ADDENDUM TO PUBLIC HEALTH ASSESSMENT
UNITED CREOSOTING COMPANY
CONROE, MONTGOMERY COUNTY, TEXAS
The tables in this section contain a list of the contaminants ofconcern. We evaluate these contaminants in subsequent sectionsof this health assessment addendum, and we determine whether ornot exposure to them has public health significance. ATSDRselects contaminants based upon the following factors:
- Concentrations of contaminants on and off site.
- Field data quality, laboratory data quality, and sample design.
- Comparison of on-site and off-site concentrations with background concentrations, if available.
- Comparison of site-related concentrations with ATSDR Health Assessment Comparison (HAC) values for (1) noncarcinogenic endpoints and (2) carcinogenic endpoints.
- Community health concerns
In the data tables that follow the title "On-site Contamination,"the fact that a contaminant is listed does not mean that exposurewill cause adverse health effects. Instead, the list indicateswhich contaminants will be evaluated further in the healthassessment addendum. When selected as a contaminant of concernin one medium, that contaminant will be reported in all media.The data tables include the following acronyms:
|= Environmental Media Evaluation Guide|
|= Environmental Protection Agency Action Level|
|= Health Assessment Comparison Value|
|= Maximum Contaminant Level Goal|
|= Minimal Risk Level|
|= Not Detected|
|= Proposed Maximum Contaminant Level Goal|
|= Reference Dose|
ATSDR Health Assessment Comparison (HAC) values are contaminantconcentrations for specific media. They are used to selectcontaminants for further evaluation. Those values includeEnvironmental Media Evaluation Guides (EMEGs), and other relevantguidelines. In this health assessment addendum, EPA-AL are EPAhealth-based action levels for mixtures of carcinogenicpolycyclic aromatic hydrocarbons (PAHs) and carcinogenic dioxinand furan mixtures. The carcinogenic PAHs have been convertedinto benzo(a)pyrene equivalents and summed as total benzopyreneequivalents. The carcinogenic dioxins and furans have beenconverted to 2,3,7,8-tetrachlorodibenzodioxin (TCDD) equivalentsand summed as total TCDD equivalents. EPA's Maximum ContaminantLevel Goal (MCLG) is a drinking water health goal. EPA believesthat the MCLG represents a level at which no known or anticipatedadverse effect on the health of persons should occur, and whichallows an adequate margin of safety. Proposed MaximumContaminant Level Goals (PMCLGs) are MCLGs that are beingproposed. The MRL is an estimate of daily human exposure to acontaminant below which adverse, non-cancerous health effects areunlikely to occur. EPA's Reference Dose (RfD) is an estimate ofthe daily exposure to a contaminant that is unlikely to causeadverse health effects.
We conducted a search of the Toxic Chemical Release Inventory (TRI) for the site and for the zip code area of the site. Reported releases included 20 different compounds from a total ofthree facilities, none of which are on site. None of the reported chemical releases are the same compounds as the contaminants of concern identified at the United Creosoting Company site.
The environmental media sampling events discussed in this healthassessment addendum were conducted in two phases. Sampling forthe remedial investigation took place between December 1984 andAugust 1985. Those environmental data were evaluated in thehealth assessment, but will be reviewed in more detail in thisaddendum. In 1990, field sampling was conducted for thesupplemental site investigation. During initial samplingactivities, soil, surface water, ground water, biota, and airsamples were collected. The supplemental field sampling wasdesigned to fill in existing data gaps and to facilitateremediation.
The on-site area includes the Tanglewood East subdivision, SiscoConstruction, Clarke Distributing Company, and a vacant area atthe southeastern corner of the original site. Contaminants ofconcern identified during sampling activities were polycyclicaromatic hydrocarbons (PAHs), chlorinated dibenzodioxins/dibenzofurans (CDD/CDFs), and pentachlorophenol. The most toxicchlorinated dioxin, 2,3,7,8-tetrachlorodibenzo-dioxin, was notfound at the site.
Surface soil samples (0 to 6 inches) were taken at 83 locations in the 1984-1985 sampling effort, and at 59 sampling locations in the 1990 sampling event. The highest concentrations of surface soil contamination were found along the Tanglewood East - Clarke Distributing property line. That area corresponds to the United Creosoting Company's former processing areas. High concentrations of surface soil contamination were also characterized by the presence of "tar mats" (accumulations of asphaltic wastes), and stained soils. Elevated levels of PAHs to 2800 mg/kg and pentachlorophenol to 150 mg/kg, were detected in residential surface soils in 1984-1985 (see Table 1). Those areas are near the former waste ponds and along the fence linebetween the vacant area and the Tanglewood East subdivision. Surface soil in a vacant lot in the Griffith Street cul-de-saccontained the highest level of total PAHs with 15,750 mg/kg. Less surface-soil contamination was detected in the industrialareas than in the residential areas in the 1984-1985 sampling(Table 2).
In 1990 sampling, total carcinogenic PAHs and total carcinogenicCDD/CDFs were calculated for each soil sample taken. The resultsof each carcinogenic PAH found was converted into benzo(a)pyreneequivalents and summed to obtain total benzopyrene equivalents. The carcinogenic CDD/CDFs were converted into2,3,7,8-tetrachlorodibenzodioxin (TCDD) equivalents.
|Pentachlorophenol (PCP)||ND - 150||ND - 65||100||EMEG|
|POLYCYCLIC AROMATICS (PAHS)|
|ND||ND - 460||NONE||NONE|
|Acenaphthene||ND - 2600||ND - 220||3,000||RfD|
|Anthracene||ND - 970||ND - 160||15,000||RfD|
|Dibenzofuran||ND||ND - 210||NONE||NONE|
|Fluoranthene||ND - 700||ND - 190||2,000||RfD|
|Fluorene||ND - 84||ND - 260||2,000||RfD|
|Naphthalene||ND||ND - 620||200||RfD|
|Phenanthrene||ND - 970||ND - 1800||5,000||RfD|
|Pyrene||ND - 2800||ND - 340||1,500||RfD|
|ND - 1700||ND - 34||5,000||MRL|
|Benzo(a)anthracene||ND - 2000||ND - 50||5,000||MRL|
|Benzo(a)pyrene||ND - 650||ND - 32||5,000||MRL|
|Benzo(g,h,i)perylene||ND - 84||ND - 0.56||5,000||MRL|
|Benzo(k)fluoranthene||ND - 1700||ND - 140||5,000||MRL|
|Chrysene||ND - 2000||ND - 50||5,000||MRL|
|ND - 0.00036||ND - 0.00042||0.00005||MRL|
|Pentachlorodibenzodioxin||ND - 0.0073||ND - 0.0016||NONE||NONE|
|Hexachlorodibenzodioxin||ND - 0.0076||ND - 0.27||NONE||NONE|
|Heptachlorodibenzodioxin||ND - 0.720||0.0022 - 0.520||NONE||NONE|
|Octachlorodibenzodioxin||0.0049 - 6.0||0.0077 - 1.050||NONE||NONE|
|ND - 0.140||ND - 0.021||NONE||NONE|
|Heptachlorodibenzofuran||ND - 0.890||ND - 0.790||NONE||NONE|
|Octachlorodibenzofuran||ND - 1.50||ND - 0.500||NONE||NONE|
|Pentachlorophenol (PCP)||ND - 26||ND - 1100||100||EMEG|
|POLYCYCLIC AROMATICS (PAHS)|
|ND - 260||ND - 940||NONE||NONE|
|Acenaphthene||ND - 210||ND - 860||3,000||RfD|
|Anthracene||ND - 6.3||ND - 280||15,000||RfD|
|Dibenzofuran||ND - 250||ND - 930||NONE||NONE|
|Fluoranthene||ND - 220||ND - 980||2,000||RfD|
|Fluorene||ND - 280||ND - 1100||2,000||RfD|
|Naphthalene||ND - 130||ND - 1200||200||RfD|
|Phenanthrene||ND - 1500||ND - 7400||5,000||RfD|
|Pyrene||ND - 370||ND - 1600||1,500||RfD|
|ND - 24||ND - 7.7||5,000||MRL|
|Benzo(a)anthracene||ND - 36||ND - 180||5,000||MRL|
|Benzo(a)pyrene||ND - 38||ND - 5||5,000||MRL|
|Benzo(g,h,i)perylene||ND - 12||ND - 5.3||5,000||MRL|
|Benzo(k)fluoranthene||ND - 24||ND - 24||5,000||MRL|
|Chrysene||ND - 6.3||ND - 130||5,000||MRL|
|ND||ND - 0.00531||0.00005||MRL|
|Pentachlorodibenzodioxin||ND - 0.00125||ND - 0.021||NONE||NONE|
|Hexachlorodibenzodioxin||0.0013 - 0.030||ND - 0.007||NONE||NONE|
|Heptachlorodibenzodioxin||0.033 - 0.350||ND - 0.410||NONE||NONE|
|Octachlorodibenzodioxin||0.0077 - 0.63||ND - 0.240||NONE||NONE|
|ND - 0.047||ND - 0.018||NONE||NONE|
|Heptachlorodibenzofuran||0.0057 - 0.150||ND - 0.037||NONE||NONE|
|Octachlorodibenzofuran||0.0053 - 0.180||ND - 0.012||NONE||NONE|
Elevated levels of total carcinogenic PAHs were found in the residential areas on site that ranged up to 84 mg/kg (benzo(a)pyrene equivalents) (See Table 3). Fourteen residential surface samples exceeded the EPA residential health action levels for carcinogenic PAHs. These elevated samples were scattered, although the highest number of samples were taken between Arlington and Brewster Streets and between Columbia and Darnell Streets. Nine of the elevated samples weretaken near the fence line separating the residential and industrial areas.
Elevated levels of total carcinogenic CDD/CDFs were found in residential areas on site that ranged up to 0.016 mg/kg (TCDD equivalents). Several residential surface samples exceeded theEPA residential health action level for carcinogenic CDD/CDFs. Five of those samples were taken around residences near the fenceline separating the residential and industrial areas. The othertwo soil samples were taken between Columbia and Darnell Streets. In the industrial areas, no surface soil samples exceeded the EPAaction levels for CDD/CDFs or for carcinogenic PAHs (Table 4). Pentachlorophenol was detected up to 510 mg/kg in the industrialareas.
As part of the 1984-1985 sampling activities, vacuum cleaner bags, air conditioner filters, and wipe samples were collected from five homes. In addition, wipe samples were collected at ten locations from structures at Sisco Construction and Clarke Distributing. Semivolatile organics were not detected in any wipe samples or vacuum cleaner bags taken from residences. Air conditioner filters were tested for CDD/CDFs. CDD/CDFs were detected in samples taken from three homes, but at levels near detection limits. Industrial wipe samples were negative for semi-volatile organics with the exception of one sample. That sample contained CDD/CDF and pyrene. Visual inspection indicated that the sample was from creosoted lumber remaining from the United Creosoting Company.
Subsurface soil samples were collected from depths of one foot to 25 feet. Data collected during the remedial investigation indicate the presence of contamination in two main locations. One elevated contaminant concentration is underneath the formersite of the tank pond and coal tar distillation unit. The arealies at the southern boundary of the Sisco Construction property,with a portion lying on Clarke Distributing property. The secondarea of elevated contaminant levels is mainly within thenorthwestern corner of Clarke Distributing property, in theformer location of the waste ponds. In both locations in
|Pentachlorophenol (PCP)||ND - 37||ND - 93||100||EMEG|
|POLYCYCLIC AROMATICS (PAHS)|
|ND||ND - 7.3||NONE||NONE|
|Acenaphthene||ND - 0.67||ND - 34||3,000||RfD|
|Anthracene||ND - 710||ND - 41||15,000||RfD|
|Dibenzofuran||ND - 21||ND - 15||NONE||NONE|
|Fluoranthene||ND - 110||ND - 260||2,000||RfD|
|Fluorene||ND - 73||ND - 35||2,000||RfD|
|Naphthalene||ND - 0.076||ND - 12||200||RfD|
|Phenanthrene||ND - 160||ND - 86||5,000||RfD|
|Pyrene||ND - 160||ND - 160||1,500||RfD|
|CARCINOGENIC PAHS (total)||ND - 84.02||ND - 25.42||0.333||EPA-AL|
|3,4-Benzo(b)fluoranthene||ND - 11||ND - 41||5,000||MRL|
|Benzo(a)anthracene||ND - 35||ND - 73||5,000||MRL|
|Benzo(a)pyrene||ND - 72||ND - 29||5,000||MRL|
|Benzo(g,h,i)perylene||ND - 38||ND - 10||5,000||MRL|
|Benzo(k)fluoranthene||ND - 130||ND - 0.72||5,000||MRL|
|Chrysene||ND - 97||ND - 34||5,000||MRL|
|Dibenzo(a,h)anthracene||ND - 12||ND - 5.5||5,000||MRL|
|Ideno(1,2,3-cd)pyrene||ND - 36||ND - 11||5,000||MRL|
|TOTAL DIOXINS/FURANS||0.0000017 - 0.0164||ND - 0.00234||0.0013||EPA-AL|
|Pentachlorodibenzodioxin||ND - 0.004||ND||NONE||NONE|
|Hexachlorodibenzodioxin||ND - 0.203||ND - 0.025||NONE||NONE|
|Heptachlorodibenzodioxin||ND - 1||ND - 0.247||NONE||NONE|
|Octachlorodibenzodioxin||ND - 2.8||ND - 1.79||NONE||NONE|
|ND||ND - 0.037||NONE||NONE|
|Pentachlorodibenzofuran||ND - 0.003||ND - 0.16||NONE||NONE|
|Hexachlorodibenzofuran||ND - 0.053||ND - 0.087||NONE||NONE|
|Heptachlorodibenzofuran||ND - 0.137||ND - 0.211||NONE||NONE|
|Octachlorodibenzofuran||ND - 0.420||ND - 0.499||NONE||NONE|
1 From Weston, 1990 as reported in the Site Investigation, 1990.
2 Expressed as Benzo(a)pyrene Equivalents
3 Screening level applies to residential surface soil
4 Dioxins and furans are expressed as 2,3,7,8 - TCDD Equivalents
|Pentachlorophenol (PCP)||ND - 510||ND - 96||100||EMEG|
|POLYCYCLIC AROMATICS (PAHS)|
|ND||ND - 32||NONE||NONE|
|Acenaphthene||ND - 99||ND - 220||3,000||RfD|
|Anthracene||ND - 92||ND - 100||15,000||RfD|
|Dibenzofuran||ND||ND - 190||NONE||NONE|
|Fluoranthene||ND - 710||ND - 220||2,000||RfD|
|Fluorene||ND - 71||ND - 190||2,000||RfD|
|Naphthalene||ND||ND - 67||200||RfD|
|Phenanthrene||ND - 820||ND - 480||5,000||RfD|
|Pyrene||ND - 610||ND - 620||1,500||RfD|
|CARCINOGENIC PAHS (total)||ND - 2.182||ND - 0.2172||403||EPA-AL|
|Benzo(a)anthracene||ND - 150||ND - 34||5,000||MRL|
|Benzo(a)pyrene||ND - 38||ND - 13||5,000||MRL|
|Benzo(b)fluoranthene||ND - 100||ND - 18||5,000||MRL|
|Benzo(g,h,i)perylene||ND - 0.800||ND - 4.4||5,000||MRL|
|Benzo(k)fluoranthene||ND||ND - 13||5,000||MRL|
|Chrysene||ND - 140||ND - 35||5,000||MRL|
|Dibenzo(a,h)anthracene||ND||ND - 0.570||5,000||MRL|
|Ideno(1,2,3-cd)pyrene||ND - 0.530||ND - 5.6||5,000||MRL|
|TOTAL DIOXINS/FURANS||0.0000049 - 0.007034||ND - 0.001184||0.023||EPA-AL|
|Hexachlorodibenzodioxin||ND - 0.041||ND - 0.003||NONE||NONE|
|Heptachlorodibenzodioxin||ND - 0.437||ND - 0.072||NONE||NONE|
|Octachlorodibenzodioxin||0.005 - 1.32||ND - 0.383||NONE||NONE|
|Pentachlorodibenzofuran||ND - 0.002||ND||NONE||NONE|
|Hexachlorodibenzofuran||ND - 0.037||ND - 0.005||NONE||NONE|
|Heptachlorodibenzofuran||ND - 0.168||ND - 0.046||NONE||NONE|
|Octachlorodibenzofuran||ND - 0.500||ND - 0.066||NONE||NONE|
2 Expressed as Benzo(a)pyrene Equivalents
3 Screening level applies to industrial surface soil
4 Dioxins and furans are expressed as 2,3,7,8 - TCDD Equivalents
1984-1985, elevated levels of pentachlorophenol (up to 1100mg/kg), naphthalene (up to 1200 mg/kg), and pyrene (up to 1600mg/kg) were identified. Tables 1 through 4 show the ranges ofcontaminants found in on-site subsurface soil in residential andindustrial areas.
Sediment samples were collected from five locations during 1984-1985 sampling. One of the five locations was less than 200 feet off site and downstream. At each sample location, threeseparate samples were taken: one stream bed composite, one bankcomposite, and one over-bank composite. Table 5 shows theranges of contaminants found in on-site sediment samples. Samples from three locations in the now vacant industrial areacontained several contaminants of concern includingpentachlorophenol, PAHs, and CDD/CDFs.
Samples taken from Alligator Creek did not show evidence ofcontamination.
Ground water sampling was conducted during the 1984-1985 sampling event. The map in Appendix D shows the locations of the monitoring wells. The ground water sampling conducted at that time used fourteen existing shallow monitoring wells todetermine ground water flow direction and the extent of thecontamination into the shallow water-bearing zones. The shallowwater-bearing zones include the unconfined (20-40 feet) andsemi-confined (40-60 feet) zones. Also, 15 new monitoring wellswere installed in the shallow zones. Table 6 shows the levels ofcontamination found in the shallow water-bearing zones.
Well data collected from the shallow unconfined zone showed semi-volatile organic contamination near the former waste ponds,with migration to a point 800 feet southwest of the pond. Thehighest levels of PAHs were found in a monitoring well on thesoutheastern end of Brewster Street near the fence lineseparating the residential and industrial areas. Thesemi-confined zone lies directly beneath the shallow unconfinedwater-bearing zone. Data from a monitoring well that is on thenorth side of Clarke Distributing near a former waste pond, andwhich is within the shallow semi-confined zone, showedcontamination with semi-volatile organics, including naphthalene
|CHEMICAL NAME||SEDIMENT SAMPLES|
(0-0.5 feet) mg/kg
|Pentachlorophenol (PCP)||ND - 38||100||EMEG|
|POLYCYCLIC AROMATICS (PAHS)|
|Anthracene||ND - 75||15,000||RfD|
|Fluoranthene||ND - 150||2,000||RfD|
|Phenanthrene||ND - 11||5,000||RfD|
|Pyrene||ND - 120||1,500||RfD|
|ND - 150||5,000||MRL|
|Benzo(a)anthracene||ND - 77||5,000||MRL|
|Benzo(a)pyrene||ND - 68||5,000||MRL|
|Benzo(g,h,i)perylene||ND - 38||5,000||MRL|
|Benzo(k)fluoranthene||ND - 150||5,000||MRL|
|Chrysene||ND - 75||5,000||MRL|
|Pentachlorodibenzodioxin||ND - 0.00040||NONE||NONE|
|Hexachlorodibenzodioxin||ND - 0.015||NONE||NONE|
|Heptachlorodibenzodioxin||ND - 0.240||NONE||NONE|
|Octachlorodibenzodioxin||ND - 0.400||NONE||NONE|
|ND - 0.010||NONE||NONE|
|Heptachlorodibenzofuran||ND - 0.037||NONE||NONE|
|Octachlorodibenzofuran||ND - 0.027||NONE||NONE|
|CHEMICAL NAME||GROUND WATER|
|Pentachlorophenol (PCP)||ND - 220||20||EMEG|
|POLYCYCLIC AROMATICS (PAHS)|
|ND - 750,000||NONE||NONE|
|Acenaphthene||ND - 490,000||600||RfD|
|Anthracene||ND - 140,000||3,000||RfD|
|Dibenzofuran||ND - 410,000||ONE||NONE|
|Fluoranthene||ND - 280,000||400||RfD|
|Fluorene||ND - 410,000||400||RfD|
|Naphthalene||ND - 1,200,000||40||RfD|
|Phenanthrene||ND - 830,000||1,000||MRL|
|Pyrene||ND - 450,000||300||RfD|
|Pentachlorodibenzodioxin||ND - 0.0018||NONE||NONE|
|Hexachlorodibenzodioxin||ND - 0.0029||NONE||NONE|
|Heptachlorodibenzodioxin||ND - 0.066||NONE||NONE|
|Octachlorodibenzodioxin||ND - 0.48||NONE||NONE|
up to 2,000 µ/L, and pentachlorophenol up to 180 µ/L. Westonestimated that the plume of ground water contamination extendsupto 1,400 feet to the south of the former waste ponds in theshallow semi-confined zone. Five monitor wells were installed inthe lower water-bearing zone (60-80 feet). No semivolatilecontaminants were found in this water zone. There are reportedto be at least 60 wells used for domestic and public drinkingwater, and for industrial purposes within two miles downgradientfrom the site. All were screened at a minimum of 66 feet, withmost being screened at 100 feet or more.
Storm water run-off samples were collected on December 4, 1984,and stream flow samples were collected on December 10, 1984. Nosemi-volatile organic contaminants were detected in the siterun-off samples. Pentachlorophenol was detected (14 µ/L) at one surface-water sampling location. That sample was taken from a pool of water standing in a ditch containing contaminated soilsin the now vacant Clarke area.
Air monitoring was conducted in two steps. On October 1, 1984, before any site activities, baseline levels were determined witha portable organic vapor analyzer (OVA). Volatile organics werenot detected in any part of the site, including areas of apparentcontamination. Ambient air monitoring was also conducted upwindand downwind of the site on two separate occasions. Samplingconducted on December 2, 1984 provided a baseline before soildisruption. On December 12, 1984, air sampling was conductedwhile boring into the former waste ponds. During both samplingevents, samples were collected at three locations, one upgradientand two downgradient. Air monitoring was also conducted inassociation with field drilling activities to determine possiblecontaminant releases during subsurface soil disturbances. Allsamples were analyzed for volatile organic peaks with the OVA. None of the samples produced peaks significantly above ambientlevels; therefore, no air monitoring samples were analyzed in alaboratory.
A vegetation survey and tree core analyses were completed in conjunction with 1984 site investigation sampling activities. Tree cores were taken from eleven loblolly pines on site and tenloblolly pines off site. On-site vegetation showed signs ofstress in areas directly south of the Clarke Distributingcomplex. Tree core data indicated that on-site trees wereconsiderably shorter than corresponding off-site trees of thesame species and age. In both samples, the estimated ages of thetrees were taken into account when comparing heights.
Sampling of crawfish took place at three locations, one of whichwas upstream from the site. Attempts to sample minnows wereunsuccessful. Semi-volatile organic analyses showed resultsbelow detection limits in all crawfish samples, but the detectionlimits were high (11-22 mg/kg). According to Weston, the highdetection limits probably resulted from the presence of othernaturally occurring organics within crawfish tissue.
A very limited number of off-site samples were taken: two soil samples, one sediment sample, one surface-water sample, ground- water samples at two upgradient locations, and four ambient air samples for volatile organic compounds (VOCs). No contaminationwas detected in those samples. Contamination was visible on siteand significantly decreased away from the process area. Thecontaminated portion of the site itself comprises about 20 to 30acres of land used intensively for wood treatment processing andstorage. The remainder of the original 100-acre tract wasdensely wooded and undisturbed until the development of theTanglewood East subdivision.
In 1984-1985, all analyses for semi-volatile organics and the CDD/CDFs were carried out in accordance with the project QualityAssurance/Quality Control (QA/QC) Plan, according to the FinalSite Investigation Report. The analytical laboratories ran such internal QA/QC checks as daily calibrations and spike recovery. Spikes are known amounts of specific chemical constituents addedby the laboratory to selected samples to test the appropriatenessand to recover efficiencies of specific analytical methods. External QA/QC checks were made by the field team through thesubmittal to the laboratory of known sample entities, such asduplicates and blanks, without informing the laboratory of thenature of the sample. Duplicates are identical splits ofindividual samples that are analyzed by the laboratory to testfor method reproducibility. A sample management system wasimplemented to track all samples at all times and to assure that recommended sample holding times were not exceeded.
In 1990 sampling, an overall comprehensiveness goal of 90% was established for the project. The overall comprehensivenessincluded the following:
- completeness for soil samples for CDD/CDFs and base/neutral/acid extractable organics (semi-volatile organics at this site), and
- the number of samples meeting hold times, precision goals, and accuracy goals.
The overall project comprehensiveness was about 88.5%, mainlybecause hold times were exceeded for approximately 17% of the samples analyzed for CDD/CDFs. According to the Data EvaluationReport of the Focused Site Investigation, the results for thosechemicals were used with reservation. The report indicated thatsince CDD/CDFs tend to degrade very slowly over time, theconcentrations of those chemicals will not change significantlyover time.
During the January 21, 1991, site visit, teen-age boys were observed climbing the privacy fence into the area from which thesix homes had been removed. Despite the presence of signs,locks, and a eight-foot privacy fence, trespassers are an ongoingproblem. In addition to the possible exposure risks, trespassers may injure themselves while trying to climb the fence. Other than the possible hazards outlined here, the United Creosoting Company site appeared to be an unusually cleanand orderly site.
To determine if residents are exposed to contaminants on thesite, ATSDR evaluates the environmental and human components thatlead to human exposure. A pathway consists of five elements: asource of contamination; transport through an environmentalmedium; a point of exposure; a route of human exposure, and anexposed population.
ATSDR identifies exposure pathways as completed, potential, or eliminated. Completed pathways require that the five elements exist, indicating that exposure to a contaminant has occurred, is occurring, or will occur. Potential pathways, however,require that at least one of the five elements be missing, butcould come into being. Potential pathways indicate that exposureto a contaminant could have occurred already, could be occurringnow, or could occur in the future. Eliminated pathways requirethat at least one of the five elements be missing and that itwill never be present. Completed and potential pathways may alsobe classified as eliminated when they are unlikely to exist.
Data collected during environmental sampling identified levels of contamination in surface soil, subsurface soil, sediments, andshallow ground water. The main contaminants of concern are PAHs,pentachlorophenol, and CDD/CDFs. The United Creosoting Companysite is on the western Gulf Coastal Plain, where soils weredeposited in stream bed and deltaic formations during thePleistocene era. The surface soils are in the Conroe andSplendora series and are underlain by the Willis sand formation. Those soils vary from gravelly sand to silty clays.
With the great variation in soil particle size, from coarse gravels to fine silt and clays, the potential for filtration, and adsorption and absorption of the contaminants onto the soil isextremely high. That has possibly minimized contaminantmigration and may be responsible for the high levels ofcontamination in the 0 - 1.5 foot levels indicated by the soilsampling data.
Pentachlorophenol, PAH, and CDD/CDF contamination was found in surface and subsurface soils in on-site residential and industrial areas. That pathway will be discussed further in theHuman Exposure Pathways section.
At this site, shallow ground water exists in two inter-connected zones of unconfined to semi-confined water-bearing sands. Below that, a clay layer functions as an aquitard. That aquitard limits communication between the two shallow water- bearing zones and any deeper aquifers. It also appears to act as a barrier for contaminant migration. The shallow water- bearing zones are not currently used as a water source, and due to their low productivity it is unlikely that they will be tapped in the future. Therefore, that potential exposure pathwaycan be eliminated because it is unlikely ever to exist.
The major aquifers below this site, in order of depth, are the Chicot, the Evangeline, and the Jasper. The Chicot and theEvangeline are heavily used as drinking water sources. Waterquality in the Jasper is variable and only the upper portion isused as a source of drinking water. The semi-confined nature ofthe shallow water-bearing zone has made it possible to clearlydefine the extent of contamination through well logging, samplingand ground resonancing.
Pentachlorophenol is soluble in water and is present throughout the shallow water-bearing zone at levels as high as 220 µg/L. PAHs were detected up to 1,200,000 µg/L. PAHs have a high affinity for adsorption to soil particles. That is reflected bythe significant decrease in concentrations of PAHs as the soilsampling depth increases. With ground water, the clay layer 30to 40 feet below the site surface appears to have formed abarrier to the vertical migration of contaminants into the lowerwater-bearing zones. Due to soil adsorption characteristics,dilution of PAHs, and the low water solubility of creosote,contamination of the shallow water-bearing zones decreases as thedistance from the waste ponds increases. Sampling indicates thatthe contaminant plume has migrated in a southwesterly directionapproximately 800 feet in the unconfined zone, and approximately1,400 feet in the semi-confined zone, but has not surfaced at anyknown location. The nearest municipal well is located one milewest-northwest of the site and is screened at 825-1190 feet. Therefore, it should not be impacted by this plume.
Vertical migration velocities were calculated to assess the potential for the downward flow of ground water through the confining clay layer. The number of years required for groundwater to completely penetrate the clay was estimated at about 100years. As a result of this analysis, there appears to be a lowpotential for downward vertical migration of contaminants fromthe shallow water-bearing zone to the lower water-bearing zone. Based on the topographic data, measured water table elevations,and slope of the shallow water bearing zone, it is unlikely thatthe shallow zone ground waters discharge into Alligator Creek.
Surface water drains to the southwest at the United Creosotinglocation. Surface water flows through the Tanglewood East subdivision and into Alligator Creek. Alligator Creek flows intothe west fork of the San Jacinto River. No evidence ofcontaminant migration was present in surface water samplingconducted in the area of Alligator Creek. Therefore, thatpathway can be eliminated.
Sediment samples from Alligator Creek showed no evidence of contaminant migration. Three sediment samples taken at the Clarke vacant area did show evidence of pentachlorophenol and PAH contamination. Those samples were taken from areas of visible contamination and where there was visible evidence oferosion. Further characterization of area sediments is necessary to determine the nature of contaminant migration by this route. According to EPA Region 6, they plan to takeadditional samples from the creek.
In 1990, an air pathway analysis was conducted to estimate theair quality impact of the remediation activities. The air pathway analysis uses a combination of modeling and/or monitoring methods to assess actual or potential contaminant exposure. Levels of concern were determined for each compound(for which an ambient concentration was estimated). These levelstook in account sensitive populations and length of exposures. The resultant predicted maximum 24-hour and annual concentrationexposures were at levels below concern for contaminants found atthe United Creosoting Company site.
Bioaccumulation is a possible means of contaminant transport andaccumulation, but probably not a significant environmentalpathway at this site. PAHs are fat-soluble and can concentratein fish and mammals, and to a limited extent in vegetation,especially aquatic vegetation. Data from crawfish sampling didnot indicate the presence of contaminants. All results werebelow the 11 - 22 mg/kg detection levels, and similar levels werefound for upstream and downstream samples. However, thedetection limits for those samples were very high. Bioaccumulation is most significant for aquatic organisms and toa lesser extent for terrestrial plants and animals. No samplingwas done to determine contaminant concentration and possiblebioaccumulation in area plants.
PAHs can accumulate in terrestrial plants through the roots or foliage. Uptake rates depend on the concentrations, solubility,and molecular weights of the PAHs and the plant species. Ratiosof PAH concentrations in vegetation to those in soil can rangefrom 0.001 to 0.18 for total PAHs and from 0.002 to 0.33 forbenzo(a)pyrene (Toxicological Profile for Polycyclic AromaticHydrocarbons).
Very little information is available on plant uptake of pentachlorophenol, but one study indicated that lettuce grown onsoil treated with pentachlorophenol contained residues of thatchemical. No information could be found on plant uptake of theCDD/CDFs found on site, but limited data on 2,3,7,8-TCDD, asimilar compound, indicate that this chemical does not bioaccumulate in crop plants. In one report, the edible portions of root vegetables contained much less 2,3,7,8-TCDD than the surrounding soils (Toxicological Profile for2,3,7,8-Tetrachlorodibenzo-p-dioxin).
Several human exposure pathways are possible due to the presenceof contaminated media at and around the United Creosoting Companysite. The potential exists for exposures to result from contactwith contaminated surface soil, subsurface soil, and sediments. Human exposure resulting from dermal contact with contaminatedsoils and sediments is a pathway of concern. An additionalpotential exposure pathway is the ingestion of contaminated soilor plants. Ingestion of contaminated plants might have occurredin the past, but no sampling of vegetation was done in 1984-1985or in 1990 to indicate whether or not contamination was present. Potentially exposed populations include remediation workers, arearesidents, and trespassers in restricted site locations.
The current public water supply does not draw from wells screened in the shallow water-bearing zone. Future human exposure pathways would be of concern if water from this zone were used for drinking. This is unlikely because the low yieldof this aquifer makes it unsuitable for use, and water in thearea is supplied by the city water system.
Primary exposure pathways from soil contamination include ingestion and dermal contact with contaminated soil. Surface soil contamination in areas of Tanglewood East subdivisionprovides a complete exposure pathway for area residents. Tracking contaminated soil into homes and into areas adjacent tothe site may also occur. Populations at risk of exposure includearea residents, remedial workers, and trespassers in restrictedareas.
For remediation, contaminated soil in the residential area willbe excavated and moved to the industrial area, and the yardsreplaced with clean fill. Contaminated soil in the industrialarea will be excavated and treated by a critical fluid extractionsystem prior to being permanently placed under a cap in theindustrial area. Remedial activities will temporarily increase,through excavation and movement of contaminated soils, thepotential for exposure of workers and trespassers through dermalcontact with exposed soils, ingestion of exposed soils, andinhalation of contaminated dusts.
In this section, we discuss the health effects in persons exposed to specific contaminants; evaluate state and local data bases, and address specific community health concerns. To evaluate health effects, ATSDR has developed a Minimal Risk Level (MRL) for contaminants commonly found at hazardous waste sites. The MRL is an estimate of daily exposure of persons to a contaminant below which non-cancerous, adverse health effects are unlikely to occur. MRLs are developed for each route of exposure, such as ingestion and inhalation, and for length of exposure, namely acute (less than 14 days), intermediate (15 to364 days), and chronic (greater than 364 days). ATSDR presentsthe MRLs in its Toxicological Profiles series. Thosechemical-specific profiles provide information on health effects,environmental transport, human exposure, and regulatory status.In the following discussion, we used ATSDR Toxicological Profilesfor polycyclic aromatic hydrocarbons, pentachlorophenol, and2,3,7,8-Tetrachlorodibenzo-p-dioxin.
Polycyclic Aromatic Hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs) are a class of structurally related compounds. As a group, these compounds have similar characteristics.
Exposure to PAHs through ingestion of contaminated surface soilsand skin contact with them may have occurred and may still be occurring among residents of the Tanglewood East subdivision andemployees of Sisco Construction Company and Clarke Distributing. Using the highest total PAH concentration detected in residentialsurface soil (15,750 mg/kg), the ingestion exposure for adultsand older children does not exceed ATSDR's acute MRL of 0.1mg/kg/day for benzo(a)pyrene and other PAHs. The ingestionexposure for younger children (1 year through 6 years of age),does exceed the ATSDR MRL. That MRL, however, is based on ananimal study in which developmental effects were seen in theoffspring of mice following in utero exposure to benzo(a)pyrene. In determining the exposure doses, we assumed that youngerchildren (16 kg) ingest 200 mg of soil per day; that olderchildren (35 kg) ingest 100 mg of soil per day, and that adults(70 kg) ingest 50 mg of soil per day. Studies in animals haveshown that PAHs can cause harmful effects on the liver and blood.The levels of PAHs at which those effects were first seen are500-fold higher than the estimated dose for younger children.Therefore, the maximum level of PAHs found in the residentialsoil at Tanglewood East subdivision are unlikely to cause thoseeffects in younger children at the estimated soil ingestion rate. ATSDR does not have MRLs for skin exposure to PAHs. For that reason, it is difficult to determine the health effects from skin exposure. Adverse skin effects have been noted in animals with acute and subchronic dermal exposures to PAHs. Those effects include destruction of sebaceous glands (glands in the skin which secrete fatty substances), skin ulcerations, hyperplasia (abnormal increase in number of skin cells), and overgrowth of the outer layer of the skin. Dermal exposure to certain PAHs, such as anthracene and phenanthrene, followed by exposure to sunlight may result in photoxic effects such as erythema (redness of the skin), urticaria (elevated patches of skin), and burning and itching. Persons with pre-existing skin conditions may be more sensitive to the adverse dermal effects of PAHs (ATSDR Toxicological Profile for Polycyclic Aromatic Hydrocarbons).
Several of the PAHs, including benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, chrysene, dibenzo(a,h)anthracene, and ideno(1,2,3-cd)pyrene havecaused tumors in laboratory animals through ingestion, skincontact, and inhalation. Epidemiologic studies of workers occupationally exposed to PAHs have provided limited evidence that PAH exposure may contribute to increased incidence of skin,lung, and genitourinary cancers. The most likely exposure routesin the occupational settings were through inhalation and skincontact with those compounds. Although inhalation ofcontaminated dusts is possible in the residential and industrialsections of the United Creosoting Company Site, that route ofexposure is unlikely. Scientific data are insufficient at thistime for determining whether cancer is possible from theingestion of and skin contact with the levels of PAHs found inthe surface soils at the United Creosoting Company Site. Thelevels of PAHs to which workers were exposed through skin contactin occupational studies are higher than the levels found in soilsin the Tanglewood East Subdivision and on-site industrial areas.
Pentachlorophenol was detected in on-site surface and subsurfacesoils, sediment, and ground water. Residents in the TanglewoodEast Subdivision and workers in the on-site industrial areascould have been and could be exposed to pentachlorophenol throughingestion of and skin contact with contaminated surface soils. The highest levels of pentachlorophenol in surface soils were 150mg/kg in the residential area and 510 mg/kg in the industrialarea. ATSDR has set an acute MRL of 0.05 mg/kg/day and anintermediate MRL of 0.002 mg/kg/day for pentachlorophenol. Basedon the soil ingestion rates for adults and children discussedunder PAHs and the highest levels of pentachlorophenol found, theingestion exposures for adults and children do not exceed ATSDR'sacute and intermediate MRLs. The estimated exposed doses also donot exceed EPA's chronic RfD of 0.03 mg/kg/day.
Animal studies have indicated that long-term exposure (greater than 14 days) to low levels of pentachlorophenol can have adverse effects on the liver, kidney, nervous system, and immunesystem. Studies have also indicated that long-term exposure tolow levels of pentachlorophenol encountered in the workplace cancause damage to the liver, kidney, blood, and nervous system. The levels of pentachlorophenol found in the on-site areas atUnited Creosoting Company site are unlikely to result in thoseadverse health effects.
ATSDR could not locate any adequate studies that described significant levels of skin exposure to pentachlorophenol. Occupational exposures to pentachlorophenol have been associatedwith severe skin eruptions. Nonoccupational exposures to woodtreated with pentachlorophenol have been associated withpemphigus vulgaris (a serious skin disease characterized byblisters and loss of skin) and chronic urticaria (a disorder ofthe skin characterized by itchy pink or white wheals). Skineffects discussed above may have resulted from impurities presentin pentachlorophenol from the manufacture of this chemical (ATSDRToxicological Profile for Pentachlorophenol). The toxic dermaleffects of pentachlorophenol appear to be most serious followinghigh-dose, acute exposure.
Sufficient evidence exists from animal studies to suggest that pentachlorophenol might cause cancer in humans. No convincing evidence has been obtained from human epidemiological studies that indicate that pentachlorophenol causes cancer in humans. Case reports suggest a possible association between cancer (Hodgkin's disease, soft tissue sarcoma, and acute leukemia) andoccupational exposure to technical pentachlorophenol that mayhave had other contaminants. Using animal studies, we estimatethat residents who live in the Tanglewood East subdivision andwere exposed to the highest levels of pentachlorophenol found inthe residential area would have no increased risk of cancer. Weestimate that workers who work in the on-site industrial areaswould have no apparent increased risk of cancer from exposure tothe highest level of pentachlorophenol detected in the industrialareas.
Chlorinated Dioxins/Dibenzofurans (CDDs/CDFs)
CDDs/CDFs were detected in on-site surface and subsurface soils,sediment, and ground water. According to the documents reviewed,the most toxic chlorinated dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), was not detected at the UnitedCreosoting Company site.
Residents in the Tanglewood East subdivision and workers in the on-site industrial areas could have been exposed and could beexposed to CDDs/CDFs through ingestion of and skin contact with contaminated surface soils. EPA has developed a procedure for estimating the relative potency of CDD/CDF mixtures compared to the potency of 2,3,7,8-TCDD by assigning each related compound apotency factor. The individual estimated potencies of the CDD/CDFs are summed to obtain total 2,3,7,8-TCDD equivalents. The toxicological information for 2,3,7,8-TCDD can then be applied to CDD/CDF mixtures.
ATSDR has set an acute MRL of 0.0000001 mg/kg/day and an intermediate MRL of 0.000000001 mg/kg/day for 2,3,7,8-TCDD. Based on the highest levels of CDD/CDFs (expressed as 2,3,7,8- TCDD equivalents) found in the on-site residential and industrial areas, the ingestion exposures for younger children slightly exceed ATSDR's acute MRL for 2,3,7,8-TCDD; ingestion exposures for older children and adults do not exceed ATSDR'sacute MRL for that chemical. Ingestion exposures for both younger and older children and for adults exceed ATSDR's intermediate MRL for 2,3,7,8-TCDD.
Animal studies have indicated that 2,3,7,8-TCDD may cause liver damage; severe loss of body weight; damage to the immune system,and adverse reproductive effects including spontaneous abortionsand malformations in animal offspring. Adverse effects of thatchemical on the immune system, reproductive system and developingfetuses have not been found in humans, but some evidence hassuggested that 2,3,7,8-TCDD might cause liver damage, weightloss, and digestive disorders in humans. Chloracne is the onlyconfirmed effect in humans produced by certain compoundscontaminated with 2,3,7,8-TCDD. Chloracne is a skin diseasecharacterized by blackheads, cysts, pustules, and inflammatory(pain, redness, and swelling) skin changes of varying degrees ofseverity. A minimum toxic dose of 0.0001 mg/kg has beensuggested to produce adverse noncancer health effects in humans(ATSDR Toxicological for 2,3,7,8-TCDD). Although the ingestionexposures for younger children exceed the acute MRL for2,3,7,8-TCDD and the ingestion exposures for all age groupsexceed the intermediate MRL for this chemical, all estimatedexposures are well below the 0.0001 mg/kg level. Therefore, itis unlikely that residents and workers would develop skin, liver,or digestive disorders from past or present exposures to themaximum levels of CDD/CDFs found at the United Creosoting Companysite. Results from animal studies clearly indicate that2,3,7,8-TCDD causes cancer in laboratory animals. Severalepidemiological studies of human populations exposed toherbicides contaminated with 2,3,7,8-TCDD have shown anassociation with cancer that included an increased incidence ofsoft tissue sarcomas, lymphomas, and stomach cancer. Theevidence from human epidemiology studies is not conclusivebecause of inadequate exposure information and concomitantexposures to other chemicals. Other epidemiological studies havefound no association between exposure to substances containing2,3,7,8-TCDD and cancer.
Using animal studies, we estimate that residents who live in theTanglewood East subdivision and who were exposed to the highestlevels of CDD/CDFs (in TCDD equivalents) could have a lowincreased risk of developing cancer. While the number of extracancers above the background cancer numbers might theoreticallyincrease slightly, 2,3,7,8-TCDD induced cancers among residentsin the Tanglewood East subdivision are unlikely to occur. Inaddition, the actual risk may be lower because (1) 2,3,7,8-TCDDother CDD/CDFs have not been shown to cause cancer in humans, (2) the risk estimate is based on a mathematical equation usingassumptions that estimate the upper bound of risk, and (3)assumptions are used to estimate the maximum amount of exposureto CDD/CDFs (in TCDD equivalents).
We estimate that employees who work in on-site industrial areas would have no apparent increased risk of cancer.
Guided by the concern of excessive cancer in Montgomery County,Texas, the TDH Environmental Epidemiology Program staff conductedan evaluation of cancer mortality in cooperation with the TDH Cancer Registry Division. Table 7 summarizes the results of that evaluation. For the years 1981-1989, the number of deaths from lung cancer among male and female residents in Montgomery County were slightly higher than expected, compared with statewide rates. For the same time period, a slight excess in the number of deaths from bladder cancer among males was also statistically significant. Standardized mortality ratios for those cancers were greater than 1.00, and the lower limits of the 95 per cent confidence limits exceeded 1.00.
The presented county data on cancer mortality may not be representative of cancer mortality for the site population; however, the health concern was expressed about the county population. Census- and zip code-specific cancer mortality dataare not available through the TDH Bureau of Vital Statistics or
|95% Confidence |
Expected numbers of deaths are based on the State rates.
the Cancer Registry Division. Furthermore, data are notavailable on the potential roles that smoking and occupationalexposures might have in the slight excesses of lung and bladdercancer mortality found among Montgomery County residents. Occupational exposures to PAH mixtures have been associated with lung and genitourinary cancers, but at exposures much higher thanwhat would be encountered at the United Creosoting Company site.
We have addressed each of the community concerns about health as follows.
- The effect of remediation on air quality.
Part of the 1990 Focused Site Investigation included air modeling to determine the effects that remediation might have onair quality. The air modeling effort indicated that air emissions during remediation will not be a health concern. According to EPA, remediation will be designed so as to minimizeair emissions, and the area will be extensively monitored for airemissions. Also EPA has indicated that residents who are havingtheir yards replaced, and residents adjacent to those yards, willbe offered temporary relocation.
- Concerns regarding odors present in areas adjacent to the site.
Air monitoring around on-site areas in 1984 did not indicate anysignificant presence of airborne contaminants. Temporary releases of volatile organics were noted during certain activities in which the soil was disturbed; but, none of thevolatile organic peaks measured by the portable organic vaporanalyzer were above ambient levels. An ambient air quality monitoring program will be established and operated throughout the site remediation. Dust control measures will be implementedthroughout the activities to reduce the potential for releases ofsemi-volatiles and particulates. The presence of odors does notnecessarily mean a contaminant is causing adverse health effects. In the future, odors are most likely to occur (if they occur atall) during site remediation activities involving excavation ofsoils. EPA has indicated that the necessary controls will be inplace to prevent adverse health effects from air releases.
- The risk associated with eating vegetables grown in areas around the site.
Some plants can take up PAHs through the roots or foliage. Ratios of PAH concentrations in vegetation to those in soil can range from 0.001 to 0.18 for total PAHs and from 0.002 to 0.33 for benzo(a)pyrene (ATSDR Toxicological Profile for PolycyclicAromatic Hydrocarbons).
Limited data on 2,3,7,8-TCDD, which can be applied to the CDD/CDFs found at the United Creosoting site indicate that thischemical does not bioaccumulate in crop plants.
Pentachlorophenol may bioaccumulate in the food chain, but that chemical was not detected in most of the surface soil samples inthe on-site residential area. Residents may want to review theresults of their soil samples and contact TDH or ATSDR if theyhave questions about specific vegetables grown in their yards. Risk of exposure to site contaminants could vary from no risk tosome risk depending on the levels of contaminants found in soils,the types of vegetables grown, and the frequency and amounts atwhich these vegetables are eaten. Once the soil is replaced inyards exceeding EPA's health action levels, any concerns aboutsite contaminants accumulating in home-grown vegetables should bealleviated.
- Risks associated with digging in gardens, and other related activities.
In the Section Toxicological Evaluation, exposure doses throughingestion of soil were estimated using the highest levels ofcontaminants found. Based on those exposure doses, acute healtheffects are unlikely to occur. Skin contact to any soilcontaminants can be minimized by wearing water-resistant gardengloves and washing hands and any exposed skin with soap and waterafter contact with the soils. Residents whose surface soilsamples in their yards exceed any of EPA's health action levelsmight want to further reduce their risk by avoiding digging inyard soil until it is replaced through remediation.
- Concerns that rashes might be related to site contaminants.
Several site contaminants including certain PAHs,pentachlorophenol, and possibly the chlorinated dioxins (if their skin effects are similar to 2,3,7,8-TCDD) have been associated with skin disorders. Reports of skin problems with these compounds have generally been with exposure to higher concentrations of the compounds than found in the residential surface soils at the United Creosoting Company NPL site. ATSDR does not have MRLs for skin exposure to PAHs, pentachlorophenol,or chlorinated dioxins. Therefore, it is difficult to predictthe dermal effects from skin exposure to the site contaminants atthe levels found at the United Creosoting Company NPL site. Thespecific skin problems that have been associated with exposure toPAHs, pentachlorophenol and chlorinated dioxins are discussed inthe Toxicological Implications section of this Addendum.
- The need for an epidemiological study to determine if anyadverse health effects have occurred from past exposure to contaminants.
As part of this Health Assessment Addendum, the ATSDR HealthActivities Recommendations Panel (HARP) has reviewed theAddendum to determine appropriate follow-up activities. ATSDRhas developed criteria to determine whether a health studyshould be conducted at a site and what type of study should bedone. On September 11, 1991, this Addendum was reviewed by HARPfor follow-up activities. ATSDR has determined that this sitemeets the criteria for both a disease and symptom prevalencestudy and site-specific surveillance activities.