1

MEMORANDUM

DATE: October 25, 2011

SUBJECT: Emissions Data and Acute Risk Factor Used in Residual Risk Modeling: Pesticide Active

Ingredients, Polyether Polyols, and Group IV Polymers and Resins

1.0 INTRODUCTION AND BACKGROUND

The purpose of this memorandum is to provide information on the Environmental Protection Agency (EPA) Risk and Technology Review (RTR) database used in estimating residual risk for the Pesticide Active Ingredients (PAI), Polyether Polyols (PEPOs), and Group IV Polymers and Re sins (P&RIV) Maximum Achievable Control Technology (MACT) source categories. These MACTs cover only major sources.

Section 112 of the Clean Air Act (CAA) establishes a two

- stage regulatory process to address emissions of hazardous air pollutants (HAPs) fr om stationary sources. In the first stage, section 112(d) requires the EPA to develop technology

- based standards for categories of industrial sources. In the second stage, known as the residual risk stage, section 112(f)(2) requires EPA to assess the

healt h and environmental risks that remain after sources come into compliance with MACT. If additional risk reductions are necessary to protect public health with an ample margin of safety or to prevent adverse environmental effects, EPA must develop standards to address these remaining

risks.

2.0 DEVELOPMENT OF THE DATA SET USED IN RESIDUAL RISK MODELING

The 2005 National Air Toxics Assessment (NATA) National Emissions Inventory (NEI) data served as the starting point for this assessment. Using the process MACT codes 1 , a list of facilities in the Pesticide Active Ingredients (PAI), Polyether Polyols (PEPOs), and Group IV Polymers and Resins (P&RIV) source categories (MACT codes: PAI

- 0911, PEPOs

- 1625, P&RIV

- 1302, 1318, 1331, 1328, 1338) was developed. This facilit y list was used to create a subset of the NEI that contained facility wide emissions data for each facility in the source categories. Facility information was checked against compliance databases and permit information to ensure that the facilities were

su bject to the relevant rules. Specific changes to data within each source category are discussed in 2.1, 2.2, and 2.3.

Upon the request of industry trade groups such as the American Chemistry Council (ACC) and the Society of Chemical Manufacturers & Affili ates (SOCMA), the 2005 NATA NEI data was voluntarily reviewed by industry for correctness of facility names, Source Classification Codes (SCC), MACT codes, emissions, location (latitude and longitude coordinates) and other modeling parameters contained in the NEI. The proposal revisions were reviewed on a case by case basis and were accepted where appropriate. For these 3 source categories, revisions were made at 10 facilities.

1 Assigning data with MACT codes allows EPA to determine reductions attributable to the MACT program. The NEI associates MACT codes corresponding to MACT source categories with stationary major and area source data.2

EPA conducted an extensive review of the location coordinates for all facilitie s in the 3 source categories. Locations were visually reviewed using Google Earth. Adjustments were made for approximately 40% of the coordinates based on these visual evaluations.

Stack and fugitive parameters that did not meet EPA Quality Assurance (QA) routines and standards were corrected. Permit data and input from industry was used to make area/major source designations. Finally, a standard QA of the modeling file was conducted.

Risks associated with facilities covered by the PAI, PEPOs, and P&RIV M ACT standards were modeled using the resulting file. Specific revisions to each data set are discussed below.

2.1 DEVELOPMENT OF PAI DATA SET

The 2005 NATA NEI data had 18 facilities that were documented as having emissions sources subject to the PAI MACT. In the review of additional information, one facility, NEI11879 was determined to be permanently shut down. Therefore, there were 17 total

fa cilities in the PAI source category. Supplemental emissions information within the source category was received from and accepted for NEI7211 and NEIMIB4942. Supplemental emissions information for sources not in the source category was also accepted for NE I11295 and NEI11906. Some emissions sources at NEI11906 were reassigned to the source category after input from the facility.

2.2 DEVELOPMENT OF PEPOs DATA SET

The 2005 NATA NEI data had 49 facilities that were documented as having emissions sources subject to the PEPOs MACT. In the review of additional information from industry, Title V permits, and permitting authorities, this list was reduced to 25 facilities. Supplemental emissions information within the source category was received from and accepted for NEI11906, NEI6013, and NEI8011. Some emissions sources at NEI11906 were reassigned out of the source category after input from the facility. Supplemental emissions information for sources not in the source category was also accepted for NEI11295,

NEI11906 , NEI12483, NEI7296, and NEI8011. Additionally, updated stack parameters for some emissions not in the source category were received and accepted for NEI56265.

2.3 DEVELOPMENT OF P&RIV DATA SET

The 2005 NATA NEI data had 48 facilities that were documented a s having emissions sources subject to the P&RIV MACT. In the review of additional information from industry, Title V permits, and permitting authorities, this list was reduced to 32 facilities. Sources subject to P&RIV belong to one or more of the followin g 7 source categories of thermoplastics: acrylonitrile

- butadiene

- styrene resin (ABS), styrene

- acrylonitrile resin (SA), methyl methacrylate

- butadiene

- styrene resin (MBS), polystyrene resin (PS), polyethylene terephthalate resin (PET), methyl methacrylate a crylonitrile butadiene styrene resin (MABS), and nitrile resin (although only the first 5 of the 7 source categories currently have operating facilities in the U.S.). Supplemental emissions information was received for: NEI8510 (some emissions were reassig ned out of the PET source category) and NEI11906 (some emissions were reassigned out of ABS and some were reassigned to SA). Emissions information for sources not in the source categories was also accepted for NEI11295 and NEI11906.3

3.0 ACUTE RISK

As outline d in Appendix B: Analysis of Data on Short

- Term Emission Rates Relative to Long

- Term

Emission Rates (Palma and Smith, 2009), short

- term emission rates can be estimated based on annual average rates in order to assess risk associated with acute exposure. Fo r RTR rulemakings, unless more detailed information is available, it is generally assumed that the 1

- hour emission rate for each facility exceeds the annual average hourly emission rate by tenfold, and that this tenfold emission spike could coincide with w orst

- case meteorological conditions and the presence of a human receptor at the facility boundary. This method was developed as a means of screening for potentially significant acute exposures. This factor of ten was applied to all average annual hourly

em ission rates for a source, with two exceptions, described in 3.1 and 3.2. Changes to the data that were made after modeling was complete that affect the risk assessment are described in 4.0.

3.1 EMISSIONS FACTOR FOR ACUTE RISK BASED ON LONG

- TERM VOC EMISSIONS

Figure 1 describes the relationship of the ratio between the event emission rate to the long

term emission rate and the long

- term VOC releases. A conservative value of ten was chosen as the factor which to multiply all emissions in order to model acute r isk (Palma and Smith, 2009). However, the relationship in Figure 1 suggests that the highest ratios were produced by facilities whose routine VOC emissions were relatively small and therefore facilities that have large VOC emissions also have a smaller rat io of event emission rate to long

- term emission rate. Based on this relationship, a factor of two was used for facilities that have long

- term VOC releases of greater than 200 lb/hr (or 876 tpy), as calculated from the 2005

NEI. A list of facilities where w e used the factor of two instead of ten is provided in Appendix 7 of the risk assessment document.4

Figure 1

. Relationship between ratio of event to duration emission rate and total amount emitted during the event. (Palma and Smith , 2009)

3.2 EMISSIONS FACTOR FOR ACUTE RISK BASED ON PROCESS KNOWLEDGE

A factor of two for acute risk was chosen for emissions from equipment leaks. However, this factor was chosen after most of the risk assessment was already complete and was therefore only applied to several facilities showing the highest risk. The factor of two was chosen because emissions from equipment leaks are inherently different from other emission sources at chemical manufacturing facilities. While we believe that it is possible that worst

- case short

- term emission episodes from sources such as process vents, stacks, or flares may be as high as ten times the annual average due to events such as upsets or process flow variability, this does not apply to equipment leaks. Equipment l eaks are not affected acutely by variable flow in a system and thus cannot emit in the same way as aforementioned emission sources during a large

- scale upset. If an event causing a pressure increase occurred in a process stream where a leak was present, we would not expect the toxic vapor analyzer (TVA) used as a part of EPA Method 21 to give a higher reading because the concentration read by the TVA is only a function of the composition of the process stream. The emissions estimate is

based on this concent ration measurement and has already incorporated variability, as discussed below. While releases from emission sources such as pressure relief devices are an acute risk issue because they are generally high concentration releases for short durations, equipm ent leaks pose more of a chronic risk issue because they are generally a small emission rate over a long period of time. Therefore, we do not believe that emissions from equipment leaks pose a large acute risk.

Additionally, a large uncertainty factor has already been incorporated into the emission rate estimates from equipment leaks and we have determined that it was not appropriate to add another level of uncertainty to this. To calculate emissions from equipment leaks in this industry, screening is cond ucted on a regular basis and when a leak is measured using EPA5

Method 21, a predetermined emission factor from EPA’s Protocol for Equipment Leak

Emission Estimates document is applied. When these emission rates for equipment leaks were developed, EPA used data from a number of different studies of bagged samples at petroleum and synthetic organic chemical manufacturing facilities. In these studies, EPA measured for leaks using EPA Method 21 and where leaks were found, the concentration was recorded, the lea k was bagged, and an estimate of the mass emission rate was calculated from the bagged sample. From the results of these studies, mass emission rates were found to vary up to five orders of magnitude for a given EPA Method 21 concentration reading. A

corre lation was developed based on these results, which was inherently biased towards higher emission rates. A more detailed discussion on how these correlations were developed can be found in Appendix B of EPA’s Protocol for Equipment Leak Emission Estimates document. Based on this information, we do not believe it is appropriate to add yet another order of magnitude of uncertainty to emissions from equipment leaks, and that a factor of two is more appropriate. A list of facilities where we used the factor of two instead of ten is provided in Appendix 7 of the risk assessment document.

4.0 DATA REVISIONS AFFECTING RISK ANALYSIS

Some revisions to the data set were made post

- modeling after receiving additional information from other regulatory entities or industr y. Part of these changes reflected facilities which were shut down or no longer operating. Other information received reflected changes in the source category of certain emission points or that a specific process unit had been shut down within a facility. These changes were not made directly to the modeling file, as they would cause changes in the modeling itself. Instead, this information can be used qualitatively to understand the risk results. This information is detailed below:

NEINC0595 is not in the PEPOs source category NEI12483 is not in the PEPOs source category

NEI41302 has been shut down NEI43310 has ceased operations The hexachlorobenzene emission point at NEI11906 should actually be attributed to the PAI source category and not PEPOs

NEI45591 h as closed the PET production process and acetaldehyde emissions are almost

zero Phosgene emissions in the PAI source category at NEI 8596 are incorrect and should reflect one fugitive emission point and one stack emission point, both of 0.01 tpy, totaling 0.02 tpy The arsenic emission point at NEIWV0390007 is not in the PAI source category

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