found on the role that process water might play in releasing copper ions and 

iodide ions to surface water as a result of potential contact of process water with manufactured 

products. Whether process water would be expected to come into contact with any or all of the 

manufactured products into which cuprous iodide is incorporated is not known. Process water 

that contacts these manufactured products could be released to industrial wastewater treatment 

facilities that subsequently discharge treated effluent to surface water. Without information on 

the amount of copper and iodine ions that could potentially be present in process water and 

subsequently be discharged to surface water following industrial wastewater treatment, 

environmental release cannot be estimated. Consequently, the potential for aquatic organisms to 

be exposed to copper and iodine ions released to surface water following industrial waste 

treatment of process water that comes into contact with these manufactured products cannot be 

quantified, which represents an uncertainty in this risk assessment. Although this is a gap in the 

risk assessment, based on the amount of projected volume of copper iodide, the multiple use sites

for this active ingredient, and the other sources of copper and iodine in the environment, the lack 

of information about the exposure from manufacturing process is not of concern. 

The proposed registration includes multiple use sites such as plastics, coatings, adhesives and 

fibers. Cuprous iodide would be expected to be tightly bound in most matrices. Of the 

manufactured products to which cuprous iodide is incorporated as a preservative, the highest 

potential for leaching would be expected to be from fibers via down-the-drain discharges that 

occur during fabric washing at institutional facilities, commercial establishments, and residences. 

Down-the-drain discharges would be expected to enter domestic wastewater treatment facilities. 

Any copper and iodine not removed during domestic wastewater treatment could be released to 

surface water via domestic wastewater effluent. Cuprous iodide would be expected to be more 

tightly bound into the matrices of other manufactured products and washing/rinsing would be 

expected to be infrequent. Consequently, leaching potential from other manufactured products 

would be expected to be considerably lower than from fibers and there is relatively low potential 

for down-the-drain releases to occur. 

The probabilistic dilution model (PDM) option of the Down-the-Drain (DtD) module of E-FAST 

(EPA, 2007) was used to estimate magnitude of exposure of freshwater aquatic organisms in the 

surface water column to copper ion, iodine, and copper iodide released from domestic 

wastewater treatment plants. Key input parameters include: the maximum annual production 

volume of copper iodide; concentrations of concern (COCs) for copper ion, iodine, and copper 

iodide; and percent removal of copper ion, iodine, and copper iodide during wastewater 

treatment. Model outputs are expressed as days per year of exceedance of concentrations of 

concern for aquatic organisms. Estimates of exposure were developed for both a high-end 

scenario (i.e., 10th percentile of the distribution of the ratio of 7Q10 stream flows to plant flows) 

and for an average case scenario (i.e., the median of the distribution of the ratio of 7Q10 stream 

flows to plant flows). The 7Q10 is the lowest 7 consecutive-day stream flow over a 10-year 

period. 
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The value of the maximum annual production volume of cuprous iodide used as an input to the 

Down-the-Drain module of E-FAST was 77,000 kilograms per year (170,000 pounds). This 

value is based on the maximum projected amounts of cuprous iodide expected to be produced 

annually over a 5-year period from 2014 through 2018 (Ag-Chem Consulting, 2014). For copper 

ion, the percent removal during wastewater treatment was assumed to be 84.2 percent (EPA, 

2000). This estimate is based on a 50-POTW study conducted through EPA’s Office of Water. 

For iodine and copper iodide, in the absence of data on removal during wastewater treatment, 

EPA conservatively assumed that there would be no removal during wastewater treatment.

3.2 Fabric Leaching Study Summary

Primary exposure in the environment is expected to result from leaching of cuprous iodide from 

treated fabrics. A fabric leaching study showed that when woven (polyester) and non-woven 

(polyethylene) treated fabrics were soaked and agitated to simulate a washing machine cycle, 

limited leaching occurred. A total amount of 0.003% of copper, and 0.016% of iodide leached in 

a 60 minute cycle which is consistent with the limited solubility of cuprous iodide (Ksp of CuI = 

1 x 10-12). The type of fabric did not affect overall leaching. This required study provided 

information that the leaching from fabrics is low, but this information was not used 

quantitatively because the amount of leaching did not reach equilibrium in the 60 minute cycle

used in the submitted study. 

3.3 Ecological Effects Data 

The ecotoxicity endpoints used for the environmental risk assessment are obtained from 

guideline toxicity studies conducted for wildlife, aquatic organisms, and plants (40 CFR §158). 

Because cuprous iodide will dissociate in water, exposure of organisms to discharge water 

reaching the aquatic environment will be predominantly to copper and iodine ions. However, all 

antimicrobial active ingredients must be supported by a minimal data set consisting of four 

studies: avian acute oral, fish acute toxicity, aquatic invertebrate toxicity, and green algae 

toxicity. Acceptable avian, daphnid, and green algae studies are available for cuprous iodide

(Table 7). The fish toxicity study submitted did not determine an LC50 nor establish that it 

exceeds 100 ppm ai (i. e., is practically nontoxic). However, because there was no mortality nor 

signs of intoxication at the highest test concentration (251 μg CuI/L), the study is adequate to 

support any use for which the aquatic EEC for CuI is less than the NOAEC. If the EEC exceeds 

the NOAEC, additional testing at higher concentrations would be needed. Further, even though 

there were no chronic endpoints for iodine or cuprous iodide, results for acute endpoints 

available for the three chemical substances tested indicate that neither iodine or cuprous iodide 

would be expected to be more toxic than copper. Chronic ecotoxicity data are anticipated to be 

required for iodine under Registration Review.
11

Table 7 - Ecotoxicity Endpoints for Cuprous Iodide

Taxa Toxicity Toxicity

category MRID no.

Birds

(Northern bobwhite)

LD50 = 1416 mg ai/kg bw Slightly toxic 49485701

Freshwater fish

(Fathead minnow)

LC50 >251 μg CuI/L

(NOAEC = 251 μg CuI/L)

Not determined 49510802

Freshwater invertebrate

(Daphnia)

EC50 = 88 μg CuI/L Very highly toxic 49510801

Algae

(Green algae)

EC50 = 158 μg CuI/L

NOAEC = 53 μg CuI/L

NA 49485801

The ecotoxicity endpoints for copper (Table 8) and iodine (Table 9) are presented below. The 

available endpoints indicate that copper is very highly acutely toxic to aquatic organisms and can 

adversely impact reproduction and growth at concentrations 3-fold lower than acute values. The 

database for iodine is largely incomplete, but the available acute endpoints indicate that iodine is 

highly toxic to freshwater fish and aquatic invertebrates. 

Table 8 - Ecotoxicity Endpoints for Copper

Receptors Scenario Toxicity Endpoint1 Toxicity

Category

EPA Study

ID

Fish:

Freshwater

(Salmonids) 

Acute GMAV = 31.4 μg ai/L Very highly toxic

EPA 2010

Chronic ACR = 3.22 NA

Estuarine/marine

(Flounder)

Acute GMAV = 12.7μg ai/L Very highly toxic

Chronic ACR = 3.23 NA

Aquatic invertebrates:

Freshwater

(Daphnia)

Acute GMAV = 4.1 μg ai/L Very highly toxic

EPA 2010

Chronic ACR = 3.22 NA

Estuarine/marine

(Mussel)

Acute GMAV = 11.5 μg ai/L Very highly toxic

Chronic ACR = 3.23 NA

Aquatic plants:

Vascular

(Duckweed) NA 48-h EC50 = 2300 μg ai/LNOAEC = 100 μg ai/L NA 43363604

Algae

(Green algae) NA 48-h EC50 = 3.1 μg ai/LNOAEC = 2.0 μg ai/L NA 43363603

Birds:
12

Northern 

bobwhite Acute LD50 = 98 mg Cu/kg-bw Moderately toxic 00067456

1 Genus Mean Acute Values (GMAV) are from the EPA Office of Water’s Water Quality Criteria 

Document for Copper as cited in EPA 2010; Acute-to-Chronic Ratios (ACR) are from EPA 2010

Table 9 - Ecotoxicity Endpoints for Iodine

Taxa Scenario Toxicity Endpoint Toxicity

Category

EPA Study

ID

Fish:

Freshwater

(Bluegill) Acute 96-h LC50 = 610 μg ai/L Highly toxic 43044501

Aquatic invertebrates:

Freshwater

(Daphnia) Acute 48-h EC50 = 330 μg ai/L Highly toxic 42961001

Birds:

Northern 

bobwhite Acute LD50 >2000 mg ai/kg bw Practically nontoxic 43138401

3.4 Estimation of Risks to Aquatic Organism

For iodine and copper iodide, acute and chronic listed/endangered and non-listed COC values 

were developed directly from acute and chronic toxicity endpoints. LC50 values from acute 

toxicity tests for aquatic vertebrates and EC50 values from acute toxicity tests for aquatic 

invertebrates were divided by 2 to develop acute COCs for non-listed aquatic organisms. COCs 

for chronic effects for non-listed aquatic vertebrate and invertebrate species were based on No 

Observed Adverse Effects Concentrations (NOAECs) from chronic tests conducted on these 

organisms. LC50 values from acute toxicity tests for aquatic vertebrates and EC50 values from 

acute toxicity tests for aquatic invertebrates were divided by 20 to develop acute COCs for listed 

aquatic organisms. COCs for chronic effects for non-listed aquatic vertebrate and invertebrate 

species were based on No Observed Adverse Effects Concentrations (NOAECs) from chronic 

tests conducted on these organisms. 

Acute COCs for non-listed aquatic vascular plants and algae are based on EC50 values when 

these data were available. Chronic COCs for listed/endangered aquatic vascular plants and algae 

are based on NOAEC values when these data were available.

Copper acute toxicity values were based on Genus Mean Acute Values (GMAV) for aquatic fish 

and invertebrates and copper chronic toxicity values were derived based on the product of the 

Genus Mean Acute Value (GMAV) and the Acute to Chronic Ratio (ACR) for representative 

aquatic fish and invertebrates. GMAV values were divided by 2 to derive copper acute COC 

values for non-listed freshwater fish and invertebrates and by 20 for listed/endangered freshwater 
13

fish and invertebrates. The product of GMAV and ACR values for representative aquatic fish 

and invertebrates was used to derive chronic COC values for copper.

Upper bound risks from exposure to estuarine/marine organisms in the water column and 

sediments were not quantified since toxicity endpoints for iodine and copper iodide and end-ofpipe concentrations of copper, iodine, and copper iodide were not available. While the DtD 

module of E-FAST is an appropriate tool for estimating concentrations of chemical substances in 

flowing water bodies, it is not appropriate for tidally-influenced water bodies, such as estuaries 

and oceans, or static water bodies, such as lakes and ponds. However, since low exposures were 

expected in freshwater, there is no expectation that estuarine and marine water concentrations 

would be of concern.

Screening Level Down–the–Drain Assessment

Tables 10 through 12 present screening-level estimates of the number of days per year of 

exceedance of concentrations of concern (COCs) for freshwater aquatic organisms downstream of 

domestic wastewater treatment plants that receive influent from institutional facilities, commercial 

establishments, and residences that discharge leachate from washing fabrics treated with cuprous 

iodide. In all cases, the wastewater treatment plant influent volume was assumed to be 77,000 

kilograms of copper iodide per year. Table 10 presents estimates of the number of days per year 

of exceedance of COCs for copper ion, Table 11 presents estimates of the number of days per year 

of exceedance of COCs for iodine, and Table 12 presents estimates of the number of days per year 

of exceedance of COCs for cuprous iodide.

Table 10 - Screening-Level Estimates for Copper Ion (84.2 Percent WWTP Removal)

COCs for Copper Ions

Number of Days per Year of COC Exceedance 

High-end Average

Acute COCs (Freshwater Organism)

16 ppb (Freshwater Fish) <1 <1

2 ppb (Freshwater Invertebrates) 1 <1

3 ppb (Non-listed algae) <1 <1

2300 ppb (Non-listed aquatic vascular plants) <1 <1

Endangered/Listed COCs

1.6 ppb (Freshwater Fish) 2 <1

0.2 ppb (Freshwater Invertebrate) 72 8

2.0 ppb (listed algae) 1 <1

100 ppb (listed vascular plants) <1 <1

Chronic COCs

101 ppb (Freshwater Fish) <1 <1

13.2 ppb (Freshwater Invertebrates) <1 <1
14

Table 11 - Screening-Level Estimates for Iodine (No WWTP Removal)

COCs for Iodine

Number of Days per Year of COC Exceedance

High-end Average

Acute COCs (Freshwater Organism)

16 ppb (Freshwater Fish) <1 <1

2 ppb (Freshwater Invertebrates) <1 <1

3 ppb (Non-listed algae) No Endpoint No Endpoint

2300 ppb (Non-listed aquatic vascular plants) No Endpoint No Endpoint

Endangered/Listed COCs

1.6 ppb (Freshwater Fish) <1 <1

0.2 ppb (Freshwater Invertebrate) <1 <1

2.0 ppb (listed algae) No Endpoint No Endpoint

100 ppb (listed vascular plants) No Endpoint No Endpoint

Chronic COCs

101 ppb (Freshwater Fish) No Endpoint No Endpoint

13.2 ppb (Freshwater Invertebrates) No Endpoint No Endpoint

Table 12 -Screening-Level Estimates for Cuprous Iodide (No WWTP Removal)

COCs for Copper Iodide

Number of Days per Year of COC Exceedance

High-end Average

Acute COCs (Freshwater Organism)

16 ppb (Freshwater Fish) <1 <1

2 ppb (Freshwater Invertebrates) <1 <1

3 ppb (Non-listed algae) <1 <1

2300 ppb (Non-listed aquatic vascular plants) No Endpoint No Endpoint

Endangered/Listed COCs

1.6 ppb (Freshwater Fish) 1 <1

0.2 ppb (Freshwater Invertebrate) 12 1

2.0 ppb (listed algae) No Endpoint No Endpoint

100 ppb (listed vascular plants) No Endpoint No Endpoint

Chronic COCs

101 ppb (Freshwater Fish) No Endpoint No Endpoint

13.2 ppb (Freshwater Invertebrates) No Endpoint No Endpoint

Generally, for any assessment, if the probabilistic modeling predicts the acute COC (one-half of 

the LC50 or EC50) determined for any key aquatic receptor group is exceeded for one day or 

more, based on results from the high-end scenario (i.e., the 10th percentile of the ratio of the 

7Q10 stream flows to WWTP flows), then potential acute risks to such receptors cannot be ruled 

out. If the acute COC is exceeded for one day or more based on an average case scenario (i.e., 
15

the 50th percentile of the ratio of the 7Q10 flows to WWTP flows), then potential acute risks to 

such receptors have a higher possibility of occurrence.

Further, if the chronic COC (i.e., NOAEC) determined for any key aquatic receptor group is 

exceeded for more than 20 days based on the results from the high-end scenario, then potential 

chronic risks to such receptors cannot be completely ruled out. If the chronic COC determined 

for any key aquatic receptor group is exceeded for 20 days or more based on an average case 

scenario, then potential chronic risks to such receptors have a higher possibility of occurrence

For copper, no acute COCs for non-listed aquatic organisms were predicted to be exceeded for 

one day or more for either the average case scenario or the high-end scenario. For the high-end 

scenario, acute COCs for copper were predicted to be exceeded 2 days for endangered freshwater 

fish, 72 days for endangered/listed freshwater invertebrates, and 1 day for endangered/listed 

algae. For the average case scenario, acute COCs for copper were predicted to be exceeded for 8 

days for endangered freshwater invertebrates.

No acute COCs for iodine or for copper iodide were exceeded for one day or more for those nonlisted or endangered aquatic organisms for which toxicity endpoints were available. 

Although no toxicity endpoints for aquatic plants were available for iodine or copper iodide,

estimates of the number of days per year of exceedance of acute COCs for aquatic plants 

exposed to iodine under the circumstances that were modeled would be expected to be lower 

than the COCs for copper.

The acute COC for listed/endangered freshwater invertebrates exposed to cuprous iodide was 

predicted to be exceeded for 12 days per year for the high-end scenario and for one day for the 

average case scenario. 

No chronic COCs were exceeded for 20 days or more for copper ion. Even though there were no 

chronic endpoints for iodine or cuprous iodide, results for acute endpoints available for the three 

chemical substances tested indicate that neither iodine or cuprous iodide would be expected to be 

more toxic than copper. Consequently, potential chronic risks from exposure of aquatic 

freshwater organisms to iodine and cuprous iodide would be expected to be negligible under the 

circumstances modeled.

No chronic COCs were exceeded for 1 day for copper ion. There were no chronic endpoints for 

iodine or cuprous iodide, however, even if equal toxicity to copper was assumed, no exceedances 

would be predicted by the DTD modeling. Consequently, potential chronic risks from exposure 

of aquatic freshwater organisms to iodine and cuprous iodide would be expected to be negligible 

under the circumstances modeled.

Characterization of Environmental Exposure Modeling Estimates 

The estimates of risks to aquatic organisms downstream of domestic WWTPs that receive 

copper, iodine, and cuprous iodide via leaching during washing of treated fabrics are based on 

worst case assumptions and would not be expected to occur under actual environmental 
16

conditions. There are a number of assumptions that contribute to potential risks to aquatic 

organisms being overestimated, including:

 The maximum amount of cuprous iodide produced annually, 77,000 kilograms, was 

assumed to be incorporated solely into woven fabrics, which would be expected to have 

the highest leaching potential of any of the products into which cuprous iodide would be 

incorporated. Presumably, some cuprous iodide would be incorporated into other 

products into which cuprous iodide would be tightly bound into a matrix and would have 

negligible or lower potential for leaching.

 The maximum annual production volume of cuprous iodide was assumed to be released 

to surface water bodies downstream of domestic wastewater treatment facilities over a 

one-year period. The data submitted on leaching from fabrics was not used since this 

conservative approach that assuming the maximum annual production volume was 

released to surface water over a one-year period demonstrated that potential risks to 

aquatic organisms were generally negligible. 

 Presumably, cuprous iodide would remain in products into which it has been incorporated 

for a considerably longer time.

 Estimates of risks to aquatic organisms assumed that none of the iodine and cuprous

iodide that leached and entered domestic WWTPs would be removed during wastewater 

treatment.

 Although 84% of copper was assumed to be removed during waste water treatment, 

sorption of remaining copper ions to suspended solids in the water column and to 

sediments was not quantified. Copper ions would be expected to partition to suspended 

solids and sorb to sediment rather than remain in the dissolved phase of the water 

column. E-FAST modeling was unable to account for this phenomenon.

There are some factors, however, that may contribute to underestimates of exposure. These 

include:

 If higher amounts of cuprous iodide are produced annually than the maximum annual 

amount of 77,000 kilograms, estimates of risk would be higher.

 Although there were gaps in ecotoxicity endpoints for aquatic organisms for iodine and 

copper iodide, aquatic organisms are presumed to be more sensitive to copper than to 

iodine or copper iodide. Estimated risks could be higher if certain taxa of aquatic 

organisms were shown to be more sensitive to iodine or copper iodide.

 Risks were not estimated from manufacturing processes for incorporating copper iodide 

into materials. Although the overall amount of copper, iodine, and cuprous iodide 

released from industrial use facilities may be small, exposure is possible. However,

based on the amount of projected volume of copper iodide, the multiple use sites, and the 
17

other potential sources of copper and iodine in the environment, these exposures are 

considered to be negligible.

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