MEMORANDUM

Date: January 8, 2014

Subject: Revised MACT

- Allowable Emissions and Risks for the Pesticide Active Ingredient

Production, Polyether Polyols Production, and Group IV Polymers and Resins Source Categories

From: Lesley Stobert, EC/R Incorporated

To: Nick Parsons, EPA/OAQPS/SPPD

_________________________________________________________________________________

The purpose of this memorandum is to present analyses related to “MACT

- allowable” emissions levels and risks for the Pesticide Active Ingredient Production (PAI), Polyether Polyols Production (PEPO), and Group IV Polymers and Resins (P&R IV) source categories that are being
addressed under EPA’s residual risk and techn ology review (RTR) program. This is a revision to a previous memo developed for the proposed rulemaking for these source categories to consider the revised emissions data that was received during the comment period and the revised estimates of risks
based on these data.

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 (NESHAP) contai ned 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
levels. In a ddition 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 “MACT

- allowab le” 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 estimated maximum r isk levels based on the actual emission levels for each source category, 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 the MACT

- allowable emission le vel 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 Based on A ctual 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 PAI, PEPO, and P& R IV Source

Categories Based On Actual Emissions Levels

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

noncancer TOSHI 2

Pesticide Active Ingredient (PAI) Production 6 0.7

Polyether Polyols (PEPO) Production 30 0.7

Group IV Polymers and Resins 3

Acrylic

- Butadiene

- Styrene (ABS) Production 20 0.3

Methyl Methacrylate

- Butadiene

- Styrene (MBS) Production 1 0.02

Polyethylene Terephthalate (PET) Production 10 0.4

Polystyrene Production (PS) 0.08 0.006

Styrene

- Acrylonitrile (SAN) Production 0.4 0.003

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 based on respiratory effects for the PAI, PEPO, PET, and SAN, neurological effects for PS, the spleen for AB S, and reproductive effects for MBS.

3 Two additional source categories are regulated by the P&R IV MACT standards no longer have any operating facilities in the U.S., and none are anticipated to begin operation in the future. For these source categories, Methyl Methacrylate

Acrylonitrile

- Butadiene

- Styrene Production and Nitrile Resins Production, risks were not estimated.

2.0 Approach to Estimating Risks from MACT

- Allowable Emission Levels

Detailed MACT

- allowable emissions information is not available on an emission point

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 betw een 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
le vels. For example, if MACT

- allowable emissions were estimated to be three times as high as actual3

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 ass umption regarding the 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 numer ous built in conservative 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

- oc currence of peak emissions 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. Th e addition of another factor to
account for the MACT

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

- allowable acute risks. Therefore, this analysis does not discuss acute risks or
estimate acute risks for the MA CT

- allowable emissions level.

3.0 Results of Analysis

a. Group IV Polymers and Resins Source Categories

The Group IV Polymers and Resins NESHAP addresses emissions from the following types of emission sources for all five source categories: (1) storage tanks, (2) continuous process vents, (3) batch process vents, (4) equipment leaks, (5) wastewater, and (6) heat exchange systems. Table 2 summarizes the formats of the standards for these emission points.

Table 2. Formats of Standards for the Group IV Polymers and Resins NESHAP

Emission Source Type Format of Primary Standard Storage Tanks Equipment Standards

Continuous Process Vents Performance Standard (% reduction) a

Batch Process Vents Performance Standard (% reduction) Equipment Leaks Work Practice Standards

Wastewater Equipment Standards, Performance Standard Heat Exchange Systems Work Practice Standards

a The NESHAP contains an alternative standard for some source categories or subcategories to reduce emissions on a kg emissions/Mg product basis

The ability to estimate MACT

- allowable emissions for specific emission points, or for specific
emi ssion point types, is largely dependent on the format of the standards. 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 working conditi on (as required), there would not be a difference in the actual emissions level and the level allowed by the standard. Similarly, there would
be no difference between actual and MACT

- allowable emissions for emission sources subject to work practice require ments, provided that facilities are not conducting additional work practices proven to reduce emissions beyond those required in the rule. We are not aware of any such situations at facilities in these five Group IV Polymers and Resins source categories. T herefore, for equipment4

leaks, storage vessels, heat exchange systems, and process contact cooling towers, which are subject to equipment and work practice standards, we believe that the actual emission levels are a reasonable
estimation of the levels allo wed by the standard.

For wastewater emission sources, the regulation includes an assortment of equipment and performance standards. As discussed above, it is reasonable to assume that the actual emissions from those sources subject to equipment standards are representative of the MACT

- allowable emissions. 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

- allowable emissions.

Howe ver, 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.

For continuous and batch process vents, which are s ubject to performance standards, we believe that there may be situations where sources are utilizing control devices that achieve reductions greater than the required percent reduction (i.e., 98% for continuous process vents and generally 90% for batch pro cess vents). However, for continuous process vents, the continuous monitoring requirements of the rule result in situations where reductions greater than these percent reductions are required on a continuous basis. Specifically, owners and operators are re quired to conduct performance tests to demonstrate initial compliance. 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 indicative of the control device performance achieved during the test. Ongoing compliance is then determined based on the monitoring of this parameter as compared to the established level (e.g., if t he 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 emission reduction during the performance test, the temperature level established based on monitoring data collected during the test would be reflective of a 99 percent reduction. Thus, the performance level required by the rule would, in effect, be 99 percent. Because of these requirements, we assume that the actual emission levels are
a reasonable estimation of MACT

- allowable emissions for continuous process vents.

For batch process vents, similarly to continuous process vents, owners and operators are required to conduct performance tests of control devices to demonstrate the control efficiency of the device and identify the parameter level that corresponds with the required emissions reduction efficiency. This parameter must then be monitored during batch events and be within the established range to demonstrate compliance. While it is possible that the demonstrated control efficiency is above the 90% reduction requirement of the standard, the standard also allows for the 90% reduction to be achieved by controlling only selected batch emission episodes or portions of selected batch

em ission episodes to achieve an overall reduction of 90%. If a source controls all portions of all batch emission episodes to a level above 90%, the actual emissions for that source would be less than the allowable emissions. However, we are not aware of any such overcontrol. Therefore, we believe that the actual batch process vent emission levels are a reasonable estimation of the levels allowed by the
standard.

Facilities producing polystyrene using a continuous process, PET using a continuous dimethyl terephthalate, or PET using a continuous terephthalic acid process may choose to comply with an emission limitation based on production, rather than a 98% percent reduction requirement. These5

limits were put into place based on the use of condensers and other recovery technologies in the industry as an alternative to the percent reduction requirements applicable to combustion equipment.
This alternate standard forma t was selected because for this technology, HAP are reduced to a specific level, dependent on the vaporization and condensation properties of the HAP, but the technology is not particularly sensitive to the initial HAP concentration in the uncontrolled gas stream. Facilities in these source categories generally are complying with the rule requirements using these recovery technologies, and are not known to be using any versions of these technologies that achieve better performance than required to meet the emission limits. Therefore, for the facilities in these source categories, we estimate the actual emissions are equal to the MACT

- allowable emissions. In addition, for the primary HAP used and emitted by facilities in these source categories, recovery
tech nologies should be capable of reducing HAP to 98% or more. Therefore, if any facilities are actually using combustion control rather than recovery technology, emissions would be approximately the same and would be equal to the MACT

- allowable level for eith er compliance
format.

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 Group IV Polymers and Resins

NESHAP

.

b. Polyether Polyols Production

The Po lyether Polyols Production NESHAP addresses emissions from the following types of emission sources: (1) storage tanks, (2) continuous process vents, (3) batch process vents, (4) equipment leaks, (5) wastewater, and (6) heat exchange systems. Table 3 summar izes the formats of the standards for these emission points.

Table 3. Formats of Standards for the Polyether Polyols Production NESHAP

Emission Source Type Format of Primary Standard Storage Tanks Equipment Standards

Process Vents Performance Standard (% reduction) a Equipment Leaks Work Practice Standards

Wastewater Equipment Standards, Performance Standard Heat Exchange Systems Work Practice Standards

a The NESHAP contains an alternative standard to reduce emissions on a kg emissions/Mg product bas is

As in the P&R IV MACT standards, for equipment leaks, storage vessels, and heat exchange systems, which are subject to equipment and work practice standards, we believe that the actual
emission levels are a reasonable estimation of the levels allowed b y the standard. We also believe that the actual emission levels are a reasonable estimation of the levels allowed by the standard for wastewater emission sources, which are regulated by equipment and performance standards.

For process vents, all HAP associated with units producing polyether polyols using tetrahydrofuran are required to be reduced by 98%. For existing units producing polyther polyol products using epoxides, all epoxide HAP are required to be reduced by 98%, w hile non

- epoxide organic HAP are required to be reduced by 98% for continuous process vents and by 90% for batch process vents and process vents that use organic HAP in catalyst extraction. It is possible that some of the process vents that are only requir ed to achieve 90% emissions reduction in non

- epoxide organic6

HAP actually achieve 98% emissions reduction. In these cases, 10% of non

- epoxide organic HAP
would be emitted at the MACT

- allowable level, and it is possible that facilities are actually only
emi tting 2% (i.e., 98% emissions reduction). The maximum ratio of MACT

- allowable to actual emissions is therefore 10/2 = 5. Because it was not possible to determine whether an emissions point was a process vent or other type of emissions source or whether any point was associated with a certain type of polyether polyol unit in the NEI, this ratio of 5 was applied to all non

- epoxide organic HAP emissions associated with point (rather than fugitive) sources to be conservative. The MIR based
on actual emissions i s 30, which is caused predominantly by ethylene oxide (an epoxide) emissions. The application of this factor to non

- epoxide organic emissions does not increase risk for any emissions receptors beyond this level. In addition, the maximum TOSHI based on actu al emissions is 0.7, which is based predominantly on emissions of acrolein from fugitive sources. The application of
this factor to non

- epoxide organic emissions from point sources does not increase risk for any receptors beyond this level. Therefore, even though the non

- epoxide HAP MACT

- allowable emissions are five times higher than the actual emissions, there is no appreciable difference in the

MACT

- allowable risk levels.

Facilities producing polyether polyol products using epoxides may choose to comply with an epoxide emission limitation based on production, rather than a percent reduction requirement. These limits were put into place to allow facilities to take credit for reacting their product to completion in an extended cookout process, which reduces emissions of ethylene oxide and propylene oxide. However, during MACT development, industry commented that the emission factor format based on the lowest emissions per production would restrict facilities from making certain polyols classes that have high er emissions of epoxides. To allow for a variety of polyether polyol products to be made, the percent reduction format was chosen as the MACT standard with the alternative of meeting the emission factor limit. Facilities with units that make polyols classe s with higher emissions of epoxides most of the time will likely comply with the percent reduction limit for those units because it would not be possible to comply with the emission factor format. For these units, we believe that there may
be situations wh ere sources are utilizing control devices that achieve reductions greater than the required percent reduction (i.e., 98% for existing process vents). However, as with P&R IV continuous process vents, the monitoring requirements of the rule result in situat ions where reductions greater than these percent reductions are required because parameters are monitored based on an established level which is reflective of actual operating conditions. Because of these requirements, we
assume that the actual emission le vels are a reasonable estimation of MACT

- allowable emissions for these process vents.

Polyether polyol units that make polyols classes with lower epoxide emissions may comply with the emission factor format. The MACT standard in this format is 0.019 kg ep oxide emissions per Megagram of product made for all process vents from the unit for existing sources, determined on an annual basis. In general, it is possible that units could emit at levels lower than this standard, which
would result in the actual emis sions being lower than the MACT

- allowable emissions. Epoxide emissions vary depending upon the polyether polyol product made, and we are not aware of any such routine overcontrol that would cause emissions to be substantially lower. However, to investigate this situation further, we compared actual reported emissions in the NEI to the emissions that would be expected if facilities emit at the standard level and operate at capacity. Using information from MACT development to estimate the number of small, med ium, and large facilities based on capacity and the average capacities for those sized facilities, we determined the average emissions that would be expected if all facilities emitted epoxide emissions at the level of the standard in the emissions7

factor f ormat. The resulting total epoxide emissions from process vents for the source category is estimated to be 22 tons per year (TPY). This information is shown in Table 4. This total process vents epoxide emissions value was compared to the total epoxide emis sions that may be attributed to process vents in the NEI data, which was determined based on the source category code (SCC) and the point source emission release type. In the NEI data this value is approximately 38 TPY. The emissions contributing to this v alue are shown in the Appendix to this document. Using these assumptions, emissions from process vents are less when using the emission factor than the reported actual emissions. Therefore, we do not have reason to believe that facilities are using this em ission factor standard format and achieving emissions reduction beyond that required by the standard, and
we assume that the actual emission levels are a reasonable estimation of MACT

- allowable emissions for these process vents.

Table 4. Epoxide Emissions at Average Capacity for PEPO Facilities Complying with the
Emission Factor Standard Format

Total
Number
of
Facilities Facility

Size Percent
of Total
Facilities

at Facility
Size Number

of
Facilities

at Facility
Size Average Capacity Mg/yr Average

Capacity
Utilization

% Average
Utilized Capacity (Mg/yr) Epoxide

Emissions (TPY)

Per Facility

at
Utilized Capacity
with 0.19 kg/Mg
Emitted Epoxide

Emissions (TPY)

Per

source Category
Size Segment Total

Epoxide
Emissions (TPY) for
Source Category

23 Small 30 7 27,488 87.95 21,175 0.51 3.94

29.26 Medium 21 5 43,635 82.59 36,038 0.75 3.64 Large 49 11 129,001 72.86 93,990 1.96 22.14

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 Polyether Polyols NESHAP

.

c. Pesticide Active Ingredient Production

The Pesticide Active Ingredient Production NESHAP addresses emissions from the following types of emission sources: (1) storage tanks, (2) process vents, (3) equipment leaks, (4) wastewater, (5) bag dumps and product dryers, and (6) heat exchange systems. Table 5 summarizes the formats of the standards for these emission points.

Table 5. Formats of Standards for the Pesticide Active Ingredient Production N ESHAP

Emission Source Type Format of Primary Standard Storage Tanks Equipment Standards

Continuous Process Vents Performance Standard (% reduction) Equipment Leaks Work Practice Standards

Wastewater Equipment Standards, Performance Standard Bag Dumps and Product Dryers Emission Limit (concentration limit) Heat Exchange Systems Work Practice Standards8

As in the P&R IV and PEPO MACT standards, for equipment leaks, storage vessels, and heat exchange systems, which are subject to equipment and work pra ctice 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 wastewater emission sources, which are regulated by equipment and performance standards. For bag dumps and product dryers, particulate matter from these sources is controlled with fabric filters. As the level of the standard, 0.01 grains per dry standard cubic foot ( gr/dscf), is typical of the level of control achieved by fabric filters, we believe the actual emissions level using this equipment is a reasonable estimation of the level allowed by the standard.

For process vents, the standard requires 98% emission reduction of organic HAP for process vents with control devices installed after November 10, 1997 (the proposal date of the standard) and 90% control for process vents with controls installed on or before that date. It is possible that some of the process vents that are only required to achieve the 90% emissions reduction actually achieve 98% emissions reduction. In these cases, 10% of organic HAP would be emitted at the MACT

- allowable level, and it is possible that facilities are actually only emitting 2% (i.e., 98% emissions reduction).
The maximum ratio of MACT

- allowable to actual emissions is therefore 10/2 = 5. Because it was not possible to determine whether an emission point was a process vent or other type of emissions source in the NEI, this ratio o f 5 was applied to all organic HAP emissions associated with point (rather than fugitive) sources to be conservative. The MIR based on actual emissions is 6, which is caused entirely by fugitive emission points, and the maximum TOSHI is 0.7, which is cause d entirely by non

- organic HAP emissions. The application of the factor of 5 to point source organic HAP emissions results in an
MIR of 7 and a TOSHI of 0.8.

For halogenated process vents, the standard requires 94% reduction in HCl and Cl 2 emissions
if un controlled emissions for all process vents within a process exceed 6.8 Mg/yr HCl and Cl 2 emissions. From information gathered during development of the MACT, many process vent totals
exceeded this threshold. 1 It is possible to achieve 99% or greater emissions reduction with equipment commonly used in the chemical manufacturing industry, and such reduction is required by other NESHAP, including the Hazardous Organic NESHAP (HON), P&R IV, and others. It is possib le that some of the process vents that are only required to achieve 94% emissions reduction actually achieve
99% emissions reduction of HCl and Cl 2 emissions . In these cases, 6% of these HAP would be
emitted at the MACT

- allowable level, and it is possible that facilities are actually only emitting 1% (i.e., 99% emissions reduction). The maximum ratio of MACT

- allowable to actual emissions is therefore 6/1 = 6. Because it was not possible to determine whether an emission point was a process vent or other type of emissions source in the NEI, this ratio of 6 was applied to all HCl and chlorine emissions associated with point sources, to be conservative. The maximum TOSHI is 0.7, which is caused entirely by non

- organic HAP emissions from a combination of fugitive and point source emissions points. The application of the factor of 6 to the HCl and chlorine emissions from point
sources results in a MACT

- allowable TOSHI of 4.

The resulting risks based on the application of the organic HAP ratio of 5 and the HCl and Cl 2 emissions ratio of 6 are shown in the “MACT

- allowable” level risks shown in Table 6.

1 1 Basis and Purpose Document for the Pesticide Active Ingredient Production NESHAP

. U.S. EPA. July 1997.9

Table 6. Summary of Estimated Inhalation Risks for the PAI, PEPO, and P&R IV Source

Categories 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

Pesticide Active Ingredient Production 6 0.7 7 4

Polyether Polyols Production 30 0.7 30 0.7

Group IV Polymers and Resins

Acrylic

- Butadiene

- Styrene (ABS)
Production 20 0.3 20 0.3

Methyl Methacrylate

- Butadiene

Styrene (MBS) Production 1 0.02 1 0.02

Polyethylene Terephthalate (PET)
Production 10 0.4 10 0.4

Polystyrene Production (PS) 0.08 0.006 0.08 0.006

Styrene

- Acrylonitrile (SAN)
Production 0.4 0.003 0.4 0.003

## Appendix

Polyether Polyols Production Epoxide Emissions Associated with

Process Vents in the NEIA

- 1A

- 2