19640 Federal Register / Vol. 72, No. 74 / Wednesday, April 18, 2007 / Proposed Rules 

inserted only in an inverted repeat 

orientation or lacking an initiation 

codon for protein synthesis such that no 

PVC-protein is produced in the plant. 

(2) The Agency determines after 

review that viruses that naturally infect 

the plant containing the PVCP-PIP are 

unlikely to acquire the coat protein 

sequence through recombination and 

produce a viable virus with significantly 

different properties than either parent 

virus. 

(c) The criterion in paragraph (c) of 

this section is satisfied if either 

paragraph (c)(1) or paragraph (c)(2) of 

this section applies: 

(1) The genetic material that encodes 

the pesticidal substance or leads to the 

production of the pesticidal substance: 

(i) Is inserted only in an inverted 

repeat orientation or lacking an 

initiation codon for protein synthesis 

such that no PVC-protein is produced in 

the plant, or 

(ii) Encodes only a single virtually 

unmodified viral coat protein. Multiple 

PVC-proteins could each separately 

meet this criterion. Chimeric PVCproteins do not qualify. 

(2) The Agency determines after 

review that the genetic material that 

encodes the pesticidal substance or 

leads to the production of the pesticidal 

substance: 

(i) Encodes a protein that is minimally 

modified from a coat protein from a 

virus that naturally infects plants, or 

(ii) Produces no protein. 

(d)(1) Records to support exemption 

determinations made by the developer 

of a PVCP-PIP under paragraphs (a)(1), 

(b)(1), or (c)(1) of this section; to support 

a submission of information under 

paragraphs (a)(2), (b)(2), or (c)(2) of this 

section; or to support a certification 

made by the developer that a PVCP-PIP 

meets § 174.21(b) and/or § 174.21(c) 

must be maintained by the developer of 

the product for the duration of time that 

the PVCP-PIP is sold or distributed. 

Such records must be made available for 

inspection and copying, or otherwise 

submitted to the Agency for review 

upon request by EPA or its duly 

authorized representative. 

(2) Information adequate to support 

claims for an Agency-determined 

exemption must be submitted for review 

to the Office of Pesticide Programs, 

Attention: PVCP-PIP Exemption. 

(3) A statement notifying the Agency 

and certifying the accuracy of any 

determination made by the developer 

that a PVCP-PIP meets § 174.21(b), 

§ 174.21(c), paragraph (a)(1) of this 

section, paragraph (b)(1) of this section, 

and/or paragraph (c)(1) of this section 

must be signed by the developer and 

submitted to the Office of Pesticide 

Programs, Attention: PVCP-PIP 

Exemption. Any such statement must be 

submitted at the time of a first 

submission, if any, of information under 

paragraph (d)(2) of this section for a 

particular PVCP-PIP. If a PVCP-PIP 

satisfies paragraphs (a)(1), (b)(1), and 

(c)(1)) of this section and §§ 174.21(b) 

and (c), the developer must submit a 

notification to the Agency of that 

determination and certify that the 

PVCP-PIP qualifies for exemption under 

FIFRA, i.e., that the PVCP-PIP meets 

§§ 174.21(a), (b), and (c).This 

certification must contain: 

(i) The name of the crop (including 

genus and species) containing the 

PVCP-PIP. 

(ii) The name of the virus from which 

the coat protein gene was derived. 

(iii) The name of the virus(es) to 

which resistance is conferred. 

(iv) When available, a unique 

identifier. 

5. By revising § 174.480 to read as 

follows: 

§ 174.480 Scope and purpose. 

This subpart lists the inert ingredients 

that may be used in a plant-incorporated 

protectant listed in subpart B of this part 

and whose residues are either exempted 

from the requirement of a tolerance 

under FFDCA or no tolerance would 

otherwise be required. 

6. By adding § 174.486 to read as 

follows: 

§ 174.486 Inert ingredients that may be 

used with PIPs in certain plants. 

The following must be used in a plant 

that satisfies § 174.27(a) in order to be 

exempt from the requirements of FIFRA. 

(a) Beta-D-glucuronidase (GUS) from 

Escherichia coli and the genetic material 

necessary for its production. 

(b) Neomycin phosphotransferase II 

(NPTII) and the genetic material 

necessary for its production. 

(c) Phosphomannose isomerase (PMI) 

and the genetic material necessary for 

its production. 

(d) CP4 enolpyruvylshikimate-3- 

phosphate (CP4 EPSPS) and the genetic 

material necessary for its production. 

(e) Glyphosate oxidoreductase (GOX 

or GOXv247) and the genetic material 

necessary for its production. 

(f) Phosphinothricin acetyltransferase 

(PAT) and the genetic material 

necessary for its production. 

(g) Partial tetracycline resistance gene 

under the control of a bacterial promoter 

as present in papaya line 55–1. 

[FR Doc. E7–7297 Filed 4–17–07; 8:45 am] 

BILLING CODE 6560–50–S 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 174 

[EPA–HQ–OPP–2006–0643; FRL–8100–5] 

RIN 2070–AD49 

Exemption from the Requirement of a 

Tolerance under the Federal Food, 

Drug, and Cosmetic Act for Residues 

of Plant Virus Coat Proteins that are 

Part of a Plant-Incorporated Protectant 

(PVC-Proteins); Supplemental 

Proposal 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: EPA is proposing to exempt 

from the Federal Food, Drug, and 

Cosmetic Act (FFDCA) section 408 

requirement of a tolerance, residues of 

coat proteins from viruses that naturally 

infect plants that humans consume 

when such coat proteins are produced 

in living plants as part of a plantincorporated protectant (PIP) and the 

criteria proposed for this exemption are 

met. EPA believes there is a reasonable 

certainty that no harm will result from 

aggregate exposure to such residues, 

including all anticipated dietary 

exposures and all other exposures for 

which there is reliable information. This 

proposed exemption would eliminate 

the need to establish a maximum 

permissible level in food for these 

residues. 

DATES: Comments must be received on 

or before July 17, 2007. 

ADDRESSES: Submit your comments, 

identified by docket identification (ID) 

number EPA–HQ–OPP–2006–0643, by 

one of the following methods: 

• Federal eRulemaking Portal: http:// 

www.regulations.gov. Follow the on-line 

instructions for submitting comments. 

• Mail: Office of Pesticide Programs 

(OPP) Regulatory Public Docket (7502P), 

Environmental Protection Agency, 1200 

Pennsylvania Ave., NW., Washington, 

DC 20460–0001. 

• Delivery: OPP Regulatory Public 

Docket (7502P), Environmental 

Protection Agency, Rm. S–4400, One 

Potomac Yard (South Bldg.), 2777 S. 

Crystal Dr., Arlington, VA. Deliveries 

are only accepted during the Docket’s 

normal hours of operation (8:30 a.m. to 

4 p.m., Monday through Friday, 

excluding legal holidays). Special 

arrangements should be made for 

deliveries of boxed information. The 

Docket Facility telephone number is 

(703) 305–5805. 

• Instructions: Direct your comments 

to docket ID number EPA–HQ–OPP–


hsrobinson on PROD1PC76 with PROPOSALS2
Federal Register / Vol. 72, No. 74 / Wednesday, April 18, 2007 / Proposed Rules 19641 

2006–0643. EPA’s policy is that all 

comments received will be included in 

the docket without change and may be 

made available on-line at http:// 

www.regulations.gov, including any 

personal information provided, unless 

the comment includes information 

claimed to be Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Do not submit information that you 

consider to be CBI or otherwise 

protected through regulations.gov or email. The regulations.gov website is an 

‘‘anonymous access’’ system, which 

means EPA will not know your identity 

or contact information unless you 

provide it in the body of your comment. 

If you send an e-mail comment directly 

to EPA without going through 

regulations.gov, your e-mail address 

will be automatically captured and 

included as part of the comment that is 

placed in the docket and made available 

on the Internet. If you submit an 

electronic comment, EPA recommends 

that you include your name and other 

contact information in the body of your 

comment and with any disk or CD-ROM 

you submit. If EPA cannot read your 

comment due to technical difficulties 

and cannot contact you for clarification, 

EPA may not be able to consider your 

comment. Electronic files should avoid 

the use of special characters, any form 

of encryption, and be free of any defects 

or viruses. 

Docket: All documents in the docket 

are listed in the docket index. Although 

listed in the index, some information is 

not publicly available, e.g., CBI or other 

information whose disclosure is 

restricted by statute. Certain other 

material, such as copyrighted material, 

is not placed on the Internet and will be 

publicly available only in hard copy 

form. Publicly available docket 

materials are available either in the 

electronic docket at http:// 

www.regulations.gov, or, if only 

available in hard copy, at the OPP 

Regulatory Public Docket in Rm. S–

4400, One Potomac Yard (South Bldg.), 

2777 S. Crystal Dr., Arlington, VA. The 

hours of operation of this docket facility 

are from 8:30 a.m. to 4 p.m., Monday 

through Friday, excluding legal 

holidays. The Docket Facility telephone 

number is (703) 305–5805. 

FOR FURTHER INFORMATION CONTACT: 

Melissa Kramer, Hazard Assessment 

Coordination and Policy Division 

(7202M), Office of Science Coordination 

and Policy, 1200 Pennsylvania Ave., 

NW., Washington, DC 20460–0001; 

telephone number: (202) 564–8497; fax 

number: (202) 564–8502; e-mail address: 

kramer.melissa@epa.gov. 

SUPPLEMENTARY INFORMATION: 

I. General Information 

A. Does this Document Apply to Me? 

You may be potentially affected by 

this action if you are a person or 

company involved with agricultural 

biotechnology that may develop and 

market PIPs. Potentially affected entities 

may include, but are not limited to: 

• Pesticide and other agricultural 

chemical manufacturing (NAICS code 

32532), e.g., establishments primarily 

engaged in the formulation and 

preparation of agricultural and 

household pest control chemicals. 

• Food manufacturing (NAICS code 

311), e.g., establishments primarily 

engaged in the manufacturing of food or 

feed. 

• Crop production (NAICS code 111), 

e.g., establishments primarily engaged 

in growing crops, plants, vines, or trees 

and their seeds. 

• Colleges, universities, and 

professional schools (NAICS code 

611310), e.g., establishments of higher 

learning which are engaged in 

development and marketing of virusresistant plants. 

• Research and development in the 

physical, engineering, and life sciences 

(NAICS code 54171), e.g., 

establishments primarily engaged in 

conducting research in the physical, 

engineering, or life sciences, such as 

agriculture and biotechnology. 

This listing is not intended to be 

exhaustive, but rather provides a guide 

for readers regarding entities likely to be 

affected by this action. Other types of 

entities not listed in this unit could also 

be affected. The North American 

Industrial Classification System 

(NAICS) codes have been provided to 

assist you and others in determining 

whether or not this action might apply 

to certain entities. To determine 

whether you or your business may be 

affected by this action, you should 

carefully examine the applicable 

provisions of 40 CFR part 174. If you 

have questions regarding the 

applicability of this action to a 

particular entity, consult the person 

listed under FOR FURTHER INFORMATION

CONTACT. 

B. What Should I Consider as I Prepare 

My Comments for EPA? 

1. Docket. EPA has established a 

docket for this action under docket ID 

number EPA–HQ–OPP–2006–0643. 

Publicly available docket materials are 

available either in the electronic docket 

at http://www.regulations.gov, or, if only 

available in hard copy, at the Office of 

Pesticide Programs (OPP) Regulatory 

Public Docket in Rm. S–4400, One 

Potomac Yard (South Bldg.), 2777 S. 

Crystal Dr., Arlington, VA. The hours of 

operation of this docket facility are from 

8:30 a.m. to 4 p.m., Monday through 

Friday, excluding legal holidays. The 

Docket Facility telephone number is 

(703) 305–5805. 

2. Tips for preparing your comments. 

When submitting comments, remember 

to: 

i. Identify the document by docket ID 

number and other identifying 

information (subject heading, Federal 

Register date and page number). 

ii. Follow directions. The Agency may 

ask you to respond to specific questions 

or organize comments by referencing a 

Code of Federal Regulations (CFR) part 

or section number. 

iii. Explain why you agree or disagree; 

suggest alternatives and substitute 

language for your requested changes. 

iv. Describe any assumptions and 

provide any technical information and/ 

or data that you used. 

v. If you estimate potential costs or 

burdens, explain how you arrived at 

your estimate in sufficient detail to 

allow for it to be reproduced. 

vi. Provide specific examples to 

illustrate your concerns and suggest 

alternatives. 

vii. Explain your views as clearly as 

possible, avoiding the use of profanity 

or personal threats. 

viii. Make sure to submit your 

comments by the comment period 

deadline identified. 

II. What Action is the Agency 

Proposing? 

EPA is proposing to exempt the 

following from the FFDCA section 408 

requirement of a tolerance: Residues of 

coat proteins from viruses that naturally 

infect plants that humans consume as 

part of a normal diet, including any 

metabolites or degradates of those coat 

proteins, when such coat proteins are 

produced in living plants as part of a 

PIP and the criteria proposed for this 

exemption are met. The proposed 

criteria are intended to clearly identify 

and exempt only those residues for 

which a long history of safe exposure 

and consumption can support 

exemption. EPA believes there is a 

reasonable certainty that no harm will 

result from aggregate exposure to such 

residues, including all anticipated 

dietary exposures and all other 

exposures for which there is reliable 

information. This proposed exemption 

would eliminate the need to establish a 

maximum permissible level in food for 

these residues. 


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III. What is the Agency’s Authority for 

Taking this Action? 

EPA is proposing to establish this 

tolerance exemption on its own 

initiative under sections 408(e) and (c) 

of FFDCA, 21 U.S.C. 346a(c) and (e). 

Under FFDCA section 408, EPA 

regulates pesticide chemical residues by 

establishing tolerances limiting the 

amounts of residues that may be present 

in or on food or by establishing 

exemptions from the requirement of a 

tolerance for such residues. Food 

includes articles used for food or drink 

by humans or animals. A food 

containing pesticide residues may not 

be moved in interstate commerce 

without an appropriate tolerance or an 

exemption from the requirement of a 

tolerance. 

Section 408 of FFDCA applies to all 

‘‘pesticide chemical residues,’’ which 

are defined as residues of either a 

‘‘pesticide chemical’’ or ‘‘any other 

added substance that is present on or in 

the commodity or food primarily as a 

result of the metabolism or other 

degradation of a pesticide chemical’’ (21 

U.S.C. 321(q)(2)). FFDCA defines 

‘‘pesticide chemical’’ as: ‘‘any substance 

that is a pesticide within the meaning of 

the Federal Insecticide, Fungicide, and 

Rodenticide Act, including all active 

and inert ingredients of such pesticide’’

(21 U.S.C. 321(q)(1)). The Federal 

Insecticide, Fungicide, and Rodenticide 

Act (FIFRA) section 2(u) defines 

‘‘pesticide’’ as: ‘‘(1) any substance or 

mixture of substances intended for 

preventing, destroying, repelling, or 

mitigating any pest, (2) any substance or 

mixture of substances intended for use 

as a plant regulator, defoliant, or 

desiccant, and (3) any nitrogen 

stabilizer. . .’’ (7 U.S.C. 136(u)). Under 

FIFRA section 2(t), the term ‘‘pest’’

includes: ‘‘(1) any insect, rodent, 

nematode, fungus, weed, or (2) any 

other form of terrestrial or aquatic plant 

or animal life or virus, bacteria, or other 

microorganism. . . which the 

Administrator declares to be a pest. . .’’

subject to certain exceptions (7 U.S.C. 

136(t)). 

Section 408(c)(2)(A)(i) of FFDCA 

allows EPA to establish an exemption 

from the requirement for a tolerance (the 

legal limit for a pesticide chemical 

residue in or on a food) only if EPA 

determines that the exemption is ‘‘safe.’’

Section 408(c)(2)(A)(ii) of FFDCA 

defines ‘‘safe’’ to mean 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 all 

other exposures for which there is 

reliable information.’’ This includes 

exposure through drinking water and in 

residential settings, but does not include 

occupational exposure. Pursuant to 

section 408(c)(2)(B) of FFDCA, in 

establishing or maintaining in effect an 

exemption from the requirement of a 

tolerance, EPA must take into account 

the factors set forth in section 

408(b)(2)(C) of FFDCA, which require 

EPA to give special consideration to 

exposure of infants and children to the 

pesticide chemical residue in 

establishing a tolerance and to ‘‘ensure 

that there is a reasonable certainty that 

no harm will result to infants and 

children from aggregate exposure to the 

pesticide chemical residue. . . .’’

Additionally, section 408(b)(2)(D) of 

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.’’

EPA performs a number of analyses to 

determine the risks from aggregate 

exposure to pesticide residues. First, 

EPA determines the toxicity of 

pesticides. Second, EPA examines 

exposure to the pesticide through food, 

drinking water, and through other 

exposures that occur as a result of 

pesticide use in residential settings. 

Section 408(e)(1)(C) of FFDCA also 

grants EPA the authority to establish 

‘‘general procedures and requirements 

to implement this section’’ (21 U.S.C. 

346a(e)(1)(C)). 

IV. Context 

A. What is the Relationship of this 

Proposal to Other Regulatory 

Requirements under FIFRA and FFDCA? 

When the genetic material that 

encodes an entire or a portion of a plant 

virus coat protein is introduced into 

living plants with the intention of 

preventing or mitigating viral disease in 

the plants, the genetic material and any 

substances produced from the genetic 

material constitute a type of pesticide 

termed a ‘‘plant virus coat protein plantincorporated protectant’’ or ‘‘PVCPPIP.’’ PVCP-PIPs meet the FIFRA section 

2(u) definition of ‘‘pesticide’’ because 

they are introduced into plants with the 

intention of ‘‘preventing, destroying, 

repelling, or mitigating any pest. . .’’ (7 

U.S.C. 136(u)) and plant viruses meet 

the FIFRA section 2 definition of ‘‘pest’’

(7 U.S.C. 136(t)). PVCP-PIPs are 

considered pesticide chemicals under 

FFDCA which defines a ‘‘pesticide 

chemical’’ as ‘‘any substance that is a 

pesticide within the meaning of the 

Federal Insecticide, Fungicide, and 

Rodenticide Act, including all active 

and inert ingredients of such pesticide.’’

As such, residues of PVCP-PIPs in or on 

food (hereinafter simply ‘‘in food’’) are 

subject to FFDCA section 408. 

Since PVCP-PIPs are a relatively 

newly described type of pesticide, the 

discussion in this unit provides 

information explaining how this FFDCA 

proposed action on residues of the plant 

virus coat protein portion of a PVCP-PIP 

(called here the ‘‘PVC-protein’’) would 

affect the FFDCA and FIFRA status of 

the complete PVCP-PIP. To this end, 

several pieces of information are 

presented: A description of the 

anticipated residues of PVCP-PIPs; a 

discussion of the FFDCA status, either 

current or proposed, of all anticipated 

PVCP-PIP residues; a discussion of what 

would be considered in determining the 

FFDCA status of the complete PVCPPIP; and a discussion of how the FFDCA 

status of PVCP-PIP residues relates to 

the FIFRA status of the PVCP-PIP. 

1. What are the components of a PIP? 

A PIP is defined at 40 CFR 174.3 as ‘‘a 

pesticidal substance that is intended to 

be produced and used in a living plant, 

or in the produce thereof, and the 

genetic material necessary for 

production of such a pesticidal 

substance. It also includes any inert 

ingredient contained in the plant, or 

produce thereof.’’

2. What are the anticipated residues 

of PVCP-PIPs? Based on the definition 

of a PIP, EPA anticipates residues of a 

PVCP-PIP would include residues of 

any PVC-protein; the nucleic acids 

associated with the PVCP-PIP, e.g., the 

genetic material encoding the PVCprotein; and any inert ingredient as 

defined for PIPs at 40 CFR 174.3. Each 

of these three classes of residues will 

also include any metabolite and 

degradate of that class in accordance 

with FFDCA section 201 that defines a 

‘‘pesticide chemical residue’’ as ‘‘a 

residue in or on raw agricultural 

commodity or processed food of (A) a 

pesticide chemical; or (B) any other 

added substance that is present on or in 

the commodity or food primarily as a 

result of the metabolism or other 

degradation of a pesticide chemical’’ (21 

U.S.C. 321(q)(2)). 

3. What is the FFDCA status of each 

identified class of residues? For the 

complete PVCP-PIP to be exempt from 

FFDCA section 408, all three classes of 

PVCP-PIP residues listed above must be 

exempt, i.e., residues of the PVCprotein, the nucleic acids associated 

with the PVCP-PIP, and any inert 

ingredient as defined for PIPs at 40 CFR 

174.3. The units below discuss the 

status of residues of the PVC-protein 

under this proposed action, the status of 

residues of the nucleic acids associated 


hsrobinson on PROD1PC76 with PROPOSALS2
Federal Register / Vol. 72, No. 74 / Wednesday, April 18, 2007 / Proposed Rules 19643 

with the PVCP-PIP, and the status of 

residues of inert ingredients. 

i. Residues of PVC-proteins. Residues 

in this category consist of residues of 

the PVC-protein and any metabolites or 

degradates of that protein. This proposal 

would exempt from tolerance 

requirements residues of PVC-proteins 

that meet certain criteria. 

Coat proteins are those substances 

that viruses produce to encapsulate and 

protect the viral nucleic acid and to 

perform other important tasks for the 

virus, e.g., assistance in viral 

replication, movement within the plant, 

and transmission of the virus from plant 

to plant by insects (Ref. 1). Current 

scientific information suggests that 

prevention or mitigation of disease by 

some PVCP-PIPs may be proteinmediated because for certain PVCP-PIPs 

efficacy is correlated with the 

concentration of coat protein produced 

by the transgene (Ref. 2). In proteinmediated resistance, the coat protein is 

thought to impede the infection cycle by 

interfering with the disassembly of 

infecting viruses (Ref. 3). In such cases, 

EPA would consider the PVC-protein to 

be the pesticidal substance. Residues of 

such PVC-proteins and their metabolites 

and degradates that meet the proposed 

criteria would be covered by this 

proposal. 

In transgenic plants employing a 

second mechanism of resistance called 

post-transcriptional gene silencing 

(PTGS), prevention or mitigation of viral 

disease is not correlated with the level 

of PVC-protein expression. Indeed, virus 

resistance can occur even when a coat 

protein gene expresses untranslatable 

RNA sequences and no PVC-protein is 

detected. In PTGS, RNA fragments 

appear to be pesticidal substances (Ref. 

3). (See Unit II.E. of the companion 

document published elsewhere in this 

Federal Register for a more detailed 

description of PTGS.) Even when PTGS 

is the mechanism of resistance, any 

PVC-protein that might be produced is 

part of the PVCP-PIP. Residues of such 

PVC-proteins and their metabolites and 

degradates that meet the proposed 

criteria are also covered by this 

proposal. 

ii. Residues of nucleic acids. Residues 

in this category include residues of the 

genetic material necessary for the 

production of the pesticidal substance 

and the genetic material for any inert 

ingredient as defined at 40 CFR 174.3. 

Residues in this category would also 

include residues of any nucleic acids 

effecting the pesticidal action of the 

PVCP-PIP, e.g., residues of nucleic acids 

involved in PTGS. 

‘‘Nucleic acids’’ are defined at 40 CFR 

174.3 as ‘‘ribosides or deoxyribosides of 

adenine, thymine, guanine, cytosine, 

and uracil; polymers of the deoxyribose5’-monophosphates of thymine, 

cytosine, guanine, and adenine linked 

by successive 3’-5’ phosphodiester 

bonds (also known as deoxyribonucleic 

acid); and polymers of the ribose-5’- 

monophosphates of uracil, cytosine, 

guanine, and adenine linked by 

successive 3’-5’ phosphodiester bonds 

(also known as ribonucleic acid). The 

term does not apply to nucleic acid 

analogues (e.g., dideoxycytidine), or 

polymers containing nucleic acid 

analogues.’’ Nucleic acids are currently 

exempt from FFDCA tolerance 

requirements. See 40 CFR 174.475 and 

66 FR 37817 (July 19, 2001) (FRL–6057–

5). EPA is not proposing to amend this 

exemption. 

iii. Residues of any inert ingredient. 

Residues in this category consist of 

residues of any inert ingredient that is 

part of a PVCP-PIP and any metabolite 

or degradate of an inert ingredient. An 

inert ingredient for a PIP is defined at 

40 CFR 174.3 as ‘‘any substance, such as 

a selectable marker, other than the 

active ingredient, where the substance is 

used to confirm or ensure the presence 

of the active ingredient, and includes 

the genetic material necessary for the 

production of the substance, provided 

that genetic material is intentionally 

introduced into a living plant in 

addition to the active ingredient.’’

A tolerance or tolerance exemption is 

required for residues of any substance in 

food that meets the 40 CFR 174.3 

definition of an inert ingredient (e.g., a 

selectable marker intentionally 

introduced into the plant as part of a 

PVCP-PIP such as a protein conferring 

resistance to an herbicide). Part 180 and 

part 174, subpart W, of 40 CFR list inert 

ingredients for which tolerance 

exemptions have been established. If an 

inert ingredient is not listed at part 180 

or part 174, subpart W, an applicant 

would need to petition the Agency in 

accordance with 40 CFR 180.7 to obtain 

a tolerance or tolerance exemption for 

residues of that particular inert 

ingredient in order for food containing 

residues of the PVCP-PIP to move in 

interstate commerce—even if all other 

residues of the PIP are exempt. 

4. What is the relationship between 

the FIFRA status of a PVCP-PIP and the 

FFDCA status of its residues? A 

tolerance exemption does not exempt a 

PVCP-PIP from FIFRA regulation. 

However, in order for a PVCP-PIP in 

food plants to be exempted from FIFRA 

regulation, a tolerance exemption must 

exist for all residues associated with a 

PVCP-PIP or FFDCA requirements must 

be otherwise met. (See the general 

qualification for exemption under 

FIFRA at 40 CFR 174.21(b).) The FIFRA 

status of a PVCP-PIP is determined 

based on factors in addition to FFDCA 

section 408 considerations because 

FIFRA requires the Agency to consider 

additional risk and benefit issues 

beyond those addressed under section 

408 of FFDCA. Concurrently with this 

proposed FFDCA exemption, the 

Agency is publishing a proposal under 

which PVCP-PIPs might meet the 

general qualification for FIFRA 

exemption at 40 CFR 174.21(a) based on 

different criteria than the criteria in this 

proposal. 

B. What is the History of this Proposal? 

1. Scientific input. EPA sponsored (or 

cosponsored with other Federal 

agencies) six conferences relevant to 

development of this proposed rule: On 

October 19–21, 1987, a meeting on 

‘‘Regulatory Considerations: 

Genetically-Engineered Plants’’ at 

Cornell University in Ithaca, NY; on 

September 8–9, 1988, a ‘‘Transgenic 

Plant Conference’’ in Annapolis, MD; on 

November 6–7, 1990, a conference on 

‘‘Pesticidal Transgenic Plants: Product 

Development, Risk Assessment, and 

Data Needs’’ in Annapolis, MD; on April 

18–19, 1994, a ‘‘Conference on 

Scientific Issues Related to Potential 

Allergenicity in Transgenic Food Crops’’

in Annapolis, MD; on July 17–18, 1997, 

a ‘‘Plant Pesticide Workshop’’ in 

Washington, DC; and on December 10–

12, 2001, a conference on ‘‘Assessment 

of the Allergenic Potential of 

Genetically Modified Foods’’ in Chapel 

Hill, NC. Information from these 

conferences has been incorporated as 

appropriate in development of this 

proposed rule. 

EPA has requested the advice of two 

scientific advisory groups at five 

meetings while developing its approach 

to PIPs. On December 18, 1992, EPA 

convened the FIFRA Scientific Advisory 

Panel (SAP) to review a draft policy on 

PIPs (then called plant-pesticides) and 

to respond to a series of related 

questions posed by the Agency dealing 

primarily with EPA’s approach under 

FIFRA. On July 13, 1993, EPA requested 

the advice of a Subcommittee of the 

EPA Biotechnology Science Advisory 

Committee (BSAC) on a series of 

scientific questions dealing with EPA’s 

approach to PIPs under FFDCA. On 

January 21, 1994, EPA asked for advice 

on the Agency’s approach to PIPs under 

both statutes at a joint meeting of the 

SAP and the BSAC. To evaluate more 

recent scientific advances, EPA again 

brought these issues to the SAP on 

October 13–14, 2004. On December 6–

8, 2005, EPA requested the SAP to 

respond to a series of scientific 


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questions related to this proposal. EPA 

carefully considered advice from all five 

meetings in the development of this 

proposed rule. 

2. Federal Register documents. The 

history of this proposal consists of the 

original proposed exemption that 

appeared in the November 23, 1994 

Federal Register (59 FR 60545) (FRL–

4755–4), a supplemental document that 

appeared in the May 16, 1997 Federal 

Register (62 FR 27149) (FRL–5716–6), 

and a supplemental document which 

appeared in the July 19, 2001Federal 

Register (66 FR 37855) (FRL–6760–4). 

i. November 23, 1994. EPA published 

a package of five separate documents in 

the November 23, 1994 Federal Register 

which described EPA’s policy and 

proposals for PIPs under FIFRA and 

FFDCA (59 FR 60496, 60519, 60535, 

60542, and 60545). In one of these 

documents (59 FR 60545), EPA 

proposed to exempt from the 

requirement of a tolerance, residues of 

plant virus coat proteins produced and 

used in living plants as a plantincorporated protectant (then called a 

plant-pesticide). The proposed 

exemption from the requirement of a 

tolerance read as follows: 

‘‘Residues of coat proteins from plant 

viruses, or segments of the coat proteins, 

produced in living plants as plantpesticides are exempt from the 

requirement of a tolerance’’ (59 FR 

60547). 

ii. May 16, 1997. In August of 1996, 

Congress enacted the Food Quality 

Protection Act (FQPA), which amended 

FFDCA and FIFRA. On May 16, 1997, 

EPA published a supplemental 

document in the Federal Register (62 

FR 27149) to provide the public with an 

opportunity to comment on EPA’s 

analysis of how certain FQPA 

amendments to FFDCA and FIFRA 

apply to the proposed exemption from 

the requirement of a tolerance for 

residues of PVC-proteins. 

In that supplemental document, EPA 

explained how most of the substantive 

factors that the amended FFDCA 

requires EPA to consider in evaluating 

pesticide chemical residues had been 

considered in the Agency’s 1994 

proposed tolerance exemption. Even 

though the Agency may not have used 

the terminology specified in FQPA, EPA 

did take into account most of the same 

factors in issuing its 1994 proposal to 

exempt residues of PVC-proteins, or 

segments of such proteins, from FFDCA 

tolerance requirements. EPA therefore 

sought comment on the requirements 

imposed by FQPA that the Agency had 

not addressed in its 1994 proposal, 

specifically: 

a. EPA’s conclusion that there are no 

substances outside of the food supply 

that may have a cumulative toxic effect 

with residues of PVC-proteins, 

b. EPA’s conclusion that there are no 

substances outside of the food supply to 

which humans might be exposed 

through non-occupational routes of 

exposure that are related via a common 

mechanism of toxicity to residues of 

PVC-proteins, 

c. Any available information on PVCproteins causing estrogenic effects, 

d. EPA’s rationale, described in 

greater detail, for concluding that PIPs 

are likely to present a limited exposure 

of pesticidal substances to humans in 

which the predominant, if not the only, 

route of exposure will be dietary, and 

e. EPA’s rationale, described in 

greater detail, for concluding that the 

Agency’s analysis concerning the 

dietary safety of food containing PVCproteins applies to infants and children 

as well as adults. 

iii. July 19, 2001. In July of 2001, EPA 

published a supplemental document in 

the Federal Register (66 FR 37855) to 

provide the public with additional 

opportunity to comment on the FIFRA 

and FFDCA exemptions for PIPs that the 

Agency proposed in 1994 but had not 

yet finalized by 2001. EPA also 

requested comment on the information, 

analyses, and conclusions pertaining to 

PVCP-PIPs contained in the NRC report 

entitled ‘‘Genetically Modified PestProtected Plants: Science and 

Regulation’’ (Ref. 4). In addition, the 

public was given an opportunity to 

comment on a clarification of the 

language in the original 1994 proposal 

on PVCP-PIPs that EPA was considering 

in response to public comment. The 

purpose of the clarification was to 

circumscribe more clearly those 

residues proposed for exemption. 

The documents, including associated 

public comments, and the reports of the 

meetings described above are available 

in the public dockets established for 

each of the associated rulemakings as 

described in Unit XII.B. 

This proposed rule completely 

supersedes these previous proposals. 

EPA does not intend to respond to 

comments submitted on those 

proposals. Thus, individuals who 

believe that any comments submitted on 

any of the earlier proposals remain 

germane to this proposal should submit 

them (or relevant portions) again during 

this comment period. 

C. Rationale Supporting the Proposed 

FFDCA Tolerance Exemption 

EPA’s base of experience with viruses 

infecting food plants has led the Agency 

to draw three conclusions on which it 

is relying to support this proposed 

tolerance exemption for residues of 

PVC-proteins in food. First, virusinfected plants have always been a part 

of the human and domestic animal food 

supply. Most crops are frequently 

infected with plant viruses, and food 

from these crops has been and is being 

consumed without adverse human or 

animal health effects. Second, plant 

viruses are not infectious to humans, 

including children and infants, or to 

other mammals. Third, plant virus coat 

proteins, while widespread in food, 

have not been associated with toxic or 

allergenic effects to animals or humans. 

These conclusions are derived from a 

base of experience and information 

sufficient to support this proposed 

tolerance exemption. 

1. Always been part of food supply 

without adverse effects. Virus-infected 

food plants have always been a part of 

the human and domestic animal food 

supply (Refs. 5, 6, 7, 8, 9, and 10). Most 

plants are infected by at least one virus, 

and components of plant viruses, 

including coat proteins, are often found 

in the produce of crop plants. For 

example, at the beginning of this 

century virtually every commercial 

cultivar of potatoes grown in the United 

States and Europe was infected with 

either one or a complex of potato 

viruses (Ref. 10). Even plants that show 

no disease symptoms are often found to 

be infected with viruses (Refs. 9 and 11). 

In addition, a common agricultural 

practice used since the 1920s for 

protection against viral disease involves 

intentionally inoculating healthy plants 

with a mild form of a virus in order to 

prevent infection by a more virulent 

form (Ref. 11). A recent analysis of viral 

sequences isolated from fecal samples of 

healthy humans showed the presence of 

large quantities of plant pathogenic 

viruses from 35 different plant virus 

species with evidence suggesting dietary 

origins for the most prevalent (Ref. 12). 

A great deal of information supports the 

ubiquitous appearance of plant viruses 

in foods, and to date there have been no 

reports of adverse human or animal 

health effects associated with 

consumption of plant viruses in food. 

The National Research Council (NRC) 

observed in its 2000 report that 

‘‘[h]uman or animal consumption of 

plants with viral coat proteins is widely 

considered to be safe, on the basis of 

common exposure to these types of 

proteins in nontransgenic types of food’’

(Ref. 4). The FIFRA SAP addressed the 

issue of dietary risk at its December 18, 

1992 meeting (Ref. 13). The SAP stated, 

‘‘Since viruses are ubiquitous in the 

agricultural environment at levels 

higher than will be present in transgenic 


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plants, and there has been a long history 

of ‘contamination’ of the food supply by 

virus coat protein, there is scientific 

rationale for exempting transgenic 

plants expressing virus coat protein 

from the requirement of a tolerance.’’

The FIFRA SAP again discussed PVCproteins on October 11–13, 2004, and 

‘‘agreed that (because of the human 

history of consuming virus infected 

food), unaltered PVCPs do not present 

new dietary exposures’’ (Ref. 14). The 

2005 SAP also agreed that 

‘‘[h]istorically, virus infected plants 

have been a part of the human and 

domestic animal food supply without 

adverse human or animal health effects’’

(Ref. 15). 

In general, EPA anticipates that 

dietary exposure through human and 

animal consumption of plants 

containing residues of PVC-proteins that 

would qualify for the proposed 

exemption will be similar to or less than 

the dietary exposure to plant virus coat 

proteins currently found in food plants 

naturally infected with viruses. 

Experiments have shown the amount of 

PVC-protein found in plants containing 

a PVCP-PIP to be as much as one 

hundred- to one thousand-fold lower 

than the amount of plant virus coat 

protein found naturally in virus-infected 

plants, even when the resistance is 

believed to be mediated by the PVCprotein itself (Refs. 8 and 16). The 

difference in amount of PVC-protein 

present is even more marked for virusresistant plants employing resistance 

mediated by RNA. In such cases, little 

to no detectable coat protein is 

produced in a plant containing a PVCPPIP (Refs. 3 and 17). Such information 

conforms to information EPA has 

received from the scientific advisory 

groups the Agency has consulted (see 

Unit IV.B.1.). Although the Agency 

believes that the PVC-proteins which 

qualify for this proposed tolerance 

exemption are safe at any level given the 

long history of human dietary exposure 

to high levels of such proteins, the 

anticipated low levels of exposure to 

PVC-proteins in food lend additional 

support to this proposed exemption. 

2. Not infectious to humans. Any 

virus/host relationship is characterized 

by a high degree of specificity (Ref. 8). 

Plant viruses usually infect plants only 

within a certain taxonomic group and 

are unable to infect humans or other 

vertebrates (Refs. 18 and 19). Cellular 

machinery for processing genetic 

material is highly specific. For example, 

plant viruses are unable to recognize 

and attach to the specific sites on 

mammalian cells needed to penetrate 

the cell membrane, and plant viruses 

cannot be processed by mammalian 

cellular machinery. Plant viruses 

therefore do not and cannot infect 

mammals and other vertebrates. In 

addition, multiple virus components in 

addition to the coat protein have a role 

in and are necessary for plant infection. 

Plant viral coat proteins alone are not 

infectious to plants, and whole, intact 

plant viruses are not infectious to 

humans. Therefore, it is reasonable to 

assume that a single component of plant 

viruses, e.g., the PVC-protein, will not 

be infectious to humans. 

3. No toxic or allergenic effects to 

animals or humans. Humans and 

domestic animals have been and are 

exposed to plant viruses in the food 

supply because most crops are 

frequently infected with plant viruses. 

Food from these crops has been and is 

being consumed with no indication of 

human or animal toxicity related to 

plant virus infections. Additionally, in 

experiments where purified plant virus 

preparations have been injected into 

laboratory animals, no adverse effects 

have been reported (Ref. 17). 

Furthermore, the Agency is not aware of 

any coat protein from a virus that 

naturally infects plants that has been 

identified as a food allergen for humans. 

Finally, the amount of PVC-protein 

likely to be found in food is anticipated 

to generally be lower than the amount 

of virus coat protein found in food 

naturally infected with plant viruses (as 

discussed in Unit IV.C.1.).The 2005 SAP 

questioned whether an increased 

propensity for allergies in humans 

affects the relevance of the history of 

safe use to the current safety of virus 

coat proteins. Several studies have 

documented a general increase in atopy 

in human populations; these studies 

show that over the last several decades 

there has been an increasing proportion 

of human populations that have an 

allergic sensitization to particular 

allergens (Refs. 20, 21, and 22). 

However, there is no reason to believe 

that PVC-proteins in the environment 

would have any impact on this 

phenomenon. EPA is aware of no 

evidence that previously nonallergenic 

substances are now able to elicit an 

immune response, and no plant virus 

coat proteins have ever been identified 

as allergens. Moreover, the amount of 

plant virus coat protein in the 

environment is not expected to increase 

due to the use of PVCP-PIPs. On the 

contrary, PVCP-PIPs generally express 

PVC-protein at levels below that found 

in natural virus infections, and the 

virus-resistant phenotype conferred by 

PVCP-PIPs should significantly reduce 

levels of natural virus infection in 

plants, thereby decreasing the amount of 

plant virus coat protein in the 

environment where PVCP-PIPs are 

deployed. 

D. Key Issue: Determination of Natural 

Virus Variation 

A key issue facing EPA in developing 

this exemption is how to clearly 

describe for regulatory purposes those 

PVC-proteins that are within the range 

of naturally occurring plant virus coat 

proteins and to which the rationale 

discussed in Unit IV.C. therefore 

applies. If a plant virus coat protein 

gene is isolated in nature and not 

modified, the PVC-protein would 

clearly be within the range of natural 

variation. However, many coat protein 

genes are modified in creating a PVCPPIP, e.g., to increase product efficacy or 

allow appropriate expression in the 

plant. Some of these modifications may 

affect a PVC-protein, although most of 

these variations would not be expected 

to differ significantly (e.g., in terms of 

toxicity or allergenicity) from the 

naturally occurring coat protein. In fact, 

given the considerable variation in 

naturally occurring viral coat proteins, it 

is also possible that naturally occurring 

plant viruses exist with some of the 

minor modifications that could 

conceivably be introduced into PVCproteins. 

However, EPA’s task of defining this 

variation is complicated by the variable 

nature of plant virus genomes and the 

fact that the full extent of variation for 

even a single plant virus is currently 

unknown. Sequencing of plant virus 

genomes has revealed that a large 

number of variants exist within most 

populations of both RNA and DNA 

viruses. Due to this inherent 

heterogeneity in virus populations, they 

are often described as ‘‘quasispecies’’

that exist as a pool of different 

sequences varying around a consensus 

sequence (Refs. 23, 24, and 25). 

Genetic variation in virus populations 

arises due to several processes including 

mutation, recombination, and 

reassortment. Mutation is a change in 

the genetic material that most 

commonly occurs when replication 

errors lead to incorporation of an 

incorrect nucleotide into the daughter 

sequence (Ref. 26). New virus variants 

are also generated by recombination, the 

natural process that occurs during 

replication of DNA or RNA whereby 

new combinations of genes are 

produced. Recombination is more likely 

to occur the more closely related viruses 

are, but recombination between 

different viral species is also believed to 

occur (Refs. 27 and 28). Evidence of past 

recombination having led to the creation 

of new DNA and RNA viruses has been 


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found in a number of different groups 

including bromoviruses (Ref. 29), 

caulimoviruses (Ref. 30), luteoviruses 

(Ref. 31), nepoviruses (Ref. 32), 

cucumoviruses (Ref. 33), and 

geminiviruses (Refs. 27 and 34). 

Sequence analysis of viruses from the 

family Luteoviridae indicated that this 

family has evolved via both intra- and 

inter-familial recombination (Ref. 35). In 

viruses with segmented genomes, 

variation may also be caused by 

reassortment whereby entire segments 

are exchanged between viruses (Ref. 36). 

Attempts to describe the range of 

variation for naturally occurring plant 

virus coat proteins are complicated not 

only by variation within species but also 

by variation among species (See Ref. 37 

for review). For example, cucumber 

mosaic cucumovirus (CMV) has a 

relatively high degree of variation (Ref. 

38) compared to tobacco mild green 

mosaic tobamovirus (Ref. 39). The 

greater variability in CMV would be 

expected based on the relatively wide 

host range and relatively high 

recombination rate of this virus. Such 

wide-ranging, inherent variability 

confounds attempts to establish 

meaningful estimates of normal 

variability for coat proteins of plant 

viruses as a group. 

A large number of viral coat protein 

sequences are currently available in the 

literature and in public sequence 

repositories, e.g., the National Center for 

Biotechnology Information. However, 

EPA has concluded that no single 

standard could capture the degree of 

variation across all viruses, and 

hundreds of plant viruses have been 

identified to date (Ref. 40). It would be 

at best impractical for EPA to describe 

individually for all virus groups all 

potential modifications that would 

produce a PVC-protein that falls within 

the range of natural variation given the 

vast (and yet still incomplete) amount of 

data that currently exists. The 2005 SAP 

concurred with these conclusions: 

‘‘Currently, it is extremely difficult to 

identify modifications that would be 

expected to be ‘within the range of 

natural variation for all virus families’. 

This would require prior knowledge of 

the natural variation limits of the 

individual PVC proteins, which is not 

available. Specific modifications can be 

identified that would raise potential 

concerns, but it is not clear that it is 

possible to create a comprehensive list 

of these changes for all virus families’’

(Ref. 15). 

At the present time, insufficient 

information exists to develop a standard 

that would describe a priori the degree 

to which a PVC-protein could be 

modified and yet still remain within the 

natural variability of plant virus coat 

proteins found in virus populations 

either generally or for any species in 

particular. In light of this, and relying 

extensively on the advice of the 2005 

FIFRA SAP meeting (Ref. 15), EPA has 

developed two proposals to exempt 

PVC-protein residues from the 

requirement of a tolerance: 

1. A categorical exemption for a 

subset of PVC-proteins based on 

developer self-determination that the 

encoded PVC-protein is virtually 

unmodified when compared to an entire 

unmodified coat protein from a virus 

that naturally infects plants that humans 

consume in toto or in part, and 

2. An exemption for more extensively 

modified proteins that is conditional on 

an Agency determination after review 

that the encoded PVC-protein is 

minimally modified when compared to 

an unmodified coat protein from a virus 

that naturally infects plants that humans 

consume in toto or in part. 

E. Structure of the Proposed FFDCA 

Tolerance Exemption 

1. Proposed categorical exemption. 

Under the proposed exemption at 

§ 174.477(a), when the encoded PVCprotein is virtually unmodified when 

compared to an entire unmodified coat 

protein from a virus that naturally 

infects plants that humans consume in 

toto or in part, the residues of the PVCprotein would be exempt from the 

requirement of a tolerance without 

Agency review. If the PVC-protein is 

expressed from a plant virus coat 

protein gene that was isolated from a 

virus found naturally in a food plant in 

the United States and was not modified, 

the PVC-protein would meet this 

criterion. Additionally, a PVC-protein 

would meet this criterion if the 

developer has evidence showing it has 

an amino acid sequence that is virtually 

unmodified when compared to an 

unmodified plant virus coat protein 

sequence from a virus that naturally 

infects plants that humans consume, 

e.g., as found in a database. Although 

EPA cannot a priori identify all existing 

natural coat protein variants, the 

requirement of being virtually 

unmodified when compared to an entire 

unmodified coat protein ensures that 

the exempted PVC-protein falls within 

the existing base of experience on which 

the proposed exemption relies. 

EPA intends, with the requirement 

that the PVC-protein be virtually 

unmodified when compared to ‘‘an 

entire unmodified coat protein,’’ to 

exclude from the categorical exemption 

residues of modified PVC-proteins, e.g., 

PVC-proteins containing insertions, 

deletions, or amino acid substitutions 

(except as described below by the 

definition of virtually unmodified), as 

well as chimeric PVC-proteins that are 

encoded by a sequence constructed by 

fusing portions of two or more plant 

virus coat protein genes. EPA is 

proposing to exclude such PVC-proteins 

from the categorical exemption because 

of advice from the 2005 SAP that 

insufficient information exists at this 

time to allow EPA to describe a priori 

a single standard articulating which of 

these types of changes would be 

consistently expected to fall within the 

natural range of variation of viruses 

and/or which types of changes could be 

determined not to affect toxicity or 

allergenicity without any EPA review 

(see Unit IV.D.). 

The Agency proposes to define the 

term ‘‘unmodified’’ to mean, ‘‘having or 

coding for an amino acid sequence that 

is identical to an entire coat protein of 

a naturally occurring plant virus.’’ The 

Agency is considering several options 

for defining the term virtually 

unmodified. Under this proposal, any 

virtually unmodified PVC-protein 

would qualify for a tolerance exemption 

without Agency review. Under one 

option, this term would mean, ‘‘having 

or coding for an amino acid sequence 

that is identical to an entire coat protein 

of a naturally occurring plant virus, 

except for the addition of one or two 

amino acids at the N- and/or C-terminus 

other than cysteine, asparagine, serine, 

and threonine and/or the deletion of one 

or two amino acids at the N- and/or Cterminus.’’ As noted by the 2005 SAP, 

the terminal ends of a protein ‘‘are the 

least structurally constrained regions of 

a protein. As such, the ends can be 

thought of as being essentially 

‘unstructured,’ and therefore unlikely to 

serve as allergenic epitopes or to make 

major contributions to the overall 

structure of the molecule. Addition (or 

deletion) of one or two amino acids is 

unlikely to change this.’’ However, the 

SAP also noted the possibility that the 

addition of amino acids such as cysteine 

with side chains that could promote 

cross-linking or aggregation between 

molecules or other amino acids that can 

serve as sites for post-translational 

modifications should be evaluated on a 

case-by-case basis (Ref. 15). EPA has 

identified cysteine, asparagine, serine, 

and threonine as the amino acids 

containing side chains that could 

promote cross-linking or serve as sites 

for post-translational modifications. 

EPA therefore excludes the addition of 

these amino acids from the proposed 

definition of virtually unmodified. The 

2005 SAP report mentioned alanine as 

an amino acid involved in 


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glycosylation; however, EPA has found 

no evidence that alanine is involved in 

glycosylation or promotes cross-linking. 

The Agency has therefore not excluded 

the addition of alanine under the 

definition of virtually unmodified. 

The Agency is also considering two 

possible changes to the above definition 

of virtually unmodified. The first 

change would remove the restriction 

that cysteine, asparagine, serine, or 

threonine may not be added to the 

naturally occurring protein. Under this 

alternative, a PVC-protein would qualify 

for the tolerance exemption without 

Agency review if it has an amino acid 

sequence that is identical to an entire 

coat protein of a naturally occurring 

plant virus except for the addition, 

substitution, or deletion of one or two 

amino acids at the N- and/or Cterminus. The rationale underlying such 

an alternative would be that addition of 

any amino acid to the N- or C-terminus, 

e.g., including those that could be 

glycosylated, is unlikely to introduce 

any concern. In order for an amino acid 

to be glycosylated, a protein must also 

have a specific enzyme recognition site. 

The creation of such a recognition site 

by the addition, substitution, or deletion 

of one or two amino acids, particularly 

at the end of the protein, is expected to 

be extremely rare because it would 

involve randomly producing a set of 

amino acids involved in a specific 

interaction. The addition of an amino 

acid with a side group that is capable of 

forming a covalent bond, e.g., cysteine, 

is likewise unlikely to alter the safety of 

the expressed protein. Such amino acid 

residues would typically be unavailable 

due to interactions that occur within the 

protein’s normal folding conformation. 

A plant virus coat protein is large 

enough that protein functionality or 

chemistry would not be dramatically 

different from a PVC-protein that is 

identical except for its possessing two 

additional amino acids at the N- and/or 

C-terminus. As previously stated, the 

2005 SAP said the terminal ends of a 

protein ‘‘are the least structurally 

constrained regions of a protein’’ (Ref. 

15). In addition, virus coat proteins are 

self-assembling, structural proteins that 

contain elements necessary for 

continual infection and replication of 

the entire virus particle. As a structural 

element of a virus particle, one 

important function of the coat protein is 

the ability to interact with itself to form 

stable particles. Most if not all plant 

virus coat proteins will naturally 

aggregate (Refs. 41 and 42), so the 

addition of amino acids that could 

promote cross-linking or aggregation 

would not fundamentally change the 

nature of the PVC-protein. 

The second change to the above 

definition of virtually unmodified that 

the Agency is considering would allow 

truncated proteins to fall under the 

definition. Under this alternative, a 

PVC-protein would be exempt without 

Agency review if it has an amino acid 

sequence that is identical to a single 

contiguous portion of a coat protein of 

a naturally occurring plant virus, except 

for the addition or substitution of one or 

two amino acids at the N- and/or Cterminus of the single contiguous 

portion other than cysteine, asparagine, 

serine, and threonine. EPA intends that 

‘‘identical to a single contiguous 

portion’’ would exclude proteins with 

internal modifications. The rationale 

underlying such an alternative would be 

that truncated PVC proteins have been 

reported to occur in nature (Ref. 43), as 

pointed out by the 2005 SAP. ‘‘Naturally 

occurring truncated forms of the PVCs 

could be generated by posttranscriptional and translational events, 

including incomplete translation due to 

routine errors causing a ribosome to 

dissociate from an mRNA, posttranslational processing, the presence of 

a mutation that introduces a premature 

stop codon, or by infrequent translation 

initiation at downstream AUGs. . . . 

Whether the truncation is at the N- or 

C-terminus is not relevant to 

allergenicity or toxicity’’ (Ref. 15). The 

SAP also said, ‘‘Determining whether 

PVC-proteins containing terminal 

deletions, or any other modifications, 

are within the range of natural variation 

would require the development of a 

database of the natural variation and 

truncated forms of PVC-proteins that 

occur naturally. If a truncated PVCprotein does fall within the range of 

natural variation, the likelihood of 

increased toxicity and allergenicity 

would be low’’ (Ref. 15). However, such 

a database may not be necessary because 

the potential for toxicity and 

allergenicity of a whole plant virus coat 

protein is low enough that the 

likelihood of a truncated form of such 

a protein being toxic or allergenic would 

not rise to the level requiring regulation. 

Such a change in toxicity or 

allergenicity would require the 

truncation to expose new allergenic 

epitopes or specific recognition/binding 

sites in the protein that could make the 

protein toxic, but there is no indication 

that plant virus coat proteins possess 

such regions. The 2000 SAP indicated 

that ‘‘[i]n general, peptide fragments 

that result from the breakdown of 

proteins are less toxic than the intact 

protein’’ (Ref. 44). 

Either of the changes discussed above 

could be adopted alone, or both could 

be adopted together. If EPA adopts both 

changes, a PVC-protein would be 

exempt from the requirement of a 

tolerance without Agency review if it 

has an amino acid sequence that is 

identical to a single contiguous portion 

of a coat protein of a naturally occurring 

plant virus; except for the addition or 

substitution of one or two amino acids 

at the N- and/or C-terminus of the single 

contiguous portion. 

EPA is proposing to require that the 

virus used as the source of the coat 

protein sequence ‘‘naturally infects 

plants that humans consume’’ as an 

additional means of ensuring the 

proposed exemption is limited to PVCPPIPs that fall within the base of 

experience discussed previously in this 

unit. This phrase is intended to limit the 

proposed exemption to residues of PVCproteins that are already part of the 

normal human diet as naturally 

occurring plant virus coat proteins or 

are minimally modified from such 

proteins (see Unit IV.C.1.). The 

exemption would not extend to PVCproteins encoded in part by sequences 

from animal or human viruses. 

EPA proposes to define the term 

‘‘naturally infect’’ to mean ‘‘infect by 

transmission to a plant through direct 

plant-to-plant contact (e.g., pollen or 

seed), an inanimate object (e.g., farm 

machinery), or vector (e.g., arthropod, 

nematode, or fungus). It does not 

include infection by transmission that 

occurs only through intentional human 

intervention, e.g., manual infection in a 

laboratory or greenhouse setting.’’ The 

Agency is proposing this definition 

specifically to exclude transmission that 

occurs only through intentional human 

intervention because such transmission 

would have little relevance to normal 

human dietary exposure. Viruses that 

may be able to infect plant species in a 

laboratory or greenhouse setting through 

manual infection may not ever infect 

such species in nature. EPA intends to 

include within this definition viruses 

that are likely to have been part of the 

human diet due to their ability to spread 

without intentional human intervention. 

EPA recognizes that humans may play 

an inadvertent role in infection (e.g., by 

transmitting the virus on farm 

machinery). Such unintentional (and 

often unavoidable) transmission can be 

an important means of virus 

transmission, leading to the presence of 

natural virus coat proteins in food 

plants that humans consume. EPA 

therefore includes this mode of 

transmission in the definition of 

naturally infect to encompass those 

viruses that would be expected to be at 


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least occasionally found in the plant 

and therefore be a normal constituent of 

the human diet. To further clarify that 

the proposed exemption applies only to 

coat proteins from plant viruses, EPA is 

specifically including the word ‘‘plant’’

as an adjective in the name, i.e., ‘‘PVCproteins’’ are ‘‘plant virus coat 

proteins.’’

EPA has considered whether to limit 

the proposed exemption to PVCproteins from PVCP-PIPs based on 

viruses that naturally infect the 

particular food plant in which the PVCprotein is expressed. EPA must address 

whether there would be any safety 

issues raised from exposure to PVCproteins if the virus used to create the 

PVCP-PIP does not naturally infect the 

particular plant species into which the 

PVCP-PIP is inserted. A PVC-protein 

may be expressed in a food plant that 

the virus does not naturally infect when 

heterologous resistance to a particular 

virus is conferred through a different 

virus’ coat protein gene (e.g., Ref. 45). 

However, the Agency believes such 

PVC-proteins could be safely exempted 

from tolerance requirements because 

these proteins would still reasonably be 

expected to be part of the normal diet 

as long as they naturally infect plants 

used as food. Based on their broad host 

range, plant viruses are known generally 

to infect a wide variety of plants that 

humans consume. People generally eat 

a broad range of food plants through 

which they would reasonably be 

expected to be exposed to a wide variety 

of plant virus coat proteins (Ref. 12). In 

addition, EPA is not aware that any 

plant viral coat proteins have been 

identified as allergens, so it is unlikely 

that a person with food allergies avoids 

a particular food plant because of an 

allergic reaction to a viral coat protein. 

Based on this rationale and in the 

absence of contravening evidence, EPA 

concludes that a PVC-protein expressed 

in a plant that is not normally infected 

by the virus from which the PVCprotein was derived would raise no 

safety issues as long as the 

corresponding virus infects other plants 

that are consumed by humans. 

When EPA asked the 2005 SAP to 

comment on this issue, the Panel 

‘‘expressed some disagreement as to 

whether the level of risk associated with 

human exposure to any protein is solely 

dependent on the protein itself. One 

Panel member concluded that the host 

producing the protein is of secondary 

importance. Others expressed concern 

related to expression of PVC-proteins in 

plants that are known to be highly 

allergenic such as peanut’’ (Ref. 15). The 

Panel did not elaborate on the rationale 

for such concerns at this point in the 

SAP report. EPA’s interpretation of this 

issue is that the concern is due to the 

possibility, articulated elsewhere in the 

Panel report, that ‘‘the changed 

infectivity status of the plant may also 

induce changes in the overall protein 

expression pattern of the plant. Thus, in 

various tissues of the plant, natural 

plant proteins that have been identified 

as allergens may be expressed to a 

different, and in some cases, higher 

extent compared to a non-infected or a 

virus-infected plant without PVCP-PIP. 

In particular, pathogenesis-related (PR) 

proteins are known to be very inducible, 

and their expression levels may vary 

many-fold. Several pathogenesis-related 

proteins have been described as 

allergens (Breiteneder et al. 2000 and 

2004), most notably the major birch 

pollen protein Bet v1 (Breiteneder et al. 

1989). An increased expression of PRproteins in pollen could increase both 

the risk of sensitization and the risk of 

elicitation of allergic reactions’’ (Refs. 

15, 46, 47, and 48). This concern is 

distinct from the concern that EPA 

addressed above, namely that the PVCprotein itself may introduce an allergen 

into a food source where it is not 

anticipated to be found. The issue the 

SAP raised would generally be 

addressed by the Food and Drug 

Administration (FDA) in evaluating 

food composition. However, EPA has 

not found evidence that introduction of 

a PVCP-PIP would affect induction of 

PR proteins per se. PR proteins are a 

normal constituent of plants because 

plants express such proteins in response 

to environmental stresses, including 

virus infection, exposure to certain 

chemicals, and wounding. Some plant 

tissues even constitutively express such 

proteins, e.g., those likely to be attacked 

by pests or exposed to environmental 

stresses such as ultra-violet (UV) 

irradiation (Ref. 49). Moreover, given 

the large number and variety of 

pathogens (including viruses) 

encountered by plants in the field, and 

given differences in the virus-infectivity 

status of plants that occur naturally, 

humans consume varying amounts of 

PR proteins as part of the normal diet. 

The level found in plants containing a 

PVCP-PIP is therefore expected to be 

within the range of natural variation. 

EPA has also considered whether a 

geographic limitation on this proposed 

categorical exemption would be 

necessary to ensure that the exemption 

extends only to residues that are part of 

the U.S. diet; i.e., that the proposed 

exemption would only extend to PVCproteins that are part of a PVCP-PIP 

constructed from a virus that occurs 

naturally in the United States. EPA 

believes that such a limitation is 

unnecessary to ensure that the PVCproteins proposed for exemption fall 

within the base of experience 

supporting the proposal. Humans have 

long consumed viruses infecting food 

plants with no adverse effects. Given the 

extent of modern market practices in 

which food is shipped globally for 

human consumption, human dietary 

exposure to all viruses that infect food 

plants is likely to occur broadly. The 

lack of any known adverse effects 

attributable to plant viruses suggests 

that plant virus coat proteins in the diet 

are safe to humans. 

EPA has also considered whether 

additional conditions are necessary to 

ensure that the expression level of 

virtually unmodified PVC-proteins 

found in plants is no greater than the 

level of plant virus coat protein 

generally found in a natural virus 

infection. The 2005 SAP suggested that 

‘‘for both modified and unmodified 

proteins, the Agency might wish to 

consider. . . expression levels’’ when 

determining whether to exempt a PVCprotein from tolerance requirements 

(Ref. 15). The SAP apparently based this 

suggestion on the assumption that EPA 

considered exposure level to be an 

important component of a PVC-protein 

risk assessment given that the Agency’s 

background material for the Panel 

indicated that the dietary exposure to 

PVC-proteins is anticipated to be similar 

to or less than the dietary exposure to 

plant virus coat proteins currently 

found in food plants naturally infected 

with viruses. However, even though 

EPA addresses exposure level in 

evaluating safety (e.g., see Unit IV.C.1.), 

the Agency also believes that the PVCproteins that qualify for this proposed 

exemption are safe at any level that 

could be produced in a plant. Humans 

have been exposed to plant virus coat 

proteins over long periods of time at 

varying and sometimes high levels, and 

to date there is no indication that any 

plant virus coat protein is an allergen or 

a toxin. The Agency therefore believes 

that the hazard associated with PVCproteins that are virtually unmodified 

from natural plant viral coat proteins is 

sufficiently low that it does not rise to 

the level warranting regulation, even if 

in some cases exposure to a PVC-protein 

might be greater than the exposure to 

the corresponding natural plant virus 

coat protein. Nevertheless, the Agency 

regards the anticipated low levels of 

exposure through food to the PVCproteins covered by this proposal as 

additional support for this proposed 

categorical exemption. According to the 

2005 SAP, ‘‘On a per cell basis, it is 


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almost certain that all viral gene 

products are expressed at higher levels 

in virus-infected than transgenic plants’’

(Ref. 15). 

2. Proposed exemption conditional on 

Agency determination. The Agency 

recognizes that product developers 

frequently modify the genetic material 

of a PVCP-PIP, e.g., in order to achieve 

greater efficacy (Ref. 50) and that most 

of these changes would be unlikely to 

result in proteins affecting potential 

dietary risk. However, the Agency 

cannot at this time articulate a criterion 

that would ensure all PVC-proteins with 

such modifications fall within the base 

of experience supporting the proposed 

exemption. 

The question of how to objectively 

define criteria on which the regulated 

community may rely to determine a 

priori how much a virus coat protein 

may be modified and still fall within the 

range of natural variation is a key 

challenge. EPA first considered the 

question of how to describe residues 

that fall within the base of experience 

supporting exemption when the Agency 

issued its proposal on November 23, 

1994 (59 FR 60539). In the July 19, 2001 

supplemental notice (66 FR 37865), EPA 

again addressed the question of how to 

describe PVCP-PIPs that fall within the 

recognized base of experience 

supporting the proposed categorical 

exemption. 

In October 2004, the FIFRA SAP was 

asked to consider the degree and ways 

a plant virus coat protein gene might be 

modified while still retaining scientific 

support for the idea that humans have 

consumed the products of such genes 

for generations and that such products 

therefore present no new dietary 

exposures (Ref. 14). They responded, 

‘‘There was no clear consensus on how 

much change would be necessary to 

invalidate this assumption, although 

there was general agreement that the 

appropriate comparison is to the range 

of natural variation in the virus 

population.’’ The 2005 SAP also 

addressed this question. They concurred 

that, ‘‘it is extremely difficult to identify 

modifications that would be expected to 

be ‘within the range of natural variation 

for all virus families’. . . . Given the 

possible range of natural variations for 

PVC proteins, it would be appropriate to 

assess whether specific modifications 

are within natural variation limits of the 

PVC protein on a case-by-case basis’’

(Ref. 15). 

EPA believes that developing 

objectively defined criteria on which the 

regulated community could rely to 

determine whether a modified PVCprotein falls within the natural range of 

variation for a particular virus is not 

currently feasible because the Agency 

knows of no generally applicable, 

established baseline for what constitutes 

the range of natural variation of a virus. 

EPA thus does not believe that 

proposing an exemption that would 

allow developers to self-determine 

eligibility of modified PVC-proteins 

would be supportable. Rather, EPA is 

proposing that under proposed 

§ 174.477(b), the residues of such a PVCprotein would be exempt only if the 

Agency determines after review that the 

encoded PVC-protein is minimally 

modified when compared to an 

unmodified coat protein from a virus 

that naturally infects plants that humans 

consume in toto or in part. 

In determining whether a PVC-protein 

is minimally modified from a natural 

viral coat protein, EPA will consider 

first how similar the PVC-protein is to 

a natural viral coat protein by evaluating 

information on the PVCP-PIP genetic 

construct, PVC-protein deduced amino 

acid sequence, and biochemical 

characterization of the PVC-protein as 

expressed in the plant (e.g., molecular 

weight to evaluate potential posttranslational modifications). EPA might 

also evaluate developer-submitted 

analyses that characterize the PVCprotein sequence relative to the range of 

natural coat protein variation found in 

public sequence databases. Those PVCproteins determined to be similar to a 

natural viral coat protein would be 

further evaluated to determine whether 

the modified PVC-protein is as safe as 

an unmodified protein by considering 

information from an amino acid 

sequence comparison with known 

protein toxins and allergens. The type 

and extent of information that would 

need to be provided in order for EPA to 

determine whether a PVC-protein is 

minimally modified and therefore 

qualifies for the exemption would be 

determined on a case-by-case basis. 

The 2005 SAP identified certain 

modifications that might raise potential 

concerns when considering if a protein 

is minimally modified, including ‘‘the 

addition or removal of protease 

recognition sites, the addition or 

removal of cysteine residues involved in 

internal cross-links, the addition or 

removal of proline residues that act as 

secondary structure ‘break points,’ and 

the addition or removal of asparagines 

and alanines involved in glycosylation’’

(Ref. 37). By contrast, the report 

identified ‘‘[m]odifications such as 

single amino acid substitutions with 

biochemically similar amino acids that 

do not affect secondary or tertiary 

structure’’ as potentially being of 

relatively little concern (Ref. 37). EPA 

would consider this guidance as 

appropriate in evaluating individual 

exemption petitions to determine 

whether a protein is minimally 

modified. 

Regarding the 2005 SAP suggestion 

that EPA might wish to consider 

expression levels in determining 

whether to exempt a PVC-protein from 

tolerance requirements, the Agency 

believes that such an evaluation is not 

necessary to determine whether a PVCprotein is minimally modified. EPA 

would necessarily have to find such 

proteins to be similar to a natural viral 

coat protein in order for them to qualify 

for this proposed exemption. EPA 

believes that minimally modified PVCproteins are safe at any level for the 

same reasons discussed above for 

virtually unmodified proteins (Unit 

IV.E.1.). In both cases, the hazard 

associated with PVC-proteins qualifying 

for this proposed tolerance exemption is 

sufficiently low that it does not rise to 

the level warranting regulation, even if 

in some cases exposure to a PVC-protein 

might be greater than the exposure to 

the corresponding natural plant virus 

coat protein. (However, see Unit XI. for 

a discussion of how exposure level 

could possibly be considered under the 

proposed exemption structure when 

reviewing minimally modified 

proteins.) 

Under proposed § 174.477(b), the 

procedures for obtaining a 

determination that a PVC-protein fits 

under the tolerance exemption would be 

no different than those currently 

provided under the statute for obtaining 

a tolerance exemption. A person can file 

a submission requesting a determination 

(21 U.S.C. 346a(d)) of whether a 

particular PVC-protein fits under the 

tolerance exemption, or the Agency can 

initiate an action to issue a 

determination (21 U.S.C. 346a(e)). After 

a person files a submission under 

FFDCA section 408(d)(1) proposing that 

a particular PVC-protein falls under this 

exemption because it is minimally 

modified from a natural plant virus coat 

protein, FFDCA section 408(d)(3) 

requires that the Administrator 

determine whether a petition meets the 

requirements of the statute and publish 

a summary of the petition and other 

required information in the Federal 

Register within 30 days of making that 

determination. Alternatively, the 

Administrator may publish a notice of 

proposed rulemaking and provide a 

period of generally not less than 60 days 

for public comment. In either case, EPA 

will publish any final rule exempting a 

PVC-protein from the requirement of a 

tolerance in the Federal Register and 

allow 60 days for any person to file 

objections thereto (21 U.S.C. 346a(g)(2)). 


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Currently no fees would be associated 

with either the proposed categorical 

exemption under § 174.477(a) or the 

Agency’s determination under proposed 

§ 174.477(b) that a particular PVCprotein fits under the tolerance 

exemption. 

For residues of a PVC-protein that 

would not qualify for this proposed 

exemption under either § 174.477(a) or 

(b) because the Agency cannot 

determine that the encoded PVC-protein 

is minimally modified from an 

unmodified coat protein from a virus 

that naturally infects food plants, an 

applicant may petition the Agency for 

an individual tolerance exemption 

under FFDCA section 408 (see also 40 

CFR 180.7). 

F. Tolerance Issues Associated with 

Unintended Protein Production when 

Virus Resistance is Mediated through 

Post-Transcriptional Gene Silencing 

Section 408 of the FFDCA does not 

require a tolerance or tolerance 

exemption if residues will not be 

present in food moving in interstate 

commerce. However, with the exception 

of residues that meet the requirements 

proposed at § 174.477(a), the mere fact 

that a developer may not detect residues 

during product development will not 

protect the food from seizure if residues 

are subsequently found following 

commercialization, either because 

detection techniques improve or 

because the protein is unexpectedly 

produced. If such an event occurs and 

no tolerance exemption exists for 

residues of that PVC-protein (regardless 

of its safety), any food containing the 

PVC-protein residues would be 

adulterated and subject to seizure. In 

addition, any FIFRA exemption that 

may have been applicable for the PVCPPIP would no longer be valid because 40 

CFR 174.21(b) would no longer be 

satisfied. Any sale or distribution of 

such a PVCP-PIP would constitute sale 

and distribution of an unregistered 

pesticide, in violation of FIFRA section 

12(a)(1). 

The 2005 SAP suggested that the 

construction of certain PVCP-PIPs may 

offer a reasonable level of assurance that 

PVC-protein production would not 

occur, i.e., transgene insertions where 

the transcribed segment lacks an 

initiator codon or insertions of 

transcribed inverted repeat constructs 

that constitutively produce transcripts 

that are folded into double-stranded 

RNA as the immediate product of 

transgene transcription (Ref. 15). 

However, for other types of constructs, 

questions remain about circumstances 

under which PVC-protein might be 

detected and/or produced in food at 

some point after commercialization 

even though PVC-protein may not have 

been detected and/or produced during 

product development. For example, it is 

known that in some cases PTGS must be 

triggered before transgene RNA 

production can be effectively 

suppressed. Lindbo et al. (Ref. 51) used 

tobacco etch virus (TEV) to infect 

transgenic tobacco plants containing a 

TEV coat protein gene. Plants 

temporarily developed symptoms but 

were able to recover from infection. 

Recovered transgenic plant tissue 

showed significantly reduced levels of 

transgene mRNA, and PVC-protein was 

undetectable. However, plant tissues 

unchallenged with virus did express 

PVC-protein, suggesting that in at least 

some cases of PTGS-induced virus 

resistance, PVC-protein may be 

produced until virus infection occurs. 

Be ́clin et al. (Ref. 52) showed that in 

transgenic tobacco lines expressing a bglucuronidase (uidA) transgene, 

suppression of transgene expression 

always occurs but is initiated at 

different plant developmental stages: 

Either 15 days after germination or 2 

months post-germination. Prior to PTGS 

initiation, transgenic protein is 

expressed, suggesting that in at least 

some cases lack of protein production 

may only occur after a certain 

developmental stage is reached. 

Likewise, Pang et al. (Ref. 53) found that 

plant developmental stage plays an 

important role in the timing of PTGS 

initiation. 

Experiments demonstrating that plant 

developmental stage determines PTGS 

initiation suggest that any 

environmental factors influencing plant 

growth would also affect the amount of 

time before RNA and protein production 

is effectively suppressed. At least one 

experiment has looked more directly at 

the influence of environmental factors 

on PTGS. Szittya et al. (Ref. 54) 

demonstrated that cold temperatures 

inhibited transgene-induced RNA 

silencing leading to increased levels of 

transgene mRNA, although they did not 

report on the level of transgenic protein. 

In addition to temporal changes in 

protein production that may be 

influenced by varying environmental 

conditions, PTGS may also be 

associated with variation in protein 

expression across different plant tissues. 

Plant lines expressing a nitrate 

reductase transgene were found to 

display PTGS in leaves and stem tissue 

but not in shoot apical or axillary 

meristems (Ref. 52). As in other 

experiments (Ref. 51), transgene protein 

was not detectable and transgene mRNA 

levels were significantly reduced in 

plant tissue displaying PTGS. However, 

plant tissue in which gene silencing 

does not occur showed normal levels of 

transgene mRNA, and transgenic protein 

was produced. 

It has been shown that PTGS can be 

suppressed by viruses that encode 

certain suppressor proteins leading to 

loss of the virus-resistant phenotype 

conferred by a PVCP-PIP. For example, 

Savenkov and Valkonen (Ref. 55) 

showed that resistance to Potato virus A 

(PVA) in Nicotiana benthiana could be 

overcome when plants were challenged 

with Potato virus Y (PVY). Although 

levels of transgene mRNA in healthy 

transgenic plants were extremely low or 

below the detection limit, transgene 

mRNA was readily detectable in PVYinfected plants where suppression of 

gene silencing had apparently occurred. 

The study did not report whether PVCprotein was produced from the 

transgene mRNA. 

The 2005 SAP was asked to comment 

on issues associated with protein 

production in the case of plants 

containing a PVCP-PIP that confers 

resistance through an RNA-mediated 

mechanism. The Panel responded that 

‘‘[g]iven the wide variety of conditions 

that can modulate the transition from 

PTGS to no PTGS for non-[inverted 

repeat (IR)] transgenes. . .it is likely that 

a non-IR transgene insertion that retains 

an initiation codon for protein synthesis 

will make at least a low level of protein 

in at least some plant tissues over the 

course of its development, especially in 

the field where there is exposure to 

environmental extremes and virus 

infections. Thus, these PVCP-PIP plants 

may accumulate virus-derived mRNA 

and proteins in these situations’’ (Ref. 

15). EPA notes that the Panel further 

concluded that ‘‘[b]ecause of low levels 

of accumulation and sequence identity 

to the natural viral pathotypes. . .these 

PVCP-PIPs pose similarly low risks’’ as 

PVCP-PIPs that produce no protein (Ref. 

15). However, any PVC-protein residue 

in food that is not covered by a 

tolerance or tolerance exemption would 

constitute an adulterant of the food 

supply irrespective of the protein’s 

safety or the level at which it is 

detected. 

The above considerations suggest that 

many factors should be considered in 

making a determination of whether 

residues of a PVC-protein will be 

present in food derived from a crop 

containing a PVCP-PIP. Due to the 

serious consequences of having an 

unapproved residue in the food supply 

(as discussed earlier in this unit), EPA 

strongly recommends that developers 

consult with the Agency before 

determining that no tolerance or 

tolerance exemption for the PVC-protein 


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would be necessary based solely on the 

premise that no residues of the protein 

are anticipated to be present. EPA 

expects that the Agency would conclude 

no PVC-protein tolerance exemption 

would be necessary for insertion events 

where the transgene either lacks an 

initiation codon for protein synthesis or 

is inserted in an inverted-repeat 

orientation, provided that evidence is 

given to the Agency to verify the 

characteristics of the insertion event. 

For such constructs, the 2005 SAP 

indicated the PVCP-PIP ‘‘could be safely 

determined to have no [PVC-protein] 

expression regardless of plant tissue, 

developmental stage, environmental 

conditions, or exposure to virallyencoded suppressors of PTGS’’ (Ref. 15). 

For all other types of PVCP-PIP 

insertion events, EPA is considering 

several approaches under FFDCA for 

PVC-proteins that are not readily 

detectable, but which the SAP indicated 

would likely be produced under some 

circumstances (Ref. 15), some of which 

might result in the PVC-protein being in 

food. EPA does not currently have a 

preferred approach and presents several 

options to promote full consideration of 

the issues. These options are not 

necessarily mutually exclusive, and the 

approach pursued may vary depending 

on the characteristics of the PVCP-PIP 

under consideration. The discussion 

below relates only to proteins that EPA 

review would determine to be 

minimally modified, i.e., proteins that 

are similar, but not identical to natural 

plant virus coat proteins. Virtually 

unmodified PVC-proteins would be 

covered under the proposed tolerance 

exemption without any Agency action. 

The discussion is not relevant to 

proteins that would not be able to 

qualify under this proposal as either 

virtually unmodified or minimally 

modified because the proposed 

tolerance exemption would not cover 

such proteins regardless of how EPA 

implements the exemption. 

Under one approach, when no PVCprotein is detected during product 

development, EPA would not issue a 

determination of whether the PVCprotein is minimally modified (and 

therefore falls under this proposed 

tolerance exemption). Section 408 of 

FFDCA does not require a tolerance or 

tolerance exemption for foods that do 

not bear any residues, and such an 

approach would be consistent with 

current EPA practice regarding chemical 

pesticide residues in that tolerance 

determinations are not generally issued 

for substances when residue studies 

demonstrate that detectable residues 

will not be present in food. However, if 

food is subsequently found bearing 

residues of the PVC-protein, that food 

would be adulterated and subject to 

seizure unless and until EPA could 

make a determination that the PVCprotein is minimally modified and is 

therefore covered by this proposed 

tolerance exemption. 

Any adulterant in the food supply 

would likely cause public concern and 

great expense—whether or not the PVCprotein were subsequently determined 

to be safe. The Agency also notes that 

these costs are not necessarily borne by 

the product developer, but rather may 

disproportionately affect farmers and/or 

food producers because any adulterated 

food would be subject to seizure or 

recall. The Agency is considering this 

approach under the assumption that the 

absence of detectable protein using 

rigorous testing could give reasonable 

assurance that PVC-protein residues 

would not be found in food and 

therefore a tolerance determination 

would be unnecessary to prevent 

adulteration of the food supply. EPA 

would expect developers to provide the 

Agency with data acquired during 

product development that demonstrates 

no PVC-protein residues in food would 

be reasonably anticipated during the 

commercial life of the PVCP-PIP. For 

example, such data could be obtained 

by testing for protein and/or mRNA 

production in all plant tissues and all 

developmental stages that are harvested 

for food production under a variety of 

circumstances and environmental 

conditions representative of those that 

the plant may experience during its 

commercial cultivation. Challenge with 

a known PTGS suppressor protein 

introduced by a replicating virus vector, 

genetic crosses, or agro-infiltration (Ref. 

56) may also in some cases be a 

sufficient and less burdensome 

technique to show that no PVC-protein 

is able to be translated from the PVCPPIP. The potential to elicit protein 

production from silenced transgenes has 

been shown by studies investigating 

whether particular proteins are able to 

suppress such silencing (Ref. 56). The 

2005 SAP discussed such a technique, 

indicating that ‘‘[t]o determine if PTGSbased PVCP-PIP plants have the 

potential to produce proteins, the most 

effective test is to use viral suppression 

of PTGS. In this type of assay, the PVCPPIP plants are infected with viruses 

from the potyvirus, cucumovirus, and 

tombusvirus genera. These viruses 

encode different classes of PTGS 

suppressor proteins. . . Protein and RNA 

are then extracted from the infected 

plant tissue and assayed for the 

presence of the PVCP-PIP accumulated 

full-length RNA and protein. Standard 

tests for protein detection are ELISA and 

immunoblot (‘Western’ blot) analyses 

with specific antibodies. Triplicate 

experiments should be sufficient to 

determine that the results of these tests 

are reproducible’’ (Ref. 15). Given that 

FFDCA does not require a developer to 

demonstrate that no tolerance 

exemption is necessary, EPA would 

require such testing as a condition of 

either registering or exempting the 

PVCP-PIP under FIFRA. 

If the developer detects a PVC-protein 

during the course of investigating 

potential PVC-protein production, e.g., 

through challenge with a suppressor 

protein, this protein would only be 

covered under the proposed categorical 

tolerance exemption, i.e., without any 

Agency action, if the protein falls within 

the definition of a virtually unmodified 

PVC-protein. Therefore, unless the 

protein is virtually unmodified from a 

natural plant virus coat protein, EPA 

would expect a developer to provide the 

Agency with information for a 

determination of whether the PVCprotein qualifies as minimally modified 

and meets the proposed conditional 

tolerance exemption. (See Unit IV.E.2. 

for a discussion of the factors EPA 

intends to consider in making this 

determination.) 

When possible, EPA would expect to 

see biochemical characterization of the 

PVC-protein. However, EPA recognizes 

that such characterization may be 

difficult or even impossible in some 

cases. For example, when only very low 

levels of protein are produced, it may be 

difficult to obtain sufficient amounts of 

protein for biochemical 

characterization. In addition, EPA 

recognizes the cost and burden of 

producing sufficient protein for such 

characterization may not be warranted 

for PVC-proteins given that an 

evaluation based on the construct 

sequence alone could consider most of 

the issues EPA intends to evaluate when 

determining whether a PVC-protein is 

minimally modified (see Unit IV.E.2.). 

EPA is therefore also considering a 

second approach to addressing PVCproteins that are not detected during 

product development but whose 

presence as residues in food cannot be 

ruled out for the commercial life of the 

PVCP-PIP. Under this approach, EPA 

would evaluate the PVC-protein to 

determine whether it qualifies as 

minimally modified from a natural plant 

virus coat protein and is thus eligible for 

this proposed tolerance exemption 

based only on its amino acid sequence 

as deduced from the sequence of the 

inserted gene. EPA notes the advice of 

the 2005 SAP that ‘‘[i]t is critical to 

evaluate the protein as expressed in the 


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host, including factors such as posttranslational modifications’’ (Ref. 15). 

Nevertheless, EPA considers evaluating 

the protein as expressed in the host to 

be less important for minimally 

modified PVC-proteins than for many 

other types of proteins. A PVC-protein 

would not be expected to have 

significantly different post-translational 

modifications than a plant virus coat 

protein produced in a virus-infected 

plant. Because plant viruses replicate in 

plant cells as part of their normal life 

cycle, any post-translational 

modifications are expected to be the 

same for a PVC-protein expressed from 

a plant transgene as for a plant virus 

coat protein expressed from a viral 

genome in a virus-infected plant. 

As a third alternative, EPA is 

considering whether the Agency could 

expand this proposed tolerance 

exemption to cover all PVC-proteins 

that would be produced from constructs 

where resistance is demonstrated to 

EPA to be mediated through PTGS, e.g., 

those that confer virus resistance in the 

absence of detectable protein 

production for at least some period of 

time. The rationale for this alternative 

would be, as indicated by the 2005 SAP, 

that ‘‘PTGS-based virus resistance 

requires greater than 90% RNA 

sequence homology between the PVCPPIP transgene and the target virus, 

indicating that the viral mRNA and 

protein produced in PVCP-PIP plants 

will be nearly identical to the viral 

pathotype that occurs in the United 

States’’ (Ref. 15). To implement this 

alternative, the Agency would have to 

be able to conclude, without any caseby-case examination, that any PVCprotein produced from a PVCP-PIP that 

mediates resistance through PTGS 

would be safe. Even if a PVC-protein 

were detected before product 

deployment, such a protein would not 

need any evaluation by the Agency in 

order to be covered by this tolerance 

exemption. The rationale for this 

approach would be that any such PVCprotein would meet the conditions of a 

minimally modified protein (as 

discussed in Unit IV.E.2.) given the 

necessity for transgene transcript 

sequence similarity to natural plant 

virus coat protein sequences in order for 

PTGS to effectively function. Although 

EPA does not believe it could identify 

a priori which modifications would be 

within the range of natural variation for 

the protein, under this rationale the 

induction of PTGS would be an a priori 

indicator that such a PVC-protein is 

within the range of natural variation of 

the protein. The 2005 SAP suggested 

that all PTGS-based PVCP-PIPs would 

‘‘pose similarly low risks’’ as those that 

would have no protein expression under 

any circumstances (Ref. 15), giving 

scientific support for this option. 

However, the Agency notes that this 

advice is not entirely consistent with 

advice regarding PVC-protein safety 

received by the Panel. For one, both the 

2004 and 2005 SAPs were unable to 

endorse a tolerance exemption for PVCproteins other than those that are 

virtually unmodified from a natural 

plant virus coat protein unless the 

Agency performed a case-by-case review 

of some nature. PVC-proteins could be 

encoded for by a nucleic acid sequence 

that meets the 90% similarity required 

for PTGS to function but fail to be 

virtually unmodified from a natural 

virus coat protein (see Unit IV.E.1.). 

Moreover, the 2005 SAP recommended 

that ‘‘[d]etermining whether PVCproteins containing terminal deletions, 

or any other modifications, are within 

the range of natural variation would 

require the development of a database of 

the natural variation and truncated 

forms of PVC-proteins that occur 

naturally’’ (Ref. 15). While PTGS 

requires a relatively high sequence 

similarity with natural virus coat 

proteins to function, only a portion of 

the coat protein gene is necessary, 

suggesting that many truncated proteins 

would be encompassed in this 

exemption without any review of 

whether they occur naturally. (See, 

however, EPA’s discussion of whether 

truncated proteins could be determined 

to be exempt without Agency review in 

Unit IV.E.2.) The 2005 SAP also 

suggested that a low level of protein 

expression would indicate low risk, but 

prior SAPs and other scientific experts 

have been unable to establish a 

threshold below which the level of 

protein would not present concerns 

with respect to food allergenicity (Refs. 

57 and 58). 

V. Toxicological Profile 

Consistent with section 408(b)(2)(D) 

of FFDCA, EPA has reviewed the 

available scientific data and other 

relevant information in support of this 

proposed action and considered its 

validity, completeness, and reliability 

and the relationship of this information 

to human risk. EPA has also considered 

available information concerning the 

variability of the sensitivities of major 

identifiable subgroups of consumers, 

including infants and children. 

EPA’s risk assessment was based 

primarily on an analysis of human 

experiences with the breeding and 

cultivation of agricultural plants as well 

as food preparation and consumption. 

EPA combined human experience in 

consuming food containing coat 

proteins from viruses that naturally 

infect plants with knowledge of plant 

genetics, plant physiology, 

phytopathology, microbial ecology, 

ecology, biochemistry, and plant 

breeding to evaluate the potential risks 

of the residues of PVC-proteins 

qualifying for this proposed exemption. 

EPA considered the nature of any 

toxic effects that might be caused by 

residues of PVC-proteins proposed for 

exemption. As mentioned above, coat 

proteins from plant viruses that 

naturally infect plants are widespread in 

foods (Refs. 6, 7, and 10) and are not 

associated with toxic or pathogenic 

effects in humans or vertebrates (Refs. 

18 and 19). Residues of PVC-proteins 

qualifying for this proposed exemption 

are virtually unmodified or minimally 

modified from other coat proteins from 

viruses that naturally infect food plants 

and that have been safely consumed for 

hundreds if not thousands of years. 

Given this long history of safe use and 

the fact that toxicity is an unusual 

property among proteins in general (Ref. 

59), consumption of food containing 

residues of PVC-proteins qualifying for 

this proposed exemption is not expected 

to present a toxic effect on humans or 

animals. 

EPA considered the available 

information on the various dietary 

consumption patterns of consumers and 

major identifiable consumer subgroups 

as it pertains to residues of PVCproteins in food. Plant virus coat 

proteins are, and always have been, 

widespread in all food from crop plants 

since most plants are susceptible to 

infection by one or more viruses. Thus, 

all consumers and all major identifiable 

consumer subgroups are, and have been, 

exposed to plant virus coat proteins. 

Implementation of this proposed 

exemption is not expected to alter the 

current consumption patterns of plant 

virus coat proteins except perhaps to 

reduce exposure through a decrease in 

virus-infected plants. Therefore, EPA 

does not expect any special sensitivities 

to arise due to the consumption of 

residues of PVC-proteins that are 

proposed to be exempted. 

VI. Aggregate Exposures 

In examining aggregate exposure, 

section 408 of FFDCA directs EPA to 

consider available information 

concerning exposures from the pesticide 

residue in food and all other nonoccupational exposures, including 

drinking water from ground water or 

surface water and exposure through 

pesticide use in gardens, lawns, or 

buildings (residential and other indoor 

uses). 


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EPA considered the available 

information on the likely aggregate 

exposure level of consumers to PVCproteins qualifying for this proposed 

exemption and to other related 

substances, including exposures to plant 

virus coat proteins occurring through 

natural processes such as viral infection 

of a food plant. This analysis included 

a consideration of exposures from 

dietary sources as well as from other 

non-occupational sources. 

The PVC-proteins qualifying for this 

proposed exemption and plant virus 

coat proteins that occur naturally are 

both produced in living plants and are 

subject to the natural processes of 

degradation and decay that all biological 

materials undergo. They are broken 

down by enzymatic processes of living 

organisms into constituent parts that are 

used as building blocks for other 

biological substances (Ref. 60). Because 

of their biodegradable nature, neither 

PVC-proteins nor naturally occurring 

plant virus coat proteins bioaccumulate 

(i.e., build up in tissues because the 

body is unable to either break the 

substance down or eliminate it) or 

biomagnify (i.e., progressively build up 

in successive trophic levels because it 

bioaccumulates in the bodies of 

organisms lower in the food chain). 

Humans ingesting naturally occurring 

plant virus coat proteins and residues of 

PVC-proteins qualifying for this 

proposed exemption in food are likely 

to quickly degrade them and use their 

constituent elements as nutrients. 

Because of these characteristics, there 

is limited potential for exposures to 

PVC-proteins qualifying for this 

proposed exemption beyond direct 

physical exposure to a plant. In most 

cases, the predominant exposure route 

will be dietary. In general, EPA 

anticipates that dietary exposure to 

PVC-proteins qualifying for this 

proposed exemption through human 

and animal consumption of plants 

expressing PVC-proteins will be similar 

to, or less than the amounts of plant 

virus coat proteins currently consumed 

through food plants that are infected 

naturally with viruses (see Unit IV.C.1.). 

Exposure through other routes is 

unlikely because the substances are in 

the plant tissue and thus are found 

either within the plant or in close 

proximity to the plant. EPA expects 

non-dietary exposure (i.e., non-food 

oral, dermal, and inhalation) in non–

occupational settings to be negligible. 

A. Dietary Exposure 

EPA considered the consequences of 

dietary exposure to PVC-proteins that 

are the subject of this proposed 

exemption. A large base of experience 

exists, including information on human 

dietary exposure, for foods that contain 

coat proteins from viruses that naturally 

infect plants. As plant virus coat 

proteins are ubiquitous in food, EPA 

concluded that all humans are exposed 

to plant virus coat proteins throughout 

their lives as part of their diet. Neither 

naturally occurring plant virus coat 

proteins nor the PVC-proteins qualifying 

for this exemption are toxic, and there 

is no evidence that consumption in food 

of residues of PVC-proteins qualifying 

for this proposed exemption would lead 

to any harm. 

1. Food. As mentioned in Unit IV.C.1., 

the Agency has concluded that dietary 

exposures to PVC-proteins qualifying for 

this proposed exemption will be similar 

to or less than the amounts of plant 

virus coat proteins currently found and 

consumed in food plants that have been 

naturally infected by viruses. Even if 

there were notable exposure to PVCproteins, there is no evidence that PVCproteins are toxic to humans. Moreover, 

the Agency is not aware of any coat 

protein from a virus that naturally 

infects plants that has been identified as 

a food allergen for humans. The 

residues that are proposed to be 

exempted by this Federal Register 

document would not differ substantially 

from residues of naturally occurring 

plant virus coat proteins. 

2. Drinking water exposure. EPA also 

evaluated potential non–occupational 

exposures in drinking water. Residues 

of PVC-proteins that qualify for this 

proposed exemption are produced 

inside the plant itself. When the plant 

dies or a part is removed from the plant, 

microorganisms colonizing the tissue 

immediately begin to degrade it using 

the components of the plant tissue 

(including residues of PVC-proteins) as 

building blocks for making their own 

cellular components or for fueling their 

own metabolisms. PVC-proteins and 

naturally occurring plant virus coat 

proteins are subject to the same 

processes of biodegradation and decay 

that all biological materials undergo and 

are not known to either bioaccumulate 

or biomagnify (Ref. 60). Even if they 

were to reach surface waters (e.g., 

through plant parts or pollen falling into 

bodies of water), they are unlikely to 

present anything other than a very 

negligible exposure in drinking water 

drawn either from surface water or 

ground water sources due to 

biodegradation of these residues. 

B. Other Non-Occupational Exposure 

Residential exposure to PVC-proteins 

qualifying for this proposed exemption 

would be limited. Residential exposure 

could occur through use of PVCP-PIPs 

in ornamental plants or in plants grown 

in home gardens. Such exposure to 

PVC-proteins is expected to be 

negligible on a per-person basis 

compared to exposure to PVC-proteins 

and natural plant virus coat proteins in 

the diet. Furthermore, PVC-proteins 

qualifying for this exemption would not 

be toxic, and there is no evidence that 

exposure to such PVC-proteins would 

lead to any harm. 

1. Dermal exposure. Residues of PVCproteins qualifying for this proposed 

exemption may be present in sap or 

other plant exudates and thus may 

present some limited opportunity for 

dermal exposure to persons coming 

physically into contact with the plant or 

raw agricultural food from the plant. 

Individuals preparing meals are those 

most likely to experience dermal contact 

with the residues on a non-occupational 

basis. As noted by the 2005 SAP, PVCproteins’ ‘‘natural exposure route may 

be via oral ingestion. However, 

genetically modified expression of 

PVCP-PIPs would lead to the presence 

of [PVC-proteins] in other plant 

compartments such as pollen grains 

which lead to other sites of exposure 

including respiratory and cutaneous 

surfaces’’ (Ref. 15). However, the 

potential amount involved in such 

exposure on a per person basis is likely 

to be negligible in comparison to 

potential exposure through the dietary 

route to PVC-proteins and natural plant 

virus coat proteins (Ref. 61). Moreover, 

PVC-proteins qualifying for this 

proposed exemption or naturally 

occurring plant virus coat proteins that 

occur in food are unlikely to cross the 

barrier provided by the skin (Ref. 62). 

2. Inhalation exposure. Pollen could 

potentially contain residues of PVCproteins qualifying for this proposed 

exemption. Individuals (e.g., those 

visiting, living, or working near enough 

to farms, nurseries, or other plantgrowing areas to be exposed to windblown pollen) may be exposed to the 

pollen through inhalation. On a per 

person basis, the potential amount of 

pollen involved in these exposures is 

likely to be negligible in comparison to 

potential exposure through the dietary 

route (Ref. 61). Some members of the 

2005 SAP indicated that ‘‘[i]ntroduction 

of new proteins to pollens and other 

plant materials may have the potential 

to cause problems, and consideration by 

the Agency is warranted’’ (Ref. 15). As 

the Panel explained, ‘‘While plant 

viruses systemically infect plant tissues, 

there is tissue specific regionalization of 

viruses. Therefore [plant virus coat 

proteins] would be restricted within 

certain compartments. Transgenic 

expression of some PVC-PIPs would 


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promote [PVC-protein] expression in 

different plant tissues relative to what 

would naturally occur (i.e., all cells). 

This could lead to heightened levels of 

[PVC-proteins] in certain tissues (i.e., 

pollen grains) and the effects 

(specifically to allergenicity) are not yet 

known. This has implications for nondietary exposure of plant proteins. In 

some instances, [plant virus coat 

protein’s] natural exposure route may be 

via oral ingestion. However, genetically 

modified expression of PVCP-PIPs 

would lead to the presence of [PVCproteins] in other plant compartments 

such as pollen grains which lead to 

other sites of exposure including 

respiratory and cutaneous surfaces’’

(Ref. 15). However, other Panel 

members felt that ‘‘unless there is 

evidence that PCVP-PIPs are expressed 

on the surface of pollen grains in a 

manner different from expression in 

wild-type plants, the risk of increased 

allergy from exposure to pollen is nonexistent’’ (Ref. 15). The Agency also 

notes that in order for expression of a 

PVC-protein to be a concern, the protein 

would have to be expressed on the 

surface of the pollen grain, it would 

have to actually be an antigenic protein, 

and it would have to elicit an allergic 

response through secondary exposure. 

The Agency considers that this 

sequence of events is very unlikely to 

occur, in part because no plant virus 

coat proteins have been identified as 

being allergenic, and PVC-proteins 

qualifying for this exemption are 

virtually unmodified or minimally 

modified from natural plant virus coat 

proteins. Therefore, it is unlikely that 

inhalation exposure to PVC-proteins in 

pollen would result in adverse effects. 

VII. Cumulative Effects 

EPA examined the available 

information on residues of PVC-proteins 

qualifying for this proposed exemption 

for cumulative effects with other 

substances, including natural plant 

virus coat proteins. Plant virus coat 

proteins are nontoxic proteins that are 

widespread in food from plants. They 

have not been associated with toxic 

effects to animals or humans (see Unit 

IV.C.3.). EPA is therefore not aware of 

any other substances that could have a 

common mechanism of human toxicity 

with residues of PVC-proteins 

qualifying for this exemption and 

cannot identify any cumulative effects 

of such residues with any other 

substances. 

VIII. Safety Factor for Infants and 

Children 

A. In General 

Section 408(b)(2)(C) of FFDCA 

provides that EPA shall apply an 

additional tenfold margin of safety for 

infants and children in the case of 

threshold effects to account for prenatal 

and postnatal toxicity and the 

completeness of the information base on 

toxicity and exposure unless EPA 

determines that a different margin of 

safety will be safe for infants and 

children. Margins of safety are 

incorporated into EPA risk assessments 

either directly through use of a MOE 

analysis or through using uncertainty 

(safety) factors in calculating a dose 

level that poses no appreciable risk to 

humans. 

B. Prenatal and Postnatal Sensitivity 

EPA considered available information 

on the dietary consumption patterns of 

infants and children as it pertains to 

residues in food of PVC-proteins 

qualifying for this proposed exemption. 

The range of foods consumed by infants 

and children is in general more limited 

than the range of foods consumed by 

adults. Most newborns rely on breast 

milk or formula-based products for 

nutrition, although some infants are fed 

soy-based products. Infants may begin 

as early as 4 months of age to consume 

solid foods that are based on foods 

consumed by the general adult 

population albeit in different 

proportions and with processing to 

facilitate swallowing. As infants and 

children mature, more and more of the 

foods normally consumed by adults 

become part of their diets, and the 

relative proportions of the different 

types of food consumed change to more 

closely resemble an adult diet. Because 

plant viruses are ubiquitous in plant 

foods, EPA concluded that infants and 

children are exposed to plant virus coat 

proteins from the time they begin to eat 

food of plant origin. As the diets of 

humans change from infancy through 

childhood and into adulthood, there is 

some possibility that the amount of 

plant virus coat proteins being 

consumed may change, with those 

consuming the greatest amounts of food 

of plant origin most likely exposed to 

the most plant virus coat protein. 

However, there is no evidence that such 

changes are likely to result in 

disproportionately high consumption of 

foods containing plant virus coat 

proteins among infants and children in 

comparison to the general population. 

Furthermore, PVC-proteins qualifying 

for this proposed exemption are not 

toxic, and there is no evidence that any 

amount of exposure to such PVCproteins in food would lead to any 

harm. 

EPA considered available information 

on the potential for special 

susceptibility of infants and children, 

including prenatal and postnatal 

toxicity, to residues of PVC-proteins 

qualifying for this proposed exemption. 

PVC-proteins in food are not toxic. 

There is no scientific evidence that 

residues of such PVC-proteins in food 

would have a different effect on infants 

and children than adults due to 

neurological differences between 

infants, children, and adults. 

The Agency’s consideration of 

cumulative effects of the residues of 

PVC-proteins qualifying for this 

proposed exemption on the general 

population also included consideration 

of effects for infants and children. 

Neither naturally occurring plant virus 

coat proteins nor PVC-proteins 

qualifying for this proposed exemption 

are toxic when consumed as part of the 

diet, and EPA is not aware of any 

substances that might have a common 

mechanism of toxicity with these PVCproteins. There is no scientific evidence 

indicating any potential for adverse 

effects on infants and children due to 

cumulative exposure to residues of such 

PVC-proteins. EPA concludes that there 

is no evidence of a common mechanism 

of toxicity between PVC-proteins 

qualifying for this proposed exemption 

and any other substances, and therefore, 

no cumulative effects of these PVCproteins would reasonably be 

anticipated. 

C. Conclusion 

There is a complete toxicity base of 

information for PVC-proteins that are 

the subject of this proposed exemption, 

and exposure data are estimated based 

on data that reasonably account for 

potential exposures. For residues of 

PVC-proteins qualifying for this 

proposed exemption, EPA has 

determined that a tenfold margin of 

safety is not necessary to protect infants 

and children. As noted in Unit IV.C., 

EPA based its assessment of exposure 

and toxicity on the long history of safe 

human and animal consumption of food 

containing plant virus coat proteins. 

EPA also relied upon information from 

the disciplines of plant genetics, plant 

physiology, plant virology, microbial 

ecology, ecology, biochemistry, 

molecular biology, and plant breeding. 

Based on all of this information, EPA 

concludes that PVC-proteins qualifying 

for this proposed exemption in food are 

not toxic and may be safely consumed, 

including by infants and children. There 

is no evidence that exposure to such 


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PVC-proteins in food, including changes 

in exposure because of changes in the 

relative proportions of the different 

types of food consumed from infancy 

through childhood and into adulthood, 

leads to any harm. Thus, on the basis of 

valid, complete, and reliable 

information, EPA has concluded that 

residues in food of PVC-proteins 

qualifying for this proposed exemption 

are safe for infants and children and that 

an additional margin of safety need not 

be applied. 

IX. Other Considerations 

A. Endocrine Disruptors 

Based on available information that 

plant virus coat proteins are ubiquitous 

in foods and have no known adverse 

effects when consumed as part of the 

diet (see Unit IV.C.), EPA does not 

expect residues of PVC-proteins 

qualifying for this proposed exemption 

to cause estrogenic or other endocrine 

effects. In the May 16, 1997 

supplemental document, EPA 

specifically requested comment on PVCproteins causing estrogenic effects. No 

information was received indicating that 

either naturally occurring plant virus 

coat proteins or PVC-proteins that 

qualify for this proposed exemption 

might cause estrogenic or other 

endocrine effects. If EPA becomes aware 

of a potential for estrogenic or endocrine 

effects from exposure to residues of 

such PVC-proteins, the Agency will 

reexamine this proposed tolerance 

exemption in light of that information. 

B. Analytical Method(s) 

EPA has concluded that even though 

methodology exists to detect residues of 

PVC-proteins (Refs. 63, 64, and 65), 

there is no need to employ a practical 

method for detecting and measuring the 

level of residues of PVC-proteins 

qualifying for this exemption. There is 

no reason to believe that the residues of 

PVC-proteins proposed to be exempted 

in this Federal Register document 

would behave any differently than 

naturally occurring plant virus coat 

proteins in food. There is a reasonable 

certainty that no harm will result from 

exposure to any amount of residues in 

food of such PVC-proteins. Because 

these residues may be present in food at 

any level without causing harm, EPA 

has concluded that an analytical method 

is not required for detecting and 

measuring the level of residues of these 

PVC-proteins in food. EPA consulted 

with the Department of Health and 

Human Services (HHS) in making this 

determination. 

C. Codex Maximum Residue Level 

There are no Codex maximum residue 

levels established for PVC-proteins. 

X. Preliminary Determination of Safety 

for U.S. Population, Infants, and 

Children 

Based on the information discussed in 

this document and that discussed in the 

1994 Federal Register documents, the 

supplemental documents, and the 

associated record as described in Unit 

XII.B., EPA preliminarily concludes that 

there is a reasonable certainty that no 

harm will result to the U.S. population, 

infants, and children from aggregate 

exposures to residues of PVC-proteins 

that qualify for this proposed 

exemption. Many years of experience 

with growing, preparing, and 

consuming food from plants containing 

plant virus coat proteins and 

information generated through years of 

study of the food supply (Refs. 6, 7, 8, 

9, 10, and 66) indicate that adverse 

effects due to aggregate exposure to 

PVC-proteins qualifying for this 

proposed exemption through dietary, 

non-food oral, dermal, and inhalation 

routes are highly unlikely. 

XI. Request for Comment 

EPA requests comment on whether 

this proposed tolerance exemption 

identifies those PVC-proteins that are 

unlikely to result in new dietary 

exposures. When commenting, please 

use the terminology conventions 

adopted in this document, i.e., use 

‘‘plant virus coat protein’’ when 

referring to the protein produced 

naturally from a plant virus, and use 

‘‘PVC-protein’’ when referring to the 

protein component of a PVCP-PIP. The 

Agency requests comment on the 

following specific issues: 

1. EPA requests comment on the 

options discussed in Unit IV.E.1. for 

defining virtually unmodified. Under 

the Agency’s proposed rule, virtually 

unmodified proteins would be exempt 

from the requirement of a tolerance 

without Agency review. Under one 

option, virtually unmodified would be 

defined as having or coding for an 

amino acid sequence that is identical to 

an entire coat protein of a naturally 

occurring plant virus; except for the 

addition of one or two amino acids at 

the N- and/or C-terminus other than 

cysteine, asparagine, serine, and 

threonine and/or the deletion of one or 

two amino acids at the N- and/or Cterminus. However, the Agency is 

considering removing the limitations on 

which amino acids may be added and 

on the number of amino acids that may 

be truncated from either end of a PVCprotein. 

2. In addition to the types of changes 

discussed in the paragraph above, EPA 

requests comment on whether any other 

class of potential PVC-protein 

modifications (e.g., a particular number 

of amino acid substitutions) would 

always be expected to produce a PVCprotein as safe as an unmodified plant 

virus coat protein such that the protein 

would not warrant a case-by-case 

Agency review for a tolerance 

exemption. The Agency also requests 

that commenters indicate whether the 

number and combination of such 

modifications has any relevance to the 

product’s safety. In October 2004, the 

FIFRA SAP was asked to consider the 

degree and ways a plant virus coat 

protein gene might be modified while 

still retaining scientific support for the 

idea that humans have consumed the 

products of such genes for generations 

and that such products therefore present 

no new dietary exposures (Ref. 14). 

They responded that ‘‘[t]here was no 

clear consensus on how much change 

would be necessary to invalidate this 

assumption, although there was general 

agreement that the appropriate 

comparison is to the range of natural 

variation in the virus population.’’ This 

question was also addressed by the 2005 

SAP which concurred that ‘‘it is 

extremely difficult to identify 

modifications that would be expected to 

be ‘within the range of natural variation 

for all virus families’. . . Given the 

possible range of natural variations for 

PVC proteins, it would be appropriate to 

assess whether specific modifications 

are within natural variation limits of the 

PVC protein on a case-by-case basis’’

(Ref. 15). Commenters should 

specifically address this advice when 

formulating comments. 

3. EPA requests comment on whether 

there would be any safety issues 

associated with exposure to PVCproteins if the virus used to create the 

PVCP-PIP does not naturally infect the 

particular plant species into which the 

PVCP-PIP is inserted. A PVC-protein 

may be expressed in a food plant that 

the virus does not naturally infect when 

heterologous resistance to a particular 

virus is conferred through a different 

virus’ coat protein gene (e.g., Ref. 45). 

Such PVC-proteins could be safely 

exempted from tolerance requirements 

if these proteins are reasonably expected 

to be part of the current diet, as 

discussed in Unit IV.E.1. In light of the 

uncertainty surrounding the SAP’s 

remarks concerning this issue (see Unit 

IV.E.1.), EPA requests comment on 

whether there would be any safety 

issues associated with exposure tothe 


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PVC-proteins themselves if the virus 

used to create a PVCP-PIP does not 

naturally infect the particular plant 

species into which the PVCP-PIP is 

inserted. 

4. EPA requests comment on whether 

the Agency should consider the level of 

PVC-protein expression in determining 

whether a PVC-protein is virtually 

unmodified or minimally modified and 

thus exempt from tolerance 

requirements. EPA concurs with the 

2005 SAP that ‘‘exposure level is an 

important component of an allergenicity 

risk assessment’’ (Ref. 15). However, it 

can be argued that PVC-proteins that are 

virtually unmodified or minimally 

modified when compared to natural 

plant viral coat proteins are of 

sufficiently low hazard that the 

potential risk does not rise to the level 

warranting regulation, even in the rare 

case that exposure to a PVC-protein 

might be greater than the exposure to 

the corresponding natural plant virus 

coat protein. Although EPA’s review of 

PVC-proteins to determine if they are 

minimally modified could allow the 

Agency to consider PVC-protein 

expression level relative to natural 

levels of plant virus coat proteins, the 

Agency is unsure how this factor could 

be readily incorporated into the criteria 

for a developer-determined tolerance 

exemption; EPA anticipates needing to 

consider the appropriateness of data 

designed to address these questions on 

a case-by-case basis. Therefore, if 

protein expression level is considered a 

necessary factor in evaluating whether 

to exempt a virtually unmodified PVCprotein from tolerance requirements, 

EPA seeks comment on how such 

considerations could be articulated in a 

clear, unambiguous criterion. 

5. EPA requests comment on the 

Agency’s options for how to view a 

PVC-protein that would not meet the 

definition of virtually unmodified and is 

not detected during product 

development if the construct suggests 

that its production is likely to occur in 

at least some plant tissue at some point 

in time (see Unit IV.F.). Specifically, 

EPA requests comment on the relative 

costs and benefits of allowing a PVCPPIP that does not produce detectable 

PVC-protein residues in food during 

product development to be sold or 

distributed without a PVC-protein 

tolerance exemption in place. EPA is 

particularly interested in information 

about the likelihood that protein would 

fail to be detected during product 

development but subsequently be 

detected in food. The Agency is also 

interested in comments on conditions 

under which protein detection protocols 

could be conducted to provide adequate 

assurance that such events would not 

occur, e.g., any key environmental 

parameters that should be varied during 

testing. 

EPA also requests comment on 

whether obtaining characterization data 

of a plant-produced PVC-protein for a 

tolerance review is scientifically feasible 

in all cases where the PVCP-PIP 

insertion event contains a translation 

initiation codon and is not present in an 

inverted repeat orientation. The Agency 

would like to know for any given crop 

how technically difficult it would be to 

attempt to induce protein production 

through challenge with a known PTGS 

suppressor protein, e.g., through 

introduction by a replicating virus 

vector, genetic crosses, or agroinfiltration (Ref. 56). In addition, EPA 

would like to know how likely it is that 

such techniques could yield sufficient 

quantities of PVC-protein for analysis 

(e.g., mass spectrometry or glycosylation 

analysis). The Agency would also be 

interested in hearing of additional 

techniques that could be employed to 

obtain plant-produced PVC-protein in 

cases where PTGS normally prevents 

accumulation of protein but is not 

expected to be consistently activated, 

thereby leading to PVC-protein 

production. 

Regarding the second alternative 

presented for PVC-proteins associated 

with PTGS, EPA requests comment on 

the value of the additional information 

gained by analyzing an actual PVCprotein as produced in the plant where 

the inserted nucleotide sequence 

suggests it would be minimally 

modified from a natural plant virus coat 

protein, e.g., to consider potential posttranslational modifications, relative to 

the reduced burden and cost of 

analyzing safety based on the deduced 

amino acid sequence from the insert 

alone. 

Regarding the third alternative 

presented, EPA requests comment on 

the rationale that would be used to 

support expanding this tolerance 

exemption to cover all PVC-proteins 

produced by a PVCP-PIP that mediates 

resistance through PTGS, i.e., that any 

such protein would meet the conditions 

of a minimally modified protein as 

discussed in this document given the 

necessity for transgene transcript 

sequence similarity to natural plant 

virus coat protein sequences in order for 

PTGS to effectively function. In 

particular, EPA requests comment on 

how to reconcile this option with prior 

advice of the SAP (as discussed in Unit 

IV.F.). 

6. EPA requests comment on whether 

PVC-proteins that the Agency has 

reviewed and has determined are 

minimally modified and therefore are 

exempt from the requirement of a 

tolerance under proposed § 174.477(b) 

should be listed in the CFR as is the 

current practice for individual tolerance 

exemptions associated with other types 

of PIPs. If so, EPA requests comment on 

whether the listing should indicate the 

specific modifications of the reviewed 

proteins, given that each determination 

would apply only to proteins with those 

modifications. EPA is aware that in the 

past, developers have found such 

listings to be useful for international 

trade reasons, as governments rely on 

EPA tolerances to support import 

decisions. 

XII. References 

A. Books, Articles, and Reports Used in 

Preparing this Proposed Rule 

1. Callaway A., Giesman-Cookmeyer 

D., Gillock E.T., Sit T.L., Lommel S.A. 

The multifunctional capsid proteins of 

plant RNA viruses. Annual Review of 

Phytopathology 2001; 39:419-60. 

2. Powell P.A., Sanders P.R., Tumer 

N., Fraley R.T., Beachy R.N. Protection 

against tobacco mosaic virus infection 

in transgenic plants requires 

accumulation of coat protein rather than 

coat protein RNA sequences. Virology 

1990; 175:124-30. 

3. Goldbach R., Bucher E., Prins M. 

Resistance mechanisms to plant viruses: 

an overview. Virus Research 2003; 

92:207-12. 

4. National Research Council. 

Genetically Modified Pest-Protected 

Plants: Science and Regulation. 

Washington, DC: National Academy 

Press, 2000. 

5. Dewan C., Pearson M.N. Natural 

field infection of garlic by garlic yellow 

streak virus in the Pukekohe area of 

New Zealand and associated problems 

with the introduction of new garlic 

cultivars. New Zealand Journal of Crop 

and Horticultural Science 1995; 23:97- 

102. 

6. McKinney H.H. Mosaic diseases in 

the Canary Islands, West Africa, and 

Gibraltar. Journal of Agricultural 

Research 1929; 39:557-78. 

7. Provvidenti R., Gonsalves D. 

Occurrence of zucchini yellow mosaic 

virus in cucurbits from Connecticut, 

New York, Florida, and California. Plant 

Disease 1984; 68:443-6. 

8. Palukaitis P. Virus-mediated 

genetic transfer in plants. In: Levin M, 

Strauss H. Risk Assessment in Genetic 

Engineering. New York: McGraw-Hill, 

1991:140-62. 

9. Jones L., Anderson E., Burnett G. 

The latent virus of potatoes. Journal of 

Phytopathology 1934; 7:93-115. 

10. Beemster A.B.R., de Bokx J.A. 

Survey of properties and symptoms. In: 


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de Bokx J.A., van der Want J.P.H. 

Viruses of Potatoes and Seed Potato 

Production. Wageningen: Pudoc, 

1987:84-93. 

11. Fulton R. Practices and 

precautions in the use of cross 

protection for plant virus disease 

control. Annual Review of 

Phytopathology 1986; 24:67-81. 

12. Zhang T., Breitbart M., Lee W.H., 

Run J-Q, Wei CL, Soh SWL et al. RNA 

viral community in human feces: 

prevalence of plant pathogenic viruses. 

PLoS Biology 2006; 4:e3. 

13. FIFRA Scientific Advisory Panel 

(Subpanel on Plant Pesticides). Minutes 

of the December 18, 1992 Meeting on A 

Set of Scientific Issues Being 

Considered by the Agency in 

Connection with the Proposed 

Regulation of Plant Pesticides. 1992. 

14. FIFRA Scientific Advisory Panel. 

Minutes of the October 13-15, 2004 

Meeting on Issues Associated with 

Deployment of a Type of PlantIncorporated Protectant (PIP), 

Specifically those Based on Plant Viral 

Coat Proteins (PVCP-PIPs). 2004. 

15. FIFRA Scientific Advisory Panel. 

Minutes of the December 6-8, 2005 

Meeting on Plant-Incorporated 

Protectants Based on Virus Coat Protein 

Genes: Science Issues Associated with 

the Proposed Rule. 2005. 

16. Quemada H. Food safety 

evaluation of a transgenic squash. OECD 

Workshop on Food: Provisionsal 

Proceedings of the Safety Evaluation. 

Paris: OECD, 1994:71-9. 

17. Hull R. Matthews’ Plant Virology, 

Fourth ed. San Diego: Academic Press, 

2002. 

18. Miller J. Biotech boosts natural 

bounty. Today’s Chemist at Work 2000; 

9:38-44. 

19. Elbehri A. Biopharming and the 

Food System: Examining the Potential 

Benefits and Risks. AgBioForum 2005; 

8:18-25. 

20. Downs S.H., Marks G.B., Sporik 

R., Belosouva E.G., Car N.G., Peat J.K. 

Continued increase in the prevalence of 

asthma and atopy. Archives of Disease 

in Childhood 2001; 84:20-3. 

21. von Mutius E., Weiland S.K., 

Fritzsch C., Duhme H., Keil U. 

Increasing prevalence of hay fever and 

atopy among children in Leipzig, East 

Germany. Lancet 1998; 351:862-6. 

22. Heinrich J., Hoelscher B., Frye C., 

Meyer I., Wjst M., Wichmann H-E. 

Trends in prevalence of atopic diseases 

and allergic sensitization in children in 

Eastern Germany. European Respiratory 

Journal 2002; 19:1040-6. 

23. Naraghi-Arani P., Daubert S., 

Rowhani A. Quasispecies nature of the 

genome of Grapevine fanleaf virus. 

Journal of General Virology 2001; 

82:1791-5. 

24. Schneider W.L., Roossinck M.J. 

Genetic diversity in RNA virus 

quasispecies is controlled by host-virus 

interactions. Journal of Virology 2001; 

75:6566-71. 

25. Kim T., Youn M.Y., Min B.E., Choi 

S.H., Kim M., Ryu KH. Molecular 

analysis of quasispecies of Kyuri green 

mottle mosaic virus. Virus Research 

2005; 110:161-7. 

26. Roossinck M.J. Mechanisms of 

plant virus evolution. Annual Review of 

Phytopathology 1997; 35:191-209. 

27. Zhou X., Liu Y., Calvert L., Munoz 

C., Otim-Nape G.W., Robinson DJ et al. 

Evidence that DNA-A of a geminivirus 

associated with severe cassava mosaic 

disease in Uganda has arisen by 

interspecific recombination.Journal of 

General Virology 1997; 78:2101-11. 

28. Desbiez C., Lecoq H. The 

nucleotide sequence of Watermelon 

mosaic virus (WMV, Potyvirus) reveals 

interspecific recombination between 

two related potyviruses in the 5’ part of 

the genome.Archives of Virology 2004; 

149:1619-32. 

29. Allison R.F., Janda M., Ahlquist P. 

Sequence of cowpea chlorotic mottle 

virus RNAs 2 and 3 and evidence of a 

recombination event during bromovirus 

evolution. Virology 1989; 172:321-30. 

30. Chenault K.D., Melcher U. 

Phylogenetic relationships reveal 

recombination among isolates of 

cauliflower mosaic virus.Journal of 

Molecular Evolution. 1994; 39:496-505. 

31. Gibbs M.J., Cooper J.I. A 

recombinational event in the history of 

luteoviruses probably induced by basepairing between the genomes of two 

distinct viruses. Virology 1995; 

206:1129-32. 

32. Le Gall O.L., Lanneau M., 

Candresse T., Dunez J. The nucleotide 

sequence of the RNA-2 of an isolate of 

the English serotype of tomato black 

ring virus: RNA recombination in the 

history of nepoviruses. Journal of 

General Virology. 1995; 76:1279-83. 

33. Masuta C., Ueda S., Suzuki M., 

Uyeda I. Evolution of a quadripartite 

hybrid virus by interspecific exchange 

and recombination between replicase 

components of two related tripartite 

RNA viruses. Proceedings of the 

National Academy of Sciences. 1998; 

95:10487-92. 

34. Pita J.S., Fondong V.N., Sangare 

A., Otim-Nape G.W., Ogwal S., Fauquet 

C.M. Recombination, 

pseudorecombination and synergism of 

geminiviruses are determinant keys to 

the epidemic of severe cassava mosaic 

disease in Uganda. Journal of General 

Virology 2001; 82:655-65. 

35. Moonan F., Molina J., Mirkov T.E. 

Sugarcane yellow leaf virus: an 

emerging virus that has evolved by 

recombination between luteoviral and 

poleroviral ancestors. Virology 2000; 

269:156-71. 

36. Worobey M., Holmes E.C. 

Evolutionary aspects of recombination 

in RNA viruses. Journal of General 

Virology 1999; 80:2535-43. 

37. Garcı ́a-Arenal F., Fraile A., 

Malpica J.M. Variability and genetic 

structure of plant virus populations. 

Annual Review of Phytopathology 2001; 

39:157-86. 

38. Rodrigues-Alvarado G., Kurath G., 

Dodds J.A. Heterogeneity in pepper 

isolates of cucumber mosaic virus. Plant 

Disease 1995; 79:450-5. 

39. Fraile A., Malpica J.M., Aranda 

M.A., Rodriguez-Cerezo E., GarcaArenal F. Genetic diversity in tobacco 

mild green mosaic tobamovirus 

infecting the wild plant Nicotiana 

glauca. Virology 1996; 223:148-55. 

40. Brunt, A.A., Crabtree, K., Dallwitz, 

M.J., Gibb, A.J., Watson, L., and 

Zurcher, E. Plant Viruses Online: 

Descriptions and Lists from the VIDE 

Database Version: 20th August 1996. 

http://image.fs.uidaho.edu/vide/. 

41. Kurganov B.I., Rafikova E.R., 

Dobrov E.N. Kinetics of thermal 

aggregation of tobacco mosaic virus coat 

protein. Biochemistry (Moscow) 2002; 

67:525-33. 

42. Liu H., Boulton M.I., Oparka K.J., 

Davies J.W. Interaction of the movement 

and coat proteins of Maize streak virus: 

implications for the transport of viral 

DNA. Journal of General Virology 2001; 

82:35-44. 

43. Sacher R., Ahlquist P. Effects of 

deletions in the N-terminal basic arm of 

brome mosaic virus coat protein on 

RNA packaging and systemic infection. 

Journal of Virology 1989; 63:4545-52. 

44. FIFRA Scientific Advisory Panel. 

Report of the June 6-7, 2000 Meeting on 

Mammalian Toxicity Assessment 

Guidelines for Protein Plant Pesticides. 

2000. 

45. Dinant S., Blaise F., Kusiak C., 

Astier-Manifacier S., Albouy J. 

Heterologous resistance to potato virus 

Y in transgenic tobacco plants 

expressing the coat protein gene of 

lettuce mosaic potyvirus. 

Phytopathology 1993; 83:819-24. 

46. Breiteneder H., Pettenburger K., 

Bito A., Valenta R., Kraft D., Rumpold 

H. et al. The gene coding for the major 

birch pollen allergen Betv1, is highly 

homologous to a pea disease resistance 

response gene. The EMBO Journal 1989; 

8:1935-8. 

47. Breiteneder H., Ebner C. 

Molecular and biochemical 

classification of plant-derived food 


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allergens. The Journal of Allergy and 

Clinical Immunology 2000; 106:27-36. 

48. Breiteneder H., Radauer C. A 

classification of plant food allergens. 

The Journal of Allergy and Clinical 

Immunology 2004; 113:821-30. 

49. Ebner C., HoffmannSommergruber K., Breiteneder H. Plant 

food allergens homologous to 

pathogenesis-related proteins. Allergy 

2001; 56:43-4. 

50. Davis M., Ying Z. Development of 

papaya breeding lines with transgenic 

resistance to Papaya ringspot virus. 

Plant Disease 2004; 88:352-8. 

51. Lindbo J.A., Silva-Rosales L., 

Proebsting W.B., Dougherty W.G. 

Induction of a highly specific antiviral 

state in transgenic plants: Implications 

for regulation of gene expression and 

virus resistance. The Plant Cell 1993; 

5:1749-59. 

52. Be ́clin C., Berthome ́ R., Palauqui 

J.C., Tepfer M., Vaucheret H. Infection 

of tobacco or Arabidopsis plants by 

CMV counteracts systemic posttranscriptional silencing of nonviral 

(trans)genes. Virology 1998; 252:313-7. 

53. Pang S-Z, Jan F.J., Carney K., Stout 

J., Tricoli D.M., Quemada H. et al. Posttranscriptional transgene silencing and 

consequent tospovirus resistance in 

transgenic lettuce are affected by 

transgene dosage and plant 

development. Plant Journal 1996; 9:899- 

909. 

54. Szittya G., Silhavy D., Molna ́r A., 

Havelda Z., Lovas A, Lakatos L. et al. 

Low temperature inhibits RNA 

silencing-mediated defence by the 

control of siRNA generation. The EMBO 

Journal 2003; 22:633-40. 

55. Savenkov E.I., Valkonen J.P.T. 

Coat protein gene-mediated resistance to 

Potato virus A in transgenic plants is 

suppressed following infection with 

another potyvirus. Journal of General 

Virology 2001; 82:2275-8. 

56. Li W.X., Ding S.W. Viral 

suppressors of RNA silencing. Current 

Opinion in Biotechnology 2001; 12:150- 

4. 

57. FIFRA Scientific Advisory Panel. 

Minutes of the July 17-18, 2001 Meeting 

on A Set of Scientific Issues Being 

Considered by the Environmental 

Protection Agency Regarding: 

Assessment of Additional Scientific 

Information Concerning StarLinkTM

Corn. 2001. 

58. FIFRA Scientific Advisory Panel. 

Minutes of the November 28, 2000 

Meeting on A Set of Scientific Issues 

Being Considered by the Environmental 

Protection Agency Regarding: 

Assessment of Scientific Information 

Concerning StarLinkTM Corn. 2000. 

59. Pariza M., Johnson E. Evaluating 

the safety of microbial enzyme 

preparations used in food processing: 

update for a new century. Regulatory 

Toxicology and Pharmacology 2001; 

33:173-86. 

60. Berg J., Tymoczko J., Stryer L., 

Clarke N. Biochemistry, 5th ed. New 

York: W. H. Freeman and Company, 

2002. 

61. Environmental Protection Agency. 

Issue Paper on Dermal and Inhalation 

Exposure to Plant Substances. 2000. 

62. Guy R.H., Hadgraft J. Principles of 

skin permeability relevant to chemical 

exposure. In: Hobson DW. Dermal and 

Ocular Toxicology: Fundamentals and 

Methods. Boca Raton: CRC Press, 

1991:221-46. 

63. Huguenot C., van den Dobbelsteen 

G., de Haan P., Wagemakers C., Drost G., 

Osterhaus A. et al. Detection of tomato 

spotted wilt virus using monoclonal 

antibodies and riboprobes. Archives of 

Virology 1990; 110:47-62. 

64. Rocha-Pena M., Lee R., Niblett C. 

Development of a dot-immunobinding 

assay for detection of citrus tristeza 

virus. Journal of Virological Methods 

1991; 34:297-309. 

65. Sukhacheva E., Novikov V., 

Plaksin D., Pavlova I., Ambrosova S. 

Highly sensitive immunoassays for 

detection of barley stripe mosaic virus 

and beet necrotic yellow vein virus. 

Journal of Virological Methods 1996; 

56:199-207. 

66. Hull R., Covey S.N., Dale P. 

Genetically modified plants and the 35S 

promoter: assessing the risks and 

enhancing the debate. Microbial Ecology 

in Health and Disease 2000; 12:1-5. 

B. Additional Information 

EPA has established an official record 

for this rulemaking. The official record 

includes all information considered by 

EPA in developing this proposed rule 

including documents specifically 

referenced in this action, any public 

comments received during an applicable 

comment period, and any other 

information related to this action, 

including any information claimed as 

CBI and any information received in any 

of the related dockets mentioned in this 

unit. This official record includes all 

information physically located in the 

dockets described in the following 

paragraphs, as well as any documents 

that are referenced in the documents in 

the dockets. 

1. The docket identified by the docket 

control number OPP–300370 for the 

document entitled ‘‘Proposed Policy: 

Plant-Pesticides Subject to the Federal 

Insecticide, Fungicide, and Rodenticide 

Act and the Federal Food, Drug, and 

Cosmetic Act’’ (59 FR 60496, November 

23, 1994) (FRL–4755–2). 

2. The docket identified by the docket 

control number OPP–300369 for the 

document entitled ‘‘Plant-Pesticides 

Subject to the Federal Insecticide, 

Fungicide and Rodenticide Act; 

Proposed Rule’’ (59 FR 60519, 

November 23, 1994) (FRL–4755–3). 

3. The docket identified by the docket 

control number OPP–300368 for the 

document entitled ‘‘Plant-Pesticides; 

Proposed Exemption From the 

Requirement of a Tolerance Under the 

Federal Food, Drug, and Cosmetic Act’’

(59 FR 60535, November 23, 1994) 

(FRL–4758–8). 

4. The docket identified by the docket 

control number OPP–300371 for the 

document entitled ‘‘Plant-Pesticides; 

Proposed Exemption From the 

Requirement of a Tolerance Under the 

Federal Food, Drug, and Cosmetic Act 

for Nucleic Acids Produced in Plants’’

(59 FR 60542, November 23, 1994) 

(FRL–4755–5). 

5. The docket identified by the docket 

control number OPP–300367 for the 

document entitled ‘‘Plant-Pesticides; 

Proposed Exemption From the 

Requirement of a Tolerance Under the 

Federal Food, Drug, and Cosmetic Act 

for Viral Coat Proteins Produced in 

Plants’’ (59 FR 60545, November 23, 

1994) (FRL–4755–4). 

6. The docket identified by the docket 

control number OPP–300370A for the 

document entitled ‘‘Plant-Pesticide 

Subject to the Federal Insecticide, 

Fungicide, and Rodenticide Act and the 

Federal Food, Drug, and Cosmetic Act; 

Reopening of Comment Period’’ (61 FR 

37891, July 22, 1996) (FRL–5387–4). 

7. The docket identified by the docket 

control number OPP–300368A for the 

document entitled ‘‘Plant-Pesticides; 

Supplemental Notice of Proposed 

Rulemaking’’ (62 FR 27132, May 16, 

1997) (FRL–5717–2). 

8. The docket identified by the docket 

control number OPP–300371A for the 

document entitled ‘‘Plant-Pesticides; 

Nucleic Acids; Supplemental Notice of 

Proposed Rulemaking’’ (62 FR 27142 

May 16, 1997) (FRL–5716–7). 

9. The docket identified by the docket 

control number OPP–300367A for the 

document entitled ‘‘Plant-Pesticides; 

Viral Coat Proteins; Supplemental 

Notice of Proposed Rulemaking’’ (62 FR 

27149, May 16, 1997) (FRL–5716–6). 

10. The docket identified by the 

docket control number OPP-300369A 

for the document entitled ‘‘PlantPesticides, Supplemental Notice of 

Availability of Information’’ (64 FR 

19958, April 23, 1999) (FRL–6077–6). 

11. The docket identified by the 

docket control number OPP-300368B for 

the document entitled ‘‘Exemption 

From the Requirement of a Tolerance 


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Under the Federal Food, Drug, and 

Cosmetic Act for Residues Derived 

Through Conventional Breeding From 

Sexually Compatible Plants of PlantIncorporated Protectants (Formerly 

Plant-Pesticides)’’ (66 FR 37830, July 19, 

2001) (FRL–6057–6). 

12. The docket identified by the 

docket control number OPP–300371B 

for the document entitled ‘‘Exemption 

from the Requirement of a Tolerance 

Under the Federal Food, Drug, and 

Cosmetic Act for Residues of Nucleic 

Acids that are Part of Plant-Incorporated 

Protectants (Formerly Plant-Pesticides)’’

(66 FR 37817, July 19, 2001) (FRL–

6057–5). 

13. The docket identified by the 

docket control number OPP–300369B 

for the document entitled ‘‘Regulations 

Under the Federal Insecticide, 

Fungicide, and Rodenticide Act for 

Plant-Incorporated Protectants 

(Formerly Plant-Pesticides)’’ (66 FR 

37772, July 19, 2001) (FRL–6057–7). 

14. The docket identified by the 

docket control number OPP-300370B for 

the document entitled ‘‘PlantIncorporated Protectants (Formerly 

Plant-Pesticides), Supplemental 

Proposal’’ (66 FR 37855, July 19, 2001) 

(FRL–6760–4). 

15. The docket identified by the 

docket ID number EPA–HQ–OPP–2006–

0642 for the companion document 

entitled ‘‘Exemption under the Federal 

Insecticide, Fungicide, and Rodenticide 

Act for Certain Plant-Incorporated 

Protectants Derived from Plant Viral 

Coat Protein Gene(s) (PVCP-PIPs)’’

(FRL–8100–7) published elsewhere in 

this issue of the Federal Register. 

16. The docket identified by the 

docket ID number EPA–HQ–OPP–2006–

0643 for this document (FRL–8100–5). 

Also included in the complete official 

public record are: 

• Public comments submitted in 

response to the proposals and 

supplemental documents cited in the 

above paragraphs. 

• Reports of all meetings of the 

Biotechnology Science Advisory 

Committee and the FIFRA Scientific 

Advisory Panel pertaining to the 

development of this final rule. 

• Support documents and reports. 

• Records of all communications 

between EPA personnel and persons 

outside EPA pertaining to the proposed 

rule. (This does not include any interand intra-agency memoranda, unless 

specifically noted in the indices of the 

dockets). 

• Published literature that is cited in 

this document. 

XIII. Statutory and Executive Order 

Reviews 

This proposed rule would establish an 

exemption from therequirement of a 

tolerance under section 408 of FFDCA. 

The Officeof Management and Budget 

(OMB) has exempted these types of 

actionsfrom review under Executive 

Order 12866, entitled Regulatory 

Planning and Review (58 FR 51735, 

October 4, 1993). Because this proposed 

rule has been exempted from review 

under Executive Order 12866, this 

proposal is not subject to Executive 

Order 13211, Actions Concerning 

Regulations That Significantly Affect 

Energy Supply, Distribution, or Use (66 

FR 28355, May 22, 2001) or Executive 

Order 13045, entitled Protection of 

Children from Environmental Health 

Risks and Safety Risks (62 FR 19885, 

April 23, 1997). This proposed rule does 

not contain any new information 

collections subject to OMB approval 

under the Paperwork Reduction Act 

(PRA), 44 U.S.C. 3501 et seq., nor does 

it require any special considerations 

under Executive Order 12898, entitled 

Federal Actions to Address 

Environmental Justice in Minority 

Populations and Low-Income 

Populations (59 FR 7629, February 16, 

1994). This action does not involve any 

technical standards that would require 

Agency consideration of voluntary 

consensus standards pursuant to section 

12(d) of the National Technology 

Transfer and Advancement Act of 1995 

(NTTAA) (15 U.S.C. 272 note). Pursuant 

to the Regulatory Flexibility Act (RFA) 

(5 U.S.C. 601 et seq.), the Agency 

previously assessed whether 

establishing tolerances, exemptions 

from tolerances, raising tolerance levels 

or expanding exemptions might 

adversely impact small entities and 

concluded, as a general matter, that 

there is no adverse economic impact 

associated with tolerance actions. The 

factual basis for the Agency’s generic 

certification for tolerance actions 

published on May 4, 1981 (46 FR 

24950). Since this proposed rule will 

not have an adverse economic impact, 

EPA hereby certifies under section 

605(b) of the RFA that this action will 

not have a significant adverse economic 

impact on a substantial number of small 

entities. Tolerance actions, such as this 

proposed exemption, directly regulates 

growers, food processors, food handlers 

and food retailers, not States or tribes. 

Tolerance actions do not alter the 

relationships or distribution of power 

and responsibilities established by 

Congress in the preemption provisions 

of section 408(n)(4) of FFDCA. As such, 

the Agency has determined that this 

action will not have a substantial direct 

effect on States or tribal governments, 

on the relationship between the national 

government and the States or tribal 

governments, or on the distribution of 

power and responsibilities among the 

various levels of government or between 

the Federal Government and Indian 

tribes. Thus, the Agency has determined 

that Executive Order 13132, entitled 

Federalism (64 FR 43255, August 10, 

1999) and Executive Order 13175, 

entitled Consultation and Coordination 

with Indian Tribal Governments (65 FR 

67249, November 6, 2000) do not apply 

to this rule. In addition, this rule does 

not impose any enforceable duty or 

contain any unfunded mandate as 

described under Title II of the Unfunded 

Mandates Reform Act of 1995 (UMRA) 

(Public Law 104–4). 

As with all aspects of its proposal, 

EPA invites your comments on these 

determinations. 

List of Subjects in 40 CFR Part 174 

Environmental protection, 

Administrative practice and procedure, 

Agricultural commodities, Pesticides 

and pests, Plants, Reporting and 

recordkeeping requirements. 

Dated: April 9, 2007. 

Stephen L. Johnson, 

Administrator. 

Therefore, it is proposed that 40 CFR 

part 174 be amended as follows: 

PART 174—[AMENDED] 

1. The authority citation for part 174 

would continue to read as follows: 

Authority: 7 U.S.C. 136–136y and 21 

U.S.C. 346a and 371. 

2. By adding § 174.477 to read as 

follows: 

§ 174.477 Plant virus coat protein portion 

of a PVCP-PIP (PVC-protein); exemption 

from the requirement of a tolerance. 

(a) Residues of a PVC-protein from a 

PVCP-PIP are exempt from the 

requirement of a tolerance if the 

encoded PVC-protein is virtually 

unmodified when compared to an entire 

unmodified coat protein from a virus 

that naturally infects plants that humans 

consume in toto or in part. 

(b) When the genetic material that 

encodes the pesticidal substance or 

leads to the production of the pesticidal 

substance has been modified (e.g., 

through internal deletions, addition of 

nucleotides from other virus coat 

protein genes, or substitutions leading 

to amino acid changes), residues of the 

PVC-protein may be exempt if the 

Agency determines, after review, that 

the encoded PVC-protein has been 


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minimally modified when compared to 

an entire unmodified coat protein from 

a virus that naturally infects plants that 

humans consume in toto or in part. 

(c) Agency determinations made 

under paragraph (b) of this section may 

be made in response to a petition 

submitted in accordance with the 

provisions of 40 CFR part 177 or on the 

Agency’s own initiative. 

[FR Doc. E7–7296 Filed 4–17–07; 8:45 am] 

BILLING CODE 6560–50–S 


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