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Butylate TRED



[Federal Register: September 11, 2001 (Volume 66, Number 176)]
[Notices]
[Page 47219-47222]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr11se01-89]

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ENVIRONMENTAL PROTECTION AGENCY

[OPP-34246; FRL-6796-3]

 
Butylate; Notice of Pesticide Report on FQPA Tolerance 
Reassessment Progress and Interim Risk Management Decision

AGENCY: Environmental Protection Agency (EPA)

ACTION: Notice.

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SUMMARY: This notice constitutes the Agency's report on the Food 
Quality Protection Act (FQPA) tolerance reassessment progress and 
interim risk management decision for butylate, announces the Agency's 
decision, and releases the human health risk assessment and related 
documents supporting this decision to the public. The Agency's 
reassessment of dietary risk, including public exposure through food 
and drinking water as required by the Federal Food, Drug, and Cosmetic 
Act (FFDCA) as amended by FQPA, indicates that butylate, by itself, 
poses no risk concerns within the limits of the existing tolerances; 
therefore, no risk mitigation is needed, and no further actions are 
warranted at this time. The existing butylate tolerances remain in 
effect, until such time as a determination of whether a full 
reassessment of the cumulative risk from thiocarbamate pesticides, 
including butylate, may be needed and is considered.

DATES: Comments submitted on or before October 11, 2001 are most likely 
to be considered and will be included in the public docket.

FOR FURTHER INFORMATION CONTACT: Gary Mullins, Special Review and 
Reregistration Division (7508C), Office of Pesticide Programs, 
Environmental Protection Agency, 1200 Pennsylvania Ave., NW., 
Washington, DC 20460; telephone number: (703) 308-8044; e-mail address: 
mullins.gary@epa.gov.

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does this Action Apply to Me?

    This action is directed to the public in general, nevertheless, a 
wide range of stakeholders will be interested in obtaining information 
on the Agency's interim risk management and tolerance reassessment 
decision for butylate, including environmental, human health, and 
agricultural advocates; the chemical industry; pesticide users; and 
members of the public interested in the use of pesticides on food. 
Since other entities also may be interested, the Agency has not 
attempted to describe all the specific entities that may be affected by 
this action. If you have any questions regarding the applicability of 
this action to a particular entity, consult the person listed under FOR 
FURTHER INFORMATION CONTACT.

B. How Can I Get Additional Information, Including Copies of this 
Document and Other Related Documents?

    1. Electronically. You may obtain electronic copies of this 
document, and certain other related documents that might be available 
electronically, from the EPA Internet Home Page at http://www.epa.gov/. 
On the Home Page select ``Laws and Regulations,'' ``Regulations and 
Proposed Rules,'' and then look up the entry for this document under 
the ``Federal Register--Environmental Documents.'' You can also go 
directly to the Federal Register listings at http://www.epa.gov/
fedrgstr/. In addition, copies of documents related to the Agency's 
report on FQPA tolerance reassessment progress and interim risk 
management decision for butylate released to the public may also be 
accessed at: http://www.epa.gov/pesticides/reregistration/status.htm.
    2. In person. The Agency has established an official record for 
this action under docket control numbers OPP-34246. The official record 
consists of the documents specifically referenced in this action, and 
other related information, including any information claimed as 
Confidential Business Information (CBI). This official record includes 
the documents that are physically located in the docket, as well as the 
documents that are referenced in those documents. The public version of 
the official record does not include any information claimed as CBI. 
The public version of the official record is available for inspection 
in the Public Information and Records Integrity Branch (PIRIB), Rm. 
119, Crystal Mall #2, 1921 Jefferson Davis Hwy., Arlington, VA, from 
8:30 a.m. to 4 p.m., Monday through Friday,

[[Page 47220]]

excluding legal holidays. The PIRIB telephone number is (703) 305-5805.

II. How Can I Respond to this Action?

A. How and to Whom Do I Submit Comments?

    You may submit comments through the mail, in person, or 
electronically. To ensure proper receipt by EPA, it is imperative that 
you identify docket control number OPP-34246 in the subject line on the 
first page of your correspondence.
     1. By mail. Submit your comments to: Public Information and 
Records Integrity Branch (PIRIB), Information Resources and Services 
Division (7502C), Office of Pesticide Programs (OPP), Environmental 
Protection Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460.
     2. In person or by courier. Deliver your comments to: Public 
Information and Records Integrity Branch (PIRIB), Information Resources 
and Services Division (7502C), Office of Pesticide Programs (OPP), 
Environmental Protection Agency, Rm. 119, Crystal Mall #2, 1921 
Jefferson Davis Hwy., Arlington, VA. The PIRIB is open from 8:30 a.m. 
to 4 p.m., Monday through Friday, excluding legal holidays. The PIRIB 
telephone number is (703) 305-5805.
     3. Electronically. You may submit your comments and/or data 
electronically by e-mail to: opp-docket@epa.gov, or you can submit a 
computer disk as described in Units II.A.1. and 2 above. Do not submit 
any information electronically that you consider to be CBI. Avoid the 
use of special characters and any form of encryption. Electronic 
comments may also be filed online at many Federal Depository Libraries.

B. How Should I Handle CBI That I Want To Submit to the Agency?

    Do not submit any information electronically that you would 
consider to be CBI. You may claim information that you submit to EPA in 
response to this document as CBI by marking any part or all of that 
information as CBI. Information so marked will not be disclosed except 
in accordance with procedures set forth in 40 CFR part 2. In addition 
to one complete version of the comment that includes any information 
claimed as CBI, a copy of the comment that does not contain the 
information claimed as CBI must be submitted for inclusion in the 
public version of the official record. Information not marked 
confidential will be included in the public version of the official 
record without prior notice. If you have any questions about CBI or the 
procedures for claiming CBI, please consult the person identified under 
FOR FURTHER INFORMATION CONTACT.

III. Report on FQPA Tolerance Reassessment Progress and Interim 
Risk Management Decision

    The Agency has completed its assessment of the dietary risk of 
butylate alone, and has determined that the level of dietary risk from 
exposure as a result of currently registered uses of butylate is not of 
concern. Therefore, no mitigation measures are needed and no further 
actions are warranted at this time. The Agency may find, however, that 
further action is necessary if it is determined that thiocarbamate 
pesticides, such as butylate, share a common mechanism of toxicity. 
Such an incremental approach to the tolerance reassessment process is 
consistent with the Agency's goal of improving transparency in 
implementing FFDCA, as amended. This interim tolerance reassessment and 
risk management decision does not specifically address the reassessment 
of the existing butylate food residue tolerances as called for by 
FFDCA, as amended, because the Agency has not yet determined that 
thiocarbamate pesticides have a common mechanism of toxicity, nor 
considered the cumulative risk for the thiocarbamates, if so warranted. 
When the Agency has determined whether the thiocarbamate group of 
pesticides have a common mechanism of toxicity and has considered the 
appropriate cumulative risks, the butylate tolerances will be 
reassessed in that light. At this time, the established tolerances for 
butylate remain in effect, until such time as a full reassessment of 
the cumulative risk from thiocarbamate pesticides, such as butylate, 
may be needed and is considered.

IV. Background

    FFDCA, as amended requires EPA to review all the tolerances for 
registered chemicals in effect on or before the date of the enactment 
of FQPA. In reviewing these tolerances, the Agency must consider, among 
other things, aggregate risks from non-occupational sources of 
pesticide exposure, whether there is increased susceptibility to 
infants and children, and the cumulative effects of pesticides with a 
common mechanism of toxicity. The tolerances are considered reassessed 
once the safety finding has been made or a revocation occurs. A 
reregistration eligibility decision (RED) for butylate was completed in 
September 1993, prior to FQPA enactment, therefore, it needed to be 
updated to consider the provisions of the Act.
    FFDCA, as amended, requires that the Agency, when considering 
whether to establish, modify, or revoke a tolerance, consider 
``available information'' concerning the cumulative effects of a 
particular pesticide's residues and ``other substances that have a 
common mechanism of toxicity.'' The Agency is currently examining 
whether and to what extent thiocarbamate pesticides may share a common 
mechanism of toxicity. Preliminary determinations indicate that the 
potential to produce a common toxic effect, neuropathy (e.g., 
degeneration and demylination of the sciatic nerve), and the 
similarities in structure and metabolism, may support grouping of the 
thiocarbamates based on their ability to produce a common effect by a 
common mechanism. Assuming these assertions are correct, preliminary 
screening-level chronic cumulative dietary food risk analyses do not 
provide evidence that cumulative exposure of the human population, 
including infants and children, to the neuropathic thiocarbamates would 
raise concern of adversely affecting human health.
    The preliminary determination of whether and to what extent 
thiocarbamates pesticides may share a common mechanism of toxicity, and 
accompanying screening-level cumulative dietary analyses are to be 
presented to the FIFRA Science Advisory Panel for peer review on 
September 7, 2001. Pending their review of the information, the Agency 
expects to complete the cumulative risk assessment for thiocarbamate 
pesticides, at which time, provided the risk analyses concludes chronic 
cumulative dietary risks are not of concern to the Agency, the butylate 
tolerances will be considered reassessed, in accordance with FFDCA, as 
amended.
    The Agency's human health findings for the thiocarbamate pesticide 
butylate, dicussed below, are presented fully in the documents: 
Butylate-HED Revised Human Health Assessment, February 26, 2001; and: 
GENEEC and SCI-GROW2 EEC's for the Current Use of Butylate on Corn for 
the Purpose of Tolerance Reassessment, August 20, 1998. These risk 
assessments and other documents pertaining to the butylate tolerance 
reassessment decision are available on the Internet at: http://
www.epa.gov/pesticides/reregistration/status.htm and the public docket 
for viewing (see Unit I.B.2).

[[Page 47221]]

V. Use Summary

    Butylate (S-ethyl diisobutylthiocarbamate) is a soil incorporated 
herbicide registered for use on corn (field, sweet, and popcorn) for 
control of grassy and broadleaf weeds and nutsedge. There are no 
registered non-food/non-feed uses, and no existing or proposed 
residential uses of butylate products. Butylate is formulated as a 
liquid emulsifiable concentrate (85.1% active ingredient), and may be 
applied preplant, at plant, postplant, and after harvest (fall) at a 
maximum single and annual application rate of 6.3 pounds of active 
ingredient per acre (lb a.i./acre). Because butylate is highly 
volatile, applications are made by ground equipment, either broadcast 
or band, and are immediately incorporated into the soil. The type of 
equipment used to apply butylate include, boom sprayer; soil injection 
equipment; and center pivot irrigation. Usage of butylate has declined 
from approximately 15 million lb a.i. in 1991 to an estimated 950,000 
lb a.i. in 1998. Butylate was not produced in 1998, and both usage and 
production are expected to continue to decline.

VI. Dietary Food Risks

    Acute dietary risk from food is calculated considering what is 
eaten in one day (in this instance, the full range of consumption 
values as well as the range of residue values in food). A risk estimate 
that is less than 100% of the acute Population Adjusted Dose (PAD) (the 
dose at which an individual could be exposed on any given day and no 
adverse health effects would be expected) is not of concern to the 
Agency. Chronic dietary risk from food is calculated by using the 
average consumption values for food and average residue values for 
those foods over a 70-year lifetime. A risk estimate that is less than 
100% of the chronic PAD (the dose at which an individual could be 
exposed over the course of a lifetime and no adverse health effects 
would be expected) is not of concern to the Agency.
    For the general population, the acute no observed adverse effects 
level (NOAEL) of 600 milligrams/kilogram/day (mg/kg/day) was 
established, based on clinical signs and acute neurotoxic effects 
(i.e., neuronal cell necrosis in the brain and degeneration of sciatic 
nerve) in the acute rat neurotoxicity study at the lowest observed 
adverse effects level (LOAEL) of 2,000 mg/kg/day. For the females (13-
50 years) population subgroup, the acute NOAEL of 40 mg/kg/day was 
established, based on decreased fetal weights and increased incidences 
of misaligned sterebrae in the rat developmental study at the LOAEL of 
400 mg/kg/day. In this study, both maternal and developmental toxicity 
were observed at the same dose (400 mg/kg/day); therefore, no increased 
susceptibility to offspring was observed. The chronic NOAEL of 5 mg/kg/
day was established, based on decreased body weight gain (not 
statistically significant) and increased relative liver weight in male 
dogs from a 12-month dog feeding study at the LOAEL of 25 mg/kg/day. 
Based on available data, butylate is not carcinogenic, and has been 
classified as a Group E ``not likely'' carcinogen; therefore, no 
chronic (cancer) dietary risk assessment was conducted.
    An uncertainty factor of 100 was applied to risk assessments to 
account for interspecies extrapolation (10X) and intraspecies 
variability (10X). The FQPA safety factor to account for enhanced 
sensitivity of infants and children was removed (reduced to 1X) since: 
The toxicology data base is complete; the developmental and 
reproductive toxicity data did not indicate increased sensitivity or 
susceptibility of rats or rabbits to in utero and/or postnatal 
exposure; unrefined dietary exposure estimates (assuming all 
commodities contain tolerance level residues) will overestimate dietary 
exposure; modeling data are used for ground and surface source drinking 
water exposure assessments resulting in estimates considered to be 
upper-bound concentrations; and there are currently no registered 
residential uses for butylate. Additionally, there is no evidence to 
support a recommendation for a developmental neurotoxicity study.
    The acute and chronic dietary exposure analyses are based on the 
Dietary Exposure Evaluation Model (DEEMTM). The 
DEEMTM analysis evaluated the individual food consumption as 
reported by respondents in the USDA 1989-1992 nationwide Continuing 
Surveys for Food Intake by Individuals (CSFII) and accumulated exposure 
to the chemical for each commodity.
    The acute dietary (food) assessment for butylate is a Tier I 
deterministic analysis at the 95th percentile, and was 
conducted using tolerance level residues (0.1 ppm) and 100% crop 
treated. Tier I analysis was also conducted for chronic assessments 
using tolerance level residues and 100% crop treated. The estimated 
acute and chronic dietary (food) exposure consumed less than 1% of the 
respective acute and chronic PADs for all population subgroups; 
therefore, dietary (food) risk is not of concern to the Agency and no 
risk mitigation measures are necessary.

VII. Dietary Drinking Water Risks

    Drinking water exposure to pesticides can occur through surface 
and/or ground water contamination. EPA considers acute (1-day) and 
chronic (lifetime) drinking water risks and uses either modeling or 
actual monitoring data, if available, to estimate those risks. Modeling 
is carried out in tiers of further refinement, and is designed to 
provide a high-end estimate of exposure.
    Based on environmental fate data, butylate is mobile to slightly 
mobile in soil. However, significant residues of butylate are not 
expected to reach surface water under most conditions, because it is 
incorporated and partitions from soil to air readily. Although, soil 
incorporation favors downward movement to ground water over surface 
runoff, significant ground water contamination is still not expected 
under most conditions. Drinking water concentrations were estimated 
using GENEEC (Tier I-surface water) and SCI-GROW (Tier I-ground water) 
computer models. The drinking water assessment for butylate was 
conducted on parent butylate only, since no degradates of concern were 
identified. While limited monitoring data from surface and ground water 
sources are available on butylate and were lower than levels predicted 
by models, Tier I modeling estimates were used to assess exposure from 
both surface and ground water sources. These estimates were low and no 
further refinement was needed.
    For acute drinking water risk, the potential (peak) concentrations 
of butylate in surface water sources is 33.1 parts per billion (ppb), 
and in ground water sources is 0.41 ppb. For chronic drinking water 
risk, potential (average) concentrations of butylate in surface water 
sources is 10 ppb, and in ground water sources is 0.41 ppb. Neither 
GENEEC nor SCI-GROW Tier I drinking water models take into account 
volatility from soil or water. Because butylate dissipates primarily by 
volatility from soil, actual butylate concentrations in drinking water 
predicted from either model are likely lower.

VIII. Aggregate Risks

    Aggregate risk looks at the combined risk from exposure through 
food, drinking water, and residential uses. Generally, all risks from 
these exposures must be less than 100% of the acute and chronic PADs. 
For butylate, the aggregate risks are limited to food and

[[Page 47222]]

water exposure, because there are no residential uses.
    To determine the maximum allowable contribution from water allowed 
in the diet, EPA first looks at how much of the overall allowable risk 
is contributed by food and then determines a ``drinking water level of 
comparison'' (DWLOC) to ascertain whether modeled or monitored 
concentrations in drinking water exceed this level. Drinking water 
concentrations that are above the corresponding DWLOC are of concern to 
the Agency. When the acute and chronic DWLOCs are compared with the 
estimated concentrations of butylate in drinking water using 
conservative modeling, surface and ground water concentrations are 
substantially lower than the DWLOCs for all populations. To assess 
aggregate risk, the acute and chronic dietary (food) risk estimates are 
combined with the corresponding surface and ground water (drinking 
water) estimated concentrations. For butylate, both the acute and 
chronic aggregate (food + drinking water) risks are less than 100% of 
the respective acute and chronic PADs, and therefore, are not of 
concern to the Agency, nor do they warrant risk mitigation measures.

IX. Residential, Occupational, and Ecological Risk

    Residential risks were not assessed for butylate. Butylate is not 
registered for home use nor is it used in and around schools, or parks. 
Thus, there is no residential exposure to assess nor aggregate with the 
dietary exposure. Additionally, worker and ecological risks were not 
assessed for butylate, because butylate is under review for tolerance 
reassessment only. Occupational and ecological risk management 
decisions were made as part of the 1993 Butylate RED and have been 
implemented.

X. Tolerance Reassessment Summary

    Tolerances are established for residues of butylate (S-ethyl 
diisobutylthiocarbamate) in/on raw agricultural commodities as defined 
in 40 CFR 180.232. Because there is no reasonable expectation of finite 
residues in meat, milk, poultry, and eggs; tolerances for residues of 
butylate in meat, milk, poultry, and eggs are not required. Further, no 
change in the 0.1 ppb commodity tolerance expression is required; 
however, the Agency intends to revise the commodity definitions. These 
tolerance commodity name revisions are given in the table below, and 
will be the subject of rulemaking. Based on a review of the residue 
data submitted, the established tolerances of butylate remain in effect 
at 0.1 ppm for all registered commodities, until such time as a 
determination of whether a full reassessment of the cumulative risk 
from thiocarbamate pesticides, such as butylate, may be needed and is 
considered. Tolerance commodity name revisions are given in the table 
below in accordance with current Agency administrative practice.
Butylate Tolerances
Commodity
Current Tolerance
(ppm)
Reassessed Tolerance
(ppm)
Corrected Commodity
Definition
Corn, field, grain
0.1
0.1
 
Corn, pop, grain
0.1
0.1
 
Corn, sweet (kernels,
plus cob with husk
removed)
0.1
0.1
Corn, sweet, kernel
plus cob with husks
removed
Corn, field, fodder
0.1
0.1
Corn, field, stover
Corn, field, forage
0.1
0.1
 
Corn, pop, forage
0.1
0.1
Corn, pop, stover
Corn, sweet, forage
0.1
0.1
 

List of Subjects

    Environmental protection, Chemicals, Pesticides and pests.


    Dated: August 29, 2001.

Lois A. Rossi,
Director, Special Review and Reregistration Division, Office of 
Pesticide Programs.
[FR Doc. 01-22754 Filed 9-10-01; 8:45 am]
BILLING CODE 6560-50-S


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