美國環(huán)境保護署制定調環(huán)酸鈣在飼料中的農藥殘留限量

1. Dietary exposure from food and feed uses. In evaluating dietary exposure to prohexadione calcium, EPA considered exposure under the petitioned-for tolerances as well as all existing prohexadione calcium tolerances in 40 CFR 180.547. EPA assessed dietary exposures from prohexadione calcium in food as follows:

i. Acute exposure. Quantitative acute dietary exposure and risk assessments are performed for a food-use pesticide, Start Printed Page 8459if a toxicological study has indicated the possibility of an effect of concern occurring as a result of a 1-day or single exposure.

No such effects were identified in the toxicological studies for prohexadione calcium; therefore, a quantitative acute dietary exposure assessment is unnecessary.

ii. Chronic exposure. In estimating chronic dietary exposure, EPA used 2003-2008 food consumption information from the U.S. Department of Agriculture's (USDA's) National Health and Nutrition Examination Survey, What We Eat in America, (NHANES/WWEIA). As to residue levels in food, the chronic assessment was based on tolerance-level residues and 100 percent crop treated (PCT).

iii. Cancer. based on the data summarized in Unit III.A., EPA has concluded that prohexadione calcium does not pose a cancer risk to humans. Therefore, a dietary exposure assessment for the purpose of assessing cancer risk is unnecessary.

iv. Anticipated residue and PCT information. EPA did not use anticipated residue or PCT information in the dietary assessment for prohexadione calcium. Tolerance level residues and 100 PCT were assumed for all food commodities.

2. Dietary exposure from drinking water. The Agency used screening level water exposure models in the dietary exposure analysis and risk assessment for prohexadione calcium in drinking water. These simulation models take into account data on the physical, chemical, and fate/transport characteristics of prohexadione calcium. Further information regarding EPA drinking water models used in pesticide exposure assessment can be found at http://www2.epa.gov/?pesticide-science-and-assessing-pesticide-risks/?about-water-exposure-models-used-pesticide.

based on the Pesticide in Water Calculator (PWC), the estimated drinking water concentrations (EDWCs) of prohexadione calcium for chronic exposures are estimated to be 29 ppb for surface water and 5.1 × 10−7 ppb for ground water.

Modeled estimates of drinking water concentrations were directly entered into the dietary exposure model. For the chronic dietary risk assessment, the water concentration of value 29 ppb was used to assess the contribution to drinking water.

3. From non-dietary exposure. The term “residential exposure” is used in this document to refer to non-occupational, non-dietary exposure (e.g., for lawn and garden pest control, indoor pest control, termiticides, and flea and tick control on pets).

Prohexadione calcium is currently registered for the following uses that could result in residential exposures: Residential lawns, ornamentals, athletic fields, parks, and golf courses. EPA assessed residential exposure using the following assumptions: Residential handler exposure is not expected because all registered labels require the use of personal protective equipment (PPE) and are not intended for application by homeowners. Short-term exposure was assessed for post-application incidental oral exposures of children 1 to less than 2 years old. The Agency assessed hand-to-mouth exposures and incidental soil ingestion from applications to turf for children. Intermediate- and long-term exposures are not expected since there are no registered or proposed uses of prohexadione calcium that result in intermediate- or long-term residential exposures.

Further information regarding EPA standard assumptions and generic inputs for residential exposures may be found at http://www2.epa.gov/?pesticide-science-and-assessing-pesticide-risks/?standard-operating-procedures-residential-pesticide.

4. Cumulative effects from substances with a common mechanism of toxicity. Section 408(b)(2)(D)(v) of FFDCA requires that, when considering whether to establish, modify, or revoke a tolerance, the Agency consider “available information” concerning the cumulative effects of a particular pesticide's residues and “other substances that have a common mechanism of toxicity.”

EPA has not found prohexadione calcium to share a common mechanism of toxicity with any other substances, and prohexadione calcium does not appear to produce a toxic metabolite produced by other substances. For the purposes of this tolerance action, therefore, EPA has assumed that prohexadione calcium does not have a common mechanism of toxicity with other substances. For information regarding EPA's efforts to determine which chemicals have a common mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see EPA's website at http://www2.epa.gov/?pesticide-science-and-assessing-pesticide-risks/?cumulative-assessment-risk-pesticides.

1. In general. Section 408(b)(2)(C) of FFDCA provides that EPA shall apply an additional tenfold (10X) margin of safety for infants and children in the case of threshold effects to account for prenatal and postnatal toxicity and the completeness of the database on toxicity and exposure unless EPA determines based on reliable data that a different margin of safety will be safe for infants and children. This additional margin of safety is commonly referred to as the FQPA Safety Factor (SF). In applying this provision, EPA either retains the default value of 10X, or uses a different additional safety factor when reliable data available to EPA support the choice of a different factor.

2. Prenatal and postnatal sensitivity. In rats and rabbits, no increased quantitative or qualitative pre- or postnatal susceptibility was observed. In the 2-generation reproductive toxicity study with rats, parental toxicity (minimal mortality) occurred at a dose well below the dose that caused decreases in offspring body weight.

3. Conclusion. EPA has determined that reliable data show the safety of infants and children would be adequately protected if the FQPA SF were reduced to 1X. That decision is based on the following findings:

i. The toxicity database for prohexadione calcium is complete.

ii. There is no indication that prohexadione calcium is a neurotoxic chemical and there is no need for a developmental neurotoxicity study or additional UFs to account for neurotoxicity.

iii. There is no evidence that prohexadione calcium results in increased susceptibility in in utero rats or rabbits in the prenatal developmental studies or in young rats in the 2-generation reproduction study.

iv. There are no residual uncertainties identified in the exposure databases. The dietary food exposure assessment was performed based on 100 PCT and tolerance-level residues. EPA made conservative (protective) assumptions in the ground and surface water modeling used to assess exposure to prohexadione calcium in drinking water. EPA used similarly conservative assumptions to assess post-application exposure of children as well as incidental oral exposure of toddlers. These assessments will not underestimate the exposure and risks posed by prohexadione calcium.

EPA determines whether acute and chronic dietary pesticide exposures are safe by comparing aggregate exposure estimates to the acute PAD (aPAD) and chronic PAD (cPAD). For linear cancer risks, EPA calculates the lifetime probability of acquiring cancer given the Start Printed Page 8460estimated aggregate exposure. Short-, intermediate-, and chronic-term risks are evaluated by comparing the estimated aggregate food, water, and residential exposure to the appropriate PODs to ensure that an adequate MOE exists.

1. Acute risk. An acute aggregate risk assessment takes into account acute exposure estimates from dietary consumption of food and drinking water. No adverse effect resulting from a single oral exposure was identified and no acute dietary endpoint was selected. Therefore, prohexadione calcium is not expected to pose an acute risk.

2. Chronic risk. Using the exposure assumptions described in this unit for chronic exposure, EPA has concluded that chronic exposure to prohexadione calcium from food and water will utilize 17% of the cPAD for children 1 to 2 years old, the population group receiving the greatest exposure. based on the explanation in Unit III.C.3., regarding residential use patterns, chronic residential exposure to residues of prohexadione calcium is not expected.

3. Short-term risk. Short-term aggregate exposure takes into account short-term residential exposure plus chronic exposure to food and water (considered to be a background exposure level).

Prohexadione calcium is currently registered for uses that could result in short-term residential exposure, and the Agency has determined that it is appropriate to aggregate chronic exposure through food and water with short-term residential exposures to prohexadione calcium.

Using the exposure assumptions described in this unit for short-term exposures, EPA has concluded the combined short-term food, water, and residential exposures result in an aggregate MOE of 2,300 for children 1 to less than 2 years old. Because EPA's level of concern for prohexadione calcium is an MOE below 100, this MOE is not of concern.

4. Intermediate-term risk. Intermediate-term aggregate exposure takes into account intermediate-term residential exposure plus chronic exposure to food and water (considered to be a background exposure level).

An intermediate-term adverse effect was identified; however, prohexadione calcium is not registered for any use patterns that would result in intermediate-term residential exposure. Intermediate-term risk is assessed based on intermediate-term residential exposure plus chronic dietary exposure. Because there is no intermediate-term residential exposure and chronic dietary exposure has already been assessed under the appropriately protective cPAD (which is at least as protective as the POD used to assess intermediate-term risk), no further assessment of intermediate-term risk is necessary, and EPA relies on the chronic dietary risk assessment for evaluating intermediate-term risk for prohexadione calcium.

5. Aggregate cancer risk for U.S. population. based on the lack of evidence of carcinogenicity in two adequate rodent carcinogenicity studies, prohexadione calcium is not expected to pose a cancer risk to humans.

6. Determination of safety. based on these risk assessments, EPA concludes that there is a reasonable certainty that no harm will result to the general population, or to infants and children from aggregate exposure to prohexadione calcium residues.

Adequate enforcement methodology (gas chromatography/mass-selective detector (GC/MSD) and liquid chromatography with tandem mass spectroscopy (LC-MS/MS)) is available to enforce the tolerance expression.

The method may be requested from: Chief, Analytical Chemistry Branch, Environmental Science Center, 701 Mapes Rd., Ft. Meade, MD 20755-5350; telephone number: (410) 305-2905; email address: residuemethods@epa.gov.

In making its tolerance decisions, EPA seeks to harmonize U.S. tolerances with international standards whenever possible, consistent with U.S. food safety standards and agricultural practices. EPA considers the international maximum residue limits (MRLs) established by the Codex Alimentarius Commission (Codex), as required by FFDCA section 408(b)(4). The Codex Alimentarius is a joint United Nations Food and Agriculture Organization/World Health Organization food standards program, and it is recognized as an international food safety standards-setting organization in trade agreements to which the United States is a party. EPA may establish a tolerance that is different from a Codex MRL; however, FFDCA section 408(b)(4) requires that EPA explain the reasons for departing from the Codex level.

The Codex has not established MRLs on alfalfa or corn for prohexadione calcium.

Therefore, tolerances with regional registration are established for residues of prohexadione calcium in or on alfalfa, forage at 0.1 ppm; alfalfa, hay at 0.1 ppm; corn, field, forage at 0.1 ppm; corn, field, grain at 0.1 ppm; and corn, field, stover at 0.1 ppm.

This action establishes and modifies tolerances under FFDCA section 408(d) in response to a petition submitted to the Agency. The Office of Management and Budget (OMB) has exempted these types of actions from review under Executive Order 12866, entitled “Regulatory Planning and Review” (58 FR 51735, October 4, 1993). Because this action has been exempted from review under Executive Order 12866, this action is not subject to Executive Order 13211, entitled “Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use” (66 FR 28355, May 22, 2001) or Executive Order 13045, entitled “Protection of Children from Environmental Health Risks and Safety Risks” (62 FR 19885, April 23, 1997), nor is it considered a regulatory action under Executive Order 13771, entitled “Reducing Regulations and Controlling Regulatory Costs” (82 FR 9339, February 3, 2017). This action does not contain any information collections subject to OMB approval under the Paperwork Reduction Act (PRA) (44 U.S.C. 3501 et seq.), nor does it require any special considerations under Executive Order 12898, entitled “Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations” (59 FR 7629, February 16, 1994).

Since tolerances and exemptions that are established on the basis of a petition under FFDCA section 408(d), such as the tolerances in this final rule, do not require the issuance of a proposed rule, the requirements of the Regulatory Flexibility Act (RFA) (5 U.S.C. 601 et seq.), do not apply.

This action directly regulates growers, food processors, food handlers, and food retailers, not States or tribes, nor does this action alter the relationships or distribution of power and responsibilities established by Congress in the preemption provisions of FFDCA section 408(n)(4). As such, the Agency has determined that this action will not have a substantial direct effect on States or tribal governments, on the relationship between the National Government and the States or tribal governments, or on the distribution of Start Printed Page 8461power and responsibilities among the various levels of government or between the Federal Government and Indian tribes. Thus, the Agency has determined that Executive Order 13132, entitled “Federalism” (64 FR 43255, August 10, 1999) and Executive Order 13175, entitled “Consultation and Coordination with Indian Tribal Governments” (65 FR 67249, November 9, 2000) do not apply to this action. In addition, this action does not impose any enforceable duty or contain any unfunded mandate as described under Title II of the Unfunded Mandates Reform Act (UMRA) (2 U.S.C. 1501 et seq.).

This action does not involve any technical standards that would require Agency consideration of voluntary consensus standards pursuant to section 12(d) of the National Technology Transfer and Advancement Act (NTTAA) (15 U.S.C. 272 note).

Pursuant to the Congressional Review Act (5 U.S.C. 801 et seq.), EPA will submit a report containing this rule and other required information to the U.S. Senate, the U.S. House of Representatives, and the Comptroller General of the United States prior to publication of the rule in the Federal Register. This action is not a “major rule” as defined by 5 U.S.C. 804(2).