PRELIMINARY PUBLIC HEALTH ASSESSMENT
ALCOA (POINT COMFORT)/LAVACA BAY
POINT COMFORT, CALHOUN COUNTY, TEXAS
This section lists contaminants of concern at the ALCOA (Point Comfort)/Lavaca Bay site. ATSDR and TDH select the contaminants of concern based upon concentrations of contaminantsfor which data are available, data quality, and a comparison of site-related contaminantconcentrations with background concentrations and Comparison Values (CVs).
Comparison Values (CVs) are contaminant concentrations for specific media (e.g., soil, water,air) which are used to select contaminants for further evaluation. Exceeding a comparison valuedoes not imply that a contaminant represents a threat to public health, but suggests that furtherevaluation is warranted. Comparison values include Non-Carcinogenic Risk Evaluation Guides(NCREGs), Cancer Risk Evaluation Guides (CREGs), and other relevant guidelines. NCREGsare based on ATSDR's Minimal Risk Levels (MRLs), EPA's Reference Doses (RfDs), or othernon-carcinogenic health comparison values; CREGs are based on risk estimates of one excesscancer in a million persons exposed over a lifetime.
The tables and text that follow include the following abbreviations and symbols:
*EMEG = Minimal Risk Level-based Environmental Media Evaluation Guide
*RMEG = Reference Dose-based Media Evaluation Guide
* MCL = Maximum Contaminant Level
* TLV = Threshold Limit Value
* MRL = Minimal Risk Level
* ppb = parts per billion
* ppm = parts per million
*µg/L = micrograms per liter (equal to parts per billion)
*mg/kg = milligrams per kilogram (equal to parts per million)
*µg/m3 = micrograms per cubic meter of air
*mg/m3 = milligrams per cubic meter of air
For the purposes of this health assessment, "on site" is defined as the ALCOA (Point Comfort)plant grounds including the former smelter area and Witco dock; the dredge spoil island west ofthe ALCOA plant; the part of Lavaca Bay which has been closed to the taking of fish and crabs. "Off site" includes the remaining parts of Lavaca Bay outside the closure area, including the area north of the causeway and Keller Bay.
Forms of mercury have been detected on site in surface soil; shallow groundwater; air; baysediment; and finfish, blue crabs, and oysters (in the past) in Lavaca Bay within the vicinity of the plant. Mercury also has been detected off site in finfish and birds. Contaminants such as lead and volatile organic compounds (VOCs) have been detected in shallow groundwater; polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) have been detected in a limited number of sediment samples.
TDH obtained and compiled the environmental data presented in this section from varioussources. The TDH Division of Shellfish Sanitation (Seafood Safety) has sampled fish, shellfish,and oysters in Lavaca Bay since the 1970s . Texas A&M University researchers collected fish, oysters, and sediment samples in 1990 . The TNRCC (and its predecessor, the Texas Water Commission), the EPA and their contractors, and ALCOA have collected fish samples as well assediment samples in the bay . ALCOA and TNRCC also analyzed shallow groundwater(monitoring well data) on the site . The Mining Safety and Health Administration (MSHA)reported air monitoring data in the form of mercury vapor concentrations at the ALCOA facility .
Shallow groundwater on site is characterized by two zones; Zone A, (which lies betweenapproximately 8 feet to 12 feet below the ground surface and Zone B (which lies betweenapproximately 14 to 42 feet below the ground surface. ALCOA installed 60 groundwatermonitoring wells in these two water bearing zones. Thirty of the wells are screened in Zone A; 28wells are screened in Zone B; and the depth of two wells could not be determined from availableinformation. The wells in both zones are widely distributed throughout the ALCOA facility: fourwells are in the bauxite storage area; twenty wells are in the chlor-alkali area, twenty-three wellsare in the vicinity of the bauxite residue (mud) lake area, and twelve wells are in the vicinity of theformer smelter area. One well is labelled as miscellaneous; its location could not be determined.
On-site shallow groundwater is contaminated with mercury, lead, volatile organic compounds,and other chemicals. Total mercury ranged from 0.10 to 95 µg/L. Total lead concentrationsranged from 1 to 523 µg/L. Gross alpha, gross beta, and total radium exceeded TNRCC drinkingwater quality standards. Table 1 presents contaminants detected by ALCOA in shallowgroundwater monitoring wells between 1982 and 1992.
On-Site Surface Water
Mercury levels greater than 1 µg/L were reported in on-site surface water during the early- andmid-1970s. Samples collected in February of 1977  from Lavaca Bay at the ALCOA dockcontained 3.0 µg/L mercury. Since the 1980s, concentrations of mercury in surface water havedecreased to less than 1 µg/L . The detection limits for these data were not available in theinformation reviewed.
On-Site Bay Sediment
In a 1990 study focused on Cox Bay, Texas A&M University researchers also collected threesediment samples in Lavaca Bay south of the causeway. Low levels of polycyclic aromatichydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were detected. Total PAHs were3.78, 39.9, and 57 ppb; total PCBs were 28.21, 155.62, and 50.03 ppb . Samples collectedfor other studies in Lavaca Bay have not included testing for these contaminants in sediments. The reliability of these results could not be determined because complete descriptions of samplingmethods and quality assurance/quality control (QA/QC) measures were not reported .
Between April and August of 1992, a consultant collected Bay sediment samples for ALCOAfrom areas both inside and outside the fishing closure area including the ship channel, the Lavacaand upper Matagorda Bays, and the dredge island. Table 2 contains data from 334 samples takenon site. Among these samples, 167 were surface sediment samples collected at 0-to-10centimeters. Samples also were collected at 10-to-20 and 20-to-50 centimeter depths . The sample with the highest mercury concentration (25.2 mg/kg) was collected on the dredge island ata depth between 0 and 10 centimeters. Although the highest overall average mercury levels are in the grassy areas of the Bay, the highest concentrations in individual samples are at the dredge spoil island (25.2 mg/kg) and Open Water Area 1 (all open waters within the TDH closure area). See Figures 2 and 3.
During EPA's expanded site inspection sampling event conducted in September 1992, 68 bottomsediment samples from the Bay were collected and analyzed for mercury . Mercury levels insediment within the area closed to the taking of fish and crabs were generally higher than levels in sediment outside of that area.
MSHA collected on-site soil samples (1-1.5 inches deep) in the vicinity of the chlor-alkali facility(R-300 building) during two inspections in 1992 [18,40]. In August, MSHA inspectors reportedobserving pooled metallic (liquid) mercury at the R-300 building. The two soil samples collectedat that time contained 92.48 and 676.6 mg/kg of mercury. In September 1992, MSHA collectedeight additional soil samples (1 to 1.5 inches deep) around the perimeter of the building; mercurylevels in these samples ranged from 2.6 to 52 mg/kg. High levels of mercury contamination in thesoil were on the west side of the chlor-alkali building.
On-Site Air Quality
No on-site air monitoring data for the time during which the chlor-alkali unit was operating areavailable; however, urine mercury concentrations of employees working in this unit were elevated. These data will be reported in the health outcome data evaluation section of this report.
|Contaminant||Date Sampled||Well Number1||Maximum Concentration||Comparison Value||NCREG Source|
|Total Mercury||June 15, 1992||CA007A||95 µg/L||2 µg/L||NA||LTHA|
|Total Lead||June 27, 1992||CA014A||523 µg/L||15 µg/L||NA||EPA action level|
|Volatile Organic Compounds|
|Benzene||January 14, 1989||SM007A||8,000 µg/L||NA||1 µg/L||NA|
|Ethylbenzene||December 12, 1988||SM006A||2,000 µg/L||1,000 µg/L||NA||RMEGchild|
|Toluene||December 12, 1988||SM006A||33,000 µg/L||2,000 µg/L||NA||RMEGchild|
|Xylenes||December 12, 1988||SM006A||8,000 µg/L||2,000 µg/L||NA||EMEGchild|
|1,2 Dichloroethane||January 14, 1989||SM007A||250 µg/L||NA||0.4 µg/L||NA|
|Chloroform||December 28, 1982||CA018B||2,800 µg/L||100 µg/L||6 µg/L||EMEGchild|
= Methylene dichloride
|December 5, 1982||CA018B||200 µg/L||600 µg/L||5 µg/L||EMEGchild|
|Carbon tetrachloride||December 28, 1982||CA018B||11,000 µg/L||NA||0.3 µg/L||NA|
|Tetrachloroethene||December 28, 1982||CA018B||200 µg/L||NA||0.7 µg/L||NA|
|Naphthalene||January 14, 1989||SM007A||77 µg/L||20 µg/L||NA||LTHA|
|Total Cyanide||June 25, 1992||LK015A/B||108 µg/L||200 µg/L||NA||RMEGchild|
|Phenols||July, 1983||MI001B||200 µg/L||6,000 µg/L||NA||RMEGchild|
|Gross a||December 5, 1982||LK014A/B||-188 pci/L||15 pci/L||NA||TNRCC3|
|Gross b||December 5, 1982||LK015A/B||4,237 pci/L||50 pci/L||NA||TNRCC|
|Total Radium||December 5, 1982||LK013B||9.7 pci/L||5 pci/L||NA||TNRCC|
1 Well number denotes locations: CA=former Chlor-Alkali area; LK=Lakes,Bauxite Lakes, MudLakes; SM=Dismantled Smelter, MI=Miscellaneous
2 CREG value is based on EPA's chemical specific slope factor
3 from drinking water standards
LTHA = Lifetime Health Advisory
|Location||Sampling Depth (cms)|
|Open Water Area 1||22||0.09U - 7.30||1.16||22||0.01UJ-6.60||1.39||22||0.01UJ-2.40||0.34|
U = the material was analyzed for but not detected above the level of the associated value. Theassociated value is either the sample quantification limit or the sample detection limit.
UJ = the material was analyzed for, but was not detected. The associated value is an estimate.
Recent air emission (stack testing) at ALCOA indicate that mercury is being released to theatmosphere; therefore, additional air sampling is planned in the Town of Point Comfort. During an August 1992 site inspection, MSHA used a Bacharach mercury vapor direct readinginstrument to sample for mercury vapors near the chlor-alkali facility. The detection limit of theinstrument was not given, nor could the instrument be calibrated. Although samples collected atground level indicated mercury was present at concentrations higher than 0.05 mg/m3, the samples were not collected in the breathing zone. Mercury vapor is much more dense than air, so mercury vapor can be present at ground level but be found at much lower concentrations in the breathing zone. All samples collected with a direct-reading instrument are instantaneous readings that represent a "snapshot" of existing conditions. The TLV is an eight-hour time-weighted average value; instantaneous results in excess of the TLV are acceptable provided the eight-hour average remains below the TLV. The single sampled collected in the breathing zone did not exceed the TLV.
In September of 1992 MSHA reinspected ALCOA using a Jerome 431 mercury vapor directreading instrument. Of the 95 air samples tested, five exceeded 0.05 mg/m3. Of these five samples, four were collected at the R-30 mercury trap area (concentration range: 0.069 - 0.631 mg/m3) and one was collected from the corner sink in the environmental lab. None of these samples were collected in the breathing zone and none were time-weighted averages.
Quarterly reports for 1993 were provided by ALCOA presenting the results of air sampling formercury conducted in the breathing zone. None of the air samples exceeded the TLV on a time-weighted average basis [30, 31, 32].
MSHA inspectors also detected hydrogen fluoride gas (0.049 and 0.004 mg/m3), fluoride (0.008and 0.086 mg/m3), coal tar pitch volatile (0.086 and 0.067 mg/m3), and sulfuric acid mist (0.02and 0.006 mg/m3) in personal samples at several locations throughout the plant . Twopersonal filter samples were collected for each of these contaminants. Measured levels did notexceed the Threshold Limit Values of 2.0, 2.5, 0.2, and 1 mg/m3 respectively, for thesecontaminants. These samples were collected as part of MSHA's routine regular inspections.
On-site Blue Crabs, Fish, and Oysters
TDH began sampling crabs in Lavaca Bay in 1970. Crabs were collected at sampling pointsidentified by State Land Tract number. The crab meat was collected for mercury analysis. Ifcomposites were prepared, they were prepared using crabs of the same size, sex and collectedfrom the same general area. Data for Blue Crabs collected inside the now-designated closure areaare summarized in Table 3. The most recent mean total mercury concentrations in Blue Crabstaken from the closure area was 0.257 mg/kg. However, this is based on a small sample size. In1992 Woodward-Clyde Consultants collected 63 blue crab samples from within the designatedTDH closure area. The mean total mercury concentration in these crab samples was 0.73 mg/kgwet weight.
|Year*||# Individuals||Range of Total Mercury** |
|Mean Total Mercury |
|1970||6||0.720 - 1.920||1.207|
|1971||8||0.420 - 2.400||1.575|
|1973||7||0.190 - 3.600||1.307|
|1974||3||0.500 - 1.270||0.957|
|1976||8||0.490 - 1.030||0.704|
|1977||6||0.580 - 0.770||0.660|
|1985||8||0.360 - 1.840||0.820|
|1986||8||0.040 - 1.510||0.456|
|1987||5||0.360 - 4.460||1.968|
|1988||28||0.077 - 1.880||0.332|
|1989||2||0.747 - 0.786||0.766|
|1990||8||0.232 - 0.661||0.381|
|1993||7||0.077 - 0.634||0.257|
* Years blue crab samples were taken
** wet weight
Mercury analyzed from crab meat
Between 1970 and 1993, 232 blue crab meat composites were sampled and tested for totalmercury. The highest total mercury concentration (4.46 mg/kg) was reported in a blue crabcomposite sample collected in 1987. Since 1970 six of 37 samples analyzed contained detectablequantities of methylmercury (1.4 to 6.6 mg/kg). The highest methylmercury concentrationreported (6.6 mg/kg) is higher than the total mercury reported for that sample (4.46 mg/kg) andmay be due to variation in the analysis methods used.
To determine whether or not contaminated fish and crabs were being sold for humanconsumption, in 1976 and 1977, TDH Division of Shellfish Sanitation sampled seafood atprocessing plants and markets in the Port Lavaca area. Twenty-nine (29) samples of crab meatwere obtained from ten processing plants; nine samples of finfish were obtained from threemarkets. All samples were analyzed for total mercury. Concentrations of total mercury in crabranged from 0.04 to 0.23 mg/kg wet weight. Mercury concentrations in the fish samples rangedfrom 0.10 mg/kg (redfish) to 0.88 mg/kg (drum) . It is not known where these fish and crabswere caught.
Fish were collected at sampling points identified by State Land Tract number. The fish werefilleted and the muscle (meat) was analyzed for mercury. Composite samples were not made. Between 1977 and 1993, 596 fish were caught and the tissue was analyzed for total mercury; 79of these fish also were analyzed for methylmercury. The average measured concentration ofmethylmercury, as a percent of total mercury, in these fish was 84%.
For the purpose of this assessment five species of finfish were selected to represent the types offinfish most likely to be caught and eaten by people fishing in the area. These species are BlackDrum, Red Drum (Redfish), Speckled Seatrout (Spotted Seatrout), Gafftop Catfish, andFlounder. TDH fish sampling data were available for most years between 1977 and 1993. Thesedata are shown in Table 4. Although mean total mercury levels vary among these species withinthe closure area, the combined mean concentration for these species have been above 1.0 mg/kgfor each year of sampling between 1977 and 1993. The highest total mercury concentration wasreported in a Black Drum caught in 1979 (11.0 mg/kg). In 1993, total mercury levels in 29 fishtaken from the closure area ranged from 0.003 to 4.62 mg/kg. The mean total mercuryconcentration of these fish was 1.398 mg/kg. By species, Red Drum and Black Drum containedthe highest mean mercury concentrations (1.943 and 1.151 mg/kg, respectively). These fishsamples adequately characterize the degree of mercury contamination in fish from the closure areaand all of them were within legal catch size.
A study conducted by Texas A&M University for Formosa Plastics in 1990 found total PCBs in acomposite oyster sample collected south of the causeway to be 1.13 mg/kg. Total PCBs in asingle fish caught south of the causeway was 0.45 mg/kg . These samples do not characterize the extent of PCB contamination in the Bay.
|Year**||# Individuals Sampled||Range of Total Mercury*** |
|Mean Total Mercury |
|1977||39||0.390 - 6.400||2.028|
|1978||107||0.050 - 6.900||2.122|
|1979||44||0.160 - 11.000||1.568|
|1981||39||0.100 - 4.900||1.151|
|1985||10||0.430 - 1.510||1.060|
|1986||10||0.100 - 3.940||1.238|
|1987||9||0.540 - 2.650||1.224|
|1988||93||0.095 - 5.600||1.072|
|1989||26||0.243 - 4.090||1.051|
|1990||32||0.174 - 6.620||1.244|
|1993||29||0.003 - 4.620||1.398|
* Includes: Black Drum, Red Drum, Speckled Trout, Gafftop Catfish, and Flounder
** Years finfish samples were taken        *** wet weight/edible portion        Mercury analyzed from fish fillet (muscle)
Extensive off-site sediment sampling has been done in the Lavaca Bay system. Backgroundmercury concentrations were determined from sediment samples collected in September 1992 atthe northernmost part of Lavaca Bay where the Lavaca River (SS-62 and SS-63) and GarcitasCreek (SS-60 and SS-61) meet the estuary. Mercury was detected at less than the contract-required detection limits (<0.12-0.18 mg/kg) in these background samples . Contamination ishighest near the spoil island and decreases with increasing distance from the island; backgroundlevels are reached at 3.5 miles from the spoil island.
Lavaca Bay sediment samples were collected by Weston, a contractor for EPA. These sampleswere taken from one to three miles from the disposal lagoon/spoil island; they had mercuryconcentrations ranging from 0.06 mg/kg (SS-41) to 0.45 mg/kg (SS-45) . In sedimentsamples SS-50 through SS-54, which were approximately 3.5 miles south of the gypsum disposallagoon on the spoil island, mercury concentrations ranged from 0.16 mg/kg (SS-54) to 0.35mg/kg (SS-53). Mercury was below detection limits in sediment samples taken from areasbeyond 3.5 miles of the gypsum disposal lagoon.
|Location||Number of Samples||Sampling Depth (cms)||Comparison Value|
|Lower Lavaca Bay bounded by the causeway, the closed area and a line drawn between Rhodes Point and Gallinipper Point||57||0.19 - 1.70||0.46||0.12-2.30||0.54||0.01-1.00||0.25||20 mg/kg**|
|Lower Lavaca Bay most distant from ALCOA from Rhodes and Gallinipper Points to Sand and Indian Points (excluding Keller Bay)||17||0.02-0.49||0.26||0.01-0.89||0.24||0.01-0.18||0.04|
|Lavaca Bay north of the Causeway||18||0.03U-0.28||0.095||0.03U-0.39||0.12||0.01J-0.19||0.07|
|Matagorda Bay southeast and east of Sand and Indian Points||30||0.03-0.37J||0.14||0.03J-0.28||0.12||0.01J-0.96||0.17|
** RMEGchild for methylmercury; the comparison value for methylmercury was selected sinceinorganic mercury is readily converted to methylmercury by bacteria. In addition the comparisonvalue for methylmercury is more conservative than the comparison value for inorganic mercury.
Between April and August of 1992 sediment samples were collected for ALCOA in areas ofLavaca Bay outside of the closure area. Table 5 contains data for 366 samples taken off site. Among these samples 122 were surface sediment samples collected at depths from 0 to 10centimeters. Samples also were collected at depths from 10 to 20 centimeters and from 20 to 50centimeters . Generally, mercury concentrations are higher in sediment between 10 and 20centimeters in depth and sediment mercury concentrations decrease as distance from ALCOAincreases.
In 1975, the mercury in sediment from Keller Bay was reported to be as high as 3.2 mg/kg. In1987, mercury in sediment from Keller Bay, composited from a core sample 1 to 8 feet deep was0.07 mg/kg ; however, compositing such a core may have "diluted" the mercury concentration,causing it to seem lower at certain depths than it may actually be.
Off-site Blue Crab and Fish Contamination
Data for Blue Crabs are summarized in Table 6. In 1993 the mean total mercury concentration inblue crabs collected outside of the closure area was 0.078 mg/kg. Highest mean mercuryconcentrations in these crabs were reported in 1970, 1971, and 1973 at 0.948, 1.23, and 1.983mg/kg, respectively. The samples were collected in areas north of the causeway and in the Bayarea along Alamo and Magnolia beaches.
|Year*||# Individuals||Range of Total Mercury|
|Mean Total Mercury|
|1970||13||0.430 - 2.000||0.948|
|1971||8||0.680 - 1.980||1.230|
|1973||3||1.050 - 3.25||1.983|
|1974||9||0.200 - 1.100||0.773|
|1975||2||0.280 - 0.450||0.365|
|1976||40||0.140 - 0.930||0.398|
|1977||17||0.160 - 1.620||0.696|
|1988||14||0.056 - 0.270||0.149|
|1989||7||0.136 - 1.030||0.435|
|1990||2||0.208 - 0.719||0.464|
|1993||5||0.047 - 0.151||0.078|
* Years blue crab samples were taken
Mercury analyzed from crab meat tissue only
Between 1977 and 1993, 103 fish in the five representative species were collected by TDH fromvarious areas of Lavaca Bay outside the fishing closure area (Table 7). Mean mercuryconcentrations for the years sampled ranged from 1.102 mg/kg in 1977 to 0.204 mg/kg in 1993;in 1993 the highest levels of mercury were reported in Red Drum (maximum, 0.482 mg/kg; mean,0.296) and Black Drum (maximum, 0.356 mg/kg; mean, 0.126 mg/kg). In 1993 mercuryconcentrations were below 0.5 mg/kg from Lavaca Bay fish from outside of the closure area.
However, in 1992, Woodward-Clyde conducted a biological study for ALCOA which includedfish sampling data southeast of ALCOA from Keller Bay . Red Drum and Flounder hadmercury levels ranging from 0.12-0.25 mg/kg and 0.08-0.25 mg/kg respectively. Five BlackDrum samples collected east of Rattlesnake Cove in Keller Bay ranged from 0.71 to 2.2 mg/kgtotal mercury with a mean total mercury concentration of 1.16 mg/kg. Fifteen Black Drumcollected south of Rattlesnake Cove in Keller Bay ranged from 0.54 to 1.5 mg/kg total mercurywith a mean total mercury of 0.85 mg/kg. All Black Drum sampled were above the TPWDmaximum allowable catch size. Fourteen Gafftop were collected south of Rattlesnake Cove inKeller Bay; the total mercury concentration ranged from 0.14 to 1.30 mg/kg with a mean totalmercury concentration of 0.48 mg/kg. One sheepshead was collected south of Rattlesnake Cove;the total mercury concentration was 1.30 mg/kg. Additional sampling in this area may bewarranted.
|Year**||# Individuals Sampled||Range of Total Mercury |
|Mean Total Mercury |
|1977||17||0.150 - 2.900||1.102|
|1978||9||0.350 - 1.300||0.733|
|1979||8||0.330 - 0.650||0.471|
|1981||2||0.410 - 0.700||0.555|
|1988||34||0.051 - 2.410||0.323|
|1993||33||0.070 - 0.482||0.204|
* Includes: Black Drum, Red Drum, Speckled Trout, Gafftop Catfish, and Flounder
** Years finfish samples were taken
Mercury analyzed from fish fillet (muscle)
Other Potential Sources of Off-Site Contamination
The Toxic Chemical Release Inventory (TRI) is an EPA database that documents contaminantsreleased by industrial facilities into the environment. It should be noted that TRI data are self-reported and only certain types of facilities are required to report. Other than ALCOA, only twofacilities in the Point Comfort area (Formosa Plastics Corporation and Texas Liquid Fertilizer)reported releases in 1991; 1991 is the most recent year for which data are available (Table 8) . The E.S. Joslin Power Station also is in the vicinity of the site but does not report to the TRI.
A Data Review Summary prepared by EPA is not yet available for this site. Woodward-Clyde hasprovided some documentation of sample quality assurance. The analysis and conclusions in thishealth assessment are valid only if the referenced information is complete and valid.
Reportedly, there are poisonous snakes on the dredge spoil island.
|Facility||Chemical||Media Released To||Quantity Released|
|Texas Liquid Fertilizer Co. Point Comfort |
FM 1593 S. Navigation District
|Ammonia||Air||3,416 lbs/rep yr|
|Phosphoric Acid||Air||6 lbs/rep yr|
|Ammonium Nitrate (solution)||Air||20 lbs/rep yr|
|Formosa Plastics Corp.|
101 Formosa Dr.
P.O. Box 400, Point Comfort 77978
|Vinyl chloride||Air |
|44,906 lbs/rep yr |
1 lb/rep yr
|Chlorine||Air||1,931 lbs/rep yr|
|36,781 lbs/rep yr |
6,988 lbs/rep yr
|Ethylene||Air||2,112 lbs/rep yr|
|1,1,2-Trichloroethane||Water||1 lb/rep yr|
|Tetrachloroethylene||Water||1 lb/rep yr|
|Dichlorodifluoromethane (CFC-12)||Air||70,000 lbs/rep yr|
|Hydrochloric acid||Air||12,651 lbs/rep yr|
|24,825 lbs/rep yr |
1,520 lbs/rep yr
|Ammonia||Air||509 lbs/rep yr|
|Copper Compounds||Water |
|333 lbs/rep yr|
2,352 lbs/rep yr
|Carbon tetrachloride||Water||1 lb/rep yr|
|Chlorobenzene||Water||6 lbs/rep yr|
|Chloroform||Water||138 lbs/rep yr|
|ALCOA Point Comfort Operations |
State Highway 35
Point Comfort 77978
|Hydrochloric acid||Air||1,005 lbs/rep yr|
|Hydrogen fluoride||Air||1,640 lbs/ rep yr|
|Sulfuric acid||Air||8,210 lbs/rep yr|
We evaluated the environmental and human components required to determine the potential forhuman exposure to contaminants at the site. This process considers five elements of an exposurepathway: a source of contamination, transport through an environmental medium, a point ofexposure, a route of human exposure, and an exposed population.
Exposure pathways are categorized as completed, potential, or eliminated. For a person to beexposed to a contaminant, the exposure pathway must be completed. An exposure pathway isconsidered to be complete when all five elements are present and exposure has occurred, isoccurring, or will occur in the future. An exposure pathway is considered to be a potentialpathway when at least one of the five elements is missing but may be completed. An exposurepathway is eliminated when one or more elements are missing and will never be present tocomplete the pathway. According to the environmental data which were available during thepreparation of this health assessment, there are two completed and four potential exposurepathways at this site. These pathways are presented in Tables 9a and 9b. Inclusion of a pathwayin the table does not necessarily imply that the pathway presents a risk to public health; anevaluation of the public health significance of each pathway will be presented in the followingsection.
Based on mercury levels detected in fish collected from within the closure area of Lavaca Baybetween 1977 and 1993, exposure to mercury has occurred among individuals who have eatenfish from this area of the Bay. Ingestion of fish may continue to be a primary route of exposure asevidenced by the people observed fishing in the closure area. However, the actual number ofpeople fishing in the closure area is unknown and may be small. Because 19 percent of the countypopulation is below the poverty level, subsistence fishing may be occurring. Additionally, since41.6 percent of women in the county are of childbearing age, a sizeable part of the total countypopulation consists of the sensitive subpopulation of concern.
Exposure to mercury has occurred in the past among people who consumed crabs caught withinthe closure area prior to its designation as "closed" in 1988. Limited sampling data suggest thatexposure also may have occurred from consuming crabs caught from various locations outside thedesignated closure area in the past. Woodward-Clyde crab mercury data collected in 1992,indicate that ingestion of crabs taken from the closure area may continue to be a route ofexposure to excessive concentrations of methylmercury. Crab traps continue to be observed inthe closure area.
|Pathway Name||Exposure Pathway Elements||Time||Estimated Number Exposed|
|Source||Environmental Media||Point of Exposure||Route of Exposure||Exposed Population|
|Fish||Past Mercury discharges from ALCOA||Fish||On-Site areas of Lavaca Bay restricted to the taking of fish/crabs||Ingestion||People eating contaminated fish||Past|
|Crabs||Past Mercury discharges from ALCOA||Crabs||On-site areas of Lavaca Bay restricted to the taking of fish/crabs||Ingestion||People eating contaminated crabs||Past|
Black Drum from Keller Bay contained mercury at levels comparable to those found in fishcollected inside the closure area. Consumption of these fish may be a potential exposure pathwaysince people may not be observing the Texas Parks and Wildlife size limits.
Anecdotal evidence and historical records suggest that workers may have been exposed tomercury in the past; however, quarterly air sampling and biological monitoring (urinalysis) dataindicate that excess exposures are not presently occurring. Although recent stack testing atALCOA indicates mercury is being released to the air, additional information is needed toconsider the significance of this potential pathway of exposure.
Former ALCOA employees have anecdotally reported finding mercury in their washing machinedrains and traps. It is possible that chlor-alkali plant workers may have inadvertently transportedmercury to their homes on their clothing. In the past, metallic mercury could have volatilized andexposed workers and family members to mercury vapor in their homes. Although it is unlikelythat exposure to mercury in these homes would continue to pose risks after 15 - 30 years, weconsider this to be a current and future potential exposure pathway.
Sediment in On-site Lagoons
Historical records show that mercury-contaminated waste was discharged into on-site bauxitelakes and on-shore lagoons. Sampling data for these impoundments were not available, butmercury may have accumulated in sediment from these lagoons. Although unlikely, it is possiblethat workers could be exposed to mercury via dermal contact or incidental ingestion if their workduties bring them into contact with the contaminated sediment.
|Pathway Name||Exposure Pathway Elements||Time||Estimated Number Exposed|
|Source||Environmental Media||Point of Exposure||Route of Exposure||Exposed Population|
|Fish||Past Mercury discharges from ALCOA||Fish||Off-site areas of Keller Bay where limited samples have shown elevated mercury||Ingestion||People eating contaminated fish||Past|
|Air||ALCOA chlor-alkali area, |
ALCOA currently operating process stacks
|Air||On Site: Chlor-alkali Unit |
Off Site: Chlor-alkali workers' homes,
Off Site: Town of Point Comfort
|Inhalation||Workers and their families, |
Town of Point Comfort
|Impoundments (On-site Lagoons)||Wastewater discharged into Impoundments (On-site Lagoons)||Sediment||On Site: ALCOA||Dermal contact, incidental ingestion||On-site workers||Past|
|Groundwater||Various site-related activities||Groundwater||Off Site: Residences using contaminated groundwater, on-site shallow groundwater||Ingestion, dermal contact||Residents using contaminated groundwater, on-site workers contacting shallow groundwater||Past|
On-site shallow groundwater is contaminated with mercury, lead, volatile organic compounds,and other contaminants. Gross alpha and beta particles and total radium have been detected inthis groundwater in the past. Workers sampling these wells could receive exposure by dermalcontact with the contaminated water if appropriate health and safety measures are not followed. If this contaminated groundwater were to get into private groundwater wells then users of thatwater would be exposed to these contaminants via the routes of ingestion and dermal contact. This pathway is not likely to be completed.
PUBLIC HEALTH IMPLICATIONS
This section discusses the possible health effects that may result from exposure to methylmercuryand other specific contaminants, evaluates state and local health data bases, and addresses specificcommunity health concerns.
Mercury is an element that occurs naturally throughout the environment; it is found in all types ofrock and can be released from rock into the atmosphere. Mercury exists in a number of chemicaland physical forms which generally can be classified as either inorganic or organic. Inorganicmercury includes liquid (metallic) mercury, mercurous mercury, and mercuric mercury. Metallicmercury has a high vapor pressure which allows it to vaporize as a monoatomic gas at roomtemperature .
Organic mercury compounds are formed when mercury combines with carbon. Methylmercury,one of the most common forms of organic mercury, can become highly concentrated in edible fishtissue. Methylmercury enters the food chain when small amounts of mercury are released tosurface water and sediment and are taken up by small organisms such as plankton. As it movesup the food chain, methylmercury bioaccumulates in fish tissue. Since methylmercury is poorlyeliminated from fish tissue and accumulates throughout the life of the fish, the highestconcentrations accumulate in large predatory fish. Some species of fish bioaccumulate mercuryby a factor of ten million.
Absorption and Distribution
Approximately 80% of inhaled mercury vapors are retained by the human body . Whenexposure occurs by ingestion, the body absorbs 90% of organic mercury and 15% of inorganicmercury. Methylmercury that is absorbed through the gastrointestinal tract distributes readily toall tissues in the body because of its ability to cross diffusion barriers and easily penetratemembranes. The high mobility of methylmercury enables tissue concentrations to remain constantrelative to blood levels. Although methylmercury is distributed throughout the body, thecompound concentrates in the liver, kidney, blood, brain, hair, and epidermis. Red blood cellscontain approximately 90% of methylmercury in blood. Both blood and hair levels are goodindicators of mercury intoxication; methylmercury is incorporated into blood and hair in equalproportions. Methylmercury concentrates in the brain more readily than inorganic mercury, butthe highest levels of methylmercury concentrate in the kidney. Methylmercury can readilytraverse the placental barrier; concentrations of methylmercury in fetal blood are generally higherthan in the maternal blood. Mercury also may be secreted in mother's milk. Organic mercury(particularly methylmercury) is excreted from the body more slowly than inorganic mercury.
Exposure to all forms of mercury has been associated with adverse health effects and all forms areconsidered poisonous . Inhaling low levels of mercury vapor (metallic mercury) has beenassociated with tremors, emotional instability, and kidney dysfunction (proteinuria and reducedfiltration). Inhaling high levels of mercury vapor has been associated with respiratory,cardiovascular, and gastrointestinal effects. Mercuric salt compounds are highly toxic and havebeen responsible for numerous fatalities, usually due to kidney failure. Ingestion ofmethylmercury has resulted in paresthesia (tingling feeling), ataxia (loss of coordination),dysarthria (inability to articulate words), deafness, motor retardation, death, and brain damage indeveloping fetuses. Infants may be as much as 10 times more sensitive to methylmercury thanadults because they excrete mercury more slowly than adults. Young children also may beparticularly sensitive to the nervous system effects of mercury; although gross methylmercuryintoxication is not often observed, subtle functional impairment of the central nervous system ismore common.
The most widely known methylmercury poisoning occurred in Minamata Bay and Niigata, Japanfrom 1953 through the early sixties. These poisonings were caused by industrial releases ofmethylmercury and other mercury compounds into the water, followed by accumulation of themercury in edible fish. The median level of total mercury in fish was estimated to be between 10and 11 mg/kg fresh weight. By 1974, a total of 1,200 cases of methylmercury poisoning wereidentified, 55 of which were fatal . People who ingested these methylmercury-contaminatedfish reported neurological symptoms including prickling or tingling sensations in the extremities;tunnel vision; hearing, taste, and smell impairment; slurred speech; unsteadiness; muscleweakness; irritability; memory loss; depression; and insomnia. Severe brain damage occurred ininfants whose mothers had eaten fish contaminated with methylmercury. The most severelyaffected children had been exposed to methylmercury during the second trimester of pregnancy.
Methylmercury poisoning also occurred in Iraq in the early 1970s; people were exposed tomethylmercury by eating bread made from wheat that had been treated with a mercury-containingfungicide. The wheat had been intended for use as seed for crops rather than for use as flour. The amount of methylmercury in the flour averaged approximately 9.1 mg/kg [45, 46]. Reportedsymptoms included paresthesia (tingling), tremors, muscle twitches, muscle weakness, paralysis,cerebellar ataxia (loss of coordination), slowed speech, blurred vision, constricted visual fields,and blindness. Deafness, blindness, incontinence, severe mental impairment, and cerebral palsy-like effects were observed in children who were exposed to mercury prenatally .
To evaluate potential non-carcinogenic health effects from exposure to methylmercury, ATSDRhas established an acute/intermediate minimal risk level (MRL) for women of child-bearing agebased on potential effects on the fetus during pregnancy. This MRL has also been used forevaluating methylmercury exposure among children. The EPA has established a chronic oralReference Dose (RfD) for adults (other than women of child-bearing age). Both the MRL andthe RfD are estimates of the daily exposure that is likely to be without appreciable risk of non-cancer adverse health effects.
The oral MRL for methylmercury of 1.2 X 10-4 milligrams of mercury per kilogram of bodyweight per day (mg/kg/day) is based on the lowest observed maternal hair level of mercuryobserved during pregnancy that was associated with delayed onset of walking in children . The oral RfD for methylmercury of 3.0 X 10-4 mg/kg/day is based on the earliest effects observedin adults (paresthesia) .
Based on estimated exposures, adverse health effects from eating fish and possibly crabs caughtfrom the closure area are possible. Children eating more than 1.4 ounces of contaminated fish permonth and pregnant women eating more than five ounces of contaminated fish per month may beat risk. Based on EPA's RfD, women beyond child-bearing age and men eating more than 16ounces of contaminated fish per month may be at risk. Assuming a normal meal size of fourounces for children and eight ounces for adults, women and children should not eat fish from theclosure area. Women past child-bearing age and men should not eat more than two meals of fishfrom the closure area per month.
The average mercury concentration in twenty Black Drum taken from Keller Bay/RattlesnakeCove was 0.927 milligrams per kilogram-wet weight. Additional data are needed to confirm thepublic health significance of eating fish from this area.
Based upon the 1992 Woodward Clyde blue crab data from the closure area, children should noteat more than 2.7 ounces of blue crabs per month, while women of child-bearing age should noteat more than 11 ounces of blue crab per month, and adult males should not eat more than 31ounces per month. Assuming a normal meal size of 4 ounces for children and eight ounces foradults, children should not eat crabs from the closure area, women should not eat more than 1 1/2meals of blue crabs per month, and adult males should not eat more than approximately one mealof blue crabs per week.
In 1978 and 1979 the Texas Department of Health attempted to obtain information on bloodmercury concentrations of area residents; however, these results have limited relevance and aredifficult to interpret since information was not provided about occupation, fish consumptionpatterns, or how participants were selected. In 1978 the Texas Department of Health obtainedand analyzed 64 blood samples from the local health department clinic, Champ Traylor MemorialHospital, and from employees at the Calhoun County Health Department. In 1979, 139 additionalblood samples were obtained from adult residents of the Lavaca Bay area. The mercury levels inall blood samples were below levels that would be expected for individuals with mercury exposure(0.02 µg mercury/g blood) .
ALCOA provided a report of employee urine mercury test results collected between 1966 and1983. During this period 6,681 samples were collected from 73 individuals who were employedin the chlor-alkali unit of the ALCOA plant . A varying number of samples were reported foreach employee. Information about length of employment and frequency of testing was notprovided. The lowest urine mercury levels were reported in a category labelled "less than 50µg/L"; this reporting level was above the mean total mercury level for the general population (4µg/L) and the maximum urine mercury concentration reported for individuals with no knownexposure to mercury (25 µg/L). The minimum detection limit of the testing method used was notprovided. Approximately 75% of sample results reported were at or above 50 µg/L. Approximately 8 % of samples were above 300 µg/L. ALCOA removed employees from thechlor-alkali unit if their urine mercury concentrations exceeded 300 µg mercury/L urine.
ALCOA also provided 1993 urine mercury test results as recorded in its quarterly mercurysurveillance [30, 31, 32]. The 29 sample results reported for June ranged from 8 to 25 µg/L with amean mercury concentration of 15.3 µg/L. None of the reported urine mercury values exceeded25 µg/L, the maximum concentration reported among individuals with no known exposure tomercury .
We have addressed each of the community concerns about health as follows:
1. Is the number of children with mental retardation in the area higher than would beexpected?
Unknown. We obtained records on the total number of individuals receiving mental health/mentalretardation services in the state and in Calhoun County through the Texas Department of MentalHealth and Mental Retardation (MHMR); however, we were unable to determine the totalnumber of children in the area who have been diagnosed with mental retardation.
2. Is the number of miscarriages in the area higher than in other areas?
Data are not available for miscarriages (0 to 20 weeks). We do have information on late fetalloss, also known as stillbirths; these occur after 20 or more weeks of gestation and are reported. From 1982 to 1992 the number of fetal deaths in Calhoun County is not higher than in the state ofTexas as a whole.
3. Are the Port Lavaca beaches, Lighthouse Beach and Magnolia Beach, safe to take ourchildren to for water-based recreation?
Yes. The levels of mercury in Bay sediment samples taken closest to these beaches are low. Exposure to these sediments during normal recreational use should not pose a health threat.
4. Could the reported worker health problems be due to exposure to site contaminants?
Reported problems include: nervousness, neurolepsy, hand tremor, ringing in the ears, shortnessof breath, pneumonia, kidney problems, stomach problems, and joint problems. Inhalation ofmetallic mercury vapor has been associated with systemic toxicity in both humans and animals. Atlow levels of exposure, the major target organs of metallic mercury induced toxicity are thekidney and central nervous system. At high exposure levels, respiratory, cardiovascular, andgastrointestinal effects have also been observed.
5. How was the restricted fishing area defined?
The restricted area (the area restricted to the taking of fish and crabs) was defined by looking atwhere in the Bay fish which were high in mercury were caught, then determining easilyrecognizable "landmarks" in the Bay which could be used by fishermen to recognize and avoid thisarea.
6. Is it okay to eat fish caught just outside the restricted area?
There are some areas outside of the closure area where mercury-contaminated fish have beenfound. In general, the average concentration of mercury in fish caught outside the closure areahas been much lower than in fish caught within the closure area.
7. Why would contamination in fish be limited to that area?
Contamination may not strictly be limited to the closure area. Fish exposed to mercury in theclosure area may migrate to other areas and be caught along with fish that are not contaminatedwith excessive concentrations of mercury. Thus, although it may be possible to find some fishoutside the closure area with high levels of mercury, on the average, the levels of mercury in fishcaught outside the closure area are low. Therefore, eating fish caught outside the closure areashould not pose a significant health threat.
Five Black Drum (fish) taken from Keller Bay had concentrations of mercury comparable to thelevels measured in fish caught inside the Lavaca Bay closure area. Although the fish with elevatedmercury concentrations were above the legal size limit, it is still possible that an individual mightkeep an oversize fish and thereby be exposed to excessive mercury concentrations. Fish fromKeller Bay should be sampled and analyzed for mercury.
8. Maps on closure signs are too hard to read. Can you describe the closure area moreclearly?
We have included a simplified map detailing the closure area. See Figure 4.