PUBLIC HEALTH ASSESSMENT
BRIO REFINING, INC.
DIXIE OIL PROCESSOR, INC.
A. ON-SITE CONTAMINATION
2. PIT RESIDUALS - BRIO/DOP SITES (see Tables following).
3. MUD GULLY SEDIMENTS - BRIO/DOP SITES (see Tables following).
ND - Not Detected
mg/kg - milligrams per kilogram
|Contaminants||DOP North||Concentration (mg/kg)|
(---) analyzed but not detected.
B. OFF-SITE CONTAMINATION:
Southbend Subdivision is outside the northern boundary of Brio north. There are five pits locatedalong the Brio north northern boundary. Soil samples were taken from the pits (backfill) andsubdivision properties to determine the lateral extent of contaminant migration. During theRemedial Investigation, soil samples were collected from multiple locations in SouthbendSubdivision residential lots at depths of 0-1 foot and 9-10 feet. In June 1988, additional soilsamples were collected from residential lots in the Southbend Subdivision at depths of 0-5 feet. These samples were analyzed for acid base/neutral compounds, VOCs, and one sample wasanalyzed for metals. Only a low level of phenanthrene (806 ug/kg) was detected. The migrationof metals from Brio north did not appear to be addressed, although data indicated high levels oflead (7,800 mg/kg), copper (182,000 mg/kg), and chromium (1,000 mg/kg) in some pits on theBrio North northern boundary. However, metals migration should not be a problem since fill wasused to raise the ground level of the subdivision along the boundary above the ground level ofBrio north.
There may have been some limited, on-site lateral migration of copper from DOP pits AA andCC. Lead and chromium in the DOP north pit subsoils were analyzed for but not detected.
Off-site NSCZ monitoring wells in Southbend Subdivision indicated high concentrations ofvolatile organic compounds near the site boundary that rapidly diminished a few hundred feetbeyond the site boundary. Since this area is served by a deep municipal well, minimal or nogroundwater exposure is anticipated.
C. PHYSICAL HAZARDS
During a site visit on January 26, 1988, a physical survey revealed much debris, old processequipment, and storage tanks. The estimated quantity of waste liquids left in the storage tanks is approximately 200,000 gallons. Only two large lagoons remain which were used in the past forprocess wastewater treatment. The two lagoons trap stormwater; periodically, the stormwater ismanually discharged. At Brio south, a large box weir was found filled with water. At DOPsouth, a large wastewater pump pit was also found filled with water. The storage tanks appearabandoned with holes in the sides of some of them. Many tanks still hold chemical residues thatmay present a future hazard due to tank corrosion. The lagoons and stump pits were at gradelevel, filled with water, and may represent a drowning hazard for trespassers.
The Brio/DOP sites are within two Standard Metropolitan Statistical Areas (SMSA) - Houstonand Galveston-Texas City, Texas. The estimated population within a one-mile radius of the site isapproximately 5,700. Census data indicate that the population in the site area is composed mostlyof young families residing in recently-developed communities that constitute suburban Houston.
No residence were within one mile of the sites prior to 1972. Three homes were built between1972 and 1976 within 1,000 feet of the sites. The Southbend subdivision was built adjacent to thenorthern boundary of the Brio site between 1980 and 1984. The subdivision is approximately 502acres, of which approximately one-half is presently developed with single-family homes. Thirty-one residences are on the NW boundary of the site, and Weber Elementary School is locatedapproximately 1,200 feet NW of the site.
The Southbend Municipal Utility District water well is located approximately 1.25 miles west andsouthwest of the site. The well is approximately 1,200 feet deep with a well casing diameter of 16inches. The depth of the screen is not known. This well supplies water for the homes in Southbend Subdivision.
Northwest of Southbend is the Sageglen Subdivision.
Approximately one mile north is the Scarsdale Subdivision.
Memorial Southeast Hospital, withapproximately 920 beds, is located approximately 3,200 feet NW of the site. The community ofFriendswood is located one to two miles to the south and southwest of the site.
Outside of the residential areas, the land is used for grazing and oil and gas production. Approximately 26 oil and gas wells are located within a half-mile radius of the site.
An athletic field is located immediately adjacent to DOP north. The field is used as a public ballpark (USA Ball Park). A well at the ball field was completed at a depth of greater than 250 feetand is reported by EPA to be used only for irrigation purposes.
Water is supplied by public or private utilities to almost all homes within a one-mile radius of theBrio/DOP site.
Population distribution by sex is comparable to the national average. The number of children(under 5 years of age) is three times the national average. The number of elderly persons (62years and older) is one-fourth the national average. Median age is three years younger than thenational average. Most employed persons (over 16 years of age) are in managerial, professional,technical, or administrative position. Seventy-five percent of the residences are owner-occupied,single-family dwellings.
A. SITE CHARACTERIZATION (DATA NEEDS AND EVALUATION)
1. Environmental Media:
The Final Summary Report, Final Endangerment Report and previous investigations conductedair, hydrologic and geologic evaluations. Sampling efforts were concentrated on groundwater,surface water, sediments of Mud Gully, soil sampling on site and off, and air.
2. Land Use and Demographics:
The nearest municipal well is over one mile from the site and is approximately 1,200 feet deep. Complete data does not appear to be available for a listing of domestic potable wells and thedepths in which they are completed within one mile of the site. These wells, if any exist otherthan those listed in the Reference 2 well inventory, should not be affected because the sitecontamination only extends a few hundred feet beyond the northeast site boundary.
The Brio/DP sites are fenced to preclude trespassing. This health assessment is based on the sitesbeing remediated or remaining undeveloped with proper maintenance of controlled access. If thesites are zoned for residential use in the future without proper remediation, his assessment wouldnot be valid.
3. Quality Assurance/Quality Control (QA/QC):
This health assessment was based on compile data from the FINAL SUMMARY REPORT,BRIO REFINING, INC. AND DIXIE OIL PROCESSORS SITE, FRIENDWOOD, TEXAS,June 1987. Environmental samples collected during the investigations were analyzed by contractlaboratories. The results were submitted to EPA Region VI for QA/QC analyses.
B. ENVIRONMENTAL PATHWAYS:
The site groundwater system is composed to two shallow confined groundwater flow zonesoverlying the Chicot aquifer system, a regional drinking water aquifer. The upper shallowgroundwater has been labeled the Numerous Sand Channel Zone (NSZC). The NSC begins at 14to 32 feet below the surface and is semi-confined by an overlying clay layer that varies from 5 to 32 feet thick. Potentiometric surface maps indicate that the water flow in the NSCZ is towards Mud Gully. A middle clay unit from 8 to 20 feet in thickness separates the NSCZ from the lower groundwater zone, the Fifty-Foot Sand Zone. The Fifty-Foot Sand Zone ranges from 35 to 45feet in thickness. Underlying the Fifty-Foot Sand is clay unit approximately 100 feet thick thatseparates the shallower water bearing units from the major water producing lower aquifers(Chicot, Evangelize, and Jasper).
1. Groundwater discharge to Mud Gully: The NSCZ is heavily contaminated by numerous sitechemicals. Groundwater flow in the NSCZ is toward Mud Gully at a rate of 3 to 70 feet per year. Since the water flow in the NSCZ is towards Mud Gully, contaminants in this zone may migratehorizontally to Mud Gully and be transported to off-site locations. Mud Gully is also used as adrainage channel for a wastewater treatment plant.
2. Groundwater pertaining to well drinking water supplies: The groundwater existing in theNSCZ under the site is contaminated (see Appendix, Tables 1 and 2). The NSCZ does not appearto be a major existing or potential drinking water source because of the poor yield of the aquifer.
The Fifty-Foot Sand zone has a small amount of contamination (see Appendix, Tables 1 and 2)from 1,1,2-trichloroethane (20 ug/l), 1,2-dichloroethane (55 ug/l), and methylene chloride (70ug/l). Reference 1 concluded that there are no known uses of groundwater from the Fifty-Foot Sandzone. However, one well (5J) was reported in the Reference 2 well inventory and is screened at adepth of 87-97 feet. No sampling was performed on this well which is approximately one-halfmile northwest of the site. Two other wells were also mentioned in the well inventory as beingnear the site (511 and A). The screened depths were listed as 260-282 feet and greater than 250feet. No sampling has been performed on well 511. Well a (located at the athletic ball field 1,000feet west of the DOP site) was tested and found not to be contaminated. These wells werereported as being located hydraulically upgradient of the site. The two wells 5J and 511 were notexpected to show any contamination because the shallow groundwater contamination plumeextends only a few hundred feet beyond the site boundaries and the deeper aquifers were notfound to be contaminated.
No surface drinking water intakes exist in the surrounding area. Drinking water sources aremostly groundwater supplied by the Municipal Utility District and the City of Houston from wellsgreater than 500-600 feet deep. A clay aquitard approximately 100 to 120 feet thick existsbetween the Fifty-Foot Sand zone and the lower aquifers. It appears unlikely that contaminantscould migrate vertically through the clay aquitard and reach the deep aquifers, except through anearth fault or a physical penetration of the clay layer (wells). It is possible for contaminated waterin the NSCZ to migrate vertically along ungrouted well casing or corroded well casing of in-useor abandoned oil and water wells, either on-site or downgradient off-site. However, EPA notedthat there were no off-site wells that intercept the contaminated NSCZ groundwater and hat on-site inactive oil wells have been plugged according to state procedures. Therefore, thiscontamination pathway was not considered further.
Other major wells that were evaluated and not found to be contaminated are: Southbend, WeberElementary, Pearland, West University, Seabrook House, and the Athletic Field baseball well westof the DOP Site.
Faults: an on-site fault runs east-west of the DOP site. If the fault intersects groundwater orother subsurface materials, the clay aquitards could be affected. There may be ap potential forcross-contamination of the aquifers. If the upward hydraulic gradient on the site persists, thereappears to be little potential for vertical contaminant migration to deeper aquifers. However, aswill be discussed below, this may not be true.
Pipeline routes: A pipeline is located on the northeast side of the Brio north site. The pipeline islocate on the northeast side of the Brio north site. The pipeline was investigated to determine ifthere are a potential for a horizontal off-site pathway. Sample analyses of backfill indicate minimaconcentrations of four contaminants in the groundwater. Based on this data and the clay backfillmaterial, he pipeline did not appear to be a significant pathway for contaminant migration.
3. vertical migration or flow from the NSCZ to the Fifty-Foot Sand: the potential exists forcontaminants to more from the NSCZ to the Fifty-Foot Sand shallow aquifers. Generalinformation indicates that an upward hydraulic gradient exists between the two zones over mostof the Brio/DOP north and south sites. There is a downward gradient at the northern corner ofthe sites. Based on the model presented in reference 2 an the upward hydraulic gradient on themost of the site, the conclusion was reached by the Final Summary Report that his was not alikely exposure pathway. However, the hydraulic gradient was calculated from potentiometricdata gathered during the months of August, October, and March. The data set may not beadequate to describe the long-term potential for vertical migration of contaminants. Hydraulicgradients can reverse with seasonal recharge events an droughts. Monthly water levelmeasurements over a one to two year period would provide would provide a better data set todetermine variations in vertical flow and contaminant migration.
Also, some dense non-aqueous phase liquids (DNAPL) were found in the NSCZ (see Appendix,Table 3). These DNAPLs are denser than water. They may counteract the upward hydraulicgradient and migrate by gravity to the Fifty-Foot Sands or downward through an earth fault TheROD required removal of DNAPLs from Pits J and Q and should eliminate or minimize themigration of these contaminants by gravity.
4. Sediment runoff to Mud Gully: Mud Gully passes through the site. About 2,000 feetdownstream, Mud Gully flows into Clear Creek. Clear Creek discharges into Clear Lake about12 miles downstream. Elevated concentrations of PAHs were found in Mud Gully sediments (271mg/kg) collected at a location between Brio north and DOP north. Chrysene, a suspected carcinogen, was detected in sediment at aconcentration of 149 mg/kg. Further downstream, PAH concentration in Mud Gully sediment samples were relatively low (21 mg/kg).
5. Surface Water: Mud Gully surface water data collected adjacent to Pit B was contaminatedwith 1,1,2-Trichloroethane (35.5 ug/1), 1,2-dichloroethane (26.1 ug/1), and chrysene (154chemicals (VOCs, PAHs) may be absorbed through the skin during contact with contaminatedsoils and sludges.
Human exposure pathways that are consistent with the environmental pathways previously discussed are:
1. Ingestion of water: The contaminated NSCZ groundwater is unsuitable for humanconsumption without treatment. From references 2, off-site contamination by the site NSCZgroundwater appears to be limited to the northern boundary of Brio-north and extends about 200feet into the Southbend Subdivision. The subdivision is on a municipal well that is 1,200 feetdeep and has no known contamination.
Reports (Reference 1 and 2) indicate that NSCZ groundwater is not a major existing or potentialdrinking water source because of the poor yield of the aquifer. Public or private utilities providedrinking water within a one-mile radius of the site. Complete data for domestic wells near the sitewas not available (other than those listed in the well inventory in Reference 2). There does notappear to be any major potable use of the shallow contaminated aquifer.
There may be a potential for contaminants to enter the Fifty-Foot Sand zone from the NSCZ zonethorough earth faults, abandoned defective wells, or well casings. EPA reported that there are nooff-site wells in the NSCZ contamination plume that may contaminate the lower aquifers and thaton-site inactive oil wells have been plugged according to state procedures. Currently, grosscontamination of the Fifty-Foot Sand does not seem to have occurred.
It will be assumed in this Health Assessment that there is no current major human consumption ofcontaminated ground water (not withstanding the two wells, 511 and 5J, which have not beensampled). It will also be assumed that the affected portions of the upper aquifers are not beingused for agricultural irrigation or for livestock watering.
Mud Gully is reportedly not being used as a drinking water source. Therefore, significant humaningestion of water from Mud Gully is not likely. Inadvertent ingestion of surface water from MudGully may occur it children or other trespassers play in or contact the water that flows through the site. However, such exposure is expected to beinfrequently because of fences and heavy underbrush that restrict access to Mud Gully.
2. Dermal contact and absorption of contaminants from surface water: Children or trespasserswho come in contact with water that flows through Mud Gully may be exposed to watercontaminants by skin contact and dermal absorption.
3. Inhalation of air and volatile emissions: The former storage pits at the sites are potentialsources of air-bourn contaminants. Both on-site workers and off-site, down-wind residents couldbe exposed to VOCs through the inhalation route.
The initial air sampling for VOCs was conducted by the Texas Air Control Board (TACB) duringJanuary-March 1985 at the Brio and DOP sites. Vinyl chloride was not detected in excess of thedetection limit of approximately 2 p[b, nor was tetrachloroethylene detected at concentration inexcess of 1 and the highest hourly average value was 65 ppb. For toluene, the 10-day average airconcentration was 16 ppb, and the highest hourly average value was 95 ppb.
Additional air sampling during warm ambient temperatures was conducted by SouthwestResearch Institute on July 10 and 11, 1985, and by the TACB on August 2, 1988. These studiesalso detected only low concentrations of air contaminants that were comparable to or less than theinitial sampling results described above.
VOCs were detected in Mud Gully surface water. Trespassers or children who play near thestream may inhale VOCs that volatilize from the water. However, a noted above, such exposuresare expected to occur infrequently.
4. Soil ingestion and dermal exposure:
Off-site surface soils:
A residential neighborhood, the Southbend Subdivision, is located northwest of the Brio-northsites. Numerous waste pits (F,I,J,K,L) were located along the northern edge off the site. To testfor possible lateral migration o contamination, soil samples were collected in the SouthbendSubdivision at distances of 60-125 feet from the pits. Soil samples collected at a depth of 0-1foot did not contain any site-related chemical contamination except for a low concentration ofPAHs (3.255 mg/kg) detected in one sample.
In June 1988, an additional 11 soil samples were collected at depths of 0-5 feet from theSouthbend residential area. An analysis of these samples did not detect the presence of anysignificant contamination. Therefore, contact with surface and subsurface oils from theSouthbend Subdivision along the northern border of the Brio property line would not be expected to pose any known health risk.
On-site surface soils:
Human exposure to soil contaminants by ingestion and dermal absorption is possible for on-siteremedial and construction workers or for trespassers. A wooden fence plus a chain-link fencetopped with three strands of barbed wire separate the Brio site from the Southbend Subdivision. Therefore, t is not likely that neighborhood residents would come into contact with waste material at the Brio site.
Mud Gully sediments:
Mud Gully may receive groundwater discharge form the NSCZ in addition to receiving surfacewater and suspended sediment runoff from the Brio and DOP sites. Several carcinogenic andnon-carcinogenic PAHs were detected in Mud Gully sediments from sampling points adjacent tothe Brio/DOP sites. The total maximum concentration of carcinogenic PAHs ranged from 2-47mg/kg. Two VOCs, 1,1,2-trichloroethane and 1,2-dichloroethane, were detected in Mud Gullysurface water samples that were collected adjacent to Pit B.
Mud Gully sediment samples collected south of Dixie Farm Road contained PAHs at a geometricmean concentration of 31 mg/kg, as well as copper (125 mg/kg) and chromium (25.5 mg/kg). Nodata on concentrations of contaminants in Mud Gully stream water from south of Dixie Farm Road were available.
5. Ingestion of Biota:
The volume and quality of water in Mud Gully are inadequate to support game fishing. However,Mud Gully may be used as a water source by cattle. Humans may therefore be indirectly exposedto contaminants from the site that may have bioaccumulated in cattle.
1. The former storage pits on the Brio site contain numerous chemicals and organic solvents. Among the chemicals that occurred most frequently and at the highest concentrations werechlorinated VOCs such as 1,2-dichloroethane, 1,1,2-trichloroethane, trans-1,2-dichloroethylene,and vinyl chloride. In general, these chemicals are toxic to the liver as the result of their metabolicconversion to highly-reactive chemical intermediates. Chronic exposure to high doses of thesechemicals can lead to varying degrees of degeneration and fatty infiltration of the liver. Laboratory experiments have also indicated that some of these compounds may be capable ofinducing liver tumors in certain strains of laboratory animals. In addition, epidemiologicalevidence has demonstrated that vinyl chloride can induce tumors of the liver (hemangiosarcoma)and other organs in exposed workers.
Contact with contaminated sludges, sediments, and soil could result in VOC exposures fromdirect ingestion or by dermal absorption. The Brio sites are not currently engaged in any chemicalproduction operations, and the only current use of the DOP sites are as storage facilities. However, if industrial operations were to resume at the site, or if remedial activities were to be conducted, there would be a potential for worker contact with contaminated materials.
It is not possible to offer quantitative estimates of health risks for on-site workers because of thewide variation in VOC concentrations and because of the lack of information on worker contactwith contaminated areas. However, under worst-case exposure assumptions, significant healthrisks could occur for unprotected on-site workers or for remedial workers.
Non-carcinogenic PAHs and lower concentrations of carcinogenic PAHs were identified in thestorage pit areas. Skin exposure to PAHs, such as anthracene, acridine, or phenanthrene,followed by exposure to sunlight, can produce phototoxic effects such as erythema, urticaria, andburning and itching of skin. These dermal reactions will usually disappear when contact with theirritant or sensitizer is eliminated.
Exposure to PAHs is also of concern because of the carcinogenicity of some PAHs and PAHmixtures. In laboratory experiments, PAHs are potent inducers of skin cancer when applieddermally to mice and rats. In addition, PAHs are carcinogenic in animals when ingested, injected, or instilled intratracheal.
Studies of human exposure to PAHs have been conducted among coke plant workers and coalgas production workers. Epidemiological studies of these workers have revealed as associationbetween occupational exposure to combustion products containing PAHs and cancer of the lung,pancreas, kidney, bladder, and skin. Interpretation of these studies is confounded by simultaneousexposure to other combustion products, as well as by additional chemical carcinogenic exposurefrom cigarette smoking.
PAHs can be absorbed through intact human skin. In addition, human skin is capable ofactivating PAHs to chemically-reactive intermediates that may be involved in chemicalcarcinogenesis. The quantity of PAHs absorbed would depend on the area and anatomicallocation of exposed skin, the contact time, the dermal permeability of individual PAHs, etc. Sincethese parameters are not known, it is not possible to quantify the risks associated with dermally-absorbed PAHs.
Copper is an essential element in man, and it has been estimated that 2.5-5 mg of copper areingested daily from dietary sources. Acute exposures to high doses of copper can causegastroenteritis in man. Chronic copper exposure in animals (especially when combined with zincand iron deficiency) can cause liver damage.
Copper is not appreciable absorbed through intact skin, so dermal contact with copper-containingsoils and sediments would not present a significant health risk. However, small qualities offcopper-containing soil could be ingested by workers at the site. Although high concentrations ofcopper were detected at both the Brio and DOP sites, copper toxicity would not be expected toresult from oral exposures. Under realistic conditions, only relatively small qualities o copper-containing soils would be ingested. In addition, homeostatic mechanisms in the human bodyregulate the gastrointestinal absorption of copper, and the liver has a large excretory capacity forexcess cooper, ad the liver has a large excretory capacity for excess copper. However, individualswith chronic liver disease, as well as rare individuals with Wilson's Disease (1 in 100,000), may be at an increased risk for copper toxicity.
If remedial activities generate dust containing high concentrations of copper, workers should be protected against dust inhalation. Potential pulmonary manifestations of copper inhalation include"vineyard sprayer's lung" metal fume fever.
Elevated concentrations of lead were also found in some pit residual samples. The ingestion oflead can cause neurotoxicity, particularly in infants and young children. Chronic lead exposurecan also have deleterious effects on hemoglobin synthesis, kidney function, and may contribute tohypertension. If the pit residues are exposed during remedial activities, precautions should betaken to prevent the ingestion of lead-contaminated materials.
2. Epidemiological studies have demonstrated that exposure to benzene can cause bone marrowtoxicity. Occupational exposure to benzene in the rubber coating, leather working, rotogravureprinting, and other industries has been correlated with an increased incidence of blood dyscrasia, aplastic anemia, and leukemia. High level exposures tobenzene have also been associated with cytogenetic aberrations in bone marrow and peripheralblood cells.
At the Brio site in 1985, the 10-day average air concentration of benzene was 7 ppb (0.007 ppm),and the highest hourly average value was 65 ppb (0.065 ppm). By comparison, air monitoring inHarris County for 6 months in 1981 revealed the 6 month average air benzene concentration to bebetween 5 and 11 ppb, and the highest hourly average concentration was 586 ppb. Therefore, airbenzene concentrations at the Brio site were comparable to those of Harrison County. Thepresent OSHA standard for occupational exposure to benzene is 10 ppm a time-weighted average. The air benzene concentration at Brio in 1985 was more than 1,000-fold less than the OSHAstandard and does not represent a significant public health threat as judged by this criterion.
Toluene as detected in air samples at Brio in 1985 at concentrations as high as 95 ppb (hourlyaverage). Other air contaminants that were detected at Brio and DOP include mesitylene (17.3ppb) and xylenes (10.8 ppb). The concentrations of these contaminants were several orders ofmagnitude less than National Institute of Occupational Safety and Health (NIOSH) and/orAmerican Conference of Governmental Industrial Hygienists recommendations for occupationalexposures and do not present a significant public health threat as judged by these criteria.
The studies conducted by the Texas Air Control Board and the Southwest Research Institute didnot detect significant concentrations of air contaminants during either winter or summermonitoring. Therefore, inhalation of contaminants from the site would not be expected to pose asignificant health risk. However, if buried contaminants are unearthed during construction orremedial activities, significant inhalation exposures could occur.
3. No surface or subsurface soil contamination was reported in the Southbend residential areanorth of the Brio property line. Furthermore, surface water flow at the northern edge of the Briosite parallels the property line before emptying into Mud Gully. No channeling of surface waterrunoff from Brio onto the residential areas as noted. Therefore, in the absence of any demonstrated, off-site soil contamination, there are no apparent health risks associated with contact with off-site soils.
4. Between the Brio north and DOP north property lines, contamination of sediment and/orsurface water from Mud Gully with PAHs and VOCs was detected. Human contact withsediment and water in this portion of the stream could result in exposure to contaminants byingestion, inhalation, or dermal absorption. However, access to this portion of Mud Billy isrestricted by fences and by heavy underbrush on both sides of the stream. Because of the limitedattraction and inaccessibility of this portion of Mud Gully, it is likely that human contact would beon an intermittent and infrequent basis.
Downstream from Dixie Farm Road, access to Mud Gully is more open. Since cattle pasture landabuts on the western edge on the stream, it is possible for cattle to drink from this portio of the stream.
No data were available on contaminant levels in water from Mud Gully south of Dixie Farm Road. Significant human ingestion of water from Mud Gully is unlikely to occur since Mud Gully andother surface streams in the area are not used for potable water supplies.
PAHs, at a geometric mean concentration of 31 mg/kg, were detected during sampling of MudBully sediment from south of Dixie Farm Road. PAHs are relatively insoluble in water and do notsignificantly concentrate in fish because they are metabolized to water soluble compounds andexcreted. No bioaccumulation data for PAHs in cattle are available. However, it has beendemonstrated in a wide variety of mammals that PAHs are readily metabolized and excreted. Therefore, it would not be expected that significant quantities of PAHs would accumulate in cattle drinking from Mud Gully.
In ruminants, dietary levels of trace elements, such as zinc, effect the absorption and toxicity ofcopper. There may be some accumulation of copper in the body, and the highest tissueconcentration is found in liver. From the available information, it is not possible to determinewhether toxicologically significant quantities of cooper wold accumulate in cattle that drank fromMud Gully ad grazed in the adjacent fields.
There may be occasional human contact with sediment in Mud Gully south of Dixie Farm Road. Contact with copper in the sediments does not present a significant health concern because of thelow likelihood for ingestion and because of the low toxicity of copper in humans. Although PAHswere also detected in stream sediment, occasional human contact with the sediments would not beexpected to result in a significant health risk.