MEMORANDUM

DATE : July 7, 2010

TO : Project file

SUBJECT: Docket Entry for Draft Screening Risk Analysis for Mercury Cell

Chlor-Alkali Plants

This memorandum introduces a draft screeni ng risk analysis for the mercury cell chloralkali industry. The draft screening analysis wa s performed to gain a preliminary understanding of the potential risks from one form of mercury (divalent mercury) emitted from mercury cell chlor-alkali plants. The draft screening analysis did not c onsider risks from other forms of mercury and the quality of the data used in the analysis has not been determined.

Because a risk analysis is not required in setting technology based MACT standards, EPA did not go forward with further ri sk analyses and peer review of the attached draft screening analysis. Moreover, because this was only a screening analysis, it di d not address several properties of mercury that the Agency consider s important in understanding risk from this particular pollutant. The analysis addressed on ly inhalation, and not ingestion as a pathway of exposure. Mercury accumulates bo th in the environment and in th e body tissues of fish, animals, and people. Mercury crosses bot h the blood-brain barrier and the placental barrier, and as such presents an exceptionally high ri sk to women, nursing and pre gnant mothers, and women who may become pregnant. The screening risk an alysis did not consid er that mercury has

accumulated in the environment as a result of this industry, that a portion of elemental mercury is converted to the more toxic mercury compounds (s uch as methyl mercury), nor did it consider

the current level of bioaccumulation within th e population. More information on the health effects of mercury are presented in the preambl e to the rule, and elsewhere in EPA’s mercury

studies.

In general, reducing the amount of mercury re leased to the air, water, and other media

also reduces the resultin g exposure, and subsequent environm ental and human health effects. Therefore, while it is informative, the attached draft screening risk anal ysis is inadequate to represent all the risks that mercury presents fr om the mercury cell chlor-alkali source category.Providing Environmental Technical Support Since 1989 

# E C 

# /

R Incorporated

501 Eastowne Drive, Suite 250 y Chapel Hill, North Carolina 27514 Telephone: (919) 484-0222 y Fax: (919) 484-0122 MEMORANDUM 

## DRAFT

DATE: February 16, 2009

SUBJECT: Screening Risk Analysis for Mercury Cell Chlor-Alkali Plants

FROM: Phil Norwood, EC/R Incorporated Darcie Smith, EC/R Incorporated

TO: Dr. Donna Lee Jones, EPA/OAQPS/SPPD/MICG

The purpose of this memo is to present the re sults of a screening risk analysis conducted for the five mercury cell chlor-alka li plants currently operating in the United States. These plants are Olin Corporation in Augusta, Georgia (Olin GA); Olin Corporation in Charleston, Tennessee (Olin TN); ERCO Worldwide in Port Edward s, Wisconsin (ERCO); PPG Industries in New Martinsville, West Virginia (PPG ); and Ashta Chemicals in Ashta bula, Ohio (Ashta). The first

section describes the data used for the analysis, followed by the results of the inhalation and multipathway screenings.

Source Data

The required inputs for the risk analysis incl ude emissions and release characteristics. Specifically, the release parameters needed for po int sources are stack hei ght, stack diameter, and exit velocity, along with the coordi nates. For area sources, the re lease parameters needed are the release height and the x and y dimensions (i.e., the length and width of the rectangular shaped area source). The mercury emission sources at mercury cell chlor-alkali plants include the cell room, the hydrogen by-product vent stream, the end-box ventilation system, and the mercury thermal recovery unit vent. Ever y plant has a cell room, but not ev ery plant has all three of the remaining sources. In addition to these mercury emission points, there are other points that emit chlorine, hydrochloric acid (HCl), and other HAP.

Emissions Data

Air toxics emissions data were obtained from the 2006 Toxics Release Inventory (TRI) and the 2002 National Emissions Inventory (NEI). Specifically, mercury emissions were

obtained from the TRI and HAP emissions and re lease characteristics were obtained from the

NEI. Table 1 shows the merc ury emissions in the 2006 TRI.DRAFT – February 16, 2009

2 Table 1. Mercury Emissions from the 2006 TRI

Mercury Emissions in pounds/yr (tons/yr) Plant Fugitive Point

Ashta 0 (0) 2 (0.0010)

ERCO 1,078 (0.54) 80 (0.040)

Olin GA 493 (0.25) 86 (0.043)

Olin TN 1,032 (0.52) 109 (0.054)

PPG 172 (0.086) 134 (0.067)

All records at the five site s were retrieved from the 2002 NEI. These records included emission points characterized by Source Classifica tion Codes (SCCs) that do not appear to be associated with mercury cell production processes. Appendix A contains a list of the SCCs at

these five sites and identifies the ones that were c onsidered to be part of the mercury cell plant. Table 2 summarizes the emissions determined to be from the mercury cell processes at each plant. Attachment B contains more detailed information from the NEI.

Table 2. Mercury Cell Chlor-Alkali Plan t HAP Emissions from the 2002 NEI

Plant State HAP Emissions (tons/yr) 1,3-dichloropropene 0.36

chlorine 0.23 Ashta OH mercury (elemental) 0.70

chlorine 0.88 hydrochloric acid 0.032 lead compounds 0.000006 mercury compounds 0.54 ERCO WI

carbon tetrachloride 0.45

chlorine 0.066 hydrochloric acid 0.0075 Olin GA mercury (elemental) 0.37

chlorine 0.33 hydrochloric acid 0.009 Olin TN mercury (elemental) 0.56 mercury compounds 0.71 methylene chloride 2.2

chlorine 0.37

chlorine 0.0075 PPG WV

hydrochloric acid 0.026

Since mercury is the primary HAP of interest, additional analysis of the mercury emissions was conducted. Table 3 compares th e mercury emissions from the 2002 NEI and the

2006 TRI.DRAFT – February 16, 2009

3 Table 3. Comparison of Mercury Emissions

Mercury Emissions (tons/yr) Fugitive Stack Plant

2002 NEI 2006 TRI 2002 NEI 2006 TRI

Ashta 0.52 0 0.18 0.0010

ERCO 0.53 0.54 0.014 0.040

Olin GA 0.29 0.25 0.077 0.043

Olin TN 0.52 0.52 0.043 0.054

PPG 0.66 0.086 0.053 0.067

With one exception, fugitive mercury cell em issions had not been measured during the time periods for which these data were reported. The fugitive mercury emissions for Ashta (NEI), ERCO, and Olin TN appear to based on the historical assumption that the mercury emission rate for cell rooms at mercury cell chlor-alkali plants is 1,300 grams per day:

(1300 g/day) x (1 lb/454 grams) x (1 ton/ 2000 pounds) x (365 days/yr) = 0.52 tons/year

It appears that the fugitive estimate for Olin GA is based on the testing program (the one exception) conducted at that facility in 2000, 1 which reported an averag e emission rate slightly below 500 grams/day. The basis for the PPG estima tes is not clear, and the zero emissions rate

from Ashta in the TRI is not realistic.

As part of their r econsideration efforts, EPA collected eight separate fugitive mercury

emission data sets from three different merc ury cell chlor-alkali plants in 2005 and 2006 to produce an estimate of fugitive mercury emissions from cell rooms. The time periods of data collection range from 6 weeks to over 30 weeks, all of which pr ovided an opportunity to include a complete range of maintenance activities and operating conditions. Two of the data sets were generated via EPA-sponsored test programs and the others were colle cted from cell room mercury monitoring systems that were validated by EPA. The daily mercury emission rates extrapolated from these data sets ranged fr om around 20 to 1,300 g/day per facility. The average daily emission rates ranged from around 420 g/day to just under 500 g/day per facility, with the mean of these average values being slightly less than 450 g/ day per facility. (73 FR 33266, June 11, 2008).

We believe that the results of this EPA pr ogram, which are consistent with the earlier EPA study at Olin GA, provide the best estimate of fugitive mercury emi ssions at a mercury cell plant. Therefore, for the purposes of this risk analysis, an annual mercury emission rate of 0.2 tons/yr (500 grams/day) was used for all plants.

The stack mercury emissions from the 2006 TRI were used as reported, with the exception of Ashta, whose mercury emissions were more than an order of magnitude lower than all the other plants. Therefore, for Ashta, the average value of a ll the other plants, 0.051 tons/yr,

1 Kinsey, J., Characterization of Mercury Emissions at a Chlor-Alkali Plant . NRMRL-RTP-236a. U.S. Environmental Protection Agency, Research Triangle Park, NC. January 2002.DRAFT – February 16, 2009

4 was assumed for their stack mercury emission ra te. For all the other (i.e., non mercury) HAP,

the values in the 2002 NEI we re used in the analysis.

Release Characteristics

As can be seen in Attachment 2, the stack pa rameters for all points appear to be default values. For the point sources, those parameters were used. Even though there are likely multiple stacks at a mercury cell plant, all stack emissi ons were modeled from a single point source.

For the fugitive emission sources, these para meters are actually point source parameters intended to simulate a fugitive type sources. We do not believe that the parameters in the NEI are adequate to represent the release characteristics of a cell room. Cell rooms, the source of the fugitive mercury emissions, are large buildings typically vented through long rectangular ridge vents. While there is a flow from the vent, these ridge vents are cove red by a cupula or other

structure that does not allow the exiting air to exit vertically fro m the building. Therefore, the cell room was modeled as a long, el evated rectangular area source.

However, specific data were not readily avai lable on every cell room. Therefore, a model

cell room ventilator was used for all plants using the available data . The peak of the cell room at the Olin GA facility is 16 meters from ground level, 2 and this was used as the height of the fugitive source for every facility. The width of the roof ventilator at Olin GA, 34 feet, 3 was used as the width of the area source. The length of the ventilator at Olin GA was 62 meters. To determine the length of the cell room ventilators at the other facilities , we used GoogleEarth, identified the cell room, and measured the leng th of the building. Where the resolution was adequate and the ventilator could be identifie d, the length of the ventilator was measured. GoogleEarth was also used to identify the coordi nates to use for the modeling. Table 4 provides the length and coordinates used for the analys is. While mercury point sources are typically adjacent to the cell room, the exact location wa s not known. Therefore, the point source was placed at the center of the cell room.

Table 4. Ventilator Lengths and Emission Point Coordinates*

Plant Length of

Ventilator

(meters) Coordinate of Southwest

Corner of Ventilator (darcie – add units) Coordinate for Point

Source (darcie – add units)

Ashta 108 41.89309, -80.74831 41.89355, -80.748506

ERCO 85 44.33708, -89.860151 44.33721, -89.859592

Olin GA 62 33.345079, -81.950657 33.345144, -81.950434
57 35.06031, -84.780723 Olin TN 65 35..06278, -84.780307 35.306448, -84.780442

PPG 77 39.750019, -80.852332 39.750312, -80.852327

* All ventilators were assumed to be at a hei ght of 16 meters and have a width of 10.4 meters (34 feet).

2 Kinsey, p. 15.

3 Kinsey, p. 26.DRAFT – February 16, 2009

5 At the PPG facility there were two othe r fugitive emission sources that did not emit mercury. These sources were modeled as point s ources using the release characteristics in the

NEI.

Screening Risk Estimates

Inhalation Risks

In order to estimate the inhalation risks fr om these mercury cell plants, the HEM3 model

was used. 4 Table 5 summarizes the results. As can be seen from the table, there is no plant with an estimated cancer risk approaching 1 in 1 million and no chronic hazard index (HI) approaching 1. Every plant has an acute HQ grea ter than 1 at the no effects (REL) level for mercury, but there was no HQ approaching 1 for any mild effects dose response value (AEGL1, ERGP, IDLH/10). More detail on these re sults is provided in Attachment C.

Table 5. Screening Inhalation Risk Results

Max Chronic HI Max Acute HQ Plant Max Cancer Risk (in 1 million) Respiratory Neurological M ild Effects No Effects

Ashta 0.04 0.03 0.02 0.01 10

ERCO 0.4 0.3 0.04 0.07 10

Olin GA * 0.002 0.009 0.0005 10

Olin TN * 0.01 0.007 0.003 10

PPG 0.01 0.03 0.03 0.4 30 * No HAP with a URE was reported to be emitted from this facility.

Multipathway Risks

The most significant mutipathway risks from mercury are due to divalent mercury. Divalent mercury emitted from a source may be deposited relatively quickly by wet and dry deposition processes, leading to a residence tim e of hours to months. In contrast, elemental mercury has an average residence time in the atmosphere of about one year and will be distributed fairly evenly in th e troposphere. While the transformation of elemental mercury to divalent mercury can result in mercury deposition to land and water, this deposition can occur far from the source due to the slow rate of elemental uptake in cloud water. It has been suggested that this mechanism is important in a globa l sense for mercury pollution, while direct wet deposition of divalent mercury is the most important locally. 5 Therefore, the multipathway risks in the area surrounding a mercury cell chlor-alkali plant would result from emissions of divalent mercury. In the 1997 Report to Congress, EPA as sumed that 30 percent of mercury emissions from mercury cell plants was divalent. 6 However, a study conducted at the Olin GA plant

4 http://www.epa.gov/ttn/fera/human_hem.html

5 U.S. Environmental Protection Agency. Mercury Study Report to Congress. Vol. 3. EPA-452/R-97-003. Office of Air Quality Planning and Standards. Office of Research and Development. 1997.

6 Report to Congress, Vol. 3.DRAFT – February 16, 2009

6 accompanying the Kinsey study found that mercury cell room emissions only consisted of around 2 percent inorganic reactive gaseous mercury. 7

As part of the Risk and Technology (RTR) program, EPA developed PB-HAP de minimis thresholds in order to provide a screening-le vel check to see if the potential exists for multipathway risks. 8 To evaluate the potential for human h ealth risks, reported emissions of PBHAPs are compared to de minimi s emission thresholds establis hed for the purposes of RTR multipathway risk assessment. Facilities w hose emissions of a PB-HAP are below the de

minimis threshold are not expected to pose significant hum an health risks. In other words, if PBHAP emissions at a facility do not exceed the de minimis level for that PB-HAP, EPA can be reasonably certain that the resul ting exposures and associated ri sks are negligible. Facilities emitting PB-HAPs in amounts exceeding the de minimis level should be the focus of more refined multipathway exposure and risk analyses for RTR. The de minimis threshold for divalent mercury is 0.183 tons/year. Table 7 pr ovides the potential diva lent mercury estimates from each plant using both the 30 and 2 percent assumptions.

Table 7. Estimation of Divalent Mercury Emissions

Divalent Mercury Emissions (tons/yr) Plant Mercury Emissions (tons/yr) Assuming 30% Assuming 2%

Ashta 0.25 7.6E-02 5.0E-03

ERCO 0.24 7.3E-02 4.9E-03

Olin GA 0.26 7.7E-02 5.1E-03

Olin TN 0.27 8.0E-02 5.4E-03

PPG 0.24 7.2E-02 4.8E-03

As can be seen from Table 7, the highest di valent mercury emission rate (0.08 tons/yr for Olin TN assuming 30 percent divalent mercury) is less than half the de minimis level. This suggests there is no need to conduct further multi pathway analysis for this source category. However, in addition to the conclusion cited a bove regarding the emissions of reactive gaseous mercury, the Landis study also concluded that me rcury cell chlor-alkali pl ants “were still found to present a significant impact on near field atmospheric merc ury dry deposition. The mean

estimated dry deposition of mercury within a 10km radius of the facility contributed the annual equivalent of 4.6 μ gm -2 (almost half of the total wet mercury deposition measured at a nearby MDN sampling site).”

7 Landis, M., Keeler, G, Al-Wa li, K., and Stevens, R. Divalent inorganic reactive gaseous mercury emissions from a mercury cell chlor-alkali plant and its impact on near-field atmospheric dry deposition. Atmospheric Environment 38 (2004). 613-622.

8 Memorandum. Burch, D., Cleland, J., Holder, C., Shapir o, A., and Turley, A. ICF International to Hollingsworth, T., Palma, T., Guinnup, D., EPA/OAQPS. Revised RTR PB-HAP De Minimis Levels and Updated Group 3 Screening Results. January 30, 2009.DRAFT – February 16, 2009A-1APPENDIX A: SCCS AT MERCURY CHLOR-ALKALI PLANT SITESSCCs Attributed to the Mercury Cell Plant30100802 Industrial Processes Chemical Manufacturing Chloro-alkali ProductionLiquefaction (Mercury Cell Process)30100805 Industrial Processes Chemical Manufacturing Chloro-alkali ProductionAir Blowing of Mercury Cell Brine30100899 Industrial Processes Chemical Manufacturing Chloro-alkali Production Other Not Classified30107002 Industrial Processes Chemical Manufacturing Inorganic Chemical Manufacturing (General) Storage/Transfer30187002 Industrial Processes Chemical Manufacturing Inorganic Chemical Storage (Fixed Roof Tanks) Hydrochloric Acid: Working LossOther SCCs at the Plant Sites Not Attributed to the Mercury Cell Plant10200202 External Combustion Boilers IndustrialBituminous/Subbituminous CoalPulverized Coal: Dry Bottom10200601 External Combustion Boilers Industrial Natural Gas > 100 Million Btu/hr10200602 External Combustion Boilers Industrial Natural Gas 10-100 Million Btu/hr10200603 External Combustion Boilers Industrial Natural Gas < 10 Million Btu/hr10201401 External Combustion Boilers IndustrialCO BoilerNatural Gas10200202 External Combustion Boilers IndustrialBituminous/Subbituminous CoalPulverized Coal: Dry Bottom30130101 Industrial Processes Chemical ManufacturingChlorobenzeneTail Gas Scrubber30130107 Industrial Processes Chemical Manufacturing Chlorobenzene DCB Crystallization30130180 Industrial Processes Chemical Manufacturing Chlorobenzene Fugitive Emissions30130101 Industrial Processes Chemical ManufacturingChlorobenzeneTail Gas Scrubber30190004 Industrial Processes Chemical Manufacturing Fuel Fired EquipmentProcess Gas: Process Heaters30190099 Industrial Processes Chemical Manufacturing Fuel Fired EquipmentSpecify in Comments Field40703602 Petroleum and Solvent Evaporation Organic Chemical Storage Fixed Roof Tanks - AromaticsBenzene: Working Loss40706008 Petroleum and Solvent Evaporation Organic Chemical Storage Fixed Roof Tanks -Halogenated Organics Chlorobenzene: Working Loss40706010 Petroleum and Solvent Evaporation Organic Chemical Storage Fixed Roof Tanks -Halogenated Organics o-Dichlorobenzene:Working Loss40706012 Petroleum and Solvent Evaporation Organic Chemical Storage Fixed Roof Tanks -Halogenated Organics p-Dichlorobenzene:Working Loss40899995 Petroleum and Solvent Evaporation Organic Chemical Transportation Specific LiquidCars/Trucks: Loading Rack40706012 Petroleum and Solvent Evaporation Organic Chemical Storage Fixed Roof Tanks -Halogenated Organics p-Dichlorobenzene:Working Loss40899995 Petroleum and Solvent Evaporation Organic Chemical Transportation Specific LiquidCars/Trucks: Loading RackDRAFT – February 16, 2009C-1ATTACHMENT B. SUMMARY OF MERCURY CELL CHLOR-ALKALI PLANT NEI DATANTI ID Name State SCC EmrelType*StackHeight(ft)StackDiameter(ft)StackTemperature(F)StackVelocity(ft/sec)StackFlowRate(ft3/min)HAPEmissions(tons/yr)chlorine 2.50E-0201 10 0.003 72 0.0003 0mercury (elemental) 5.23E-01chlorine 3.07E-01hydrochloric acid 9.00E-03NEI10894 OLIN CORP TN 3010080202 58.19 3.516 234 31.8582 9.28171mercury (elemental) 4.25E-02mercury compounds 6.55E-0101 10 0.003 72 0.0003 0methylene chloride 2.25E+003010080502 35 1 75 4.4 3.41667 mercury compounds 5.32E-0230100899 01 10 0.003 72 0.0003 0 chlorine 3.76E-0130107002 02 91 4 120 55 83.33331 chlorine 7.52E-03NEI42444PPGINDUSTRIESINCWV30187002 01 10 0.003 72 0.0003 0 hydrochloric acid 2.57E-02chlorine 8.77E-01hydrochloric acid 6.00E-03lead compounds 6.00E-0601 10 0.003 72 0.0003 0mercury compounds 5.27E-01chlorine 1.11E-02hydrochloric acid 2.65E-023010080202 58.19 3.516 234 31.8582 9.28171mercury compounds 1.40E-02NEI42973VULCANMATERIALSCO PORTEDWARDSPLANTWI30100899 02 49 1 85 7.4272 5.83333 carbon tetrachloride 4.53E-01chlorine 3.00E-03hydrochloric acid 7.50E-0301 10 0.003 72 0.0003 0mercury (elemental) 2.93E-01chlorine 6.30E-02NEIGAT$3892 OLIN CORP GA 3010080202 58.19 3.516 234 31.8582 9.28171mercury (elemental) 7.70E-021,3-dichloropropene 3.12E-01chlorine 2.35E-0101 10 0.003 72 0.0003 0mercury (elemental) 5.23E-011,3-dichloropropene 5.30E-02NEIOHT$5933ASHTACHEMICALSINCOH 3010080202 58.19 3.516 234 31.8582 9.28171mercury (elemental) 1.75E-01* EmrelType 01 = fugitive source,EmrelType02 = vertical stack sourceDRAFT – February 16, 2009C-1ATTACHMENT C. SUMMARY OF SCREENING-LEVEL RISK ESTIMATESTable C-1. Summary of Chronic RisksASHTAERCOOLINTNOLINGAPPGCancerriskMax Cancer Risk (in 1 million)0.040.40.00.01driver sourcecell roompoint sourcen/an/acell roomdriver HAP1,3-dichloropropene carbon tetrachloriden/an/amethylene chlorideNoncancer Hazard IndicesMax Respiratory HI0.030.30.010.0020.03driver sourcecell roomcell roompoint sourcepoint sourceother fugitivedriver HAPchlorinechlorinechlorinechlorinechlorineMax Neurological HI0.020.040.0070.0090.03driver sourcecell roomcell roomcell roomcell roomcell roomdriver HAPmercurymercurymercurymercurymercuryDRAFT – February 16, 2009C-2Table C-2. Summary of Acute RisksAcute Hazard Quotient (HQ)No Effects LevelMild Effects LevelSerious Effects LevelPlant/HAPrel aegl_1_1h aegl_1_8h erpg_1 aegl_2_1h aegl_2_8h erpg_2ASHTA1,3-dichloropropeneChlorine 0.070.01 0.01 0.01 0.00 0.01 0.00mercury (elemental)8 0.01 0.04 0.01ERCOcarbon tetrachloride 0.02 0.0001 0.0003 0.0001 0.00003 0.0001 0.0000chlorine 0.50.07 0.07 0.07 0.02 0.05 0.02hydrochloric acid 0.0004 0.0003 0.0003 0.0003 0.0000 0.0001 0.00003leadcompoundsmercury (elemental)13 0.01 0.07 0.01OLIN GAChlorine 0.0030.0005 0.0005 0.0005 0.0001 0.0003 0.0001Hydrochloric acid 0.0003 0.0003 0.0003 0.0003 0.0000 0.0000 0.00002mercury (elemental)11 0.01 0.06 0.01OLIN TNChlorine 0.020.003 0.003 0.003 0.0009 0.002 0.0009Hydrochloric acid0.00003 0.00003 0.00003 0.00003 0.000002 0.000005 0.000002mercury (elemental)12 0.01 0.07 0.01PPGChlorine20.3 0.3 0.3 0.09 0.2 0.09Hydrochloric acid0.020.01 0.010.010.0010.0020.001Mercury (elemental)33 0.03 0.2 0.03Methylene chloride0.01 0.00030.0003 0.0001 0.001 0.0001