UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

 WASHINGTON, D.C. 20460 

 OFFICE OF 

 PREVENTION, PESTICIDES 

 AND TOXIC SUBSTANCES 

 

By Mail

Jennifer Sass September 30, 2008 

Natural Resources Defense Council 

1200 New York Avenue, NW 

Suite 400 

Washington, DC 20005 

Re: NRDC’s comments on the Carbaryl IRED and petition to cancel registrations dated 

January 10, 2005 as well as petition to cancel carbaryl registrations dated November 26, 2007 

and submitted as part of NRDC’s comments to N-methyl carbamate cumulative. 

Dear Dr. Sass: 

This letter constitutes a partial response to the petition dated January 10, 2005 (Petition) 

submitted by the Natural Resources Defense Council (NRDC) requesting, among other things, 

that the Environmental Protection Agency (EPA or Agency) revoke all tolerances and cancel all 

registrations for carbaryl. As a preliminary matter, it should be noted that NRDC’s submission is 

in the form of comments on and requests for changes to the Carbaryl Interim Reregistration 

Eligibility Decision (IRED) published in the Federal Register on October 27, 2004 (69 Fed. Reg. 

62,663). Nonetheless, in the introduction to the comments, NRDC included a statement that 

NRDC is also petitioning the Agency to revoke all carbaryl tolerances and cancel all carbaryl 

registrations. Because of this statement in the introductory paragraph, EPA is responding to this 

submission as a petition rather than in a response to comments document. However, the Petition 

contains a number of assertions that constitute comments and that do not provide a basis upon 

which to either cancel all carbaryl registrations or revoke all carbaryl tolerances. This letter also 

serves as a partial response to NRDC’s reassertion of its Petition request submitted as part of 

NRDC’s comments on the N-methyl carbamate cumulative assessment and dated November 26, 

2007 (NMC Petition). 

I. Legal Framework 

EPA regulates pesticides under both the Federal Insecticide, Fungicide, and Rodenticide Act 

(FIFRA) and the Federal Food, Drug, and Cosmetic Act (FFDCA). FIFRA sets forth a federal 

licensing scheme for the sale, distribution and use of pesticides; FFDCA establishes the 

mechanism and standards by which EPA sets tolerances establishing allowable levels for 

pesticides in food. As a general matter, under FIFRA Section 3, before a pesticide can be 

distributed or sold in the United States, it must be registered by EPA. FIFRA Section 6 

authorizes EPA to cancel pesticide registrations that do not comply with FIFRA and, in certain 
circumstances, to suspend those registrations pending the completion of cancellation 

proceedings. Registration decisions related to non-dietary risks are governed by a “risk-benefit” 

standard; in order for EPA to register a pesticide, it must not pose “any unreasonable risk to man 

or the environment, taking into account the economic, social, and environmental costs and 

benefits of the use of any pesticide.” FIFRA §§ 2(bb) and 3(c)(5). This response only addresses 

non-dietary risk issues (dietary risk issues are being addressed in EPA’s response to the Petition 

to revoke carbaryl tolerances); whenever risks are being discusses in this document, we are 

referring to non-dietary risks. 

Because FIFRA imposes a risk-benefit standard, EPA’s decision to grant a registration (or find 

that a pesticide is eligible for reregistration) is not simply a matter of whether there are risks of 

concern, but rather whether those risks are reasonable in light of the benefits. In making 

pesticide registration decisions, EPA first typically looks to determine whether a particular use of 

an active ingredient poses a meaningful risk (often referred to as a “risk of concern”). If a use 

does not pose a risk of concern or if EPA concludes that its assessment overstates the risks such 

that the Agency determines the use will not cause any meaningful risk, EPA generally finds the 

use to be an acceptable one without looking at the benefits associated with the use. If the use 

does pose a risk of concern (either at first examination or upon further refinement of the risk 

estimate), EPA determines whether changes to the terms and conditions of use of the pesticide 

registration can feasibly and effectively mitigate the risk to acceptable levels. These changes can 

include changes to the directions for use on the product’s label (such as changes in application 

rates and methods, extending restricted entry times, requiring buffer zones where the pesticide 

may not be applied, or requiring protective clothing or equipment), or they can include changes 

to the pesticide’s formulation or packaging. If these changes are adopted voluntarily by a 

registrant, the use is then generally found to be acceptable. If a registrant does not agree to 

changes to the terms and conditions of a registration, or if effective changes cannot reasonably be 

implemented, the Agency then must determine whether the risks associated with the use are 

justified by the benefits associated with that use. If the Agency determines that cost-effective 

changes to the terms and conditions of registration are appropriate, or if the risks associated with 

the use are not justified by the benefits associated with that use, the Agency will initiate 

appropriate regulatory action under FIFRA section 6 unless the necessary changes (if any are 

possible) are made by the registrant. If, on the other hand, the Agency determines that the risks 

associated with a use are justified by the benefits, and no cost-effective changes to the terms and 

conditions of registration can be identified to mitigate those risks, the use would continue to meet 

the FIFRA standard for registration. 

 EPA decisions under section 408 of the FFDCA, on the other hand, are made through 

application of a risk-only safety standard. FFDCA §408(b)(2)(A) requires that the Agency make 

a finding that there is a “reasonable certainty of no harm” for each use of a pesticide associated 

with a pesticide tolerance. Where uses raise risk issues that are relevant under both FIFRA and 

the FFDCA, such as residential risks (which must be aggregated with dietary risks in 

determining whether a tolerance meets the FFDCA standard), EPA first looks to see whether 

tolerances meet the “reasonable certainty of no harm” standard. If affected tolerances meet this 

safety standard, the risks addressed in that determination would generally be considered to be 

acceptable without further mitigation required under FIFRA. If tolerances of a particular 

pesticide (or group of pesticides that share a common mechanism of toxicity) do not meet the 

safety standard, EPA must then determine whether to revoke or modify some or all of the 

- 2 -
tolerances relevant to that determination or, if possible and appropriate, take action under FIFRA 

to mitigate relevant risks so that any remaining tolerances meet the section 408 standard. 

A. Reregistration Eligibility Decisions 

In 1988, Congress amended FIFRA Section 4 to include a specific, five-phase process for the 

“reregistration” of pesticides containing any active ingredient contained in any pesticide first 

registered before November 1, 1984. Pub. L. 100-532, tit. I, § 102(a), 102 Stat. 2655, 2683 

(1988). In the fifth phase, EPA was required to review all the studies that have been submitted 

by the pesticide registrants for a pesticide active ingredient, as well as other relevant information, 

and decide whether or not pesticides containing the active ingredient(s) are “eligible” for 

reregistration under the risk-benefit standard in FIFRA Section 3(c)(5). After determining 

eligibility of the active ingredient, EPA must determine whether products containing these active 

ingredients and inert ingredients meet the risk-benefit standard in FIFRA Section 3(c)(5) and are 

eligible for reregistration under FIFRA § 4(g)(2)(B). To memorialize its reregistration decision, 

EPA typically issues a Reregistration Eligibility Decision (“RED”) document for each pesticide 

active ingredient being considered for reregistration. Before issuing a RED, EPA’s practice is to 

engage in a public participation process with various opportunities to comment (although FIFRA 

does not require such a comment opportunity) on the development of the risk assessments and 

risk mitigation that form the basis for the RED. When EPA issues a RED, it also typically issues 

a “data call-in” (DCI) under section 3(c)(2)(B) of FIFRA to acquire any needed product-specific 

data for the actual pesticide products that contain the active ingredients addressed in the RED. 

Following submission and review of these data and revised pesticide product labels, EPA must 

determine whether to reregister these products according to the FIFRA risk-benefit standard or 

take appropriate regulatory action. FIFRA § 4(g)(2)(D). 

B. Interim Reregistration Eligibility Decisions 

In 1996, the Food Quality Protection Act (“FQPA”) was enacted, amending FFDCA and 

FIFRA to require all pesticides whose use results in residues on food to meet new dietary risk 

standards. The FQPA also amended the FIFRA risk-benefit standard (“any unreasonable risk to 

man or the environment”) to add another element to the definition of that term: “a human dietary 

risk from residues that result from a use of a pesticide in or on any food inconsistent with the 

standard under [FFDCA Section 408].” FIFRA § 2(bb). 

FFDCA Section 408 requires EPA to establish, by regulation, tolerances (maximum legally 

permissible levels) for pesticide residues in foods. FFDCA § 408(b)(1). In other words, both 

registration and reregistration of a pesticide is contingent upon its meeting the food safety 

standard established under FFDCA Section 408 if use of the pesticide results in residues on food. 

When establishing, modifying, leaving in effect, or revoking the tolerance for a pesticide, EPA is 

required to consider whether there is a “reasonable certainty that no harm will result from 

aggregate exposures to the pesticide chemical residue . . . .” FFDCA § 408(b)(2)(A)(i). In 

conducting this assessment, EPA is required to consider, among other relevant factors, available 

information concerning the cumulative effects of such residues and other substances that have a 

common mechanism of toxicity applicable protecting human health. In its assessment, EPA 

considers the risks associated with the pesticide from aggregate exposures to residues on food 

- 3 -
and in drinking water as well as exposure from non-occupational uses (e.g., home and garden). 

Aggregate exposure encompasses exposures to other related substances, including substances 

that share a common mechanism of toxicity with the pesticide. FFDCA § 408(b)(2)(D)(v)-(vi). 

These “other” substances sharing a common mechanism of toxicity can and do include other 

pesticides.1 When EPA determines that a pesticide shares a common mechanism of toxicity with 

other substances, EPA cannot complete either the assessment or reassessment of a tolerance or a 

registration or reregistration determination until it has assessed available information regarding 

exposures to the other substances. In some instances, cumulative exposure assessments can take 

many years to complete – especially for those pesticides that may share a common mechanism of 

toxicity with a particularly large number of chemicals. For these pesticides, EPA’s practice is to 

issue an Interim RED (“IRED”) pending completion of the tolerance reassessment activities. As 

it customarily does with REDs, EPA generally affords the public an opportunity to comment on 

an IRED when it is issued.2 EPA often issues a mandatory call-in for data with the IRED. EPA 

uses DCIs to gather additional data to support reregistration decisions. An IRED memorializes 

EPA’s determination on a narrowly defined issue: whether a given active ingredient alone is 

eligible for reregistration under FIFRA Section 4, pending a cumulative assessment for 

pesticides sharing a common mechanism of toxicity. Often, IREDs delineate mitigation 

measures that would enable pesticide products to be eligible for reregistration. 

II. Background 

On June 30, 2003, the Agency completed an IRED for carbaryl, which was subsequently 

posted on EPA’s web site for public viewing. EPA published and made available for comment a 

revised IRED on October 27, 2004 (2004 Revised IRED or Carbaryl IRED). NRDC submitted 

its comments on the 2004 Revised IRED on January 10, 2005. In the introductory paragraph of 

their comments, NRDC included a statement that NRDC is also petitioning the Agency to revoke 

all carbaryl tolerances and cancel all carbaryl registrations. Insofar as NRDC’s comments 

purport to be a petition to revoke all carbaryl tolerances, the Agency published a notice of receipt 

of the petition to revoke all carbaryl tolerances for comment in the Federal Register on March 

30, 2005. (70 Fed Reg 16,281). 

In March 2005, EPA also issued generic and product-specific data call-ins (DCIs) for carbaryl. 

The generic DCI required several studies for the active ingredient carbaryl, including additional 

toxicology, worker exposure monitoring, and environmental fate data. The product DCI required 

acute toxicity and product chemistry data for all pesticide products containing carbaryl. EPA has 

received numerous studies in response to these DCIs, and, where appropriate, these studies have 

been considered in the revised risk assessments for both the N-methyl carbamate cumulative and 

for the carbaryl RED. 

In response to the DCIs, many carbaryl registrants chose to voluntarily cancel their carbaryl 

products. One technical registrant, Burlington Scientific, chose to cancel their technical 

 

1

 Carbaryl is an N-methyl carbamate pesticide. N-methyl carbamate pesticides have been determined to have a 

common mechanism of toxicity in the context of assessing human health risks. 2

 Although FIFRA requires EPA to determine whether pesticides are eligible for reregistration and to request the 

submission of additional data, EPA’s practice of preparing a RED or IRED extends above and beyond its statutory 

obligation. 

- 4 -
product,3

 leaving Bayer CropScience (Bayer) as the sole technical registrant for carbaryl. 

Approximately two-thirds of all of the carbaryl end-use products registered at the time of the 

initial carbaryl IRED (June 2003) have been canceled through this process.4

 

In June 2006, EPA determined that the uses associated with 120 of the existing carbaryl 

tolerances are not significant contributors to the overall N-methyl carbamate (NMC) cumulative 

risk and that these tolerances had no effect on the retention or revocation of other NMC 

tolerances. Therefore, EPA considered these 120 tolerances for carbaryl as reassessed on June 

29, 2006, and posted this decision on the internet site, 

http://www.epa.gov/pesticides/cumulative/carbamates commodity.pdf. On June 29, 2006, EPA 

also published a preliminary NMC cumulative risk assessment. 

 In late November 2006, EPA received data from a carbaryl comparative cholinesterase study, 

conducted to determine the comparative sensitivity of adults and offspring to cholinesterase 

inhibition by carbaryl. These data were used to revise the FQPA safety factor for carbaryl for the 

NMC cumulative risk assessment and to select new toxicology endpoints (points of departure) 

for the risk assessment. The Agency determined that it was appropriate to use the new FQPA 

safety factor and revised points of departure in both the NMC cumulative risk assessment and the 

carbaryl-specific human health risk assessment. Because this necessitated a revision of the 

carbaryl human health aggregate risk assessment, EPA also considered additional new data 

generated in response to the DCI, new methodologies, and other new information in performing 

its most recent assessment of carbaryl and in responding to this Petition. 

On September 26, 2007, EPA published a Notice of Availability for the NMC cumulative 

assessment and opened a 60 day public comment period on the cumulative assessment (72 Fed. 

Reg. 54,656). In conjunction with the NMC cumulative assessment, on September 24, 2007, 

EPA completed the carbaryl RED, which amended sections of the previously issued Carbaryl 

IRED based upon new data generated in response to the March 2005 DCI, a revised FQPA safety 

factor for carbaryl used in the NMC cumulative assessment, new methodologies, and other new 

information. The carbaryl RED was formally issued on October 17, 2007, with the publication 

of a Notice of Availability in the Federal Register (72 Fed. Reg. 58,844). EPA subsequently 

completed an addendum to the carbaryl RED, dated August 25, 2008, which incorporated the 

results of a revised occupational risk assessment and modified mitigation measures for the 

protection of workers. 

III. Petition Response 

To the extent that the carbaryl RED and revised ecological and occupational and human health 

risk assessments are not inconsistent with the reasoning in the various responses to NRDC’s 

Petition, EPA relies on those documents as well in responding to NRDC’s Petition to cancel 

carbaryl registrations. 

 

3

 EPA published a notice of receipt of a request for cancellation in the Federal Register on October 28, 2005 (70 Fed 

Reg 62,112), followed by a cancellation order issued on July 3, 2006. 

4

 Of approximately 300 carbaryl products registered in 2003, 208 product registrations have been canceled, and 4 

products have been suspended for failure to submit required product chemistry data. 

- 5 -
In terms of the issues addressed in this portion of EPA’s response to NRDC’s Petition, a 

number of the issues raised in the Petition were based upon the Carbaryl IRED and have either 

been addressed in subsequent revisions or are no longer applicable. In any event, the following 

is EPA’s response to the issues raised in the Petition and the NMC Petition relevant to NRDC’s 

contention that all carbaryl registrations should be cancelled for reasons unrelated to whether the 

carbaryl tolerances meet the safety standard of FFDCA section 408. 

A. Occupational Risks. 

NRDC raises a number of issues related to EPA’s occupational assessment. NRDC 

“recommends” that all uses be cancelled where margins of exposure (MOEs) are less than 100 

for occupational exposures. Specifically, NRDC argues that since EPA has not provided an 

adequate benefits justification for these uses, all of them should be cancelled. In addition, 

NRDC recommends that restricted entry intervals (REIs) be set so that the MOE is at least 100 

for high exposure post-application tasks. NRDC further “recommends” that EPA re-calculate its 

acceptable exposure levels, incorporating data from “recorded” worker exposure events for both 

handlers and post-application workers, including information regarding a 2003 incident in 

Florida and 2004 cholinesterase (ChE) medical monitoring data from Washington State. In so 

doing, NRDC argues that carbaryl is toxic and causes ChE inhibition at occupational exposure 

levels that EPA currently considers “safe,” even when carbaryl is used in accordance with 

current label directions. 

NRDC further criticizes EPA’s use of the Agricultural Re-Entry Task Force (ARTF) data, 

objecting to its use and requesting that EPA refrain from further use of this information until it 

has been fully evaluated by the FIFRA Scientific Advisory Panel (SAP) and subjected to public 

notice and comment. Among other things, NRDC asserts that EPA’s risk calculation methods 

underestimate occupational risk. 

1. Worker scenarios. 

NRDC identifies a number of specific agricultural scenarios for which the MOEs are less than 

100 in the 2004 Revised IRED.5

 NRDC also identifies a number of re-entry scenarios where the 

MOE is less than 100 at the time of REI established by the IRED. NRDC then mistakenly 

asserts that EPA has determined that MOEs of 100 or greater are “required” to ensure worker 

safety for short or intermediate term exposures. To the contrary, there may be circumstances 

where an MOE of less than the target number are acceptable. For example, where a use scenario 

has high benefits, where worker risk has been mitigated to the extent practical and feasible, or 

where EPA is confident that worker risks are overestimates, an MOE of less than the target may 

 

5

 For occupational risk assessments of threshold effects, the risk estimate is expressed as an MOE, which is 

compared with an MOE representing an exposure level that is considered to be not of concern. An MOE that is not 

of concern is generally considered to be a value greater than or equal to the product of all applicable safety factors 

for a pesticide. For example, if a pesticide needs a 10X factor to account for interspecies differences and 10X factor 

for intraspecies differences, the level of concern (LOC) would be an MOE of 100. To calculate the MOE for a 

pesticide, the lowest no observed adverse effect level (NOAEL) or point of departure (PoD) from the available 

studies is typically divided into human exposure to the pesticide. The higher the MOE, the less concern there is for 

a pesticide. Accordingly, if the LOCfor a pesticide is an MOE of 100, MOEs exceeding 100 would generally not be 

of concern. 

- 6 -
be acceptable. Nonetheless, in this case, as reflected in EPA’s 2007 revised occupational risk 

assessment and 2008 addendum to the carbaryl RED, the MOEs for all but one of the pesticide 

handler scenarios are now equal to or greater than the level of concern (an MOE of 100) with the 

mitigation specified. Further, post-application MOEs for re-entry workers are now ≥ 100 on the 

day of carbaryl application6 for the vast majority of crops and worker re-entry scenarios. EPA’s 

current MOE estimates for workers consider the mitigation established in the 2004 Revised 

IRED, exposure monitoring data7

 submitted for carbaryl, and revised toxicological endpoints 

(points of departure) for risk assessment. See Carbaryl: Revisions to Occupational Exposure 

and Risk Assessment, for details8

 (“2007 revised occupational assessment”). 

In the 2007 revised occupational assessment for carbaryl, the only handler scenario assessed 

by EPA that resulted in MOEs of less than the LOC of 100 was for an aerial application of a 

carbaryl bait formulation to control grasshoppers and Mormon crickets, which migrate in swarms 

and generally consume large amounts of vegetative matter in their path. These are serious 

episodic pests in the Western United States; in addition to causing severe crop loss, swarms of 

migrating insects decrease visibility to such an extent that they can cause automobile accidents. 

(See comments and photographs, EPA-HQ-OPP-2005-0077-26 and 29). 

The applicator MOE for this scenario is 36. However, the Agency believes that this value does 

not represent an unacceptable level of risk. First, the worker exposure estimate for this scenario 

is based upon data for a typical granular formulation, which consists of a carrier that releases the 

pesticide active ingredient when the formulation is applied. Carbaryl bait products used for 

grasshopper and Mormon cricket suppression consist of large extruded pellets composed of a 

homogenous blend of the pesticide active and inert ingredients. These pellets are tightly 

compressed, and not intended to release the active ingredient when the product is applied; 

instead, the entire pellet is intended to be consumed by the target pest. Second, the calculated 

exposures could overestimate risks because of the high number of acres considered in the 

assessment and the bias that occurs with such extrapolations. Moreover, the RED addendum 

specifies that for aerial application of carbaryl bait products, aircraft must have enclosed cockpits 

that are completely separate from the bait bins and the air intake vents for the cockpit must be 

located above the bait bins. (See 2008 RED addendum at 24). In addition, the carbaryl bait 

product is applied by highly trained handlers who are affiliated with state or Federal grasshopper 

and Mormon cricket suppression programs to further ensure proper use of the material. Finally, 

this is a high benefit use; carbaryl baits are the most effective pesticide product available to 

control both juvenile and adult grasshoppers and Mormon crickets which are severe pests in 

Western states. Thus, even if the MOEs are less than 100 for this use, EPA has concluded that 

the associated risks are not significant, and EPA has further determined that those risks are 

justified by the benefits for this particular use. 

 

6

 MOEs are ≥ 100 at 12 hours, indicating that the REI can be set at 12 hours for most crops and worker re-entry 

scenarios. 

7

 As part of the Generic Data Call-in, EPA received three occupational handler studies. EPA determined that two 

were acceptable: (1) Determination of Dermal and Inhalation Exposure to Workers during Application of a Liquid 

Pesticide Product by Open Cab Airblast Application to Orchard Crops. (MRID 464482-01) and (2) Determination 

of Dermal and Inhalation Exposure to Workers during Closed-System Loading and ULV Application of a Liquid 

Pesticide Product to Cotton.. (MRID 46634105). 8

 US EPA. Office of Pesticide Programs. 2007. Carbaryl: Revisions to Occupational Exposure and Risk 

Assessment. July 9, 2007. 

- 7 -
In the 2007 revised occupational assessment, all but two re-entry scenarios resulted in MOEs > 

100 at the post-application time for the REI established by the 2004 IRED. Therefore, many of 

these REIs will be adjusted to reflect the findings of the revised occupational assessment. One 

scenario with MOEs < 100 is for workers hand-harvesting cut flowers on the day of application 

(MOEs from 23 - 48) in regions where rainfall is < 25 inches per year (i.e., west of the 

Mississippi River). The MOE for cut flowers reaches 100 on day 18 after carbaryl application; 

therefore, EPA is establishing an REI of 18 days for cut flowers, including ornamentals grown 

for cuttings, where production is in outdoor areas where annual rainfall average is less than 25 

inches per year. The second scenario involves workers conducting very high contact activities of 

grape cane turning and girdling (MOE of 31 on the day of carbaryl application), which did not 

reach 100 until 6 days after application. However, these MOEs are for very high contact 

activities which generally only occur in grape culture west of the Rocky Mountains. Therefore, 

for grapes grown east of the Rocky Mountains, EPA is maintaining an REI of 48 hours and 

prohibiting the very high contact activities of cane turning and girdling until 6 days after carbaryl 

application. The REI for grapes grown west of the Rocky Mountains is established at 6 days for 

all reentry activities. 

Finally, NRDC mentions use scenarios where the IRED did not present MOEs due to a lack of 

data (i.e., animal grooming dust applications, dust applications in agriculture, hand-held fogger, 

power backpack sprayer, dipping/drenching seedlings, and tree injection). EPA found the animal 

grooming use ineligible for reregistration in the IRED, and this use was subsequently canceled. 

EPA required worker exposure monitoring studies for the remaining scenarios lacking data to 

derive MOEs in the March 2005 Generic DCI, which was sent to the two sole technical 

registrants of carbaryl, Bayer and Burlington Scientific. In response to the DCI, Burlington 

Scientific submitted a request to voluntarily cancel their registration for carbaryl technical 

pursuant to FIRFA section 6(f). EPA published a notice of receipt of this request in the Federal 

Register on October 28, 2005 (70 Fed. Reg. 62,112), followed by a cancellation order issued on 

July 3, 2006. Bayer, the sole remaining technical registrant responsible for developing data, 

requested waivers of these studies because these use scenarios are not on any Bayer technical or 

product labels (or were to be deleted from Bayer labels). Bayer subsequently requested that all 

of their carbaryl registrations bearing any of these uses be amended to delete these uses.9

 EPA 

published a Notice of receipt of this request in the Federal Register on August 20, 2008 (73 Fed. 

Reg. 49,184), and plans to approve Bayer’s request and issue a final order amending these 

registrations at the end of the comment period for the Notice. The Bayer product registrations 

will be formally amended to delete these uses by December 31, 2008. Because Bayer is not 

developing data to support the use scenarios mentioned above, EPA does not have sufficient 

information to reregister products bearing these uses on current labels, and cannot find these 

products eligible for reregistration unless the uses are deleted from product labels. Therefore, 

EPA has notified all affected registrants that these uses and application methods must be deleted 

from their carbaryl product labels. EPA has identified 54 product labels from 14 registrants 

(other than Bayer) bearing these end uses. All of these registrants have requested that their 

affected carbaryl product registrations be amended to delete these uses. EPA published the first 

Notice of Receipt of these requests from 12 registrants representing 45 products in the Federal 

Register on August 20, 2008. EPA expects the second Notice of Receipt covering the remaining 

 

9

 August 4, 2008 letter from Danielle LaRochelle, Bayer CropScience to EPA’s Office of Pesticide Programs, 

Special Review and Reregistration Division. 

- 8 -
3 registrants and their 9 products to be published in the very near future. The Agency plans to 

approve these requests after their respective comment periods close. 

 

2. Worker exposure incidents. 

NRDC claims that EPA failed to consider actual worker poisoning events at occupational 

exposure levels that EPA considers to not be of concern. NRDC recommends that EPA recalculate its acceptable exposure levels, incorporating data from “recorded” worker exposure 

events for both handlers and post-application workers. Specifically, NRDC insists that EPA 

failed to consider an incident that occurred in Florida. Similarly, NRDC claims that EPA failed 

to consider monitoring data from Washington State, asserting that carbaryl is toxic and causes 

ChE inhibition even when used according to the label instructions. 

In response to requests from NRDC, Farmworker Justice, and other stakeholders, EPA’s 

Office of Pesticide Programs prepared a report on the use of incident data in the pesticide 

program. This report was presented to the Pesticide Program Dialogue Committee (PPDC) at its 

October 17, 2007 public meeting. This document, OPP Report on Incident Information: The 

Baseline (“PPDC Incident Report”), may be found on EPA’s website at the following URL: 

http://www.epa.gov/oppfead1/cb/ppdc/2007/oct2007/session10-finalrpt.pdf

As explained in detail in the document prepared for the PPDC, incident data provide valuable 

qualitative information to EPA and available data are used in the Agency’s regulatory decisions. 

For example, incident data may provide a perspective on potential risks of a pesticide compared 

to other pesticides with a similar use. Incident data may be used to confirm the effectiveness of 

risk mitigation measures, or indicate where additional mitigation is needed, such as a change in 

product packaging. Likewise, human incident data may indicate pesticide misuse and the need 

for enforcement action. Furthermore, worker incident data may indicate where additional worker 

outreach and training are needed to increase awareness and understanding of safe use of 

pesticides. However, most incident data have limitations that prevent their use in quantitative 

risk assessment, as requested by NRDC. 

a) Florida incident 

NRDC asserts that EPA failed to consider an alleged carbaryl incident that occurred in Florida 

in April 2003. Specifically, on April 9, 2003, 21 farm workers were taken to emergency rooms 

of two hospitals near Duette, FL, after a number of harvesters (14) complained of difficulty 

breathing, headaches, dizziness, and nausea. Two workers appeared to be more affected than the 

others. One worker reported continuing symptoms for weeks after the incident and was 

ultimately successful in bringing a Workman's Compensation claim related to this incident. 

NRDC asserts that a finding by a Florida workman’s compensation judge is incontrovertible 

evidence that carbaryl was in fact the cause of the worker’s injuries. Thus, NRDC argues that 

EPA failed to consider that actual worker “poisonings” occur at occupational exposure levels 

that EPA currently considers “safe” when establishing REIs for carbaryl. 

First, EPA did consider the Florida incident. In fact, EPA conducted its own investigation and 

assessed reports and investigations conducted by the Florida Department of Health, which is 

- 9 -
affiliated with the NIOSH SENSOR10 Program, and the Florida Department of Agriculture and 

Consumer Services. Second, EPA disagrees that the “findings of fact” made by an 

administrative judge based upon the preponderance of the evidence considered in the particular 

preceding before him is dispositive for purposes of a rigorous risk assessment grounded in 

scientific data.11 Third, based upon the aforementioned investigations combined with what is 

known about the field conditions, worker activities, the toxicity of carbaryl, the carbaryl residue 

levels in the groves, and the fact that the symptoms were relatively non-specific (and could fairly 

be attributed to other causes), it does not appear that the incident is directly related to a labeled 

use of carbaryl. Indeed, based upon its assessment of carbaryl, EPA does not believe that the 

cause of the incident could have been use of carbaryl in accordance with the label. Fourth, even 

if carbaryl had been the cause of this incident, the reduced application rates and REI specified in 

the IRED and the RED addendum provides additional assurance that this situation will not be 

repeated when carbaryl is used in accordance with the label instructions. 

EPA’s Region 4 Office in Atlanta, Georgia, had the lead for the Agency’s investigation of the 

worker incident that occurred in Florida in April 2003 among workers of Dunson Harvesting 

Company that was allegedly attributed to exposure to carbaryl. EPA Headquarters staff were 

also involved in all stages of the investigation, which began in April 2003 when the Agency 

received media reports of the incident. Bayer, the carbaryl registrant, submitted a report of the 

incident on May 29, 2003, as required under FIFRA Section 6(a)(2) (the adverse effects 

reporting provision).12 When EPA initially completed the carbaryl IRED in June 2003, the 

investigations of both the Florida Department of Health and the Florida Department of 

Agriculture and Consumer Services (DACS) were underway and neither agency had drawn any 

conclusions other than Dunson Harvesting had violated the Worker Protection Standard.13 The 

Florida DACS completed its report on the analysis of residues on citrus foliage and estimated 

exposure to the workers harvesting citrus on August 15, 2003; the report concluded that exposure 

to carbaryl would not be responsible for acute toxicity to workers under the conditions 

evaluated.14 Although carbaryl residues were measured on citrus foliage, neither EPA nor 

Florida DACS could determine whether these residues were consistent with the SevinTM 80S 

label. The Florida Department of Health, Pesticide Surveillance Unit, completed its 

investigation in August 2004, concluding that there was a possible association between the 

symptoms of 18 of the 21 affected workers and carbaryl exposure, but there was insufficient 

 

10 NIOSH, National Institute for Occupational Safety and Health, Sentinel Event Notification System for 

Occupational Risks. The NIOSH SENSOR program is designed to monitor occupational poisonings via community 

environmental health personnel in various locations throughout the United States, including Universities and State 

Departments of Health. 

11 The EPA Region 4 case file summary addresses the specific issues raised by the pleadings in the workman’s 

compensation court case in more detail. See: Corbett, Richard and Jeanneane Gettle, EPA Region 4. Case File 

Summary [for] Farm-OP 64, Duette, FL. April 20, 2005. 12 Wolford, Valerie. Bayer Crop Science. 6(a)(2) report re: SEVINTM Brand Carbaryl Insecticide. Letter to EPA, 

Office Of Pesticide Programs. May 29, 2003. 

13 The Florida Department of Agriculture and Consumer Services, Bureau of Compliance Monitoring, issued a 

citation to Dunson Harvesting on June 25, 2003, for violations of the Federal Worker Protection Standard. 

14 Daiker, Davis. Florida Department of Agriculture and Consumer Services. Division of Agricultural 

Environmental Services, Bureau of Pesticides, Scientific Evaluation Section. Data Interpretation/Risk Assessment 

Regarding Potential Carbaryl Incident in Manatee County. August 15, 2003. 

- 10 -
information for the remaining 3 workers to make an association.15 The Florida Department of 

Health based its analysis on a comparison of symptoms reported by the Dunson Harvesting 

Company workers with typical symptoms associated with carbamate poisoning. However, there 

are other possible causes of such symptoms, and the pesticide application records, carbaryl 

product labels in effect, and measured carbaryl residue levels on citrus foliage at the site of the 

incident do not support a cause and effect relationship between the application of carbaryl and 

the symptoms reported by the workers. EPA completed its investigation in spring 2005; the 

results of this investigation were shared by the Director of EPA’s Office of Pesticide Programs 

with representatives of NRDC and Farmworker Justice at a meeting held in August 2005. 

The major confounding factor with respect to the effects reported by the workers is that the 

information available to the various agencies investigating the case was very limited. To 

establish worker exposure to carbaryl, clothing of the ill workers should have been analyzed for 

carbaryl residues. However, the Hazardous Materials (HAZMAT) team that responded to the 

incident on April 9, 2003, removed and destroyed workers’ clothing as part of the 

decontamination process; therefore, the clothing was unavailable for analysis for pesticide 

residues. In addition, worker blood ChE levels taken within one or two hours of worker 

exposure could corroborate exposure to a carbamate pesticide such as carbaryl. However, blood 

samples taken from the affected workers to measure ChE levels were taken several hours after 

exposure, and therefore were likely to have been too late to detect any effects from carbaryl.16 

Consequently, an analysis of blood samples for ChE depression did not confirm or rule out 

carbaryl exposure. Last, the presence of the carbaryl biomarker N-napthol in the urine of 

affected workers could have confirmed exposure; however, no urine samples were collected 

from the workers to measure levels of this biomarker. 

No new data in regard to this incident have been submitted. Thus, the information available to 

the Agency does not appear to support a conclusion that the severity of symptoms reported by 

Florida citrus harvesters in April 2003 can be attributed to carbaryl exposure resulting from 

contact with foliar residues. EPA will continue to monitor reports of worker incidents with 

pesticides including carbaryl. EPA notes that the Florida DACS issued a citation17 to the 

company that employed the harvesters for a violation of the Worker Protection Standard for a 

violation of the training requirements of the Worker Protection Standard and Florida state law. 

Florida determined that several of the injured workers had not been trained on how to protect 

themselves from exposure to pesticides. 

b) Washington State Cholinesterase Monitoring Program 

 

15 Becker, Alan. Florida Department of Health, Bureau of Community Environmental Health, Pesticide 

Surveillance Program. Powerpoint slides on occupational exposure to carbaryl and April 9, 2003 Florida farm 

worker incident. August 16, 2004. 

16 According to the handbook, Recognition and Management of Pesticide Poisonings (5th Edition,1999), “...unless a 

substantial amount of N-methyl carbamate has been absorbed and a blood sample is taken within an hour or two, it 

is unlikely that blood cholinesterase levels will be found depressed. Even under the above circumstances, a rapid 

test for enzyme activity must be used to detect an effect, because enzyme reactivation occurs in vitro as well as in 

vivo.” 17 Bronson, Charles (Florida Commissioner of Agriculture). Administrative Complaint and Warning Letter to 

Dunson Harvesting. June 25, 2003. 

- 11 -
NRDC takes issue with the fact that EPA did not include worker ChE monitoring data from 

Washington state in the Carbaryl IRED. NRDC claims that these data demonstrate that carbaryl 

causes ChE inhibition even when used according to the label instructions. The Agency was 

unable to consider the data from the Washington State cholinesterase monitoring program for the 

Carbaryl IRED because the data were not available for EPA to review. However, since the data 

first became publicly available in January 2005, the Agency has closely followed the annual 

results from the Washington ChE monitoring program and considered whether it had any impact 

on the carbaryl decision. Accordingly, any request to cancel carbaryl registrations based upon 

EPA’s alleged failure to consider ChE monitoring data from Washington State is misplaced. 

The Washington monitoring program was initiated through rulemaking by Washington state’s 

Department of Labor and Industries in December 2003; handler ChE monitoring did not begin 

until January 2004. EPA completed the carbaryl worker risk assessment and IRED decision in 

2003 and published the Amended Carbaryl IRED in October 2004. The first draft report of the 

Washington State Monitoring Program was issued in January 2005. The final report for the first 

year of the Washington Department of Labor and Industries Medical Monitoring program was 

released in March 2005. 

Specifically, starting in January 2004, Washington state required that employers offer medical 

monitoring of baseline and periodic red blood cell and plasma ChE levels for all handlers 

working with toxicity category I or II organophosphate and/or carbamate pesticides for 50 hours 

or more in a consecutive 30-day time period. Red blood cell and serum ChE levels of handlers 

meeting the aforementioned exposure criteria were monitored. The program did not then, and 

does not now, require monitoring of handlers that handle only NMC pesticides such as carbaryl 

because these compounds cause only temporary, reversible ChE inhibition that is not likely to be 

detected with monitoring. From the beginning of the program, handler participation in 

monitoring was voluntary. 

In January 2005, the program criteria were changed to require that growers offer ChE 

monitoring for pesticide handlers exposed for 30 or more hours in a consecutive 30-day period. 

If handlers chose to be monitored, handlers showing a 20% depression of ChE levels triggered a 

workplace audit; those showing a 30% depression in ChE levels were removed from work that 

could cause further exposure until their ChE levels returned to within normal limits. These 

criteria remain the same today.18 The workplace audit requires the employer to evaluate their 

worker protection program and employee pesticide handling practices, and to document this 

audit and all measures to reduce potential pesticide exposure. A January 10, 2008 directive from 

the Washington Department of Labor and Industries states that in cases where ChE depression > 

20% occurs, an employer’s failure to evaluate his worker protection program and correct 

potential sources of pesticide exposure is considered to be a violation of the rule.19 

The Washington State program was designed to identify overexposure to pesticides prior to the 

onset of illness so that interventions could be taken to prevent further pesticide exposure that 

could result in illness. The program also monitors the efficacy of an employer’s pesticide safety 

and worker protection programs. The program was not designed to provide data for use in 

quantitative worker risk assessments, such as those conducted by EPA’s Office of Pesticide 

 

18 See the document, Washington State Department of Labor and Industries 2007. Cholinesterase Monitoring of 

Pesticide Handlers in Agriculture: 2007 Final Report (December 24, 2007). 19 http://www.lni.wa.gov/Safety/Rules/Policies/PDFs/WRD3327.pdf 

- 12 -
Programs. For EPA to use the Washington program data in risk assessment, the program would 

need to monitor handlers exposed to carbaryl alone, with monitoring conducted on a daily or 

hourly basis. In addition, evaluation of ChE levels from a control group, who followed all 

pesticide handling and worker protection measures correctly, would be needed. In sum, although 

EPA reviewed data from the Washington state monitoring program, these data do not provide 

information on pesticide handlers exposed to carbaryl alone, and are therefore of limited utility 

for purposes of a rigorous, quantitative occupational risk assessment. 

The Agency continues to monitor the results of the Washington program, which show that the 

percentage of handlers showing 20% or more depression of ChE declined from 2004 to 2006, 

following education and outreach. Although a similar decline was not observed in the reported 

data for 2007, a change to the program has been identified that impacted the outcome. 

Specifically, laboratory services were transferred from the Washington State Public Health 

Laboratory (PHL) to the Pathology Associates Medical Laboratories (PAML). A review of test 

and quality control data indicated that red blood cell ChE testing by the new lab was less precise 

than that achieved by PHL, which affects the accuracy of test results. Taking this test variability 

into account, it is likely that the number of over-exposures remained at the same level or 

declined in 2007 compared to prior years. 

3. Agricultural Re-Entry Task Force (ARTF) data 

NRDC expressed concern about EPA use of a methodology for establishing a transfer 

coefficient and estimating field worker exposure to pesticides developed by the ARTF, a task 

force comprised of pesticide registrants. NRDC criticizes EPA for using the ARTF methodology 

in setting REIs for field workers because neither the ARTF protocols nor the data have been fully 

reviewed by the EPA’s FIFRA SAP. NRDC also expressed concern that the sampling 

methodology employed in the ARTF studies would underestimate worker exposure. 

The issues NRDC raises with respect to EPA’s use of data from the ARTF have been 

addressed in a number of different forums, including a joint letter to Farmworker Justice and 

NRDC dated July 7, 2007 and a more recent letter to Farmworker Justice dated January 10, 2008 

(“Farmworker Justice Letter”). Since NRDC’s Petition was filed, EPA has also presented issues 

related to use of the ARTF data to two external peer review groups: the FIFRA SAP and the 

Human Studies Review Board (HSRB). It should also be noted that the monitoring methods 

used have been included in the Agency’s guidelines for conducting exposure monitoring studies 

since the 1980s and that the method used to calculate risk estimates used in the determination of 

REIs was also described in those original guidelines. 

In summary, the studies sponsored by ARTF have been conducted in accordance with the 

established Office of Prevention Pesticides and Toxic Substances (OPPTS) guidelines for 

Worker Post-application Exposure Studies and in accordance with good laboratory practice. See

40 C.F.R. § 160. EPA conducted joint reviews of protocols used in the ARTF studies with two 

other independent regulatory agencies: California’s Department of Pesticide Regulation and 

Health Canada’s Pesticide Management Regulatory Agency. EPA has reviewed the study 

reports submitted by the ARTF before using the information in new risk assessments. These 

reviews have led EPA to conclude that the studies were conducted in a scientifically sound 

manner and the resulting data were valid. Therefore, EPA has concluded that the estimates of 

the transfer coefficients and residue dissipation curves using ARTF data were appropriate for the 

- 13 -
use in the carbaryl assessment supporting the Carbaryl IRED and in the 2007 revised carbaryl 

occupational risk assessment. 

Although NRDC asserts that the methodology chosen by the ARTF to collect residue samples 

underestimates exposure, NRDC has not provided any information in its Petition to support this 

assertion. This issue was vetted before the FIFRA SAP in January 2007 and the Agency’s 

HSRB in various recent meetings including June 2007. This issue is also addressed in the 

aforementioned letters to Farmworker Justice and NRDC. In addition, NRDC asserts that the 

ARTF categorization of crops and tasks leads to underestimation of exposure for the carbaryl 

risk assessment. Although EPA does not believe it is required to do so before using the data in a 

risk assessment for an individual pesticide, the Agency plans to present the ARTF groupings of 

crops and tasks to the FIFRA SAP in December 2008. 

In connection with its criticism of EPA’s use of the ARTF data, NRDC also asserts that EPA 

has underestimated the duration of worker exposure, both in terms of hours worked per day and 

days per year. NRDC asserts that “many” handlers and field workers “routinely work 10-12 

hour days for 6 to 7 days/week.” Petition at 5. NRDC then cites the US Department of Labor’s 

National Agricultural Worker Survey (NAWS) (2000), which reports that 56% of crop workers 

work 31-50 hours per week and 15% work more than 50 hours per week. NRDC further 

criticizes EPA’s assumption of 10 days per year for private growers and 30 days per year for 

commercial farmworkers, asserting that many farmworkers are on crews that work 6 days a week 

for weeks if not months at time. 

Regarding the matter of hours worked, EPA has concluded that the assumed 8 hour duration 

for a work day is appropriate for estimating seasonal exposures. This value is consistent with the 

average 40 hour work week for harvesting fruit and nut crops reported in the findings from the 

NAWS 2001-2002. It should be noted that the issue of workday duration and its impact on the 

results of exposure assessment will be a specific element in the charge to the panel at the 

December 2008 FIFRA SAP meeting. 

The Agency disagrees with NRDC that its current approach to estimating workers’ postapplication exposures underestimates high end exposure levels. When discussing whether to 

change one of the assumptions or input values used in the algorithm to assess exposure, it is 

important to consider how such a change would affect the overall tendency of the algorithm to 

overestimate or underestimate exposure. EPA calculates workers’ post-application exposure to 

pesticides using the assumption that workers will receive exposure for 8 hours per day for many 

weeks. 

EPA agrees that exposure depends, at least to some extent, on the number of hours a person 

works and that longer work hours probably leads to more exposure. However, hours worked is 

only one of several variables EPA considers when assessing multi-day, post-application worker 

exposure. The Agency’s algorithm also uses other variables, including the levels of pesticide 

residues available in sites where people will be working (generally dislodgeable foliar residues 

(DFR)), amount of contact a worker has with treated foliage while performing various tasks 

(transfer coefficients, (TCs)), and dermal absorption factors which are used when comparing 

worker exposure to doses from oral toxicity studies. 

When assessing exposure to agricultural pesticides, EPA relies on DFR dissipation data based 

on the maximum application rate. This is clearly an upper bound assumption. To the extent that 

a grower applies less pesticide to a site than is allowed by the label, or rain occurs between the 

- 14 -
time of pesticide application and the time a crop is harvested, the actual DFRs encountered by a 

worker would be lower, and thus the algorithm could overstate those workers’ potential 

exposure. Further, EPA assumes that the worker always enters a treated site at the earliest 

possible opportunity following application, i.e., at the expiration of any REI. EPA determines 

the level of dislodgeable residues on that day and uses the value as the input to the exposure 

algorithm. This too is an upper bound assumption. If a worker enters a treated site one or more 

days after the REI has expired, the residues to which he or she will be exposed would be 

expected to be lower (e.g., from degradation, rain, etc.) than the values used in the exposure 

algorithm. 

In addition, the TCs EPA uses are arithmetic means based on the highest exposure values 

measured for a worker conducting a certain type of activity, such as harvesting, pruning, or 

watering. Many of these TCs are based on individuals wearing short-sleeved shirts in which 

exposure to the forearm includes the inner and outer cotton dosimeter measurements representing 

the lower arm. Thus, these values also represent high-end inputs to the exposure algorithms. If a 

worker wears clothing or gloves that afford greater protection, he or she will receive less 

exposure than estimated by the exposure algorithm. The range of activity-specific TCs is also 

presented in the Science Advisory Council for Exposure policy 3.1 on the use of TCs20; the TCs 

used by EPA consistently fall in the higher end of the reported ranges. 

EPA calculates MOEs for re-entry workers using the methodology previously described in this 

document, by comparing estimates of worker exposure to a NOAEL or point of departure (PoD). 

If the toxicity studies used to derive dermal MOEs are conducted by the oral route of exposure, 

estimates of dermal absorption are generally made based on dermal penetration studies in the rat 

or comparisons of lowest observable adverse effect levels (LOAELs) from dermal and oral 

studies showing similar toxic effects. In the carbaryl IRED, EPA used a dermal absorption 

factor. For the revised carbaryl risk assessment, EPA used data from an in vitro comparative 

dermal penetration study using rat skin and human skin. These data were used to determine the 

relative dermal absorption for carbaryl in rats and humans. Details may be found in the June 28, 

2007 document, Carbaryl: Review of in vitro Dermal Absorption Study. (See Docket EPA-HQOPP-2007-0941-005). 

The Agency’s exposure algorithm makes the additional conservative assumption that, 

throughout the period over which exposure is being assessed, the worker engages in the same 

activity at different sites treated with the same pesticide. In general, to the extent the worker 

does not perform the same activities or works at sites treated with different pesticides, he or she 

will receive less exposure to the particular pesticide than is assumed in Agency risk assessments. 

However, with respect to carbaryl, recent data indicates that ChE inhibition is reversible, with 

recovery in less than 24 hours and, therefore, daily exposure is independent of the previous day’s 

exposure. Thus, for the occupational risk assessment, the daily exposure (short and intermediateterm) to carbaryl is the main duration of concern. 

In summary, since most of the assumptions and data inputs used in the exposure algorithm are 

either upper bound or high-end, EPA has concluded that the resulting estimates tend to overstate 

the potential exposure received by many workers. Further, EPA believes it is relatively unlikely 

 

20 US EPA. 2000. Science Advisory Council for Exposure, Policy 3.1 – Agricultural Transfer Coefficients. August 

7, 2000. This policy is periodically updated and is currently scheduled for review at the FIFRA SAP in December 

2-5, 2008. 

- 15 -
that there are many workers whose actual activities correspond to the conditions reflected in 

exposure estimates being generated by EPA, such as: 

• working continuously over extended periods (typically from three to 13 weeks) in sites 

treated with the same pesticide; 

• always performing the same type of activity at treated sites; 

• always working in sites that have been treated with the maximum allowed application 

rate; 

• every day entering a new treated site on the day that the REI expired; and 

• always wearing the clothing associated with the highest TCs. 

The Agency recognizes that if there are workers who meet each of the conditions specified 

above and who work more than an average of 8 hours per day, their actual exposure could 

potentially exceed that calculated by EPA. However, the Agency believes that such situations 

are unlikely to exist and therefore our current methodology does not underestimate exposures to 

workers, even where the main duration of concern is daily exposure. 

B. Ecological assessment 

In several places, NRDC points out that for aquatic and terrestrial wildlife, EPA’s ecological 

assessment finds that the risk quotients (RQs) for certain uses exceed EPA’s “level of concern” 

(LOC). Petition at 7-12. NRDC then mistakenly asserts that therefore these uses present an 

unreasonable risk, requiring further mitigation. Furthermore, NRDC asserts that EPA’s analysis 

of carbaryl concentrations in urban drainage systems underestimates exposure because it predates the cancellation of consumer uses for diazinon and chlorpyrifos. NRDC further contends 

that data show that sales of residential carbaryl products increased as diazinon and chlorpyrifos 

sales declined in advance of their phase-out dates for these uses. NRDC then finds fault with the 

Agency for not providing an adequate benefits assessment for the increased use of carbaryl. In 

addition, with respect to mammals and aquatic invertebrates, NRDC requests that EPA rerun all 

its exposure models with the mitigation specified in the Carbaryl IRED to ensure the proposed 

mitigation will adequately reduce estimated environmental concentration (EEC) values and then 

recalculate RQs. See Petition at 7-12. 

 EPA used a screening methodology for the carbaryl ecological risk assessment. This 

methodology is used as a barometer of risk to screen out use patterns that are not of risk concern 

so that the Agency can focus further attention on use patterns that may be of concern. An RQ 

exceeding a LOC in and of itself does not necessarily indicate a risk of concern; rather it 

indicates a potential area of risk concern. Further, it is not always possible for EPA to quantify 

reduction in potential ecological risk gained through mitigation using the currently available 

screening-level methodologies. In addition, EPA’s screening level risk assessment is but one 

line of evidence considered in the Agency’s carbaryl decision. For example, ecological incident 

data, which provide information about actual observed effects of carbaryl in the field also can 

provide valuable information, based on the nature of specific circumstances surrounding the data. 

- 16 -
1. Level-of-Concern (LOC) exceedances 

NRDC asserts that throughout the ecological assessment EPA has determined that the RQs 

exceed the Agency’s LOC with the implication that therefore carbaryl presents unreasonable 

risks. Petition at 8-10, 16. However, an LOC exceedance in and of itself does not necessarily 

mean that there is an actual risk of concern. Indeed, the LOCs for a screening assessment, as 

was done for carbaryl, are meant to screen out uses that are not of concern; not to determine 

definitively whether certain uses of carbaryl actually cause adverse effects on non-target 

organisms. Cancellation is not the only option available for uses that do not pass the screen; the 

Agency could refine the risk assessment, apply mitigation, or conclude that the effects are not 

unreasonably adverse, and take no further action. 

a. Estimates of Ecological Risk 

As a general matter, after the RQs are calculated, they are compared to the Agency’s LOC. 

These RQs are used by EPA to analyze potential risk to non-target organisms and the need to 

consider regulatory action. These levels are used to indicate when a pesticide use, as directed on 

the label, has the potential to cause adverse effects on non-target organisms. The Agency 

generally uses RQs to determine potential risk by comparing them to the LOC: 

• Acute Effects to Non-target Organisms (acute RQ > 0.5 for aquatic animals, mammals, 

birds); 

• Acute Effects to Federally-listed Threatened/Endangered Species (acute RQ > 0.05 for 

aquatic animals or 0.1 for mammals and birds); 

• Chronic Effects to Non-target Organisms (chronic RQ > 1 for all animals); 

• Acute Effects to Non-listed Plant Risk (RQ >1); and 

• Acute Effects to Federally-listed Threatened/Endangered Plant Risk (RQ>1). 

The Agency may determine that notwithstanding the results of its Tier I screen, further 

refinements are likely to show that the actual risk is significantly less than originally predicted, 

allowing the Agency to make a qualitative determination that the pesticide will not likely cause 

unreasonable adverse effects on the environment. This qualitative assessment may be further 

informed by the extent and nature of ecological incident data and monitoring data. Finally, the 

Agency may determine that, on balance, the benefits are sufficient to conclude that, 

notwithstanding LOC exceedances, usage of a pesticide does not cause unreasonable adverse 

effects on the environment. 

 b. Use of Ecological Incident Data 

EPA reviews available data on ecological incidents to provide an additional perspective on 

potential ecological risks. As noted in the environmental fate and ecological risk assessment 

(USEPA 200421) written in support of the interim reregistration eligibility decision and most 

recently in the endangered species effect determination for the California red-legged frog (Rana 

 

21 USEPA. 2004. Interim Reregistration Eligibility Decision Document for Carbaryl. 

http://www.epa.gov/oppsrrd1/REDs/carbaryl_ired.pdf

- 17 -
aurora draytonii) (USEPA 200722), relatively few of the reported incidents on carbaryl could 

actually be attributed to labeled use of the compound. 

The incident data available when the carbaryl IRED was completed showed one fish kill, 

where the total number of fish killed is not specified, and one bird kill involving a single bird 

that can be attributed to the registered use of carbaryl.23 As a frame of reference to aid in the 

interpretation of the carbaryl incident data, for diazinon, 492 incidents were reported in the EIIS 

(USEPA 200724), while 399 and 256 incidents were reported for carbofuran (USEPA 200825) 

and azinphos-methyl (USEPA 200726), respectively. Although the absence of incident reports 

cannot be construed as the absence of incidents, the available data suggest that given the current 

uses of carbaryl the incident data, although limited, provides a line of evidence that risk 

estimates provided in the screening-level assessment are relatively conservative. The data on 

ecological incidents of carbaryl provide an additional perspective on the RQ exceedances. 

Fish. With respect to ecological incidents involving fish reported in the EIIS, a total of three 

fish-kill incidents were reported for carbaryl. Only one of those incidents, report #B0000-501-92, 

could be credibly associated with a specific carbaryl use, i.e., to control gypsy moth in New 

Jersey. 

Birds. A total of five incidents involving birds have been reported; however, only two of the 

five can be clearly attributed to carbaryl and only one of those two could be linked to a specific 

registered use. The remaining incidents appear to have been associated with either intentional 

poisoning or the co-occurrence of much more toxic pesticides. In one incident (I012817-001) a 

single mourning dove (Zenaida macroura) was discovered dead; the animal exhibited reduced 

acetyl ChE activity and had 2.4 mg/kg of carbaryl in its stomach contents. The report suggests 

that birdseed around a feeder had become contaminated after carbaryl was applied to the 

property owner’s lawn. In a second incident (I000802-001), five blackbirds were discovered 

dead. No residue analysis was conducted on the birds but carbaryl residues were detected in a 

dead squirrel found in the vicinity; acetyl ChE activity was not reduced in the squirrel. While 

these incidents do not provide substantial evidence that carbaryl is impacting birds in the wild, 

they do suggest uncertainty regarding the sensitivity of passerine species to carbaryl, compared 

to birds such as bobwhite quail and mallard duck, for which the Agency has laboratory toxicity 

studies and associated data. 

Mammals. Although the EIIS database reported two possible incidents involving carbaryl 

exposure to mammals, neither of these incidents could be attributed to a specific use of carbaryl. 

Of the two incidents reported, one (I000802-001) involved a gray squirrel (Sciurus carolinensis) 

 

22 USEPA. 2007 Risks of Carbaryl Use to the Federally-Listed California Red Legged Frog (Rana aurora 

draytonii) Pesticide Effects Determination. http://www.epa.gov/espp/litstatus/effects/redlegfrog/carbaryl/determination.pdf. 23 There are however, a number of reported beekill incidents (approximately 41); however, of these, only two are 

clearly linked to a specific use of carbaryl where carbaryl residues have been detected in the dead bees. 24 USEPA 2007. Risks of Diazinon Use to the Federally Listed California Red Legged Frog (Rana aurora 

draytonii) Pesticide Effects Determination. http://www.epa.gov/oppfead1/litstatus/effects/redlegfrog/index.html#diazinon 25 USEPA 2008. Scientific Issues Associated with the Agency’s Proposed Action under FIFRA 6(b) Notice of 

Intent to Cancel Carbofuran. Presented to the FIFRA Science Advisory Panel meeting held on February 5, 2008. 

http://www.epa.gov/scipoly/sap/meetings/2008/february/transcript2008-02-05.pdf. 26 USEPA 2007. Risks of Azinphos-methyl Use to the Federally Listed California Red Legged Frog. 

http://www.epa.gov/oppfead1/endanger/litstatus/effects/redleg-frog/azinphos-methyl/analysis.pdf 

- 18 -
and a second involved a hairytail mole (Parascalops breweri). In neither case was information 

provided on the use of carbaryl that may have resulted in the deaths of these animals. 

Bees. A total of five bee kill incidents related to carbaryl were reported in the EIIS database in 

March 2003, when the ecological risk assessment supporting the carbaryl IRED27 was completed 

and subsequently published for comment. Two of the reports (I005855-001 and B0000-300-03) 

do not contain any data but rather reflect general concerns expressed by the American Beekeeper 

Federation and the Honey Industry Council on the role of pesticides in bee kills. The Honey 

Industry Council cited the specific use of carbaryl on alfalfa during the day. In North Carolina 

(incident #I003826-021), a bee mortality was associated with 0.8 ppm carbaryl residues; 

however, in a second incident (#I003826-009) in North Carolina, bee mortality was more likely 

attributed to methyl parathion than carbaryl. Only in one incident (I001611-002) was the use of 

carbaryl on a specific crop, i.e., asparagus in Washington, clearly associated with carbaryl 

residues in dead bees. 

Subsequent to the publication of the 2003 ecological risk assessment, EPA received public 

comments reporting numerous additional bee kill incidents associated with the use of carbaryl 

dating back to the 1990s.28 Commenters included migratory beekeepers with operations in 

Minnesota and California and beekeeper associations. The majority of these reported incidents 

occurred in Washington state and may have been associated with a range of carbaryl uses. 

Additional incidents were reported in Minnesota and were associated with the use of one 

formulation of carbaryl, Sevin® XLR, on poplar tree plantations. 

The low number of bee kill incidents captured in the EIIS as of March 2003 underscores that 

the absence of reports should not be construed as the absence of incidents. However, as an 

insecticide, carbaryl’s high acute toxicity to bees is not unexpected. Carbaryl product labels 

contain bee warning statements. Formulations of carbaryl, e.g., Sevin® XLR Plus, have also been 

developed to reduce the toxicity of the insecticide to beneficial insects. Thus, the fact that 

carbaryl use has been associated with a number of bee kill incidents dating back to the 1990s 

alone is not inconsistent with the Agency’s understanding of potential risks. It should be noted, 

however, that these previously unreported incidents have not undergone internal Agency review 

to determine the extent to which they could actually be attributed to carbaryl. A preliminary 

review of the incident data indicated that other pesticides besides carbaryl were used in the 

vicinity and some of these pesticides are considerably more toxic to bees than carbaryl. 

 2. Ecological Risk Concerns for Carbaryl 

As a preliminary matter, EPA disagrees with NRDC’s characterization that the RQs for 

carbaryl are “extremely elevated” such that they “pose an unreasonable risk.” Petition at 8. To 

the contrary, and as discussed in more detail below, the screening-level RQs for carbaryl do not 

lead to a conclusion that significant effects are expected for aquatic life and wildlife species and 

their associated ecosystems. Single and even double digit exceedances of LOCs by screeninglevel RQs do not per se pose an unreasonable risk. Rather, such levels indicate a potential risk 

concern that may warrant further evaluation, taking into consideration other lines of evidence. In 

 

27 USEPA 2003. Revised EFED Risk Assessment of Carbaryl in Support of the Reregistration Eligibility Decision 

(RED). March 18, 2003. 

28 See Docket EPA-HQ-OPP-2003-0101, items numbered 037, 042, and 043, comments submitted to EPA in June 

2003. 

- 19 -
addition, EPA has assessed the use of carbaryl and determined that in addition to specific high 

benefit uses, carbaryl’s broad spectrum pest control, low cost, benefits to integrated pest 

management and short pre harvest interval (PHI) provide benefits to agriculture. Thus, in 

evaluating carbaryl, EPA has taken into account not just the LOC exceedances but also the level 

of refinement of the assessment, other lines of evidence (for example incident and monitoring 

data), the economic and social benefits of the use of carbaryl as well as the mitigation set forth in 

the carbaryl IRED and RED, and determined that the use of carbaryl does not cause unreasonable 

adverse effects on the environment. 

 a. Level of Refinement and Lines of Evidence 

Aquatic Organisms. The scenario modeled for the screening assessment for aquatic organisms 

is conservative, consistent with its intention as a screen for adverse effects that could occur in 

vulnerable aquatic ecosystems. The modeled water body is a 1-hectare, 2-meter deep pond 

located directly adjacent to a treated field, which is a surrogate for a subset of vulnerable aquatic 

ecosystems. The models used simulate the inflow of runoff water into the pond, but no outflow. 

As a result, EECs for chronic exposure reflect degradation of the pesticide, and partitioning to 

bottom sediment, but not removal of pesticide residues via outflow from the pond. Fish and 

invertebrates living a further distance from treated areas would be exposed to a lesser extent than 

those living closer to treated areas, and many species will not spend their entire lives in one area 

within the water body. These assumptions are a reasonable reflection of the nature of exposure 

for certain vulnerable water bodies, for example stretches of headwater streams near treatment 

areas. The modeling scenario, however, does not simulate downstream changes in 

concentrations in such water bodies. 

The simulation of carbaryl application in the screening model is also conservative, 

representing a subset of vulnerable aquatic environments. The 10-hectare field in this scenario is 

assumed to be completely planted with the treated crop, and 100% of the crop is treated with 

carbaryl. The locations of the modeling scenarios were chosen for each crop to simulate soils 

with a high vulnerability for surface-water runoff (and therefore transport of the pesticide to the 

pond). These assumptions are reasonable on the scale of individual fields treated in vulnerable 

portions of the carbaryl agricultural use area, but variability in both soil type and the percentage 

of a crop treated are introduced at larger scales. While estimates of percent crop treated are not 

available at a scale that can be used quantitatively in calculating RQs, incorporating this concept 

would reduce the overall fraction of the vulnerable aquatic systems that would be impacted. 

Because of these conservative assumptions, the Agency is confident that the modeling 

approach can screen out uses that will not pose an unreasonable risk to aquatic organisms. This 

does not mean, however, that uses which do not pass the screen will pose a risk to aquatic 

organisms in carbaryl use areas. While some treated fields will be adjacent to water bodies as 

simulated, attenuation of pesticide residues in the runoff water from fields that are not adjacent 

to water bodies will reduce exposure to aquatic organisms. In the 2004 IRED the Agency 

summarized carbaryl monitoring data as an additional line of evidence in the risk assessment. 

That assessment indicated that although carbaryl was the second most widely detected 

insecticide in surface water in the U. S. Geological Survey’s (USGS) National Water Quality 

Assessment (NAWQA) monitoring program, concentrations overall were lower than those 

estimated in modeling. 

- 20 -
The Agency re-evaluated available monitoring data on carbaryl from the USGS NAWQA 

program (from 1999 – 2005) in the aforementioned 2007 California red-legged frog assessment, 

again comparing concentrations measured with model estimates. At a national scale, carbaryl 

was detected in 28% of samples (4288 of a total of 15,534 samples). Further analysis of the 

detections shows that 19 (0.4% of detections) were sufficient to exceed the non-listed aquatic 

invertebrate LOC (i.e., 0.85 μg/L). This is 0.1% of all samples collected. These exceedances 

occurred in a variety of surface waters with watersheds classified as: urban (10 of 19), 

agricultural (7 of 19) and other (2 of 19) in Washington, Texas, Virginia, California, 

Massachusetts, Connecticut, Colorado, Oregon, and Pennsylvania. The maximum measured 

concentration of carbaryl was 33.5 μg/L . The overall conclusion was that the higher detection 

frequency in urban streams (versus agricultural or mixed land uses) was consistent with data 

summarized in the 2003 assessment and that concentrations detected in urban streams (mostly 

low concentrations, a few detections in the multiple μg/L range), were also consistent with 

earlier data. 

The California red-legged frog assessment also evaluated RQ exceedances based on the 

California surface water monitoring. Based on that dataset of the 1393 total samples 

representing all land uses analyzed by gas chromatography-mass spectrometry (GCMS), 0.072 

percent (1 sample) contained levels of carbaryl sufficient to exceed the LOC for acute exposures 

to aquatic invertebrates (i.e. 0.85 μg/L); while none of the 99 total samples analyzed by highperformance liquid chromatography (HPLC) contained levels sufficient to exceed the LOC for 

aquatic invertebrates. The concentration of carbaryl in California urban watersheds was 

sufficient to exceed the LOC for acute exposures to aquatic invertebrates in 0.64 % of samples (1 

of 157 samples) analyzed by GCMS. These data represent another line of evidence of risk 

associated with carbaryl use and confirm the 2003 assessment that the screening-level risk 

assessment represents risks for a subset of vulnerable aquatic ecosystems where carbaryl is used. 

 

Exposure to Terrestrial Organisms. Although the risk assessment for terrestrial animals 

included a consideration of typical application rates, a number of conservative assumptions 

remain in the carbaryl screening-level risk assessment. For example, the Agency assumes that 

100% of the feed items consumed by terrestrial animals are treated with the pesticide under 

consideration, at the maximum label rate, maximum reported rate, and typical use rate for each 

crop. The terrestrial risk assessment assumes that the modeled species occupy the treated field 

100% of the time. Also, spray drift modeling indicates that birds or mammals living adjacent to 

the treated field will be exposed to 50% of the applied pesticide, with exposure declining to 1% 

of the application rate at a distance of 990 feet for a fine-to-medium spray. Therefore, while 

terrestrial organisms outside the treated area might be exposed to carbaryl, it would be at levels 

below those used to calculate the RQs. 

 b. Effects on Specific Taxa 

 (i) Birds 

With respect to birds, NRDC criticizes the Agency for not fully evaluating the potential for 

carbaryl to pose an acute risk to birds, despite incidents where birds were killed by carbaryl. 

- 21 -
Petition at 8. NRDC thus requests that EPA perform this type of assessment. NRDC further 

asserts that continuing to allow granular formulations is “likely to lead to harmful exposures to 

birds.” Petition at 8. In addition, NRDC asserts that studies from the open literature were 

omitted from the assessment and NRDC requests that these be included. 

None of these assertions are a basis for canceling all carbaryl registrations. Moreover, 

contrary to NRDC’s assertion, EPA has assessed acute mortality to birds. Specifically, available 

toxicity data for carbaryl, based on testing of game birds and waterfowl, shows no acute 

mortality to birds. In an acute toxicity study with mallard ducks, no mortality was seen at the 

highest dose tested, 2000 mg/kg. Therefore, the acute LD50 for mallard ducks is > 2000 mg/kg. 

Additional studies in ring-necked pheasant and California quail showed similar results (i.e., acute 

LD50 > 2000 mg/kg). In a subacute toxicity study with the same species, no effects were seen at 

5000 mg/kg, the highest dose tested; the sub-acute 5 day LD50 is therefore > 5000 ppm. Similar 

results were also seen in Northern Bobwhite quail, Japanese quail, and ring-necked pheasant (5 

day LC50 was > 5000 ppm for all species tested). Therefore, because the available toxicity data 

did not indicate that carbaryl would cause unreasonable adverse effects on birds following acute 

exposure, the Agency did not calculate acute avian RQs for carbaryl. If acute RQs had been 

calculated, the acute RQ would be less than 0.1, and not of concern. 

With respect to granular formulations, EPA has noted previously in this response that the 2007 

carbaryl RED requires watering in for granular formulations used on residential turf. This is 

expected to dissolve the granule and move the pesticide into the thatch layer of the turf where it 

is intended to kill insect pests. In dissolving the granule and moving it away from the surface, 

the chemical is less accessible to non-target animals and thus less likely to result in adverse 

effects on non-target animals. Since exposure is reduced, risk would also be reduced. Also, the 

acute oral and subacute dietary avian toxicity studies for carbaryl are just as relevant to granular 

formulations as to liquid formulations. 

Moreover, EPA did in fact conduct a comprehensive review of the available literature on the 

effects of carbaryl on non-target species. See Revised EFED Risk Assessment of Carbaryl in 

Support of the Reregistration Eligibility Decision (RED) (March 18, 2003). EPA conducted an 

additional literature search in both 2006 and 2007 to support two formal consultations with the 

U.S. National Marine Fisheries Service and the U.S. Fish and Wildlife Service (the Services) on 

endangered species, i.e., Barton Springs salamander29 and the California red-legged frog30. 

Indeed, in its revised ecological risk assessment, EPA noted that some passerine species such as 

starlings and red-winged black birds may be more sensitive to carbaryl than mallard duck, 

bobwhite quail and other bird species mentioned above. Id. However, although two studies in 

the published literature suggest that carbaryl may be moderately toxic to ring necked pheasants 

and red-winged blackbirds, and highly toxic to starlings, these data are based on simple 

screening tests, do not meet EPA data quality criteria, and are therefore not appropriate for use in 

risk assessment. In any case, to address potential uncertainty, EPA will consider an additional 

acute avian toxicity study for passerine birds. This study is a new requirement in the 2008 

revised data requirements to support pesticide registrations (see 40 CFR part 158, as amended), 

 

29 US EPA. 2007. Risks of Carbaryl Use to the Federally Listed Endangered Barton Springs Salamander (Eurycea 

sosorum). http://www.epa.gov/oppfead1/endanger/litstatus/effects/carbaryl/esa-assessment.pdf 30 US EPA. 2007 Risks of Carbaryl Use to the Federally-Listed California Red Legged Frog (Rana aurora 

draytonii) Pesticide Effects Determination. http://www.epa.gov/espp/litstatus/effects/redlegfrog/carbaryl/determination.pdf. 

- 22 -
and the need for this study will be evaluated in the problem formulation and risk assessment 

scoping for the registration review of carbaryl, scheduled to commence in 2010. 

Finally, with respect to incidents involving birds, NRDC has not identified any incidents that 

can be attributed to carbaryl that EPA failed to consider such that either EPA would change its 

assessment or determine that all carbaryl registrations should be canceled due to avian risks. As 

noted previously in this document and in the Revised EFED Risk Assessment of Carbaryl in 

Support of the Reregistration Eligibility Decision31, there is one incident in the EIIS involving 

birds related to the residential use of carbaryl. This incident resulted in the loss of a single bird. 

The relative absence of avian incidents supports the laboratory data indicating that carbaryl is 

practically nontoxic to birds on an acute oral and subacute dietary exposure basis. 

 (ii) Mammals 

With respect to mammals, NRDC asserts that EPA must adjust the mitigation so that 

“mammals are not harmed by carbaryl use” and rerun the risk assessment models based upon the 

mitigation set forth in the IRED. Petition at 8. Neither of these assertions are a basis for 

canceling all carbaryl registrations. First, FIFRA simply does not require that EPA ensure that 

non-target mammals “are not harmed.” With respect to ecological risks, EPA does not make a 

“safety” finding. Rather, EPA must determine that the pesticide does not cause unreasonable 

adverse effects on the environment, taking into account the economic, social, and environmental 

costs and benefits of the use of the pesticide. Second, requesting that EPA reassess carbaryl 

using different modeling assumptions is not a basis for cancellation. As noted previously, for 

mammals, none of the incidents reported in the EIIS data could be associated with a specific use 

of carbaryl. These data represent an additional line of evidence to indicate that carbaryl is not 

adversely affecting mammals on an acute oral or subacute dietary exposure basis in spite of 

conservative modeling scenarios that result in RQ values exceeding acute risk LOCs. 

 (iii) Fish 

With respect to fish, NRDC notes that acute and chronic RQ values were only exceeded for the 

citrus use. Petition at 9. NRDC is also “extremely concerned” with the state of EPA’s 

knowledge of incidents and request that EPA provide more detail regarding reported incidents. 

Petition at 9. Again, with respect to fish, NRDC’s petition does not provide a basis upon which 

to cancel all carbaryl registrations. Simply noting that the RQs are above the Agency’s screening 

LOC for a specific use is not a basis upon which to conclude that all uses of carbaryl cause 

unreasonable adverse effects on the environment. 

EPA used sensitive toxicity endpoints to evaluate risk as well as characterizing effects based 

on species sensitivity distributions for fish and invertebrates in the 2003 IRED. Also, in the 

carbaryl endangered species assessment conducted for the California red-legged frog (USEPA 

2007)32, EPA used an acute toxicity endpoint used for assessing risk to freshwater vertebrates, a 

96-hr LC50 of 250 μg/L which is roughly two times lower than the lower 95th percentile for the 

freshwater vertebrate acute toxicity sensitivity distribution (i.e., a 96-hr LC50 of 472 μg/L ). The 

LC50 toxicity values in the distribution ranged from 250 μg/L (highly toxic) to 20,000 μg/L 

(slightly toxic). Carbaryl was moderately toxic (96-hr LC50 range: 1,000 – 10,000 μg/L) to 78% 

 

31 See docket EPA-HQ-OPP-2003-0101. 

32 US EPA. 2007 Risks of Carbaryl Use to the Federally-Listed California Red Legged Frog (Rana aurora 

draytonii) Pesticide Effects Determination. http://www.epa.gov/espp/litstatus/effects/redlegfrog/carbaryl/determination.pdf. 

- 23 -
of the fish tested. As such, the use of this toxicity estimate of 250 μg/L results in a conservative 

assessment of risk, since the data suggest that the majority of aquatic vertebrates will be less 

sensitive to carbaryl. The range of RQs for fish calculated in the IRED using the most sensitive 

96-hr LC50 of 250 μg/L and maximum use rates was 0.09 to 0.61. The range of RQs for the 

mean of the sensitivity distribution (96-hr LC50 of 1.28 mg/L) calculated with EECs from 

maximum use rates is 0.02 to 0.12, all of which are below the acute LOC for non-listed species. 

The range for the least sensitive of the species calculated with EECs from maximum use rates is 

0.001 to 0.007, all of which are below the acute LOC for listed and non-listed species 

 Similarly, the fact that incident data are imperfect and in many cases lacks sufficient detail to 

be useful in a rigorous risk assessment is not a basis for cancellation. While NRDC has 

expressed concern regarding the state of EPA’s knowledge of incident data, the ecological risk 

assessment provides a detailed description of the carbaryl-associated data in the EIIS. As 

discussed previously in this response, the incident data provide some indication that relative to 

carbaryl’s use patterns, the number of reported incidents is low. 

 (iv) Aquatic invertebrates 

With respect to aquatic invertebrates, NRDC asserts that the RQ’s are “extremely high,” and 

requests that EPA rerun its models using as the base assumptions the mitigation set forth in the 

RED to “assure itself and the public” that the proposed mitigation is “adequate” to protect 

aquatic invertebrates. Petition at 9; see also Petition at 16. In so doing, NRDC notes that no 

aquatic ecosystem can survive without invertebrates. NRDC also “encourages” EPA to ensure 

that chronic toxicity data for estuarine/marine invertebrates are received and reviewed in a timely 

manner and that the results are incorporated into its determinations. NRDC also notes that EPA 

has not established water quality criteria for carbaryl. 

Again, with respect to aquatic invertebrates, NRDC’s petition does not provide a basis upon 

which to cancel all carbaryl registrations. Simply noting that the RQ values exceed the Agency’s 

screening LOC is not a basis upon which to conclude that all uses of carbaryl cause unreasonable 

adverse effects on the environment. As discussed previously in this response, the screening level 

modeling scenario used to evaluate risk provides a conservative estimate of exposure 

representing a subset of vulnerable ecosystems. In addition, although analysis of over 15,000 

surface water samples from the NAWQA monitoring program indicated that carbaryl was 

detected fairly frequently in a variety of ecosystems, only 0.4% of detections (0.1% of all 

samples collected) were sufficient to exceed the non-listed aquatic invertebrate LOC (i.e., 0.85 

μg/L) for the most sensitive invertebrate considered in the IRED. 

Also, while certain invertebrates may be particularly sensitive, and the RQs are derived using 

the most sensitive invertebrate in the Agency’s database, the distribution of species sensitivities 

suggests that the majority of invertebrates are considerably less sensitive to carbaryl. The acute 

toxicity estimate used for freshwater invertebrates (Daphnia magna EC50 of 1.7 μg/L) is at least 

a factor of 2X more sensitive than the other aquatic invertebrates (total of 9 species representing 

7 genera) for which data were available (96-hr EC50 range: 1.7 - 26 μg/L). The range of RQs for 

invertebrates calculated in the IRED using the most sensitive 96-hr EC50 of 1.7 μg/L, and 

average use rates, was 2 to 23. The range of RQs for invertebrates calculated in the IRED using 

the least sensitive 96-hr EC50 of 26 μg/L and average use rates is 0.13 to 1.5, with 60% of the 

RQs below the acute risk LOC for non-listed species. Based on the available information, the 

conservative use of the toxicity endpoints for the most sensitive species appears to be consistent 

- 24 -
with the relatively low number of reported ecological incidents associated with the use of 

carbaryl and the low concentrations of carbaryl in surface water detected by the USGS. 

 The Agency bases its decision not to cancel all carbaryl registrations on the screening-level 

assessment as informed by other lines of evidence, such as the species sensitivity distribution, an 

evaluation of concentrations found in monitoring data, and the benefits of carbaryl. Insecticides 

are made to control invertebrates so it is not unexpected that carbaryl is toxic to aquatic 

invertebrates if there is sufficient exposure in the environment. However, based upon available 

toxicity data, the Agency concludes that while there could be effects (e.g., mortality) to some 

aquatic invertebrate species in a subset of vulnerable waterbodies, not all species would be 

affected. In addition, existing monitoring data indicate it is unlikely that concentrations of 

carbaryl in surface water will be consistently high enough to exceed the LOC for the most 

sensitive aquatic invertebrate species. Therefore, EPA has determined that, with respect to 

aquatic invertebrates, carbaryl will not cause unreasonable adverse effects on the environment. 

Furthermore, the exposure and effects data described above do not support NRDCs contention 

that carbaryl use will cause the elimination of entire invertebrate communities as suggested. 

Although EPA does not have chronic toxicity data for estuarine/marine invertebrates, the 

Agency does not believe that carbaryl is likely to present a chronic risk concern because it 

degrades very rapidly at pH levels found in marine and estuarine environments. Nevertheless, 

EPA will revisit the data needs for carbaryl during the problem formulation and risk assessment 

scoping process for the carbaryl registration review, which is scheduled to be initiated in 2010. 

Finally, the fact that EPA’s Office of Water has not established water quality criteria for carbaryl 

is not a basis for canceling all carbaryl registrations. 

 (v) Amphibians 

With respect to amphibians, NRDC asserts that EPA did not include an assessment of 

information in the open literature in its assessment of amphibians. Petition at 9. In particular, 

NRDC references a “recently” available study (Relyea and Mills 2001) on tadpoles and predator 

cues. The Agency has reviewed the Relyea and Mills article referred to by NRDC entitled 

"Predator-induced stress makes the pesticide carbaryl more deadly to gray treefrog tadpoles 

(Hyla versicolor)" published in the February 2001 issue of the Proceedings of the National 

Academy of Science. The Agency concluded that while the paper indicates that carbaryl was 2 to 

4 times more lethal to gray treefrogs in the presence of a predator, that conclusion is confounded 

by the potential effects of water quality on mortality. In addition, the Agency did not concur 

with the author's contention that their protocol is indicative of "more realistic ecological 

conditions" than the Agency’s current battery of acute and chronic toxicity tests; all of these 

studies are conducted under rigidly controlled laboratory conditions and are not intended to be 

representative of all of the variables that may affect the toxicity of a compound in the field. 

For instance, it is difficult to design a study that can accurately reflect field conditions and 

particularly predator-prey relationships. Typically, prey demonstrate predator avoidance 

behavior in the presence of a perceived threat. In this study, tadpoles were unable to escape their 

perceived threat; predatory cues, i.e., seeing a predator (visual cues) may have protracted their 

response well beyond the chemical cues released following the salamander's consumption of 

tadpoles. It is questionable whether tadpoles would have remained in view of a potential 

predator under more realistic conditions. In refined ecological assessments, the Agency 

sometimes has mesocosm study data available to assess the risk of pesticides under "field 

- 25 -
conditions." These studies, while considerably more expensive that the Relyea and Mills 

protocol, may represent the most accurate reflection of controlled field studies. It is interesting 

to note though that while mesocosm studies may yield LC50 values similar to laboratory studies, 

they rarely provide LC50 values showing enhanced toxicity. Test species within these studies are 

better able to rely on compensatory mechanism to shield themselves from the toxic effects of 

chemicals. 

In addition to reviewing the Relyea and Mills paper, and contrary to the assertions of NRDC, 

EPA did in fact conduct a comprehensive review of the available literature on the effects of 

carbaryl on non-target species. See Revised EFED Risk Assessment of Carbaryl in Support of 

the Reregistration Eligibility Decision (RED) (March 18, 2003). EPA conducted an additional 

literature search in both 2006 and 2007 to support two formal consultations with the U.S. Fish 

and Wildlife Service (USFWS) on endangered species, i.e., Barton Springs salamander33 and the 

California red-legged frog.34 These assessments relied on fish as surrogates for aquatic phase 

amphibians. As discussed in these assessments, the fish toxicity estimate used to evaluate risks 

to amphibians was the most sensitive toxicity endpoint available. Consideration of the mean 

toxicity value from the species sensitivity distribution results in a range of RQs (at maximum 

application rates) below the acute risk LOC for non-listed fish, and below the acute risk to 

endangered species LOC for some fish included in that distribution. As noted in the more 

refined assessment for the California red-legged frog, none of the amphibian toxicity data were 

considered sufficiently robust to use quantitatively for risk assessment purposes; however, the 

available data indicate that both aquatic-phase and terrestrial-phase amphibians are orders of 

magnitude less sensitive to carbaryl than fish. 

Nevertheless, whether or not the Agency considered information available in the open 

literature with respect to amphibians, which in this case it has, is not a basis for canceling all 

carbaryl registrations. 

 (vi) Bees 

With respect to bees, NRDC “recommends” that EPA review its bee caution statement to 

determine if it can be improved to “match the intent of the law and protect pollinators.” Petition 

at 7-8. Specifically, NRDC recommends that EPA modify the second sentence of the label 

caution to prohibit application to blooming crops or weeds. In addition, NRDC “requests” that 

EPA require data on chronic exposure to bees and that EPA provide documentation that its 

mitigation proposals are adequate. Finally, NRDC requests that EPA provide more detail 

regarding reported incidents, including whether label instructions were followed. 

EPA agrees that pollinators provide an essential ecological function in both agriculture and 

wildlife ecosystems. However, merely because carbaryl is highly toxic to bees is not a basis for 

canceling all carbaryl registrations. Similarly, recommending that EPA impose certain label 

instructions is again not in and of itself a basis for canceling all carbaryl registrations. 

Nevertheless, EPA is evaluating alternative language to protect pollinators and bees in particular 

while balancing the benefits of carbaryl to agricultural industries such as apple growers (who 

 

33 US EPA. 2007. Risks of Carbaryl Use to the Federally Listed Endangered Barton Springs Salamander (Eurycea 

sosorum). http://www.epa.gov/oppfead1/endanger/litstatus/effects/carbaryl/esa-assessment.pdf 34 US EPA. 2007. Risks of Carbaryl Use to the Federally-Listed California Red Legged Frog (Rana aurora 

draytonii) Pesticide Effects Determination. http://www.epa.gov/espp/litstatus/effects/redlegfrog/carbaryl/determination.pdf. 

- 26 -
depend on carbaryl for thinning fruit early in the season). EPA has concluded that appropriate 

label instructions allow carbaryl to continue to be used without causing unreasonable adverse 

effects on bees. 

Specifically, EPA will be requiring updated environmental hazard statements for most carbaryl 

product labels, such as the following: 

• “This product is highly toxic to bees exposed to direct treatment or residues on crops or 

weeds in bloom;” 

• “Do not apply this product to target crops or weeds in bloom;” 

• “Limiting application to times when bees are least active, e.g., within 2 hours of sunrise 

or sunset, will minimize risk to bees;” and 

• “Notifying beekeepers within 1 mile of treatment area at least 48 hours before product is 

applied will allow them to take additional steps to protect their bees.” 

In addition, EPA will be requiring additional precautions under the directions for use of 

carbaryl on specific crops. Furthermore, carbaryl dust formulations, shown to be the most 

hazardous to bees, will no longer be used in agriculture (73 Fed. Reg. 49,184 (August 20, 2008)). 

The carbaryl bee labeling will vary by formulation type because the data on pesticide toxicity 

to honeybees indicate that formulation type is a significant predictor of a pesticide’s potential 

hazard to bees.35 The Agency has concluded that this revised labeling provides sufficient 

protection of pollinators. Although EPA considered additional measures, such as mandatory 

notification of beekeepers before carbaryl application and prohibition of carbaryl application 

during certain times of day, which could theoretically further protect pollinators, the Agency 

does not consider these to be feasible on a national basis and therefore is not requiring these 

measures on carbaryl labels at this time. Many states do not register bee hives nor have a 

notification system in place, so notification would be impossible because the location of hives is 

not known. Nonetheless, the revised carbaryl labeling will also contain advisory language, such 

as the examples given above, regarding notification and application timing. In addition, EPA 

continues to work with the North American Pollinator Protection Campaign (NAPPC) on 

protecting pollinators from potential adverse effects of pesticides. 

As mentioned previously, EPA disagrees with the underlying premise behind NRDC’s request 

for documentation with respect to the adequacy of the bee label statement. Again, EPA 

disagrees with the implication that before EPA can impose mitigation the Agency must have 

empirical evidence that the mitigation will provide a certain, measurable result. To the contrary, 

EPA can impose mitigation both when there is empirical evidence to support a specific 

mitigation measure (such as particular PPE) or when, in the Agency’s reasonable judgment, 

particular mitigation is necessary so that use of the pesticide does not cause unreasonable adverse 

effects on the environment. 

 

35 Johansen, Carl. 1977. Pesticides and Pollinators. Chapter in Annual Review of Entomology. Vol 22, p.177-192. 

Palo Alto, CA: Annual Reviews Inc. 

Morse, Rodger A. 1997. Honey Bees and Pesticides. Appendix 5 in Honey Bee Pests, Predators, and Diseases,

Third Edition. RA Morse and K Flottum (eds). Medina, OH: The AI Root Company. 

 

- 27 -
With respect to chronic bee data, EPA required a field pollinator study (OPPTS Guideline 

850.3040) in the March 2005 DCI to examine the potential chronic effects of carbaryl on bees. 

The DCI also required the registrant to submit a protocol to EPA for review and approval prior to 

initiation of the study. Although the registrant submitted the protocol, EPA scientists identified 

numerous issues in the protocol and these issues were not resolved to the Agency’s satisfaction 

prior to study initiation. The study was completed and found to contain numerous deficiencies. 

However, because carbaryl is no longer used on hybrid poplar plantations in the state of 

Minnesota,36 and because EPA believes that labeling can address the uncertainties regarding the 

toxicity of the SevinTM XLR PLUS formulation that the study would address, EPA is not 

requiring the study to be repeated. 

With respect to the details of incidents related to the use of carbaryl, there are limits to what is 

available to EPA. Section 6(a)(2) of FIFRA only requires pesticide product registrants to submit 

adverse effects information about their products to EPA; however, private citizens and 

State/local governments are not compelled to report adverse effects from pesticides. Therefore, 

the ability of EPA to reflect adverse effects resulting from the use of pesticides depends to a 

large extent on the cooperation of the growers and the general public to submit information that 

is both useful and timely. When such information is received, it is entered into the EIIS 

database; unfortunately, the data submitted do not always contain enough detail to be useful in a 

rigorous risk assessment. Other than a bee kill incident associated with the use of carbaryl on 

asparagus in Washington, none of the other reports on bee kills contain sufficient information to 

implicate a specific carbaryl product or a specific use of carbaryl, thereby providing a basis for 

imposing additional label restrictions. 

 (vii) Endangered species 

With respect to the endangered species, NRDC describes the number of scenarios that 

exceeded the level of concern as “too numerous to list here” and requests that EPA report RQ 

values for endangered species. Petition at 13. NRDC then criticizes the Agency for not 

implementing reasonable and prudent alternatives developed by the USFWS during a 1989 

consultation in which the USFWS concluded that carbaryl use would likely result in jeopardy for 

86 species. NRDC also criticizes the Agency for failing to re-initiate consultation. Nonetheless, 

NRDC is “encouraged” that EPA has been engaged in consultations with the National Marine 

Fisheries Service (NMFS) as well as “additional consultations with both the USFWS and 

NMFS.” Petition at 13. NRDC then requests that EPA conduct these consultations and 

implement the results in a timely manner. In the interim, NRDC requests that EPA implement 

mitigation measures that will eliminate harmful exposures to endangered species. 

EPA understands that NRDC is advocating for more stringent mitigation in order to eliminate 

all potential risk to non-target species, including endangered species. In fact, EPA has initiated 

formal consultations with the NMFS and USFWS for the California red-legged frog37 and the 

Barton Springs salamander38 in Texas as well as for 26 species of Pacific salmon and steelhead 

 

36 Personal communication (e-mail) from John Peckham, Minnesota Department of Agriculture, to C. Scheltema, 

EPA, Office of Pesticide Programs, August 13, 2008. 

37 EPA’s Effects Determination for the California Red Legged Frog was sent to the US Fish and Wildlife Service in 

October 2007. 

38 EPA’s Effects Determination for the Barton Springs Salamander was sent to Bryan Arroyo, Acting Assistant 

Director for Endangered Species, US Fish and Wildlife Service, on September 21, 2007. 

- 28 -
in the Northwest39. Consultation packages for the effects of carbaryl on the California redlegged frog, the Barton Springs salamander and Pacific salmon and steelhead (sent to the 

services in April, 2003) are available on the EPA website at the URL http://www.epa.gov/espp/. 

Once EPA initiates a consultation with the NFWS and the NMFS, the Agency must wait for the 

Services to respond. EPA has yet to receive responses from the Services for carbaryl. The next 

step in this collaborative effort is for the Services to issue a Biological Opinion stating whether 

carbaryl use is likely to adversely affect the identified Federally listed, threatened, and/or 

endangered species, and if so, identifying reasonable and prudent measures/alternatives to 

avoid/reduce risks associated with the use of carbaryl. In addition, EPA will continue to work 

with the Services during the registration review of carbaryl, which will include an assessment of 

potential risks to endangered species throughout the entire carbaryl use area. 

 c. Sub-lethal effects. 

NRDC finds fault with the Agency’s use of lethal concentration for comparison with EECs 

because the use of the acute toxicity endpoints (e.g., LD50 values for mortality) does not address 

sub-acute behavioral or physiological effects that may occur prior to mortality and yet can still 

have significant sub-lethal effects on many species including immune system suppression, 

hormone disruption, behavior effects, mutagenicity, carcinogenicity, “and others.” Petition at 

12. In addition, NRDC asserts that EPA does not substantially address indirect effects, such as 

effects on food supply and habitat, or assess the potential for synergistic or additive effects. 

Again, NRDC requests that EPA rerun its models with the mitigation set forth in the IRED and 

to “reduce or eliminate” uses where the proposed mitigation does not ensure non-target 

organisms will be protected. 

On the whole, the Agency does not consider these comments as providing a basis upon which 

to cancel all carbaryl registrations. Mortality is the acute endpoint used in ecological risk 

assessments for birds, mammals and fish for all pesticides, and has been for at least 30 years. In 

any case, what NRDC fails to take into account is that acute effects are but one aspect of EPA’s 

ecological risk assessments. Although acute toxicity endpoints (e.g. mortality) alone may not 

account for ecological hazards from sub-lethal exposures, EPA uses other data to assess 

ecological hazards, including sub-lethal effects. 

The Agency’s Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs (2004) document40, available at http://www.epa.gov/espp/consultation/ecoriskoverview.pdf, describes the assumptions and limitations regarding sub-lethal effects. For an 

ecological risk assessment, the screening risk assessment relies on the acute mortality endpoint 

as well as a suite of sub-lethal responses to the pesticide, as determined by the testing of a 

species’ response to chronic exposure conditions and subsequent chronic risk assessment. 

Examples of these measurement endpoints for birds and mammals include the following: 

 

39 EPA’s Effects Determination for Carbaryl Relative to 26 Pacific Salmon and Steelhead was sent to Don Knowles, 

Director, Office of Protected Resources, on April 1, 2003. 

40 US EPA Office of Pesticide Programs, 2004. Overview of the Ecological Risk Assessment Process in the Office 

of Pesticide Programs, U.S. Environmental Protection Agency: Endangered and Threatened Species Effects 

Washington, DC. January 23, 2004. 

- 29 -
Birds: Reproduction Maternal weight 

 Eggs laid/hen 

 Eggs cracked 

 Eggshell thickness 

 Viable embryos 

 Hatchling number 

 14-day survivors 

 Gross necropsy 

 Observations of other clinical signs 

Mammals: Two-Generation Total panel of reproduction parameters 

 Reproduction including: 

 Histopathology, parental and offspring 

 growth, weight, mating, lactation, 

 gonadal development milestones, 

 sexual organ performance and offspring 

 production 

The ecological effects characterization section of the carbaryl ecological risk assessment 

describes the results of ecotoxicology studies conducted to measure sub-lethal responses to the 

pesticide. In addition, the assessment of effects to aquatic invertebrates and aquatic and 

terrestrial plants is undertaken not only to evaluate direct effects to the survival growth and 

reproduction of these taxa, but to qualitatively evaluate them in terms of providing a forage base 

for fish and terrestrial animals. 

Finally, EPA disagrees that an assessment of the additive effects of all chemicals acting though 

a similar mode of action is necessary. To the contrary, in its screening-level assessment, EPA 

already assumes that 100% of feed for an organism is treated with carbaryl. Consequently, the 

scenario already assumes that a crop/pest complex that can be treated with an NMC is already 

100% treated with carbaryl. The Agency does not routinely include, in its screening risk 

assessments, an evaluation of mixtures of active ingredients, either those mixtures of multiple 

active ingredients in product formulations or those in the applicator's tank. In the case of the 

product formulations of active ingredients, each active ingredient is subject to an individual risk 

assessment for regulatory decision regarding the active ingredient on a particular use site. If 

effects data are available for a formulated product containing more than one active ingredient, 

they may be used qualitatively or quantitatively in accordance with the Agency’s Overview 

Document41 and the Services’ Evaluation Memorandum.42 

 

41 Ibid. 

42 US Fish and Wildlife Service (USFWS) and US National Marine Fisheries Service (NMFS). 2004. Letter from 

USFWS/NMFS to U.S. EPA Office of Prevention, Pesticides, and Toxic Substances. January 26, 2004. 

(http://www.fws.gov/endangered/consultations/pesticides/evaluation.pdf). 

- 30 -
 3. Conclusion on Ecological Risks Posed by Carbaryl. 

In sum, EPA’s screening level assessment indicates that carbaryl may present ecological risks 

of concern based upon RQs that exceed some of the Agency’s LOCs. However, consistent with 

the purpose of the screening level risk assessment, which is to determine use scenarios for a 

pesticide that do not pose a risk of concern, the parameters and assumptions for the derivation of 

carbaryl RQs are conservative. For instance, the RQs for aquatic animals were calculated using 

an exposure scenario representing a small pond located directly adjacent to a 10-hectare field, 

which is completely planted with the crop and treated with carbaryl. This represents a 

waterbody that is characteristic of a subset of vulnerable aquatic water bodies in agro-ecosystems 

nationwide. An analysis of surface-water monitoring data from the USGS NAWQA monitoring 

program provides another line of evidence that the RQs above LOCs for aquatic animals 

represents risks for a subset of vulnerable water bodies where carbaryl is used. Although 

carbaryl was detected in 28% of over 15,000 surface water samples, only 0.1% of all the samples 

collected had concentrations sufficient to exceed the non-listed aquatic invertebrate acute LOC. 

The toxicity data available in the risk assessments for carbaryl provide another line of evidence 

with which to evaluate the potential severity of risk to aquatic animals. The RQs were calculated 

using the most sensitive species in the species sensitivity distribution for each taxon. However, 

the acute toxicity endpoint for all fish species for which EPA has data spans almost two orders of 

magnitude. RQs for fish calculated with the mean toxicity value from the distribution would be 

below the non-listed acute risk LOC for fish. Similarly, the range of acute toxicity endpoint 

values for invertebrates spans more than an order-of-magnitude. Therefore, exposure in a water 

body that would lead to an exceedance of an LOC would not necessarily cause the same level of 

adverse effects throughout the assemblage of species in a water body. 

The screening-level risk assessment indicated the potential for risk to terrestrial mammals and 

invertebrates. Acute risks to birds were below the Agency’s LOC. However, the Agency also 

considered other lines of evidence in considering the risk to mammals, such as available adverse 

incident data. The number of incidents associated with carbaryl is low. Although the absence of 

incident reports cannot be construed as the absence of incidents, the available data suggest that 

current uses of carbaryl do not adversely affect non-target organisms. The incident data, 

although limited in its ability to quantify potential risks, provides a line of evidence that risk 

estimates provided in the screening-level assessment are relatively conservative. The data on 

ecological incidents of carbaryl thus provide an additional perspective on the RQ exceedances. 

Therefore, given the purpose and inherent conservatisms in the screening-level risk assessment 

approach combined with the context provided by additional lines of evidence related to the risks 

presented by carbaryl to non-listed species, EPA is satisfied that it can qualitatively determine 

that the risks posed by carbaryl to non-listed species are limited to certain taxa affecting a limited 

number of species in a subset of vulnerable environments. 

Nonetheless, EPA recognizes that for threatened and endangered species specific temporal and 

spatial refinements are often necessary to fully evaluate the risk presented by a particular 

pesticide. EPA has initiated formal consultation with the Services for several species and will 

continue to assess risk to endangered species nationwide during the registration review of 

carbaryl, which is scheduled to begin in 2010. 

- 31 -
 4. Estimating Carbaryl Risk Based on Mitigation Measures 

NRDC repeatedly requests that EPA “rerun” the risk estimates based on the mitigation set 

forth in the RED through its ecological modeling scenarios. Petition at 8-12 and 16. In so doing, 

NRDC questions the adequacy of proposed mitigation measures, asserting that EPA has provided 

no calculations or evidence that would support its assumption that the proposed mitigation will 

reduce ecological risks below the screening LOC. 

First, simply asserting that the proposed mitigation may not be adequate and further mitigation 

may be required is not a basis for canceling all carbaryl registrations. Furthermore, FIFRA does 

not require EPA to quantify or eliminate all uncertainties in it scientific assessments. As long as 

the estimates and assumptions EPA uses to bound its assessments are reasonable, EPA can fulfill 

its statutory mandate and conclude, based upon a qualitative assessment, that a pesticide does not 

cause unreasonable adverse effects on the environment. 

In addition, EPA disagrees with the implication that before EPA can impose mitigation the 

Agency must have empirical evidence that the mitigation will provide a certain, measurable 

result. To the contrary, EPA can impose mitigation both when there is empirical evidence to 

support a specific mitigation measure (such as particular PPE) or when, in the Agency’s 

reasonable judgment, particular mitigation is necessary so that use of the pesticide does not cause 

unreasonable adverse effects on the environment. Thus, EPA disagrees with the underlying 

premise behind NRDC’s request for quantitative documentation with respect to mitigation. 

EPA did evaluate the effects of some mitigation on risk estimates, by evaluating a range of 

application rates at and below maximum label rates. However, as described below, the effects of 

some mitigation measures imposed for carbaryl can only be characterized qualitatively, and 

cannot be reflected in the calculation of RQs. For example, possible increases in the use of 

carbaryl, which are anticipated by the NRDC as discussed below, would not be reflected in the 

RQs calculated for terrestrial or aquatic animals in the ecological risk assessment, because the 

Agency already assumes that 100% of the feed items consumed by terrestrial animals are treated 

with the pesticide under consideration. The amount of residue on each potential food item for 

terrestrial animals was also calculated using the maximum residues identified in the published 

literature (Hoeger and Kennaga 1972; Fletcher et al 1994)43 which serves as the basis for the 

terrestrial exposure model. Similarly, for the aquatic risk assessment, the watershed in each 

scenario is assumed to be fully planted with the crop simulated, with 100% of that crop treated 

with the pesticide. Therefore, because the actual percent crop treated is not considered, increases 

in use will still not result in an exposure scenario expected to exceed that used for the ecological 

screening risk assessment. 

In addition, maximum application rates were reduced for mosquito control, citrus, asparagus, 

and sunflowers in the IRED. Reduction in application rates is directly reflected in RQ 

 

43 Hoerger, F., and E.E. Kenaga. 1972. Pesticide residues on plants: Correlation of representative data as a basis for 

estimation of their magnitude in the environment. In F. Coulston and F. Korte, ed., Environmental Quality and 

Safety: Chemistry, Toxicology, and Technology, George Thieme Publ,. Stuttgart, West Germany, pp. 9-28. 

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the EPA food-chain 

(Kenaga) nomogram, and instrument for estimating pesticide residues on plants. Environmental Toxicology and 

Chemistry 13 (9):1383-1391.

- 32 -
reductions, as indicated in the risk assessment. Furthermore, aerial applications were prohibited 

for certain formulations applied to corn (field, pop, and sweet), grain sorghum, alfalfa, rice, and 

sunflowers.44 Prohibiting such aerial applications reduces the spray drift exposure assumed in 

the calculation of RQs for the aquatic assessment from 5% to 1% of applied carbaryl, which are 

the default assumptions for aerial and ground applications, respectively. Prohibition of aerial 

applications also decreases the distance from a treated field that foraging terrestrial animals may 

be exposed to carbaryl, and reduces the amount of carbaryl to which animals near the treated 

field will be exposed. However, as described above, the terrestrial exposure scenario used in 

screening assessments assumes that birds and mammals occupy and feed in the treated field 

100% of the time. Therefore, while reductions in the maximum application rate for some crops 

would be reflected in the respective RQs for those crops, risk reduction resulting from reductions 

in spray drift to areas away from the treated field would not be reflected in the RQs. 

The following are mitigation measures implemented to address carbaryl risks that cannot be 

modeled using existing tools, but that would reduce the overall mass of pesticide put into the 

environment: 

• Subsequent to the publication of the Carbaryl IRED, EPA canceled broadcast 

application of liquid carbaryl formulations to residential lawns. This mitigation is 

expected to reduce the amount of carbaryl available for runoff to surface water in urban 

and suburban areas. 

• A number of carbaryl uses have been canceled, including all pet uses (except pet 

collars), all direct uses on poultry and in poultry houses, and all use on wheat. 

Subsequent to the carbaryl RED, Bayer has requested cancellation of all use on millet, 

all use on succulent (fresh) peas and beans, and most use of granular formulations on 

leafy vegetables (except Brassica).45 Another carbaryl product registrant, Drexel 

Chemical company, has requested cancellation of carbaryl dust formulations used in 

agriculture. 

• In the 2007 Carbaryl RED, EPA required that all carbaryl granular products used on 

residential turf be watered in. This is expected to reduce the number of granules on the 

soil surface that could be eaten by visiting birds or mammals. In addition, watering in 

granules will reduce the amount of carbaryl that can be transported to surface water by 

runoff and erosion. 

• Bayer’s voluntary cancellation of all ultra low volume (ULV) applications of carbaryl 

used as a mosquito adulticide and cancellation of all use of dusts in agriculture is 

expected to reduce risks to honeybees, although this can not be quantified through 

EPA’s models. 46 

The mitigation and voluntary cancellations described above are expected to reduce but not 

eliminate all ecological risks; however, FIFRA does not require that all risks be eliminated. 

 

44 Wettable powder and granular formulations may no longer be applied by air, with the exception of pelleted 

carbaryl bait used in federal and state Grasshopper and Mormon cricket suppression programs. 

45 EPA published a notice of receipt of request to amend carbaryl registrations under FIFRA § 6(f) in the Federal 

Register on August 20, 2008. 

46 Dusts are the most hazardous formulation to honeybees because of greater exposure potential; therefore, the 

elimination of carbaryl dust in agriculture is expected to benefit bees. Prohibiting aerial applications will also 

reduce hazard to bees because aerial application is association with greater drift than ground application. 

- 33 -
FIFRA does, however, require EPA to also take into account the economic, social, and 

environmental costs and benefits of the use of any pesticide when making a reregistration 

eligibility decision or a decision to cancel uses. Finally, NRDC criticizes the Agency for not 

implementing mitigation solely to mitigate ecological risks. EPA believes that there is nothing 

inappropriate about mitigation that is designed to address more than one risk factor, such as 

reduced application rates that reduce both worker exposure and ecological risks. To the contrary, 

mitigation that addresses more than one risk factor is eminently reasonable. 

C. Benefits of Carbaryl 

NRDC asserts that carbaryl use exceeds the Agency’s LOCs with respect to ecological risks. 

NRDC further asserts that EPA has not provided adequate documentation demonstrating that the 

benefits of carbaryl exceed the identified ecological and worker risks. Petition at 14. In 

addition, NRDC asserts that for some uses of carbaryl there are alternatives. 

 Generally, pesticides used in residential settings provide benefits in terms of reducing pests 

that cause or carry disease, cause damage, are poisonous, or are nuisances. Similarly, pesticides 

used in commercial settings benefit people by controlling pests that may cause damage or 

interfere with manufacturing processes or result in adulterated products. The benefits of an 

agricultural pesticide are essentially the improvements in the production of food and fiber 

resulting from the pesticide use. Improvements in production can occur because the pesticide 

reduces damage caused by insects, weeds or plant pathogens, leading to an increase in output or 

improvement in the quality of the commodity. Use of a chemical pesticide may also reduce costs 

of production compared to alternative pest control measures. These benefits largely accrue to the 

users of the pesticide, i.e., farmers, in the form of higher incomes. Consumers may also benefit 

because higher production and/or lower costs translate into a cheaper and more abundant supply 

of food or fiber. 

Typically, improvements due to a pesticide are measured against the next best available pest 

control alternative, which may be chemical, biological, or mechanical. Benefits may differ 

between sites, depending on the particular pests causing damage or the available alternative 

control measures. Benefits may also differ within sites because crop production systems differ 

across agro-climatic zones. Pest problems may be specific to certain regions and alternatives 

may not be appropriate in all situations. 

As part of the reregistration process, including the IRED and RED, EPA examined the use of 

carbaryl on more than 30 agricultural and non-agricultural sites to evaluate the benefits carbaryl 

provides47. Carbaryl is more efficacious for control of some pests. In addition, less quantifiable 

benefits of carbaryl arise from several characteristics of the chemical, the regulatory 

environment, and economic factors. First, carbaryl is a broad-spectrum insecticide that may 

provide control over multiple pests with a single application. The multi-pest control achieved 

with a broad spectrum insecticide can result in fewer overall insecticide applications and lower 

 

47 The Agency completed a number of assessments investigating the use and/or benefits of carbaryl across a wide 

range of use sites in support of reregistration. 

- 34 -
costs. These benefits are often difficult to quantify as damage from secondary insects may not 

be noted until pest control practices change and secondary pests are manifested. 

Second, carbaryl can provide an alternative mode of action, which can be important in 

managing the development of insect resistance to other pesticides. Carbaryl can be used in 

rotation with other insecticides, helping to maintain the effectiveness of alternative insecticides, 

particularly in situations where few alternative insecticides are available or alternatives belong to 

a single insecticide class. 

Third, carbaryl has a relatively short PHI and REI, giving growers greater flexibility in timing 

applications and other field activities. Avoiding pest damage can be particularly critical in the 

period immediately prior to the harvest of fruits and vegetables to produce a marketable 

commodity. Reliance on insecticides with long PHIs tends to encourage more prophylactic 

treatments, which is counter to integrated pest management (IPM) programs that promote 

delaying pesticide treatments until pest populations reach damaging levels. 

Finally, carbaryl is often less expensive than other treatment options. Agriculture is highly 

competitive and producers have little or no opportunity to “brand” their products and influence 

the prices they receive. Keeping costs low can be the only means of staying competitive with 

producers in other regions, including other countries. 

All these characteristics are not important in all situations. As noted above, the magnitude of 

benefits can be crop and location specific. The rest of this section describes the benefits of 

carbaryl in a variety of crops that EPA concludes is representative of the benefits across 

agricultural uses. 

The proportion of the crop treated with a pesticide is often a good indication of its importance 

to production. For example, approximately 35-40% of acreage cultivated in apples and 

asparagus are treated each year with carbaryl, suggesting a relatively high value to producers of 

those crops. Carbaryl plays a dual role in apple production: insect control and fruit thinning48. 

No single alternative is available for both tasks. As a fruit thinning agent, carbaryl reduces the 

post-bloom number of fruit, allowing production of larger, more marketable fruit. Other 

chemical thinning agents can be severely impacted by environmental temperature (before, during 

and after application), tree vigor, fruit variety and need for precise timing of application. Poorly 

timed fruit thinning can throw a tree into a biennial production cycle, with a low production year 

followed by a high production year. In high production years, average fruit size tend to be 

smaller (resulting in lower $/lb returns), while in low production years, average fruit size tends to 

be larger. Excessively large fruit also yields lower returns. Hand thinning is generally 

prohibitively expensive except for specialty and organic apples for which growers receive higher 

prices. Carbaryl also provides superior control of white apple leafhopper. This insect may cause 

spots on the fruit with its excrement, which affects quality and reduces the price growers receive. 

The leafhopper may also pose a work place hazard during harvest. Carbaryl has the shortest PHI 

of all insecticide alternatives, allowing more flexibility for growers who can wait to see if 

 

48 US EPA Office of Pesticide Programs. 2007. Alternatives Assessment for Carbaryl Use on Apples. May 10, 

2007. 

- 35 -
leafhopper populations reach damaging levels before treating. Reliance on insecticides with 

longer PHI’s could result in prophylactic applications which could very well be unnecessary. 

The short PHI is also critical for asparagus growers49, who harvest spears at short intervals. 

Alternatives to carbaryl have longer PHI’s or are limited to a single application per year. The 

target pest, the asparagus beetle, deposits eggs on the spears making them unmarketable and 

potentially leading to the loss of all production. The severity of potential damage in combination 

with a high percent of the crop subject to pest infestation implies that much of the benefits of 

carbaryl accrue to consumers, who would otherwise face higher prices resulting from a limited 

supply of asparagus. 

Sweet and tart cherries are also quite reliant on carbaryl, with about 30% of sweet cherry 

acreage and 10% of tart cherry acreage treated annually.50 The main target pest is the cherry 

fruit fly, but there are numerous secondary pests that an application of carbaryl can 

simultaneously control. The cherry fruit fly is one of the most critical insect pests in cherry 

production; buyers sample for it constantly and a single pest can lead to the rejection of an entire 

shipment of produce. Organophosphate insecticides like azinphos-methyl have been the primary 

means of control, but there has been a major emphasis by EPA and the industry to either phase 

out or reduce their use. Carbaryl has long been a ‘back up’ treatment to maintain continuous 

protection during the relatively long intervals required between organophosphate applications. 

Carbaryl is also valuable as a rotational spray to maintain the effectiveness of other alternatives, 

such as spinosad. 

Carbaryl also provides substantial benefits in crops with relatively low percent treatment such 

as citrus, where about 5% of the crop is treated.51 Carbaryl is used on citrus to control of the 

root weevil, a pest that is currently limited in area but highly damaging as it can lead to the death 

of trees. The loss of trees has a substantial impact not only on current income, but also on future 

income of a grower since several years of production can be lost before a newly planted tree 

begins to produce fruit. Given intense competition from foreign production, especially of 

oranges, even small impacts can affect the viability of a citrus grove. Carbaryl is a key 

component of citrus weevil eradication programs which target all stages of weevil developmental 

(egg, larva, and adult). Carbaryl is the most efficacious insecticide targeting the adult stage of 

the weevil and prevents its dispersion to non-infested areas. Synthetic pyrethroids would be the 

likely alternative to carbaryl for adult weevil control. While widely used in citrus, pyrethroids 

typically target other pests, not the root weevil. 

The benefits of carbaryl in several other tree crops are more variable.52 There is relatively 

high use in pecans and pistachios (10-20% crop treated) and somewhat lower in olives (5-10%). 

There are few registered alternatives for olives and pistachios, but the target pests are sporadic. 

 

49 US EPA Office of Pesticide Programs. 2003. Summary Tables of Carbaryl Benefits Information on Selected 

Crops. May 23, 2003. 

50 Ibid. 

51 US EPA Office of Pesticide Programs. 2007. Alternatives Assessment for Carbaryl Use on Citrus. June 6, 2007; 

and US EPA Office of Pesticide Programs. 2003. Benefits Assessment for Carbaryl Use on Citrus: Impact of 

Extending the Re-entry Interval (REI). June 12, 2003. 

52 US EPA Office of Pesticide Programs. 2003. Summary Tables of Carbaryl Benefits Information on Selected 

Crops. May 23, 2003. 

- 36 -
Alternatives in pecans are primarily organophosphates and synthetic pyrethroids and carbaryl 

offers a unique mode of action to guard against resistance developing, particularly to the 

pyrethroids. Very little carbaryl is used in almond53 and walnut production. In almond 

production, carbaryl is considered a good dormant season treatment for scale when there is 

resistance to organophosphates. Synthetic pyrethroids are also an option. However, carbaryl is 

not widely used due to its toxicity to bees, upon which almond producers are very dependent for 

pollination services. 

EPA acknowledges that there are situations where the quantifiable benefits of carbaryl are 

low. In field corn,54 carbaryl is one of a number of pesticides available for control of adult corn 

rootworm, cutworm, flea beetle, grasshopper, and Japanese beetle, all of which appear to be 

rather sporadic pests. The main advantage of carbaryl may be lower treatment costs, which can 

increase a grower’s net operating revenue around 2-5%. Net operating revenue is a measure of a 

farmer’s income, although it does not consider fixed production costs. Recent increases in the 

price of corn, however, would reduce the advantage in comparison to grower income, although 

increasing fuel costs may offset such gains. 

Carbaryl is also used on a small proportion of carrot acreage,55 primarily for the control of the 

aster leafhopper, which is a disease vector. The alternatives include an organophosphate and a 

synthetic pyrethroid; according to IPM programs, the latter loses effectiveness in hot weather. 

Thus, under certain conditions, carbaryl may be the better alternative. It also provides another 

mode of action to help avoid resistance developing. In California, the major producer of fresh 

carrots, carbaryl appears to have a cost advantage. It is also worth noting that synthetic 

pyrethroids are Restricted Use Pesticides, which could limit their availability to small producers, 

while carbaryl is restricted only in California. According to the 2002 Census of Agriculture, 

80% of carrot farms are less than 100 acres, but these small producers account for less than 4% 

of the carrot acreage. 

As another indication of the importance of carbaryl in the diverse production systems in which 

it is currently available, EPA received a large number of public comments indicating support of 

the continued registration of carbaryl following publication of NRDC’s petition to cancel 

registrations of carbaryl. All comments can be found in the docket at www.regulations.gov in 

docket number EPA-HQ-OPP-2005-0077. A brief summary of the comments follows; reference 

to specific comments are annotated by their document ID number. 

Comments were received from university extension personnel (Rutgers University (0004), 

Michigan State University (0055), University of Hawai'i (0059), and Virginia Technical 

University (0061)); grower associations (US Apple Association (0058) and the Northwest 

Horticultural Council (0063)); and private growers (0006, 0035, 0039, 0040, 0046, 0047, and 

0053) indicating the importance of carbaryl in crop production. The crops covered include 

 

53 US EPA Office of Pesticide Programs, 2008. Assessment of the Benefits of Carbaryl on Almonds. September 29, 

2008. 

54 US EPA Office of Pesticide Programs. 2008. Benefits of Carbaryl to Producers of Field Corn. September 30, 

2008. 

55 US EPA Office of Pesticide Programs. 2008. Impact Assessment for the Use of Carbaryl on Carrots. September 

26, 2008. 

- 37 -
apple, blueberry, grape, peach, plum, sweet potato, and other minor crops. Bayer (0062) also 

submitted information about the use and importance of carbaryl in citrus production and for 

insect control in turf. Some comments provided information about pests controlled by carbaryl, 

discussed various alternatives to carbaryl, and described the disadvantages of these alternatives. 

Commenters stated that carbaryl is an important part of their IPM programs and provides an 

alternative to the use of organophosphates and synthetic pyrethroids. Carbaryl provides longlasting control of a wide range of pests and multiple chemicals applied multiple times would be 

necessary to replace carbaryl. Commenters also indicated that the retail produce market is very 

sensitive to insect damage and the possibility of insects in their produce. Apple growers 

discussed the importance of carbaryl as a thinning agent, indicating that other chemicals were 

sensitive to time and environmental conditions and their application could result in severe over 

thinning if temperatures increased following an application. Most commenters indicated that 

hand thinning would be the only viable option if use of carbaryl is not permitted. Several private 

growers mentioned that small operations are especially impacted by pesticide regulations. 

EPA also had a public comment period following the release of the IRED in 2004. These 

comments can be found at www.regulations.gov in docket number EPA-HQ-OPP-2003-0376. 

The Agency again received numerous comments from a wide range of interested parties 

extolling the benefits of carbaryl and are once again annotated by their document ID number as 

listed in docket EPA-HQ-OPP-2003-0376. In particular, several comments were received from 

federal and state forest officials (0013, 0014, 0015, 0016, 0018, 0020, 0035) indicating that 

carbaryl provides superior, multi-year control of bark beetles and pine beetles in forest trees on 

public and private lands when compared to alternative insecticides. Moreover, a number of 

comments were submitted substantiating the importance of carbaryl bait products as the control 

method of choice by state and federal agencies responsible for programs to control grasshoppers 

and Mormon crickets on private, state and federally held lands (0019, 0022, 0026, 0028, 0029, 

0030, 0033, 0038, 0050, 0053, 0077). 

In conclusion, while carbaryl has high-benefit uses, it also provides benefits to agricultural 

producers in several ways that are not always quantifiable, including broad-spectrum pest 

control, resistance management, flexibility in use, and cost. The benefits are not uniform across 

crops, but can be due to localized factors or specific conditions. EPA has examined the 

advantages and disadvantages of carbaryl and of alternative pest control measures across a range 

of representative uses and determined that carbaryl provides both quantifiable and unquantifiable 

benefits to agriculture. Moreover, in cases where the quantifiable benefits tend to be lower, it is 

often because usage is low. When carbaryl is not being used, it does not present an ecological 

risk. Thus, upon consideration of the ecological risks (in light of the lines of evidence informing 

the level of risk) and the benefits provided by carbaryl use, EPA has determined that carbaryl 

will not cause unreasonable adverse effects to the environment. 

D. Increased Use of Carbaryl With Phase Out of Chlorpyrifos and Diazinon. 

NRDC contends that EPA’s surface water assessment is overly optimistic because the 

monitoring data EPA relied upon pre-dates the cancellation of consumer uses for diazinon and 

chlorpyrifos. NRDC further postulates that carbaryl will fill the market void created by the 

- 38 -
phase out and cancellation of diazinon and chlorpyrifos, thereby dramatically increasing the use 

of carbaryl and presence in urban runoff. NRDC cites data obtained by the King County 

Department of Natural Resources (Washington state) on retail sales of insecticides from “big 

box” retailers between 1997 and 2001, with sales of diazinon more than ten times higher than 

sales of carbaryl. However, according to NRDC, for 2002 these data show a drop of diazinon 

sales (by a factor of two) and a ten-fold increase in carbaryl sales. NRDC also cites an article 

submitted to the Journal, Environmental Toxicology and Chemistry (Dickey and Wilson 2004), 

which predicts that if all use of diazinon in urban watersheds is replaced by carbaryl, then 

concentrations of carbaryl could be three to four times higher than historic diazinon 

concentrations, due to carbaryl’s higher mobility. Although NRDC concedes that carbaryl has a 

lower aquatic toxicity than diazinon, NRDC nonetheless contends that increased carbaryl 

concentrations would be of concern. NRDC cites additional monitoring data from King County 

that NRDC asserts shows recent surface water monitoring demonstrates rising carbaryl 

concentrations. Finally, NRDC requests that “when EPA looks at stream monitoring data for 

carbaryl, product use patterns be considered and trends in pesticide concentrations be evaluated.” 

Petition at 10-11. 

In connection with its concern about concentrations of carbaryl in drinking water, NRDC 

asserts that EPA has failed to provide adequate documentation demonstrating that the benefits of 

increased carbaryl use exceed the identified risks, especially for urban uses. In so doing, NRDC 

requests that EPA consider cancellation of uses that involve the highest ecological risks and for 

which alternative methods exist. Petition at 14. 

It appears that NRDC is primarily criticizing the Agency for not being sufficiently prospective 

with respect to use trends and urging the Agency to “use its registration powers to encourage use 

of more selective pest management tools and discourage the widespread use of combination 

pesticides.” In both cases, NRDC is particularly concerned about urban runoff. Petition at 10-

11, 14. It is, however, unclear on what basis, if any, the Petition sets forth for canceling all 

carbaryl registrations. 

EPA disagrees with NRDC’s basic premise that carbaryl alone has supplanted consumer uses 

of diazinon and chlorpyrifos or that an increase in carbaryl market share has resulted in higher 

concentrations of carbaryl in urban runoff. Although carbaryl has gained residential/consumer 

market share, other pesticides, including imidacloprid, permethrin, and other synthetic 

pyrethroids are also gaining a significant share of the consumer market. In 2001, with 

chlorpyrifos and diazinon available, carbaryl had an estimated 25% of the residential market 

share, in terms of pounds applied. Carbaryl gained market share in 2004, increasing to an 

estimated 40% of the pounds applied by homeowners. In 2006, carbaryl market share had 

decreased to 35% (Kline and Co. Inc. 200756). In an alternatives assessment for carbaryl use on 

residential lawns,57 EPA noted that carbaryl was likely to gain market share in the residential 

homeowner lawn segment due to changes in the registrations of malathion, diazinon, and 

chlorpyrifos. However, the move in market share for general lawn insects, not including white 

grubs and billbugs, is as likely to be towards permethrin and new synethetic pyrethroids as it is 

towards carbaryl. For white grub and billbug control, market share moves from the loss of major 

alternatives would likely be to permethrin and carbaryl as curative treatments and to 

 

56 Kline and Co, Inc. is a market research firm that provides information regarding consumer and professional 

markets for pesticides. 

57 Atwood D. 2007a. Alternatives Assessment for Carbaryl Use on Residential Lawns. July 13, 2007.

- 39 -
imidacloprid and halofenozide as preventative treatments. At the same time, EPA noted that use 

of carbaryl by lawn care professionals was on the decline and was expected to continue 

decreasing. At this time, the Agency does not believe that it is reasonable, prudent or 

scientifically defensible to speculate on future market trends for residential use pesticides. 

Perhaps more importantly, the available surface water monitoring data do not show a 

corresponding increase in aquatic exposure to carbaryl. In the process of reaching its 2007 

reregistration eligibility decision for carbaryl, EPA reviewed additional monitoring data and 

conducted additional surface water modeling. See Revised Carbaryl Drinking Water Assessment 

Including Time-series Simulations (May 2, 2007). Specifically, in a summary of data collected 

by the NAWQA program over a decade in the Puget Sound Basin (Embrey and Moran 2006),58

which included data on diazinon and carbaryl collected in Thornton Creek, it appears that after 

an initial increase, concentrations of carbaryl actually began to decline towards the end of 2005. 

During the first cycle, the insecticide diazinon was often detected in samples from Thornton 

Creek; some samples were at concentrations greater than 0.1 μg /L. The summary also shows a 

decrease in diazinon detections and concentrations following the announcement of the phase out 

in 2000. There is also an increase in carbaryl detection frequency and concentrations in the years 

following the announcement of the phase out of diazinon. Nonetheless, the data also appear to 

show that carbaryl concentrations began to decline toward the end of the study period in 2005, 

rarely exceeding 0.1 μg /L. In sum, based on data from additional surface water monitoring, 

EPA concludes that there does not appear to be a steady upward trend to carbaryl concentrations 

in urban areas following the phase out of diazinon and chlorpyrifos. 

In addition, a recently published paper by USGS scientists evaluated trends in concentrations 

of carbaryl in the Northeast and Midwest after the phase out of diazinon and chlorpyrifos 

insecticides in urban environments (Phillips et al. 2007).59 They compared concentrations of 

these pesticides in samples collected from 20 streams by the USGS between 1992 and 2004 and 

determined that 16 of these streams met criteria established for assessing trends of carbaryl in 

urban streams. Sample collection and analysis followed standard NAWQA procedures for 

collection and analysis. Using seasonal step trend analysis, USGS evaluated the data to identify 

trends in summer, fall/winter, and winter/spring. Although results showed a decrease in diazinon 

and chlorpyrifos concentrations following the announcement of the phase out in 2000, trends 

were not observed in carbaryl concentrations in these regions during the same time period. 

Similarly, a recent report on pesticides in California’s urban surface waters concluded that 

“urban use of pyrethroids, fipronil and (to a lesser extent) malathion are replacing diazinon and 

chlorpyrifos in the urban market.” Pesticides in Urban Surface Waters, Urban Pesticide Use 

Trends Annual Report (2006), compiled by the Urban Pesticide Pollution Prevention (UP3) 

Project.60 Similar findings were reported in 2007 by this same organization.61 

 

58 The revised carbaryl drinking water assessment incorrectly cited this as “(Embrey and Moran 2004)”. 59 Phillips, P.J., Ator, S.W., and Nystrom, E.A., 2007, Temporal changes in surface-water insecticide after the 

phaseout of diazinon and chlorpyrifos: Environmental Science and Technology, v. 41, no. 12, p. 4,246–4,251.. 

60 The UP3 project is funded by a State Water Resources Control Board of the San Fransico Estuary Project. The 

2006 annual report may be found on the internet at the URL 

http://www.up3project.org/documents/UP3_Science_Report_2006.pdf 61The 2007 UP3 report, Pesticides in Urban Surface Water. Urban Uses Trends Annual Report 2007 may be found 

at http://www.up3project.org/documents/Final_UP3_Use_Report_2007.pdf 

- 40 -
With regard to the Dickey and Wilson article submitted to the Journal, Environmental 

Toxicology and Chemistry, EPA was unable to review the article because it was unavailable to 

the Agency. EPA has since learned that this article was rejected for publication by this journal in 

January 2005. Nevertheless, EPA has reviewed a report, “Toxic Tradeoff” by Erica Shreder and 

Phillip Dickey, which was submitted to the Agency by NRDC. 62 The Agency found that this 

report does not provide any additional information with respect to this issue. It is merely a 

restatement of the supposition presented in NRDC’s petition. 

Finally, even if the use of carbaryl were increasing, increases in the use of carbaryl would not 

be reflected in the RQs calculated for terrestrial or aquatic animals in the ecological risk 

assessment. In order for the models to be effective screens, the Agency assumes that 100% of 

the feed items to which terrestrial animals are exposed are treated with the pesticide under 

consideration, at the maximum allowed label rate for each crop. For the aquatic risk assessment, 

the watershed in each scenario is modeled to be fully planted to the crop simulated, with 100% of 

that crop treated with the pesticide. Therefore, because the actual percent crop treated is not 

considered, increases in use will still not result in an exposure scenario as conservative as that 

used for the ecological screening risk assessment. 

E. Modeling for urban uses. 

NRDC contends that all urban uses should be “eliminated,” until EPA can establish a model 

and determine likely exposure. Petition at p.12. NRDC seems to be implying that EPA cannot 

make its FIFRA determination and therefore must eliminate, or cancel, all urban uses in the 

absence of specific urban modeling. 

EPA disagrees. Concentrations of carbaryl measured in surface water monitoring data were 

summarized in the IRED and updated in a 2007 assessment of carbaryl concentrations in 

drinking water (See Revised Carbaryl Drinking Water Assessment Including Time-series 

Simulations (May 2, 2007)). There have been significant efforts to monitor agricultural and 

urban areas to determine carbaryl concentrations and as a result more monitoring is available for 

carbaryl than for most other pesticides. The Agency relied on these data to meaningfully 

characterize exposure in urban environments. That assessment concluded that in urban areas, 

detections are more frequent and detected concentrations were mostly low (< 0.1 μg/L). 

Although the peak concentration reported was as high as 16.5 μg/L, concentrations of that 

magnitude were rarely measured in urban monitoring. 

EPA evaluated monitoring data from California surface waters to characterize carbaryl 

exposure and risk in urban environments. Of the 1393 total samples representing all land uses 

analyzed by GCMS, 0.072 percent (1 sample) contained levels of carbaryl sufficient to exceed 

the LOC for acute exposures to aquatic invertebrates (i.e., 0.85 μg/L); while none of the 99 total 

samples analyzed by HPLC contained levels sufficient to exceed the LOC for aquatic 

invertebrates. The concentration of carbaryl in California urban watersheds was sufficient to 

exceed the LOC for acute exposures to aquatic invertebrates in 0.64% of samples (1 of 157 

samples) analyzed by GCMS. These data represent another line of evidence of risk associated 

with carbaryl use and confirm the 2003 assessment that the screening-level risk assessment 

 

62 See docket EQP-HQ-OPP-2005-0066. 

- 41 -
represents risks for a subset of vulnerable aquatic ecosystems where carbaryl is used. Although 

these studies typically do not include low-order streams or lentic (e.g. ponds and wetlands) 

environments, they do meaningfully characterize exposure from urban runoff. 

 

Moreover, subsequent to this monitoring the Agency did take action to mitigate exposure in 

urban environments. For example, liquid broadcast uses on residential turf have been canceled. 

Furthermore, in an effort to conservatively simulate an urban environment, the Agency has 

performed additional model runs using conservative input parameters and turf scenarios. Finally, 

after consultation with the Office of Water, Office of Pesticide Programs determined not to 

implement watershed basin modeling tools for screening assessments, due to the large amounts 

of input data needed for model calibration for specific watersheds to ensure a reasonable level of 

certainty in water concentration estimates. However, subsequent to the development of the 

IRED for carbaryl, Office of Pesticide Programs has developed a conservative modeling tool to 

evaluate exposure from urban uses and has used that tool to assess carbaryl in the California redlegged frog assessment. Therefore, the Agency is using the best tools available, and believes, 

because the same assumptions of 100% crop treated for ecological risk assessment are used, that 

the modeled concentrations so derived should be considered conservative. 

F. Carbaryl Use on Tidal flats 

NRDC raises the issue of carbaryl use on tidal flats, reiterating comments received from the 

USFWS on this use of carbaryl and noting that a phase out for this use had been agreed to. 

Specifically, NRDC requests that “EPA develop a shorter timeline for phase out and assist the 

oyster growers in developing a safer alternative.” Petition at 13. 

First, EPA does not consider this request to be a basis for canceling all carbaryl registrations. 

Second, the phase out of the carbaryl special local need registration (“Section 24(c)” registration) 

for control of burrowing shrimp on oyster beds is a local agreement between the Washington 

State Department of Agriculture, and local Indian tribes, innkeepers, and environmental groups. 

EPA is not a party to this phase-out agreement or the timeline for the phase out. 

 Furthermore, EPA has conducted a comprehensive ecological risk assessment for the use of 

carbaryl to control burrowing shrimp in Willapa Bay and Grays Harbor, Washington. Based 

upon the available data, risk to non-target organisms appear to be limited to the immediate 

treatment site, i.e., dewatered mud flats at low tide. Based upon landing (weight of catch) 

reported in the commercial crab fishery, population-level effects on crabs do not appear to be 

occurring as a result of carbaryl use. 

G. Outstanding data 

NRDC requests that EPA provide an accessible list of outstanding data requirements for 

carbaryl and that this data is received and reviewed in a timely manner so as to inform the 

carbaryl risk assessment and mitigation recommendations. Petition at 15. NRDC also asserts 

that these data should be made publicly available. In particular, NRDC mentions chronic 

toxicity data for bees, chronic toxicity data for estuarine/marine invertebrates, and consultation 

packages developed for the NMFS and USFWS. These studies have been described in previous 

sections of this petition response. 

- 42 -
Again, these requests do not provide a basis for canceling all carbaryl registrations. In June 

2003, EPA found the carbaryl database to be substantially complete, sufficient to support the 

Carbaryl IRED. The list of outstanding data requirements at the time EPA completed the 

Carbaryl IRED can be found in supporting documents to the Carbaryl IRED and in Appendix B 

of the Carbaryl IRED. EPA issued a generic DCI for carbaryl in March 2005 to formally require 

the outstanding studies mentioned by NRDC. The DCI has been scanned and will be available 

as part of the public docket for this petition response. The Agency received most of the studies 

required under this DCI in 2005 and 2006; these studies were reviewed in a timely manner and 

incorporated into the revised risk assessments supporting the 2007 Carbaryl RED. 

As previously mentioned in this document, Bayer Crop Sciences, the sole technical registrant 

for carbaryl, has elected not to generate worker exposure monitoring data for certain use 

scenarios or residue data for certain food commodities. Accordingly, these uses are being 

deleted from all carbaryl product labels according to a process established by FIFRA Section 

6(f). The only remaining outstanding data requirements are as follows: 

• Carbaryl inhalation toxicity data 

• Storage stability data for various commodities 

• Worker exposure monitoring, aerial mixer/loader, bait application to large 

acreage. 

As for making data publicly available, there is an established process for accessing data 

submitted to EPA in connection with a pesticide registration, governed by statutory and 

regulatory provisions that seek to balance access with the need to protect proprietary and other 

confidential business information.63 NRDC may avail itself of that process, if it so chooses. 

IV. Conclusion 

In determining whether to grant NRDC’s petition to cancel carbaryl registrations, EPA 

considered a number of factors that are described in more detail above. The Agency considered 

the potential risks to workers and the environment and considered the benefits associated with 

carbaryl use. In terms of worker risks, carbaryl does not pose worker risks of concern, with the 

possible exception of the use to control grasshoppers and Mormon crickets. With respect to this 

particular use, there is reason to believe that the actual risks are less than those reflected by the 

calculated MOE, few workers are exposed (and those workers tend to be highly trained), and the 

use has significant benefits. 

As far as ecological risks are concerned, modeled carbaryl uses result in exceedences of the 

Agency’s screening LOCs in particular for some species of aquatic invertebrates. However, as 

discussed herein, the exceedance of a LOC does not necessarily mean that a risk is either real or 

particularly significant. Having looked more closely at carbaryl, EPA has concluded that given 

the purpose and inherent conservatisms in the screening-level risk assessment approach 

combined with the context provided by additional lines of evidence (monitoring and incident 

data) related to the risks presented by carbaryl to non-listed species, the Agency can qualitatively 

 

63 Even with respect to this issue, it is worth noting that the failure to properly disclose information to the public 

(which EPA does not concede occurred here) would not constitute a valid basis upon which EPA could cancel a 

pesticide registration. 

- 43 -
determine that the risks posed by carbaryl to non-listed species of aquatic life and wildlife are 

limited to certain taxa, in particular aquatic invertebrates, affecting a limited number of species 

in vulnerable environments. However, the Agency concludes that while there could be effects to 

some aquatic invertebrate species in a subset of vulnerable waterbodies, not all species would be 

affected. In addition, existing monitoring data indicate it is unlikely that concentrations of 

carbaryl in surface water will be consistently high enough to exceed the LOC for the most 

sensitive aquatic invertebrate species. Therefore, EPA has determined that, with respect to 

aquatic invertebrates, carbaryl will not cause unreasonable adverse effects on the environment. 

Furthermore, the exposure and effects data described above do not support NRDC’s contention 

that carbaryl use will cause the elimination of entire invertebrate communities. 

The Agency’s analyses suggest that the magnitude of benefits provided by carbaryl varies 

across different uses. As discussed herein, carbaryl conveys substantial benefits on a number of 

sites where it is widely used and where it is more efficacious than other alternatives. More 

generally, carbaryl has a relatively broad-spectrum of effectiveness against a range of pests 

(which may obviate the need for applications of multiple insecticides); it is often cheaper than 

many available alternatives; and it generally has a shorter PHI and REI than the alternatives, 

which fits well with IPM programs to discourage potentially unnecessary prophylactic 

treatments. Moreover, having an additional chemistry available can reduce the development of 

pest resistance. 

There are a number of sites where carbaryl is widely used, and in conjunction with what EPA 

concludes to be a potential for effects that would not likely cause a significant impact on 

associated aquatic ecosystems in a subset of vulnerable environments, carbaryl does not pose 

unreasonable risks when used on those sites. It also appears that there are sites for which 

carbaryl does not have significant quantifiable benefits. However, EPA does not believe 

initiating cancellation action against carbaryl on those sites is appropriate for the following 

reasons. Given the relatively low volume of carbaryl used on those sites, the Agency believes it 

likely that there is low risk associated with carbaryl’s registration for those uses. The Agency 

also believes that there is benefit in having a pesticide, with the characteristics of carbaryl, in 

reserve in case the availability of alternatives changes in the future (because, for example, of 

product cancellations or resistance development). And given carbaryl’s risk profile that indicates 

significant impacts on aquatic ecosystems are not likely, due to potential effects on some species 

of invertebrates, the Agency does not believe that the risks posed by carbaryl are unreasonable or 

that the risks merit the initiation of formal regulatory action by EPA. 

For these reasons, as well as for the reasons set forth in the 2004 IRED, the 2007 Carbaryl 

RED, and the 2008 Addendum to the Carbaryl RED (and supporting documentation for each), I 

hereby deny the Petition insofar as it seeks the cancellation of all carbaryl registrations. This 

concludes the Agency's reregistration process for carbaryl with respect to non-dietary issues. 

____________________ _________________________ 

Date Debra Edwards, Ph.D. 

Director, Office of Pesticide Programs 

- 44 -