7/26/2010 

To: Docket 

From: Elaine Manning, Sector Based Assessment Group 

Subject: Post Proposal Revisions for Polybutadiene Rubber Production Risk and 

Technology Assessment 

The attached minor revisions were made to the Polyutadiene Rubber Production source 

category risk assessment which was included in the proposal for the Group I Polymers and 

Resins; Marine Vessel Loading Operation; Mineral Wool Production; Pharmaceuticals 

Production; and Printing and Publishing Industry rulemaking issued on October 10, 2008. The 

updated Table 3.6-1 Summary of Emissions from the Polybutadiene Rubber Production Source 

Category and Table 3.6-2 Summary of Source Category Level Risk for Polybutadiene Rubber 

Production reflecting the minor changes are attached. The most significant change from the 

October 10, 2008 proposal is the change in the maximum individual risk (MIR) and hazard index 

(HI). Since the October 10, 2008 proposal we received some updated emissions information for 

the polybutadiene rubber production facilities. Based on this new emissions information, the 

MIR for cancer has gone up to 30 in a million from the previously proposed MIR of 10 in a 

million. The HI is now 0.3, up from the value of 0.2 at proposal. The acute results also changed 

slightly. The attached Appendices 1, 6, and 7 provide the supporting information for the 

changes. 

The MACT-allowable emissions of the compound (1,3-butadiene) driving the risk from 

this source category is estimated to be approximately the same as the modeled actual emissions; 

therefore, the risks results are equal. 

In addition to the risk presented by source category alone as presented in the attached 

Post-NPRM Source Category Level Risk table, additional analysis was performed to access the 

“facility-wide” risk. The results of the residual risk associated with all categories at the one 

facility (facility-wide) are presented in the attached “Source Category and Facility Wide Risk 

Results for Polybutadiene 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 facility-wide risks due to our lack of more recent 

facility-specific emissions data for some of the source categories included in the facility-wide 

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) and hazard index (HI) presented in the spreadsheet 

are based on emissions, as identified in the NATA database, from all emissions sources at the 

identified facility. The facility with the maximum facility-wide risks is estimated to have a 

cancer MIR of 30 in a million and an HI of 0.3. The source category contribution to the facilitywide risk at this facility is 100% for both the MIR and the HI. 

 
Table 3.6-1 Summary of Emissions from the Polybutadiene Rubber Production Source 

Category 

Prioritized Inhalation Dose-Response Value Identified 

by OAQPS 

HAPa Emissions 

(tpy) 

Number 

of 

Facilities 

Reporting 

HAP (5 

facilities 

in data 

set) 

Unit Risk 

Estimate for 

Cancer? 

Reference 

Concentration for 

Noncancer? 

Health Benchmark 

Values for Acute 

Noncancer? 

PBHAP? 

Hexane 1,584 4 Υ Υ 

Toluene 510 2 Υ Υ

1,3-Butadiene 74 5 Υ Υ Υ

Styrene 68 5 Υ Υ

Ethyl Benzene 23 1 Υ

Chlorobenzene 2 1 Υ Υ

Methanol 0.07 1 Υ Υ

Nickel 0.0007 1 Υ Υ Υ
Table 3.6-2 Summary of Source Category Level Risks for Polybutadiene Rubber Facilities 

Result HAP “Drivers” 

Facilities in Source Category 

Number of Major Source Facilities Estimated to 

be in Source Category 5 n/a 

Number of Facilities Identified in NEI and 

Modeled in Risk Assessment 5 n/a 

Cancer Risks 

Maximum Individual Lifetime Cancer Risk (in 1 

million) 30 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 2 1,3-butadiene 

 Greater than or equal to 1 in 1 million 4 1,3-butadiene 

Chronic Noncancer Risks 

Maximum Reproductive Hazard Index 0.3 1,3-butadiene 

Number of Facilities with Maximum Reproductive Hazard Index: 

 Greater than 1 0 n/a 

Acute Noncancer Screening Results

Maximum Acute Hazard Quotient 

12 

0.6 

0.2 

toluene (REL) 

toluene (AEGL-1) 

toluene (ERPG-2) 

Number of Facilities With Potential for Acute 

Effects 1 toluene (REL) 

Acute Noncancer Refined Results

Maximum Acute Hazard Quotient 1 toluene 

Number of Facilities With Potential for Acute 

Effects 0 

Population Exposure 

Number of People Living Within 50 Kilometers 

of Facilities Modeled 1,700,000 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 20 n/a 

 Greater than or equal to 1 in 1 million 24,000 n/a 

Number of People Exposed to Reproductive Hazard Index: 

 Greater than 1 0 n/a 

Estimated Cancer Incidence (excess cancer cases 

per year) 0.003 n/a 

Contribution of HAP to Cancer Incidence 

 1,3-butadiene 98% n/a 

 ethyl benzene 2% n/a 
Source Category and Facility-Wide Risk Results for Polybutadiene Rubber Production 

FacilityID FacilityName City State

Source 

Category 

MIR 

(in 1 

million) 

Source 

Category

Repro_HI

FacilityWide MIR 

(in 1 

million) 

FacilityWide MAX_HI

PB1_NEI7446 

LANXESS CORPORATION ORANGE TX 30 0.3 30 0.3

PB1_NEI7039 

GOODYEAR TIRE & RUBBER BEAUMONT CHEMICAL PLANT BEAUMONT TX 10 0.2 10 0.2

PB1_NEI32876 

AMERICAN SYNTHETIC RUBBER LOUISVILLE KY 3 0.05 3 0.05

PB1_NEI8307 Firestone ORANGE TX 9 0.2 10 0.2PB1_NEI33012 

FIRESTONE POLYMERS/LAKE CHARLES FACILITY SULPHUR LA 1 0.009 2 0.04

Notes: 1. NATA results (facility wide) are from the final 2005 NATA analysis, dated May 2010 and based on the 2005 NATA NEI.  RTR results (source category only) are from RTR modeling conducted in June 2010 and based on June 2010 data. 

Attachments: Appendix 1 Revised Emissions Inventory Support Memorandum  Appendix 6 Detailed Risk Modeling Results  Appendix 7 Acute Impacts Refined Analysis Figures