### 7/26/2010

To: Docket

From: Elaine Manning, Sect or Based Assessment Group

Subject: Post Proposal Revisions for Nitril e Butadiene Rubber Facilities Risk and Technology Assessment

The attached minor revisions were made to the Nitrile Butadiene source category risk assessment which was included in the proposal for the Group I Polymers and Resins; Marine Vessel Loading Operation; Mine ral Wool Production; Pharmaceuticals Production; and Printing and P ublishing Industry rulemaking issued on October 10, 2008. The updated Table 3.8-1 Summary of Emissi ons from the Nitrile Butadiene Rubber Production Source Category and Table 3.8-2 Su mmary of Source Category Level Risk
for Nitrile Butadiene Rubber Production reflec ting the minor changes are attached. The most significant change from the Octobe r 10, 2008 proposal is the change in the maximum individual risk (MIR) and hazar d index (HI). Since the October 10, 2008 proposal several nitrile butadiene rubber production facilities have stopped production. Based on the one facility left in this sour ce category, the MIR for cancer has gone down to 2 in a million from the previously proposed MIR of 60 in a million. The HI is now 0.009 down from the value of 0.9 at proposal. The attached Appendices 1 and 6 provide the supporting information for the changes.

The MACT-allowable emissions from this source category are estimated to be approximately the same as the modeled actual emissions; therefore, the risks results are equal.

In addition to the risk presented by sour ce category alone as presented in the attached Post-NPRM Source Category Leve l Risk table, additional analysis was performed to access the “facility-w ide” risk. The results of the residual risk associated with all categories at the one f acility (facility-wide) are presented in the attached “Source Category and Facility Wide Risk Re sults for Nitrile Butadiene Rubber” spreadsheet. The detailed risk modeling results for the facility -wide assessment is available in Appendix 6.
We used the National Air Toxics Assessment (NATA) database for estimating facilitywide risks due to our lack of more recent faci lity-specific emissions data for some of the source categories included in the facility-w ide analyses. Additionally, because we have not yet begun our thorough residual risk review for most source categories, we are unable at this time to estimate allowable facility-wide emissions. Thus, our facility-wide analysis is based solely on actual emissions.

The maximum individual risk (MIR) a nd hazard index (HI) presented in the spreadsheet are based on emissions, as id entified in the NATA database, from all emissions sources at the identified facility. The maximum facility-wide risks at the one facility with an operating nitrile butadiene pr ocess are estimated to be a cancer MIR of 5

### in a million and an HI of 0.03. The source cate gory contribution to th e facility-wide risk at this facility is about 30% for both the MIR and HI.

### 3.8-1 Summary of Emissions from the Nitr ile Butadiene Rubber Production Source Category

Prioritized Inhalation Dose-Response Value Identified by OAQPS

HAP Emissions (tpy) Number of
Facilities Reporting HAP

(1 facilities in data set) Unit Risk
Estimate for

Cancer? Reference
Concentration
for
Noncancer? Health

Benchmark
Values for Acute
Noncancer? PBHAP?

1,3-Butadiene 0.9 1 Υ Υ Υ Acrylonitrile 0.9 1 Υ Υ Υ

### Table 3.8-2. Summary of Source Category Le vel Risks for Nitrile Butadiene Rubber
Production

Result HAP “Drivers” Facilities in Source Category Number of Major Source Facilities Estimated to be in Source Category 1 n/a

Number of Facilities Identified in NEI and
Modeled in Risk Assessment 1 n/a

Cancer Risks Maximum Individual Lifetime Cancer Risk (in 1 million) 2 acrylonitrile, 1,3-butadiene

Number of Facilities with Maximum Individual Lifetime Cancer Risk: Greater than or equal to 100 in 1 million 0 n/a Greater than or equal to 10 in 1 million 0 n/a Greater than or equal to 1 in 1 million 1 acrylonitrile, 1,3-butadiene

Chronic Noncancer Risks Maximum Reproductive Hazard I ndex 0.009 1,3-butadiene Number of Facilities with Maximu m Reproductive Hazard Index:

Greater than 1 0 n/a Acute Noncancer Screening Results

Maximum Acute Hazard Quotient 0.002

0.0002 acrylonitrile (AEGL-1) acrylonitrile (ERPG-2)

Number of Facilities With Potential for Acute
Effects 0 n/a

Population Exposure Number of People Living Within 50 Kilometers
of Facilities Modeled 1,000,000 n/a

Number of People Exposed to Cancer Risk: Greater than or equal to 100 in 1 million 0 n/a Greater than or equal to 10 in 1 million 0 n/a Greater than or equal to 1 in 1 million 70 n/a Number of People Exposed to Reproductive Hazard Index : Greater than 1 0 n/a Estimated Cancer Incidence (excess cancer cases per year) 0.0004 n/a

Contribution of HAP to Cancer Incidence acrylonitrile 72% n/a 1,3-butadiene 28% n/aSource Category and Facility-Wide Risk Results for Nitrile Butadiene Rubber ProductionFacilityID FacilityName City StateSourceCategory MIR(1 in million)SourceCategoryRepro_HIFacility-WideMIR(in 1 million)FacilityWideMAX_HIFacility-WideHI_TYPEPercentSourcerisk isofFacilityWideriskNB1_NEI32989ZEON CHEMICALS KY,INCLOUISVILLE KY 2 0.009 5 0.03RespiratoryHI33%Notes:1. NATA results (facility-wide) are from the final2005 NATA analysis, dated May 2010 and based on the 2005 NATA NEI.RTR results (source category only) are fromRTR modeling conducted in June 2010 and based on June 2010 data.Attachments: Appendix 1 Revised Emissions InventorySupport MemorandumAppendix 6 Detailed Risk Modeling Results