A. What Is the List of Hazardous Air Pollutants?

The list of HAP includes a wide variety of organic and inorganic substances released from large and small industrial operations, fossil fuel combustion, gasoline and dieselpowered vehicles, and many other sources. The HAP have been associated with a wide variety of adverse health effects, including cancer, neurological effects, reproductive effects, and developmental effects. The health effects associated with the various HAP may differ depending upon the toxicity of the individual HAP and the particular circumstances of exposure, such as the amount of chemical present, the length of time a person is exposed, and the stage in life of the person when the exposure occurs. The list of HAP, which includes MIBK, can be found in section 112(b)(1) of the CAA. The HAP list provides the basis for research, regulation, and other related EPA activities under the CAA.

B. What Is a Delisting Petition?

A delisting petition is a formal request to EPA from an individual or group to remove a specific HAP from the HAP list. The removal of a HAP from the list eliminates it from consideration in EPA's program to promulgate national, technologybased emissions control standards. This technologybased standards program is commonly referred to as the Maximum Achievable Control Technology (MACT) program.

Petitions to add or delete chemicals from the HAP list are allowed under section 112(b)(3)(A) of the CAA. The CAA specifies that any person may petition the Administrator to modify, by addition or deletion, the list of HAP. The EPA Administrator is required under section 112(b)(3)(A) of the CAA to either grant or deny a petition to delist a specific HAP within 18 months of the receipt of a complete petition.

To delete a substance from the HAP list, CAA section 112(b)(3)(C) requires that the petitioner must provide adequate data on the health and environmental effects of the substance to determine that emissions, ambient concentrations, bioaccumulation or deposition of the substance may not reasonably be anticipated to cause any adverse effects to human health or adverse environmental effects.

C. How Does EPA Review a Petition To Delist a HAP?

The petition review process proceeds in two phases: A completeness determination and a technical review. During the completeness determination, we conduct a broad review of the petition to determine whether all of the necessary subject areas are addressed. In addition, we determine if adequate data, analyses, and evaluation are included for each subject area. Once the petition is determined to be complete, we place a notice of receipt of a complete petition in the Federal Register. That notice announces a public comment period on the petition and starts the technical review phase of our decisionmaking process. The technical review determines whether the petition has satisfied the necessary requirements and can support a decision to delist the HAP. All comments and data submitted during the public comment period are considered during the technical review.

D. How Is the Decision To Delist a HAP Made?

The decision to either grant or deny a petition is made after a comprehensive technical review of both the petition and the information received from the public to determine whether the petition satisfies the requirements of section 112(b)(3)(C) of the CAA. If the Administrator decides to grant a petition, a proposal will be published in the Federal Register announcing that decision and the opportunity for public comment. That notice would propose a modification of the HAP list and present the reasoning for doing so. However, if the Administrator decides to deny a petition, a notice setting forth an explanation of the reasons for denial will be published instead. A notice of denial constitutes final Agency action of nationwide scope and applicability, and is subject to judicial review as provided in section 307(b) of the CAA.
III. Completeness Determination and Request for Public Comment

On April 22, 1997, we received a petition from the ACC's Ketones Panel to remove MIBK from the HAP list. Because of incomplete toxicological information on MIBK, discussions between EPA and the petitioner after the submittal led to a mutual agreement to suspend review of the petition to allow time for a twogeneration reproductive study. That study was completed in 2000 and was reviewed as part of EPA's ``Toxicological Review of Methyl Isobutyl Ketone'' which was completed in March 2003 (EPA635/R03002). After the publication of that document, the petitioner submitted an addendum on October 17, 2003, requesting that we evaluate the petition for completeness and grant the petition.

After reviewing the original petition and the two addenda, we have determined that all of the necessary subject areas for a human health and environmental risk assessment have been addressed. Therefore, the petition is complete and ready for technical review. The ACC's last addendum of October 17, 2003, marked the start of the 18month technical review and decision period. Today's notice initiates our comprehensive technical review of the petition and invites public comment on the substance of the petition as described above. IV. Description of Petition

The original petition and addenda provided by the ACC contain the following information:

The petition lists three companies (Eastman Chemical, Shell Chemical, and Union Carbide) that produced 220 million pounds domestically in 1995. The petition describes MIBK as being both a solvent and chemical intermediate. When used as a solvent, it is highly efficient for dissolving a wide variety of resins. Therefore, it is widely used in surface coatings, adhesives, inks, and traffic marking paints. The MIBK is also used as a solvent in cleaning fluids and dewaxing agents, and in the extraction of fats, oils, waxes, and resins. It is used in the formulation of highsolids coatings which are being used to reduce emissions of volatile organic compounds (VOC) from many types of coatings. The MIBK is reported to occur naturally in plants and animals, and has been identified as a natural component of several foods.

According to the petition, based on the chemical and physical properties of MIBK, inhalation is the only significant route of human exposure to MIBK emissions. Using the most recent TRI data and some sitespecific data as input in a tiered air dispersion modeling approach, the petition develops estimates of the maximum annual and 24 hour concentrations anticipated to occur at the boundaries of facilities known to emit MIBK. The petition compares modeling output to available health data to conclude that, given the low concentrations anticipated to occur at facility boundaries, MIBK cannot reasonably be anticipated to cause either acute or chronic adverse health effects to people living near these facilities.

The petition discusses the results of fugacity modeling that was performed to evaluate the fate of MIBK in air, water, soil and sediment. The results of the modeling indicate that the concentrations of MIBK in water, soil, and sediment are well below levels expected to pose hazards to human health or the environment.

Dated: July 12, 2004.
Robert D. Brenner,
Principal Deputy Assistant, Administrator for Air and Radiation. [FR Doc. 0416335 Filed 71604; 8:45 am]
BILLING CODE 656050P

FOR FURTHER INFORMATION CONTACT Mr. Mark Morris, Office of Air Quality Planning and Standards, Emission Standards Division (Mailcode C40401), U.S. EPA, 109 TW Alexander Drive, Research Triangle Park, NC 27711; telephone number: (919) 5415416; fax number: (919) 5410840; email address: morris.mark@epa.gov.