July 15, 2010

1 ESTIMATION OF MACT ALLOWABLE EMI SSION LEVELS AND A SSOCIATED RISKS

AND IMPACTS FOR FOUR GROUP I POLYME RS AND RESINS SOURCE CATEGORIES

The purpose of this document is to present an alyses related to “MAC T allowable” emissions levels for four source categories covered by the Group 1 Polymers and Resins NESHAP (Polymers and Resins I NESHAP) that are being addresse d under EPA’s Risk and Technology Review (RTR) program. This program is addressing the statutor y requirements in section 112(f) and 112(d)(6) of the Clean Air Act for federal air toxics regulations. The regulations are National Emission Standards for Hazardous Air Pollutants (NESHAP) contained in 40 CF R part 63. They are commonly referred to as

Maximum Achievable Control Tec hnology (MACT) standards. The emissions data being used for the RTR risk assessments for these categories consis ts of data representative of “actual” emission

levels. In addition to the risks associated with these actual emission levels, EPA also considers the

levels of HAP emissions that sour ces could emit and still be in comp liance with the applicable MACT regulation. These emission levels are referred to as “MACT allowable” emissions. The purpose of

this memorandum is to discuss these MACT allo wable emission levels and their impact on the

baseline risks.

The Polymers and Resins I addresses nine source categories, four of which are the subject of this memorandum: Epichlorohydrin Elastomers Production, Nitrile Buta diene Rubber Production, Polybutadiene Rubber Production, and Styren e Butadiene Rubber and Latex Production.

This memorandum is organized as follows. Se ction 1 presents the estimated maximum risk

levels based on the actual emission levels for all four source categor ies, and Section 2 discusses the basic approach to estimating the risks from the MACT allowable levels. This is followed by a

discussion of the estimation of MACT allowable emissi on level, particularly as it relates to the actual

emission levels used in the risk assessments. This is followed by a presentation of the estimated risks

at these MACT allowable levels.

1.0 Risk Levels Based on Actual Emissions

The estimated maximum inhalation risks for th ese four source categories are summarized in

Table 1. These risks are based on actual emission levels.July 15, 2010

2 Table 1. Summary of Estimated Inhalation Risks for the Four Polymers and Resins I Source Categories Based On Actual Emissions Levels

Source Category Maximum individual cancer risk (in a million) 1 Maximum chronic

noncancer TOSHI 2

Epichlorohydrin Elastomers Production 10 0.1

Nitrile Butadiene Rubber Production 2 0.009

Polybutadiene Rubber Production 30 0.3

Styrene Butadiene Rubber and Latex Production 10 0.2

1 Maximum individual excess lifetime cancer risk.

2 Maximum target organ specific hazard index (TOSHI). Target organ system represented by the TOSHI varies across source categories. Maximum TOSHI is respiratory for epichlorohydrin elastomers production. Maximum TOSHI for nitrile butadiene rubber production, polybutadiene rubber production, and styrene butadiene rubber and latex production is based on reproductive effects.

2.0 Basic Approach to Estimating Risks from MACT Allowable Emission Levels

Detailed emission point-specific MACT allowabl e emissions information is not available. Therefore, modeling was not conduct ed to estimate the risks from MACT allowable emission levels.

The basic approach to estimate the risks from MACT allowable emission levels was to first estimate the relationship between the actual and MACT allowable emission levels, and then to estimate the potential risk impacts from the differences between actual and MACT allowable emissions. In general, the risk impact was assume d to be proportional to the difference in emission levels. For example, if MACT allowable emissions we re estimated to be three times as high as actual emissions, it was assumed that risks could be as much as three times as high as those estimated from the modeling conducted using actual emissions.

This assumption regarding the linear relations hip between emissions a nd risks is generally

reasonable for chronic cancer and noncancer risks. However, using this approach for acute risks would likely overestimate the impacts. The acute assessment already has built in numerous conservative assumptions. First, the acute assessment assumed a s hort-term emission rate up to 10 times that of the average longer term emission ra te. Also, the maximum acute risks assume the simultaneous occurrence of independent factors that may vary greatly, such as hourly emissions rates, meteorology, and human activity patterns. In the assessment using actual emissions, EPA assumed

that individuals remained for 1 hour at the point of maximum ambien t concentration as determined by the co-occurrence of peak emissions and worst-ca se meteorological conditions. These assumptions

would tend to overestimate actual ex posures since it is unlikely that a person would be located at the point of maximum exposure during the time of worst- case impact. The addition of another factor to

account for MACT allowable emissions level further increases the conservativeness of the estimated MACT allowable acute risks. Therefore, this anal ysis does not estimate acute risks for the MACTallowable emissions level.July 15, 2010

3 3.0 Results of Analysis

The Group 1 Polymers and Resins NESHAP addr esses emissions from the following types of

emission sources for all four sour ce categories: (1) storage tanks, (2) front-end process vents, (3) back-end process operations, (4) equipment leaks, and (5) wastewater. The process “front-end” includes pre-polymerization, reaction, stripping, and material recovery operations. In addition, the

NESHAP addresses emissions from back-end process operations for the Polybutadiene and Styrene Butadiene Rubber and Latex source categories, where the process “back-end” includes all operations after stripping (predominately drying and finishing) . Table 2 summarizes the formats of the standards for these emission points.

Table 2. Formats of Standards for Group 1 Polymers and Resins I NESHAP

Emission Source Type Format of Primary Standard Storage Tanks Equipment Standards

Front-End Process Vents Performan ce Standard (% reduction) Back-End Process (only for Polybutadiene and Styrene Butadiene Rubber) Emission Limit (kg emissions/Mg latex or crumb rubber) Equipment Leaks Work Practice Standards Wastewater Equipment Standards, Performance Standard

The ability to estimate MACT allowable emissions for specific emission points, or for specific emission point types, is largely de pendent on the format of the standa rds. For equipment standards, sources subject to the regulation are required to install specific equipment. Assuming that the equipment is maintained properly and is in good wo rking condition (as required) , there would not be a

difference in the actual emissions level and the le vel allowed by the standard. Similarly, there would

be no difference between actual and MACT allowable emissions for em ission sources subject to work practice requirements, provided that facilities are not conducting additional work practices proven to reduce emissions beyond those requir ed in the rule. We are not aw are of any such situations at facilities in these five Group 1 Polymers and Resi ns source categories. Therefore, for equipment leaks and storage vessels, which are subject to equi pment and work practice standards, we believe that

the actual emission levels are a reasonable estim ation of the levels a llowed by the standard.

For wastewater emission sources, the regulati on includes an assortme nt of equipment and performance standards. As discu ssed above, it is reasonable to assume that the actual emissions from those sources subject to equipment standards are representa tive of the MACT allowable emissions. In general, it is possible that source s could overcontrol sources subject to a performance standard. This

would result in the actual emissi ons being lower than the MACT a llowable emissions. However, for

wastewater sources, we are not awar e of any such overcontrol. Theref ore, we believe that the actual

wastewater emission levels are a reasonable esti mation of the levels allowed by the standard.

For front-end process vents, which are subject to a performance standard, we believe that there

are situations where sources are utilizing control devices that ac hieve reductions greater than the required 98 percent reduction. Howe ver, the continuous monitoring requ irements of the rule result in situations where reductions greater than 98 percent are required on a continuous basis. Specifically, owners and operators are required to conduct performance tests to de monstrate initial compliance. During the test, they are require d to monitor a specific paramete r (e.g., temperature for a thermal incinerator). From the data colle cted during the test, they are requi red to calculate a parameter levelJuly 15, 2010

4 (e.g., a minimum temperature) that is indicative of the control device performance achieved during the test. Ongoing compliance is then determined based on the continuous monitoring of this parameter as compared to the established level (e .g., if the incinerator temperature falls below the minimum temperature established during the test it would be an excursion) . Therefore, if an incinerator was achieving a 99 percent emissi on reduction during the performance test, the temperature level established based on monitoring da ta collected during the test would be reflective of a 99 percent reduction. Thus, the performance leve l required by the rule would, in effect, be 99 percent. Because of these requirements, we assu me that the actual emission levels are a reasonable estimation of MACT allowable emissions for front-end process vents.

Since there are no standards applicable to the back-end process emissions from Epichlorohydrin, and Nitrile Butadiene Rubber, the MACT allowable and actual emissions are equivalent. As shown in Table 2, the format of standards for emissions from back-end process operations at plants in the Po lybutadiene Rubber Production and St yrene Butadiene Rubber and Latex production is an emission limitation based on production. The units of the standard for Polybutadiene Rubber Production are kilograms HAP emissions allo wed per Megagram of crumb rubber product. Crumb rubber is the final product of this process, so MACT allowa ble emissions can be estimated using production data. Since actu al production data are confidential business information, an estimate of production was determined using published “namepla te” capacities. The result of this calculation is that MACT allowable emissions are approxima tely 10,600 tons/year, which is approximately seven times higher than the actual emissions of around 1,600 tons/yr for the plants in the Polybutadiene Rubber Production source category. Details of this calculation are provid ed in Attachment 1.

The units of the back-end pro cess operations standard for th e Styrene Butadiene Rubber and Latex Production source category ar e kilograms HAP emissions allo wed per Megagram of latex. Facilities subject to this standard utilize an emul sion process, where the reaction occurs in a waterbased solution forming a latex. Following the formation of this latex, steam is injected into the latex which results in the coagulation of solid rubber crumb, which is the final product. It should be noted that there are nine major source f acilities in the data set for the Styrene Butadiene Rubber and Latex Production source category. However, only three of these facilities produce rubber. At the six other facilities, the final product is styrene butadiene la tex. Therefore, they do not produce a solid product and do not have back-end processes. While an es timate of the amount of final crumb product can be obtained from “nameplate” capacities, an additional assumption regarding the re lative weight of the crumb in the latex is required. The result of this calculation is that MACT allowable emissions are approximately 1,100 tons/yr, which is around five times higher than the actual emissions of approximately 240 tons/yr from the styrene buta diene rubber production f acilities in the source category that are subject to this emission limitation. Details of this calcula tion are also provided in

Attachment 1.

Table 3 summarizes the ratios of MACT allo wable to actual emissions for the five Group 1 Polymers and Resins source categories. As di scussed above and summarized in Table 3, the only emission point type where the MACT allowable em issions levels are different from the actual emissions levels are the back-end process emissi ons from the Polybutadiene Rubber and Styrene Butadiene Rubber and Latex source categories. Ta ble 4 shows the overall back-end emission levels for these two source categories. Overall for the em issions from all sources from the category, the MACT allowable emissions from the Polybutadiene Rubber source category are seven times as high

as the actual emissions. This ratio is four fo r the Styrene Butadiene Rubber and Latex source

category.July 15, 2010

5 Table 3. Summary of MACT Allowable to Ac tual Emission Ratios for Four of the Group 1 Polymers and Resins Source Categories

Ratio of MACT Allowable Emis sions to Actual Emissions

Source Category Storage

Vessels Front-End

Process

Vents Back-End

Process Operations Equipment

Leaks Wastewater

Epichlorohydrin 1:1 1:1 1:1 1:1 1:1

Nitrile Butadiene

Rubber 1:1 1:1 1:1 1:1 1:1

Polybutadiene

Rubber 1:1 1:1 7:1 1:1 1:1

Styrene Butadiene

Rubber and Latex 1:1 1:1 5:1 1:1 1:1

Table 4. Summary of MACT Allowable to Actual Emission Emissions for Polybutadiene Rubber and Styrene Butadiene Rubber and Latex

HAP Emissions (tons/yr) Emission Source Type Actual MACT Allowable Polybutadiene Rubber Back-end process vent 1,594 10,593 Styrene Butadiene Rubber and Latex Back-end process vent 237 1,140

The risk assessment conducted for these categor ies in 2010 did not explicitly estimate risks

from individual emission sources types. However, it did identify the sources that contribute at least 90 percent of the maximum risk. Using this in formation on the risk driver emission sources, estimates were made of the upper bound impact the higher MACT-allowable back-end emissions

levels could have on the maximum risks. Following is an example of this methodology.

The maximum cancer risk from a hypothetical polybutadiene rubber production facility was 8.2 in 1 million, a which would be reported at 8 in 1 million. Assume HAP emissions from a front-end process vent contributed 85 percent of this risk and HAP emissions from a storage tank contributed 10 percent. Therefore, the sources contributing 95 percent of this maximum cancer risk, or 7.8 in 1 million, were known. Since the ratio of MACT-allowa ble to actual emissions for these source types was 1:1, this would represent the MACT-allowable ri sk from these sources. While the contribution from back-end process emissions was not explici tly reported, the upper bound contribution of the back end process emissions would be 5 percent of this maximum cancer risk based on actual emissions, or 0.4 in 1 million. A factor was applied to account for the fact that some HAP emitted from the back-end process operations are not carcinoge ns (i.e., do not have a unit risk estimate) and

would not contribute to the estimated cancer risks. The ma ss percentage of carcinogens to noncarcinogens was applied to the up per bound risk contribution to estimate the potential contribution

to the maximum cancer risk based on actual emi ssions. Assuming that the only 30 percent of the

a Note: Risks are only reported to one significant figure. However, this calculation was conducted with raw risk numbers before this rounding.July 15, 2010

6 back-end emissions, by mass, were of carcinogenic HAP , the potential risk from the back end would be 0.12 in 1 million. Applying the 7:1 factor woul d indicate that the MACT -allowable cancer risk from back-end process emissions is 0.8 in 1 million. Adding this risk to the 8.2 in 1 million MACTallowable risk from the front-end vents and stor age tanks, the upper bound ma ximum cancer risk at

the MACT-allowable level would be 9 in 1 million.

Table 5 shows the facility-specific comparis on of maximum risks ba sed on both actual and MACT-allowable emission levels for the Polybuta diene and Styrene Butadi ene Rubber and Latex source categories. As can be seen from Table 5, the maximum risks for both categories are the same

at both the actual and MACT-allo wable emission levels. Appendi x B provides details of these

estimates.

Table 5. Facility-Specific Maximum Risks Base d on MACT Allowable and Actual Emission Levels for Polybutadiene Rubber and Styrene Butadiene Rubber and Latex

Maximum individual cancer risk (in a million) Maximum chronic noncancer

TOSHI

Facility ID Actual

Emissions MACTAllowable

Emissions Actual

Emissions MACTAllowable

Emissions Polybutadiene Rubber Production

NEI32876 3 3 0.05 0.05

NEI33012 0.5 0.5 0.01 0.01

NEI7039 10 10 0.2 0.2

NEI7446 20 20 0.3 0.3

NEI8307 9 9 0.2 0.2 Styrene Butadiene Rubber and Latex Production

NEI13230 7 7 0.1 0.1

NEI33015 3 3 0.1 0.1

NEI8360 10 10 0.2 0.2 Note: The source category maximum risk from the polybutadien e source category is 30 due to the close proximately of

facilities

Following are the conclusi ons from this analysis:

• The only emission point where there is an appreci able difference in emissions at the actual

level and the MACT allowable level is back -end process operations for the Polybutadiene Rubber and Styrene Butadiene Rubber and Latex source categories.

• The maximum risks based on actual emission le vels from the Polybutadiene Rubber and Styrene Butadiene Rubber and Latex source ca tegories are based on emissions from sources other than the back-end process operations.

• The overall conclusion is that the maximum risks for the four Polymers and Resins source categories are the same for both th e actual emissions level and the MACT

allowable emissions level.July 15, 20101ATTACHMENT A. ESTIMATION OFGROUP 1 POLYMERS AND RESINSBACK-END PROCESS MACT ALLOWABLE EMISSIONSTable A-1. Estimation of MACT AllowableBack-End Emissions for Polybutadiene RubberFacility“NamePlate”Capacity1(Mg/yr)ActualProductionCapacity2(Mg/yr)MACTAllowableHAPEmissions3(kg/yr)MACTAllowableHAPEmissions(tons/yr)Actual HAPEmissions(tons/yr)AMERICAN SYNTHETIC RUBBER 180,000 162,000 1,620,000 1,782 362LANXESS 180,000 162,000 1,620,000 1,782 93FIRESTONE POLYMERS/ORANGE TX 145,000 130,500 1,305,000 1,436 70FIRESTONE POLYMERS/LAKE CHARLES LA 180,000 162,000 1,620,000 1,782 685GOODYEAR 385,000 346,500 3,465,000 3,812 384Totals 10,593 1,5941Worldwide Rubber Statistics 2007. InternationalInstitute of Synthetic Rubber Producers, Inc.2Adjusted to 90% of Nameplate Capacity to account for downtimes for maintenance shutdowns, product changeouts, etc.3 Calculated using the emission standard of 10 kg total organic HAP allowed per Mg of crumb rubber produced.Table A-2. Estimation of MACT Allowable Back-End Emissions for Styrene Butadiene RubberFacility“NamePlate”Capacity1(Mg/yr)ActualProductionCapacity2(Mg/yr)MACTAllowableHAPEmissions3(kg/yr)MACTAllowableHAPEmissions(tons/yr)Actual HAPEmissions(tons/yr)GOODYEAR HOUSTON CHEM PLT 300,000 270,000 432,000 475 153DSM COPOLYMER/BR PLANT 150,000 135,000 216,000 238 9ISP ELASTOMER 270,000 243,000 388,800 428 75Totals 1,140 2371Worldwide Rubber Statistics 2007. International Institute of Synthetic Rubber Producers, Inc.2Adjusted to 90% of Nameplate Capacity to account for down times for maintenance shutdowns, product changeouts, etc.3Calculated using the emission standard of 0.4 kg total organic HAP allowed per Mg of latex produced and assuming that the crumb rubber makes up 25 percent of thelatex by weight.()()oductionMgHAPkgyrMgpacityoductionCaActualyrkgEmissionsAPAllowableHPr4.0%25)/(Pr*)/(=