PUBLIC HEALTH ASSESSMENT ADDENDUM
CROSBY, HARRIS COUNTY, TEXAS
This section contains lists of the contaminants of concern. However, inclusion on the list does not imply that a contaminantrepresents a threat to public health. Subsequent sections ofthis Health Assessment will evaluate these contaminants todetermine if exposure to them has public health significance. ATSDR selects these contaminants based upon the followingfactors:
- Concentrations of the contaminants on and off site.
- Field data quality, laboratory data quality, and sample design.
- Comparison of site related concentrationswith Health Assessment Comparison (HAC)values for (1) non-carcinogenic endpoints and(2) carcinogenic endpoints. A contaminant isincluded if no HAC values are available.
|* HAC||= Health Assessment Comparison Value|
|* NCREG||= Non-carcinogenic Risk Evaluation Guide.|
|* CREG||= Carcinogenic Risk Evaluation Guide.|
|* PAHs||= Polycyclic Aromatic Hydrocarbons|
|* PCB||= Polychlorinated Biphenyl|
|* RfD||= Reference Dose|
|* MRL||= Minimum Risk Level|
|* EMEG||= Environmental Media Evaluation Guide|
|* ppm||= parts per million|
|* ppb||= parts per billion|
|*µg/L||= Micrograms per liter (equal to ppb)|
|*mg/Kg||= Milligrams per Kilogram (equal to ppm)|
|*µg/m3||= Micrograms per cubic meter of air|
Health Assessment Comparison Values are contaminantconcentrations for specific media that are used to selectcontaminants for further evaluation. Exceeding a HAC value doesnot imply that a contaminant represents a threat to publichealth. HAC values include Non-carcinogenic Risk EvaluationGuides, Cancer Risk Evaluation Guides, and other relevant healthrelated guidelines. NCREGs are HAC values based on ATSDR'sEMEGs, EPA's RfDs, or other non-carcinogenic health based values.EMEGs are HAC values based on MRLs. CREGs are HAC values basedon the risk of one excess cancer in a million persons exposedover a lifetime.
For the purposes of this discussion the data are presented underon-site contamination and off-site contamination subheadings. Wehave defined on-site contamination to include all data collectedfrom the lagoon as well as all data that we can definitelydetermine has come from the area inside the fence line. Althoughsome of the ground-water samples may have been taken at or nearthe fence line, for ease of presentation we have chosen toinclude all the ground-water data in one off-site contaminationsubsection.
Lagoon Sediment and Sludge
LAN collected eleven on-site sediment samples in April of 1983with nineteen additional samples collected in November of thatsame year. Additional on-site sediment sampling was carried outin June of 1986 by LAN and Resource Engineering Inc. (REI) (2). The methods used to collect the samples varied and were dependentupon water depth and the condition of the sediment (1). Sedimentsamples SE25 and SE26 were collected and composited over a depthof four feet (see Table 1). Sediment samples SE01, and SE03 weretaken at four to six inches. Lagoon sludge borings (LB-2, LB-3,LB-4, LB-5 and LB-9) were taken at depths ranging from -4.4 to -41.9 feet. The thickness of the boring was dependent upon thethickness of the sludge being sampled. Samples were alsocollected from the surface of the sludge; however, contaminationin these samples was low compared to the deeper samples,suggesting a downward migration of the contaminants towards theshallow alluvial aquifer.
With the exception of the metals, PCBs, and various pesticides,all maximum levels were found at sample sites SE25 and SE26 whichare approximately in the center of the lagoon. At theselocations benzene, 1,2-dichloroethane, 1,2-dichloropropane, andvinyl chloride were found at levels above their respective CREGvalues. Vinyl chloride also exceeded its NCREG. The heavymetals beryllium and chromium were found to exceed HAC values insediment samples SE01 and SE03. Additionally, sediment sampleSE03 contained total PCBs at a level of 507 mg/Kg, exceeding theCREG value. Other contaminants that exceeded known HAC valueswere pentachlorophenol, acenapthalene, fluoranthene, fluorene,naphthalene, phenanthrene, pyrene, and various pesticides.
Contamination in the upper layers of lagoon water (less than 15feet deep) was low with the concentrations of the volatileorganic compounds appearing to vary with seasonal temperaturechanges. A surface water sample taken in April 1983 containedtrace amounts of volatile organic contaminants, while a sampletaken in November 1983 contained no measurable volatile organiccontamination. LAN suggested that the cooler Novembertemperatures reduced the water solubilities of many of thesecompounds. Table 2 shows the data collected for the watersampled from the lagoon. Except for chromium, all maximumcontaminant concentrations were found at depths greater than 16feet. Numerous volatile and many base/neutral compounds werefound at levels exceeding HAC values.
|ON-SITE CONTAMINANT||DEPTH OF SAMPLE|
|VINYL CHLORIDE||17||NOV 1983||SW09||180||0.2||0.018||EMEG|
|NOTE: NA STANDS FOR NOT AVAILABLE.|
ENSR Consulting and Engineering (Formerly ERT) monitored fenceline air concentrations around the site from April 1987 to
|PREDICTED VALUES||HAC VALUES||HAC|
|2-CHLORO ETHYL VINYLETHER||0.920||0.293||0.132||0.023||0.035||0.035||0.040||0.023||NA||NA||NA|
* Suspected Human Carcinogen
# Average Maximum Fence line data were measured values. All other data were predicted using a section spread point source model. See text for details.
TACB indicates a NCREG based on the Texas Air Control Board health effects screening level.
August 1988 (7). To obtain maximum emissions from the lagoon,samples were taken during trial bioremediation. This involvedactively bubbling air into the lagoon. Pictures of this processshowed that the bubbling action was very intense and likely toincrease emissions. Air samples were taken in sixteen directions(N, NNE, NE, ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW, NW,NNW) around the lagoon when the wind was blowing from the lagoontoward that location. These averages were referred to as"average maximums" (AM) and were modified to more appropriateaverage values by multiplying the AM by the percent of time thatthe wind was blowing in that direction. Backgroundconcentrations were assumed to be zero.
The fence line data presented in Table 3 represent the average maximum values detected from the site at the fence line. CREGvalues were exceeded for each of the chemicals for which a CREGwas available. Additionally, carbon disulfide exceeded thehealth criteria established by the Texas Air Control Board(TACB). Although 1,2-dichloropropane and bromodichloromethaneare suspected human carcinogens, no CREG values were availablefor comparison. HAC values were not available for 2-chloro ethylvinyl ether and dibromochloromethane.
Off-site soil samples were taken from along Gulf Pump Road, alongthe various drainage pathways used by water runoff from the site,and from around the Riverdale subdivision. Figure 6 shows someof the soil sampling locations. The methods used to collect thesamples varied with some of the samples being collected by handwith a trowel. For many of the chemicals of concern, the highestvalues were found in samples SO01 and SO04 (see Figure 6). Thesesamples were taken from a depth of two to six inches andconsisted mostly of dried sludges with naphthalene, beryllium,and PCBs all exceeding their HAC values. PCBs were found toexceed HAC values at various sample depths, however, the highestvalues were found at the surface (one-half to one inch; samplelocation three). Several base/neutral PAHs were also reported;however, since there are no HAC values for these compounds wewere unable to judge the significance of the reportedconcentrations (Table 4).
In 1986, LAN reported low concentrations of PCBs in the Riverdalesubdivision at sample sites SO10 and SO11. Subsequent sampleswere also taken around Riverdale Lake, by ENSR, after the May 19,1989 flood (8). The post-flood samples contained PCBs at concentrations exceeding CREG values with concentrations as highas 253 mg/Kg. The off-site PCB contamination observed after theflood clearly indicates that, at least in the case of the 1989flood, contaminants were transported off site. It furthersuggests that contaminants may also have been moved off siteduring previous floods.
As a result of the post-flood off-site PCB contamination, EPA andFLTG remediated the contaminated areas. However, the maximumlevel, after phase II of the cleanup, of 7.1 mg/Kg still exceededthe CREG value for these compounds.
|PCBs, TOTAL (post-cleanup)||21||ENSR 89||21||0.25||0.09||EMEG/CSF|
|PCBs, TOTAL (post-cleanup)||9||ENSR 89||7.1||0.25||0.09||EMEG/CSF|
|PCBs, TOTAL (pre-cleanup)||3||ENSR 89||253||0.25||0.09||EMEG/CSF|
|PCBs, TOTAL||S004||REI 86||237||0.25||0.09||EMEG/CSF|
|PCBs, TOTAL||S001||REI 86||209||0.25||0.09||EMEG/CSF|
|NOTE: ND STANDS FOR NOT DETECTED AND NA FOR NOT AVAILABLE.|
PCB isomers were found in sediment from various off-sitelocations. These locations included the area north of U.S.Highway 90 (SE17), the old fishing hole north of the lagoon andsouth of U.S. HW90 (SE14), the slough located northwest of thelagoon and south of U.S. HW90 (SE11 and SE12), and the small pondlocated approximately 200 feet east of Riverdale (SE27). Thepattern of contamination was consistent with the water runoffflow patterns reported for the site (Figure 5). The concentration of PCB isomers at these locations ranged from 0.16mg/Kg to 24.0 mg/Kg and all exceeded the CREG value for PCBs. Volatile and base/neutral compounds did not exceed HAC values. See Table 5 for these results.
|Di-n-butyl phthalate||SE28||APR 85||0.82||NA||NA||NA|
|Di-n-octyl phthalate||SE22||APR 85||21||NA||NA||NA|
|PCBs, total||SE10||APR 85||0.16||0.25||0.09||EPA/CSF|
|PCB-1016 (surface)||SE17||APR 85||0.39|
|PCB-1260 (surface)||SE27||APR 85||0.46|
|PCB-1016 (surface)||SE14||APR 85||0.41|
|PCB 1016/1260 (surface)||SE12||APR 85||24/0.94|
|PCB 1016/1260 (surface)||SE11||APR 85||9.4/0.35|
|NOTE: NA STANDS FOR NOT AVAILABLE.|