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Proposed Registration Decision for a Product Containing the New Active 

Ingredient, Cuprous Iodide

Summary

The U.S. Environmental Protection Agency (EPA) is proposing to register a new end-use 

product, Cupron Cuprous Iodide, comprised of a new active ingredient, cuprous iodide, under the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), as amended. 

Cuprous iodide is an inorganic compound proposed to be formulated into an end-use product for 

material preservation of fibers; floor coverings; plastics, coatings, films, and laminates; and 

adhesives and sealants to control the growth of algae, mold, mildew, fungi and bacteria which 

cause unpleasant odors, discoloration, staining, deterioration, or corrosion.

Background

On July 25, 2012, EPA received an application from Cupron Inc to register an end-use product 

containing the new active ingredient, cuprous iodide (CAS Number 7681-65-4), for material 

preservation. The company submitted product chemistry, toxicology, human exposure, 

ecological effects, and environmental fate data in support of its application for registration of the 

one end-use product containing the new active ingredient. 

During the application screening, the Agency determined that additional product chemistry data

needed to be submitted to confirm the applicant’s assertion that the manufacturing process does 

not produce cuprous iodide with nanochemistry attributes. Based on additional information 

submitted by the applicant, the Agency determined that the active ingredient was appropriately 

identified as cuprous iodide and should not be identified as nano cuprous iodide.

In November 2014, the Agency determined the proposed formulation posed inhalation handler 

risks that could only be mitigated through reformulation. In March 2015, Cupron submitted a 

revised application that included a new confidential statement of formula and product chemistry 

data reflecting the product’s reformulation from a powder to a masterbatch. A masterbatch is a 

common industrial term utilized when an active ingredient is imbedded into non-friable plastic 

pellets which are then incorporated into manufactured products. 

The application is for an end-use product to be used as a materials preservative at a rate of 0.2%

to 5.0% by weight in the final article. The articles proposed to be treated are listed in Table 1.
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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

Public Comments

As required by FIFRA, the Agency published a notice of receipt of applications to register a 

pesticide product containing the new active ingredient, cuprous iodide in the Federal Register on 

October 30, 2013 (78 FR 25596), and a 30 day public comment period commenced. One 

comment from the Bay Area Clean Water Agencies was received in response to the Federal 

Register notice. 

The comment expressed concerns about the potential impact copper iodide and copper could 

have to aquatic life from release to wastewater treatment facilities and to the aquatic 

environment.

In response to this comment, the Agency refers to the August 25, 2015 risk assessment entitled, 

“Human Health and Ecological Risk Assessment for Cuprous Iodide.” As part of the risk 

assessment, the Agency conducted a screening level “down the drain” assessment that estimates 

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. No acute COCs were exceeded for copper, 

iodine, or cuprous iodide for one or more days for either the screening average case scenario or 

the screening high-end scenario for non-listed aquatic organisms. For copper at the screening 

high end scenario, listed/endangered freshwater invertebrates COCs were exceeded for up to 72 

days for copper and 12 days for copper iodide. For the screening average case scenario, the 

exceedances for endangered/listed freshwater invertebrates were 8 days for copper and 1 day for 

copper iodide. No chronic COCs were exceeded for 20 days or more for copper ion, and 

potential chronic risks from exposure of aquatic freshwater organisms to iodine and cuprous 

iodide are expected to be negligible.
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In addition to the Cuprous Iodide Risk Assessment, copper is undergoing registration review, 

and the preliminary risk assessment will be available for comment in March 2016. Registration 

review is a program intended to make sure that, as the ability to assess risk evolves and as 

policies and actives change, all registered pesticides continue to meet the statutory standard of no 

unreasonable adverse effects to human health and the environment. Chemicals are re-evaluated 

on a 15-year cycle.

The Agency is now seeking public comment under the public participation process, FIFRA 

section 3(c)(4), for this proposal to issue an unconditional registration for the proposed cuprous 

iodide product. 

Evaluation

In evaluating a pesticide registration application, the EPA assesses a wide variety of exposure 

information, (i.e., where and how the pesticide is used), environmental fate (i.e., how the 

chemical will move in the environment), and toxicity studies (i.e., effects on humans and other 

non-target organisms) to determine the likelihood of adverse effects (i.e., risk) from exposures 

associated with the proposed use of the product. Risk assessments are developed to evaluate the 

environmental fate of the compound as well as how it might affect a wide range of non-target 

organisms including humans, terrestrial and aquatic wildlife (plants and animals). On the basis 

of these assessments, EPA evaluates and approves language for each pesticide label to ensure the 

directions for use and safety measures are appropriate to mitigate the potential risk. The 

pesticide’s label communicates directions for use that are necessary for public safety. It is a 

FIFRA violation to use a registered pesticide in a manner inconsistent with its labeling.

1. Assessment of Risk to Human Health

EPA requires a wide range of studies in order to assess a pesticide. The human health effects and 

risk of cuprous iodide, as assessed in the August 25, 2015 document entitled, “Human Health 

and Ecological Risk Assessment for Cuprous Iodide” are summarized below. The Agency has 

determined that exposure to cuprous iodide via the 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, the inhalation exposure is 

negligible and thus an inhalation assessment is not needed. Therefore, the cuprous iodide human 

health risk assessment evaluates copper and iodine ions only via the oral and dermal route. The 

toxicology database to assess cuprous iodide is adequate to support the antimicrobial pesticidal 

uses of this chemical.

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

from human exposure to copper (Reregistration Eligibility Decision Document for Coppers, 

2009). Therefore, the toxicology assessment for cuprous iodide is based on data from the iodine 

toxicity database. Three human studies from the open literature examining oral and systemic 

toxicity of iodine 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. The 

data from these three studies indicate that the target organ for iodine toxicity in the human is the 

thyroid. The incidental oral and dermal iodine endpoints are based on the thyroid. 
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Additional toxicity data for either the copper or iodine are not needed 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 of the human 

thyroid. Data also demonstrate that the iodine component of cuprous iodide is not a 

developmental or reproductive toxicant (Reregistration Eligibility Decision Document for Iodine, 

2006). The Agency granted data 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 iodine to perform exposure and risk assessments for 

incidental oral and dermal exposure (see Table 2). A short-term incidental oral endpoint was 

selected to be protective of children sucking on treated articles. A dermal endpoint was selected 

to assess exposures to iodine that may occur from dermal contact with materials treated with 

cuprous iodide. A dermal absorption factor of 0.1% was used to account for the oral endpoint. 

Because cuprous iodide is formulated as a masterbatch, which consists of 20 percent a.i. 

imbedded in non-friable plastic pellets, there is negligible potential for inhalation exposure and 

thus no inhalational endpoints are selected. 

Table 2 - 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 

(MRID 49342401)

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

level, MOE = margin of exposure, RfC = reference concentration

Dietary exposure to copper iodide as a result of residues from the treated articles is not expected 

based on the label that would restrict application to nonfood contact plastics, laminates, and 

coating for countertops and conveyor belts. However, there could be exposure to copper iodide 

as a result of residues in drinking water, but exposure is expected to be low based on limited 

leaching from textiles as demonstrated in the cuprous iodide textile leaching study (M. Brooks, 

MRID 49200001). Therefore, there are no dietary concerns from food or drinking water from 

the proposed uses of cuprous iodide.

There are potential residential post application exposure and risk to humans who may be exposed 

to cuprous iodide fibers that could be used to manufacture household items such as blankets, 

towels, and apparel such as sleepwear. Given these proposed uses, dermal exposure to adults 
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and children who wear treated clothing and incidental oral exposure to toddlers who chew on

blankets, towels, and clothing were assessed. All residential risk estimates were below EPA’s 

level of concern.

Since cuprous iodide is formulated as a masterbatch which consists of 20 percent a.i. imbedded 

in non-friable plastic pellets, the exposure is negligible and thus an occupational risk assessment 

is not required.

The acute toxicity of cuprous iodide falls in the lowest acute toxicity categories of III (oral, 

inhalation, primary eye irritation) and IV (dermal and primary dermal irritation). Thus, the 

labeling precautionary signal word is “CAUTION.”

2. Assessment of Ecological Risk 

The battery of tests required to assess the ecological risks and environmental fate of cuprous 

iodide is complete. The environmental fate and ecological risks of cuprous iodide assessed in the 

document entitled, “Human Health and Ecological Risk Assessment for Cuprous Iodide” are 

summarized below. 

Cuprous iodide is slightly toxic to birds and highly toxic to aquatic invertebrates. Thus, the 

environmental hazard labeling statement, “this pesticide is toxic to aquatic organisms,” is 

required on the label. 

The value of the maximum annual production volume of cuprous iodide was assumed to be 

77,000 kilograms per year (170,000 pounds). For copper ion, the percent removal during 

wastewater treatment was assumed to be 84.2 percent (EPA, 2000). 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.

The primary pathway by which cuprous iodide would be expected to be released into the aquatic 

environment is by the leaching of cuprous iodide during in-service use of manufactured products

(i.e., fabric washing at institutional facilities, commercial establishments, and residences). 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. 

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

the aquatic environment will be predominantly to copper and iodine ions. Therefore, the 

ecotoxicity endpoints for the ecological risk assessment were obtained from the copper iodide as 

well as the copper and iodine databases. 

A screening level down the drain assessment estimates 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. Estimates of exposure were developed using 7Q10 stream flow which is 

the lowest 7 consecutive-day stream flow over a 10-year period. 
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Generally, for any assessment, if the probabilistic modeling predicts the acute COC is exceeded 

for one day or more, potential acute risks may be expected. No acute COCs for copper, iodine, 

or cuprous iodide exceeded for one day or more for either the average case scenario or the highend scenario for aquatic organisms.

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

exceeded for more than 20 days, potential chronic risks may be expected. No chronic COCs 

were exceeded for 1 day for copper ion. There wereno chronic endpoints for iodine or cuprous 

iodide;however, even if equal toxicity to copper was assumed, no exceedances would be 

predicted by the DTD modelingConsequently, potential chronic risks from exposure of aquatic 

freshwater organisms to iodine and cuprous iodide would be expected to be negligible.

Proposed Regulatory Decision

Under Section 3(c)(5) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the 

Agency is proposing to unconditionally register a new end-use product, Cupron Cuprous Iodide, 

comprised of a new active ingredient, cuprous iodide. The proposed registration is summarized 

below.

84542-O (Cupron Cuprous Iodide)

 20% cuprous iodide

 End-use Product, a material preservative to be incorporated into manufactured products 

to control the growth of algae, mold, mildew, fungi, and bacteria which cause unpleasant 

odors, discoloration, staining, deterioration, or corrosion.

The risk assessment supporting this decision can be found in the regulatory docket (Docket ID: 

EPA-HQ-OPP-2013-0433).

Public Participation

FIFRA requires public participation in the pesticide registration process for new active 

ingredients under Section 3(c)(4). The Agency explored opportunities for expanding the 

openness of the process for new active ingredients and other registration actions. In October 

2009, the Agency began implementing a public participation process for certain pesticide 

registration actions, including registration of products containing a new active ingredient, 

http://www.epa.gov/pesticides/regulating/public-participation-process.html.

The Agency will consider all public comments received during the public comment period for 

this proposal to issue an unconditional registration for the proposed cuprous iodide product. 

During the public comment period, comments should be submitted under Docket ID No. EPAHQ-OPP-2013-0433 via www.regulations.gov, mail, or hand delivery.