MEMORANDUM

Date: November 2 , 2011

Subject: MACT Allowable Emissions and Risks for the Pesticide Active Ingredient, Polyether Polyols, and Polymers and Resins IV 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 r elated to “MACT allowable”

emissions levels and risks for the Pesticide Active Ingredient , Polyether Polyols, and Polymers and Resins IV Production source categories that are being addressed under EPA’s Risk and Technology 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 (NESHAP) contained in 40 CFR part 63. The y 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 addition to the risks assoc iated 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 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 estimated maximum risk

levels based on the ac tual 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 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 Based on Actual Emissions

The esti mated 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, Polyether Polyols, and Polymers

and Resins IV Production 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 7 0.7

Polyether Polyols (PEPO) Production 3 0 0.8

Polymers and Resins IV 3

Acrylic

- Butadiene

- Styrene (ABS) Production 30 0.2

Methyl Methacrylate

- Butadiene

- Styrene (MBS) Production 0.4 0.007

Polyethylene Terephthalate (PET) Production 9 0.5

Polystyrene Production 2 0.004

Styrene

- Acrylonitrile (SAN) Production 0.03 0.0002

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, SAN, and PET and neurological

effects for polystyrene produc tion, and reproductive effects for MBS and ABS

. 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 rel ationship 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 emissio ns.3

This assumption 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 alr eady has numerous 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 independen t 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 determine d by

the co

- occurrence 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

- c ase impact. The 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 ri sks for the MACT

- allowable emissions level.

3.0 Results of Analysis

a. Polymers and Resins IV 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 Stan dards

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 condi tion (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 requ irements, 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 categorie s. Therefore, for equipment 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 allowed by the standard.4

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 sta ndards 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 emissio ns. 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.

For continuous and batch process vents, w hich are subject 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 process 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 oper ators are required 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 require d 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 le vel (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 emission reduction during the performance test, the temperature le vel 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 e mission 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 dem onstrate 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 portion s of selected batch emission 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. These 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 for mat was selected because for this technology, HAP are reduced to a5

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 g as 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 th e 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 technologies 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 either 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 Productio n

The Polyether 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. Tab le 3 summarizes 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 co ntains an alternative standard to reduce emissions on a kg emi ssions/Mg product basis

As in Polymers and Resins IV, 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 th e 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 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%, while 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 requ ired to achieve 90% emissions reduction in non

- epoxide organic 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 emitting 2% (i.e., 98% emissions reduction). The maximum ratio of MACT allowable to actual6

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 whethe r 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 application of this facto r does not have an impact on the cancer MIR or the TOSHI for the polyether polyols production source category. The MIR based on actual emissions is 3 0 , which is caused entirely by ethylene oxide emissions . The application of this factor to non

- epoxide or ganic emissions does not increase risk for any emissions receptors beyond this level. In addition, the maximum

TOSHI based on actual emissions is 0.8 , which is based predominantly on emissions of acrolein from fugitive sources . The application of this fa ctor 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 proc ess, 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 cla sses that have higher 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 classes 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 where 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 situations 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 levels 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 epoxide 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 woul d result in the actual emissions 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 lo wer. 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 est imate the number of small, medium, 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 stan dard in the emissions factor format. 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 4.7

This total process vents epoxide emissions value was c ompared to the total epoxide emissions 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. T he emissions contributing to this value 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 beli eve that facilities are using this emission 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 proce ss 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 Productio n 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 s tandards for these emission points.

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

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 Polymers and Resins IV and Polyether Polyols, 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 by the standard. W e 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 matt er 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 equip ment 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 cas es, 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 i t 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 5 was applied to all organic HAP emissions associated with point (rather than fugitive) sources to be conservative. Th e application of this factor does not have an impact on the cancer MIR or the TOSHI for the pesticide active ingredient production source category. The MIR

based on actual emissions is 7 , which is caused entirely by fugitive emission points, and the

maxim um TOSHI is 1 , which is caused entirely by non

- organic HAP emissions . The application of

th e factor of 5 to point source organic HAP emissions does not increase risk for any emissions receptors beyond this level. Therefore, even though the point source or ganic HAP MACT allowable emissions are five times higher than the actual emissions, there is no appreciable difference in the

MACT allowable risk levels.

For halogenated process vents, the standard requires 94% reduction in HCl and Cl 2 emissions

if unc ontrolled 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), Polymers and Resins IV, and oth ers. It is possible 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 proces s 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 co mbination 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 3.

1 1 Basis and Purpose Document for the Pesticide Active Ingredient Production NESHAP . U.S. EPA. July 1997.9

The resulting risks based on the application of the organic HAP rati o of 5 and the HCl and Cl 2 emissions ratio of 6 are shown in the “MACT allowable” level risks shown in Table 6.

Table 6. Summary of Estimated Inhalation Risks for the PAI, Polyether Polyols, and Polymers

and Resins IV Production Based On MACT

- Allowab le 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 7 0.7 7 3

Polyether Polyols Production 3 0 0.8 3 0 0.8

Polymers and Resins IV

Acrylic

- Butadiene

- Styrene Production 30 0.2 30 0.2

Methyl Methacrylate

- Butadiene

Styrene Production 0.4 0.007 0.4 0.007

Polyethylene Terephthalate Production 9 0.5 9 0.5

Polystyrene Production 2 0.004 2 0.004

Styrene

- Acrylonitrile Production 0.03 0.0002 0.03 0.0002

## Appendix

Polyether Polyols Production Epoxide Emissions Associated with

Process Vents in the NEIA

- 1A

- 2