MEMORANDUM

Date: December 11, 2013

Subject: MACT

- Allowable Emissions and Risks for the Acryl ic and Modacrylic Fibers, Amino/ Phenolic Resins, and Polycarbonate Production Source Categories

From: Lesley Stobert, EC/R Incorporated

To: Paula Hirtz, EPA/OAQPS/SPPD Nick Parsons, EPA/OAQPS/SPPD

______________________________________________________________________________ The purpose of this memorandum is to present analyses rela ted to “MACT

- allowable” emissions levels and risks for the Acrylic and Modacrylic Fibers Production (AMF), Amino/ Phenolic Resins Production (APR), and Polycarbonate Production (PC) source categories that are being addressed under EPA’s Risk and Technol ogy Review (RTR) program.

The RTR program is addressing the statutory 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 (NES HAP) contained in 40 CFR part 63. They are commonly referred to as Maximum Achievable Control Technology (MACT) standards. The emissions data being used for the RTR risk assessments for these categories consist of data representative of “actual” emission l evels. In addition to the risks associated with these actual emission levels, EPA also considers the levels of HAP emissions that sources could emit and still be in compliance with the applicable MACT regulation. These emission levels are referred to as “M ACT

- allowable” emissions. The purpose of this memorandum is to discuss these MACT

allowable emission levels and to relate the potential risks if facilities emitted at these levels.

This memorandum is organized as follows. Section 1 presents the estimate d maximum risk levels based on the actual emission levels for each source category, and Section 2 discusses the basic approach to estimating the risks at the MACT

- allowable levels. This is followed by a discussion of the estimation of the MACT

- allowable em ission level for each MACT standard in Section 3, particularly as it relates to the actual emission levels used in the risk assessments. This discussion is followed by a presentation of the estimated risks at these MACT

- allowable levels.

1.0 Risk Levels B ased on Actual Emissions

The estimated maximum inhalation risks for these source categories are summarized in Table 1. These risks are based on actual emission levels.2

Table 1. Summary of Estimated Inhalation Risks for the AMF, APR, and PC Production Based On Actual Emissions Levels

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

noncancer TOSHI 2

Acrylic and Modacrylic Fibers Production 20 0.1

Amino / Phenolic Resins Production 9 0.2

Polycarbonate Production 0.3 0.04

1 Maximum individual excess lifetime cancer risk.

2 Maximum target organ specific hazard index (TOSHI). Target organ system represented by the TOSHI may vary

across source cate gories. The maximum TOSHI is based on respiratory effects for the AMF, APR and PC source categories.

2.0 Approach to Estimating Risks from MACT

- Allowable Emission Levels

Detailed MACT

- allowable emissions information is not available on an emission poin t

specific level. Therefore, modeling was not conducted 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 assumed to be proportional to the difference in emission levels. For example, if MACT

- allowable emissions were 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 t he linear relationship between emissions and 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 numerous built in conser vative assumptions. First, the acute assessment assumed a short

- term emission rate up to 10 times that of the average longer term emission rate. 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 ambient concentration as determined by the co

- occurrence of peak em issions and worst

- case meteorological conditions. These assumptions would tend to overestimate actual exposures 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 anoth er factor to account for the MACT

- allowable emissions level would further increase the conservativeness of the estimated MACT

- allowable acute risks.3

Therefore, this analysis does not discuss acute risks or estimate acute risks for the MACT

allowable emissi ons level.

3.0 Results of Analysis

a. Acrylic and Modacrylic Fibers Source Category

The AMF NESHAP addresses emissions from the following types of emission sources: (1) storage vessels used to store acrylonitrile, (2) continuous process vents, (3) fug itive emissions from spinning lines, (4) wastewater, and (5) equipment leaks. Table 2 summarizes the formats of the standards for these emission points.

Table 2. Formats of Standards for the AMF NESHAP

Emission Source Type Format of Primary Standard
Acrylonitrile Storage Tanks Performance Standard (% reduction) or Equipment Standards Continuous Process Vents Performance Standard (% reduction) a Spinning Lines (new facility or facility uses a spin dope produced from a solution polymerization process) Performance Standard (% reduction) b

Equipment Leaks Work Practice Standards Wastewater Equipment Standards, Performance Standard

a The NESHAP contains alternative standards to reduce emissions on a kg emissions/hour basis for hydrogen halides and haloge ns and to reduce total organic carbon based to a specified concentration

b The NESHAP contains alternative standards to reduce emissions to a kg/Mg product basis or a specified spin dope concentration of acrylonitrile

The ability to estimate MACT

- allowa ble emissions for specific emission points, or for specific emission point types, is largely dependent on the format of the standards. For work practice standards, there would be no difference between actual and MACT

- allowable emissions for emission source s, provided the facility is not conducting additional work practices proven to reduce emissions beyond those required in the rule. We are not aware of any such situations at the one facility in this source category. Therefore, for equipment leaks, which ar e subject to work practice standards, we believe that the actual emission levels are a reasonable estimation of the levels allowed by the standard.

For wastewater emission sources, the regulation includes an assortment of equipment and performance standards. For equipment standards, the one source that is subject to the regulation is required to install specific equipment. Assuming that the equipment is maintained properly and is in good working condition (as required), there would not be a differen ce in the actual emissions level and the level allowed by the standard. In general, it is possible that sources could overcontrol emission sources subject to a performance standard. This would result in the actual emissions being lower than the MACT

- allowa ble emissions. However, for wastewater sources, we are not aware of any such overcontrol. Therefore, we believe that the actual wastewater emission levels are a reasonable estimation of the levels allowed by the standard.4

For continuous process vents, whi ch are subject to a performance standard, the sources could utilize control devices that achieve emissions reductions greater than the required 98 percent reduction of acrylonitrile or 99 percent reduction in hydrogen halides and halogens. However, the con tinuous monitoring requirements of the rule result in situations where reductions at or above these required levels are required on a continuous basis. Specifically, the owner or operator is required to conduct performance tests to demonstrate initial comp liance. During the test, they are required to monitor a specific parameter (e.g., temperature for a thermal incinerator). From the data collected during the test, they are required to calculate a parameter level (e.g., a minimum temperature) that is indica tive 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 t emperature established during the test it would be an excursion). Therefore, if an incinerator was achieving a 99.5 percent emission reduction during the performance test, the temperature level established based on monitoring data collected during the test would be reflective of a 99.5 percent reduction. Thus, the performance level required by the rule would, in effect, be 99.5 percent. Because of these requirements, we assume that the actual emission levels are a reasonable estimation of MACT

- allowable emi ssions for continuous process vents.

For acrylonitrile storage vessels, a facility may choose to either comply with a 95 or 98 percent reduction performance standard, depending on the type of control device used, or to comply with equipment standards. As discussed above, it is reasonable to assume that the actual emissions from those sources complying with equipment standards are representative of the MACT

- allowable emissions. If the facility complies using the performance standard, actual emissions reduct ions could be greater than the required reductions. The one operating facility uses a closed vent system routed to a combustion device for emissions reduction and is required to reduce emissions by 98 percent. The performance of this system is estimated to reduce emissions by over 98 percent. However, as discussed above for continuous process vents, the continuous monitoring requirements of the rule result in the situation where reduction at or above this level is required on a continuous basis. Because of these requirements, we assume that the actual emission levels are a reasonable estimation of MACT

- allowable emissions for storage vessels.

The one facility in the source category is categorized as an “existing source” and has a fiber spinning line that us es a spin dope produced from a solution polymerization process. There are no emission reduction requirements for this type of spinning line at this type of facility. Therefore, the actual emission levels are the levels allowed by the standard.

In summary, t he risks based on the “MACT

- allowable” emissions levels are shown in Table 6 and are equal to the risks at the actual emissions levels for the AMF NESHAP

.

b. Amino

/ Phenolic Resins Production

The APR NESHAP addresses emissions from the following t ypes of emission sources: (1) storage tanks, (2) continuous process vents, (3) batch process vents, (4) heat exchange systems, and (5) equipment leaks. Table 3 summarizes the formats of the standards for these emission points.5 Table 3. Formats of Standards for the APR NESHAP

Emission Source Type Format of Primary Standard
Storage Tanks (new sources only) Equipment Standards, Performance Standards (% reduction), or Concentration Limit Continuous Process Vents (new sources only) Performance Standard or Concentration Limit

Batch Process Vents Performance Standard or Concentration Limit a Heat Exchange Systems Work Practice Standards Equipment Leaks Work Practice Standards

a The NESHAP contains an alternative standard to reduce emissions on a kg emissio ns/Mg product basis

For equipment leaks and heat exchange systems, which are subject to work practice standards, we are not aware of any facilities conducting additional work practices proven to reduce emissions beyond those required by the rule. Therefore, we believe the actual emission levels are a reasonable estimation of the levels allowed by the standards for this equipment.

For storage vessels and continuous process vents, all facilities identified as currently operating major sources subjec t to the APR MACT standards are existing sources. As existing sources have no control requirements for storage vessels and continuous process vents, actual emissions are equal to allowable emissions for these sources.

For reactor batch process vents, org anic HAP are required to be reduced by 83 percent at existing sources and 95 percent at new sources. For non

- reactor batch process vents, across the collection of all non

- reactor batch process vents within the affected source, organic HAP are required to b e reduced by 62 percent at existing sources and 76 percent at new sources. All of the facilities included in the risk assessment for the source category were operating before the MACT standards for APR took effect and are therefore existing sources. For re actor batch process vents, the existing MACT floor is based on the arithmetic average of the control device performance of the top five facilities. It is likely that at least some facilities that needed to upgrade equipment to meet the MACT standard instal led equipment that achieves greater than 83 percent control, and according to the data gathered during the development of the MACT standards, this control level could be up to 95 percent. In these cases, 17 percent of organic HAP would be emitted at the MA CT

- allowable level, and it is possible that facilities are actually only emitting 5 percent (i.e., 95 percent emissions reduction). The maximum ratio of MACT

allowable to actual emissions is therefore 17/5 = 3.4. For non

- reactor batch process vents, the MA CT standard is based on the overall control for all non

- reactor batch vents, in which some may be controlled and others not controlled, but collectively achieve at least 62 percent control of organic emissions. While we do not have information on the post

- MACT controls achieved across the non

- reactor batch vents at APR facilities, to be conservative we assume that some achieve 76 percent control, which is the standard for new sources. In this case, 38 percent of organic HAP would be emitted at the MACT

- allo wable level, and it is possible that facilities are actually only emitting 24 percent (i.e., 76 percent emissions reduction). The maximum ratio of MACT

- allowable to actual emissions is therefore 38/24 = 1.6.

Because it was not possible to determine wheth er an emissions point was a reactor batch process vent, a non

- reactor batch process vent, or other type of emissions source in the NEI data6

available for this source category, we examined applying the larger of the two ratios, 3.4, to all organic HAP emiss ions associated with point (rather than fugitive) sources to be conservative. The maximum cancer risk associated with emissions from point sources is 3

- in

- 1 million. The application of the factor of 3.4 to this value results in a maximum cancer risk at the MACT

allowable emissions level of 10

- in

- 1 million. The maximum TOSHI for the source category based on actual emissions is 0.2, and is due to emissions from a point source. The application of the factor of 3.4 applied to this TOSHI results in a TOSHI at th e MACT

- allowable emissions level of approximately 0.7.

In summary, t he risks based on the “MACT

- allowable” emissions levels are shown in Table 6. The maximum individual cancer risk at the MACT

- allowable emissions level is 10

- in

- 1 million and the maximum MACT

- allow able TOSHI is 0.7 for the Amino / Phenolic Resins Production NESHAP

.

c. Polycarbonate Production

The PC NESHAP addresses emissions from the following types of emission sources: (1) storage tanks, (2) process vents, (3) equipment leaks, and (4) wastewater. Table 4 summarizes the formats of the standards for these emission points.

Table 4. Formats of Standards for the PC NESHAP

Emission Source Type Format of Primary Standard
Storage Tanks Equipment Standards (Performance standard option available for certain sizes and vapor pressures) Continuous and Batch Process Vents (for vent streams with TRE less than 2.7) Performance Standard (% reduction) a
Equipment Leaks Work Practice Standards Wastewater Equipment Standards, Performance Standar d

a The NESHAP contains alternative standards to reduce emissions on a kg emissions/hour basis for hydrogen halides and halogens and to reduce total organic carbon based to a specified concentration

As in AMF, for equipment leaks, which are subject to w ork practice standards, we believe that the actual emission levels are a reasonable estimation of the levels allowed by the standard. We also believe that the actual emission levels are a reasonable estimation of the levels allowed by the standard for wast ewater emission sources, which are regulated by equipment and performance standards.

For process vents, which are subject to a performance standard, the sources could utilize control devices that achieve reductions greater than the required 98 percent red uction of total organic HAP or 99 percent reduction in hydrogen halides and halogens. However, as discussed above for AMF process vents, the continuous monitoring requirements of the rule result in situations where reductions at or above these required lev els are required on a continuous basis. Because of these requirements, we assume that the actual emission levels are a reasonable estimation of MACT

- allowable emissions for process vents.7

For storage vessels, the requirements differ depending on the size of the tank and the vapor pressure of the stored material. The rule requires a 98 percent total organic HAP emissions reduction for tanks with capacities of 151 m 3 or more with a vapor pressure of 5.2 kilopascals (kPa) or greater. Those with a capacity bet ween 75 and 151 m 3 and a vapor pressure of 76.6 kPa or more are required to achieve 95 percent total organic HAP emissions reductions, and those with a capacity between 75 and 151 m 3 and a vapor pressure between 27.6 and 76.6 kPa may either comply with a 9 5 percent reduction performance standard or comply with equipment standards. As discussed above, it is reasonable to assume that the actual emissions from those sources complying with equipment standards are representative of the MACT

- allowable emissions. For facilities complying with performance standards, actual emissions reductions could be greater than the required reductions. While we believe it is likely that facilities control tanks to a greater degree than 95 percent, we are not aware of any situati ons where facilities are achieving significantly greater than 98 percent emissions reductions. In cases where storage vessels that are only required to achieve the 95 percent emissions reduction actually achieve 98 percent emissions reduction, they would b e emitting only 2 percent emissions while 5 percent would be emitted at the MACT

- allowable level. The maximum ratio of MACT

- allowable to actual emissions is therefore 5/2 = 2.5.

To estimate the impacts on emissions and risks considering storage tank MACT

allowable emissions, several assumptions were made for the polycarbonate production source category. In the NEI data for this source category, it was not possible to determine whether an emission point was a storage tank or another type of emissions sourc e. Based on data available for another chemical production source category, polyvinyl chloride production (PVC), the percentage of total PVC emissions that were attributed to storage vessels was approximately 0.2 percent. a For organic chemical production f acilities that contributed data for the Hazardous Organic NESHAP (HON) residual risk analysis, the percentage of total HON emissions that were attributed to controlled storage vessels was approximately 5 percent. b Based on this information, to be conservat ive, we have assumed that 5 percent of the total polycarbonate production emissions are from storage tanks. In addition, while some storage tanks already are required to meet the 98 percent control efficiency standards, we do not have information on the

nu mber of tanks or the emissions of tanks required to meet the 98 percent or 95 percent control standards. To be conservative, we assumed all storage tanks are required to meet the 95 percent control efficiency standards but are actually reducing emissions b y 98 percent. Location of the storage tanks is another factor that may affect risk results, where an increase in tank emissions in closer proximity to residences could increase risk more than tanks located further from residences. However, as the NEI data for this source category does not include different locations for the different emissions sources for three of the four facilities and only includes two locations for the other facility, we assume that the emissions at the given locations are due to all th e emissions sources. Therefore, we have assumed that 5 percent of the emissions at these locations are from storage tanks. To consider storage tank MACT

- allowable emissions, we have multiplied

a “Costs and Emission Reductions of the Proposed Standards f or the Polyvinyl Chloride and Copolymers (PVC) Production Source Category.” Memorandum from Eastern Research Group, Inc. to Jodi Howard, U.S. Environmental Protection Agency. April 13, 2011. (Docket item no. EPA

- HQ

- OAR

- 2002

- 0037

- 0097).
b EC/R Incorporated. Synthetic Organic Chemical Manufacturing Industry

– Residual Risk Assessment. Prepared for the U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards. September 2005. (Docket item no. EPA

- HQ

- OAR

- 2005

- 0475

- 0108 (Appendix G)).8

these actual emissions by 2.5 as shown in Table 5 below. This e quates to a 7.5 percent increase in total emissions for each facility.

Table 5. Polycarbonate Production Actual and Estimated Allowable Emissions

Facility Total Actual

PC Emissions (TPY) Assumed

Actual Storage Vessel Emissions Storage

Vessels Actual to A llowable Multiplication Factor Assumed

Allowable Storage Vessel Emissions Total

Allowable PC Emissions (TPY) Dow

– Freeport, TX 7.9 0.4 2.5 1 8.5
Bayer

– Baytown, TX 0.40 0.02 2.5 0.05 0.43

Sabic

– Burkville, AL 170.9 8.5 2.5 21.3 183.7

Sabic

– Mt. Vernon, IN 151.2 7.6 2.5 19 162.6

The resulting risks based on the application of the organic HAP ratio of 2.5 for storage vessels (a 7.5 percent increase in total emissions for each facility) is shown in the “MACT

allowable” level risks shown in Table 6.

Table 6. Summary of Estimated Inhalation Risks for the AMF, APR, and PC Based On MACT

- Allowable Emissions Levels
Actual MACT

- Allowable

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

chronic

noncancer TOSHI Maximum

individual cancer risk (in a million) Maximum

chronic

noncancer TOSHI Acrylic and Modacrylic Fibers Production 20 0.1 20 0.1

Amino / Phenolic Resins Production 9 0.2 10 0.7

Polycarbonate Production 0.3 0.04 0.3* 0.04*

* Allowable risks appear unchanged from actual risks because the slight risk increase (7.5 percent) did not cause a change in the presentation of risks with one significant digit