PUBLIC HEALTH ASSESSMENT
REILLY TAR & CHEMICAL CORPORATION SITE
ST. LOUIS PARK, HENNEPIN COUNTY, MINNESOTA
The goal of this section of the health assessment is to identify contaminants of concern forfurther evaluation. Chemicals listed in this section will be discussed and further evaluated insubsequent parts of the public health assessment. It is important to note that the inclusion ofchemicals in this section does not necessarily imply that they pose a threat to human health. Thissection focuses on those chemicals found either on-site or off-site that were selected ascontaminants of concern based on the following considerations:
1) To assist in selecting contaminants which produce noncarcinogenic toxic effects, ATSDRdeveloped environmental media evaluation guides (EMEGs). EMEGs are media-specific (forexample, air, water and soil) and are derived from estimates of daily doses of a chemical thathumans may take in, over a specified period of time, that are unlikely to produce adverse healtheffects. Briefly, the environmental concentration of each chemical is compared to the appropriateEMEG value. If the environmental concentration of the contaminant is greater than the EMEG,the contaminant is evaluated further for its potential health impact. If the environmentalconcentration is less than the EMEG, exposure to the contaminant in that medium (air, soil orwater) is unlikely to pose a public health hazard. EMEGs for Site contaminants are given inAppendix 1.
2) Cancer risk evaluation guides (CREGs) are media-specific comparison values that are used toselect chemicals which produce carcinogenic effects. CREGs are calculated using EPA-derivedcancer potency factors. Media-specific CREG values are defined as the estimated contaminantconcentration that will result in one excess cancer in a million persons continuously exposed overlifetime. CREGs are used in exactly the same way as are EMEGs. CREGs for Site contaminantsare listed Appendix 1.
3) Chemicals found in groundwater are considered to be chemicals of concern and are includedin this evaluation if their concentrations exceed health-based Recommended Allowable Limits(RALs) developed by MDH for contaminants in private drinking water supplies. RALs arederived for those chemicals which are most frequently found in Minnesota's groundwater. RALsfor noncarcinogens are often taken from current Drinking Water Health Advisories published byEPA Office of Drinking Water. RALs for carcinogens are derived from the potency slopes(estimates of the cancer-causing ability) from EPA Carcinogen Assessment Group and reflect anestimated lifetime excess cancer risk of 1 in 100,000. RALs for Site contaminants of concern aregiven in Appendix 2. RALs are currently applied as health-based guidelines in Minnesota.
Health Risk Limits (HRLs) are being developed by MDH using the same methodology used toderive RALs. HRLs will soon be adopted as Minnesota rules and will thus become enforceableby law.
4) Chemicals detected in other media (for example soil and air) are included as chemicals ofconcern for further evaluation if their concentrations exceed media-specific concentrationscalculated using risk assessment methodology (for example, ATSDR-derived minimal risk levels(MRLs) or EPA-derived reference doses (RfDs). The concentration values for carcinogens willreflect an excess lifetime cancer risk of 1 in 100,000.
5) Chemicals which do not exceed the comparison values used for selecting contaminants ofconcern may also present a potential health hazard. These may also be included as chemicals ofconcern based on professional judgment. There may be a concern when there are low levels ofmany chemicals (mixtures) because of the unknown consequences of exposure to mixtures. Professional judgement may also indicate a concern exists when exposure may be occurringthrough more than on route of exposure (for example through inhalation and ingestion) or whenthere are extenuating circumstances related to known or suspected exposures. Examples of thesebehaviors include subsistence fishing and pica behavior in children (a craving to ingest soil, paintchips, and other non-food items).
6) Chemicals may also be included as contaminants of concern based upon site-specificinformation or low confidence in the adequacy and the representativeness of sampling data. Forexample, releases and movement of chemicals from hazardous waste sites may be unpredictable. Chemicals are often released in pulses and monitoring results may reflect peak concentrationsfound during pulses or they may reflect lower concentrations between pulses. Therefore,chemicals not found or detected at low concentrations may be detected at much higherconcentrations in future sampling events. Additional uncertainty may be the result of geologicalvariability which is typical in Minnesota and the imprecise nature of hydrogeologiccharacterization.
7) Consideration is also given to the quality of field and laboratory data and sampling design. Community concerns about particular chemicals or health effects are also considered in selectingcontaminants of concern.
- Toxic Chemical Release Inventory (TRI) Search Information
To identify nearby facilities that may currently contribute to the contamination of air, soil, andwater near and/or on-Site, MDH searched the Toxic Release Inventory (TRI) for 1987 through1991 (10). TRI is developed by the EPA from the chemical release (air, water, and soil)information provided by certain industries.
TRI did not contain information on toxic chemical releases in either St. Louis Park or theneighboring city of Hopkins that could have contributed to the documented contamination (PAHsand phenolics) either on-Site or in investigated areas off-Site. Chemicals released by reportingfacilities in these communities were: Freon 113, sodium hydroxide (solution), sulfuric acid,acetone, toluene, xylene, trichloroethylene, and 1,1,1-trichloroethane. All these releases wereinto the air.
Groundwater samples collected from on- and off-Site locations were/are routinely analyzed forcarcinogenic PAHs and "other" PAHs. There are nine carcinogenic and twenty-three other PAHslisted in the CD-RAP. A listing of these PAHs can be found in Appendix 3 of this Public HealthAssessment. Total PAH is the sum of carcinogenic PAH plus other PAH. The concentrations ofbenzene-extractable compounds and phenol(ics) were used as a gross indicator of the relativeamount of coal tar-derived wastes present in the media.
For this Public Health Assessment, on-Site is defined by the borders established by the CD-RAP(see Figure 1).
- 1. Subsurface Soil
In 1975/1976 eight soil borings were made to depths ranging from 45 to 75 feet below ground(FBG) to collect soil samples for analysis of benzene-extractable compounds and phenol (11). Typically, a total of 7 to 14 soil samples were collected from each boring (one at each five-footinterval) beginning at 5 FBG. Two borings (SB 1, SB 2) were randomly placed in the northernportion of the Site; the other six borings (SB 3,4,5,6, and SB 13, SB 14) were specifically placedin areas suspected of being saturated with coal tar derivatives during the operation of the plant(generally in the south-central portion of the Site).
- Soil Borings 1 and 2
Benzene-extractable compounds were detected (range: 65 mg/kg-soil to 2865 mg/kg-soil) in19/21 soil samples obtained from SB 1 (boring depth = 74 feet) and SB 2 (depth = 45 feet). Thehighest concentrations were generally detected in samples taken from 5 to 15 FBG. Phenol wasdetected (range: 0.2 mg/kg-soil to 1.3 mg/kg-soil) in 11/21 soil samples. Phenol was detected inall seven samples taken from SB 2.
- Soil Borings 3, 4, 5, 6, 13 and 14
Benzene-extractable compounds were detected (range: 60 mg/kg-soil to 188,400 mg/kg-soil) in63/82 soil samples obtained from these borings. The first samples were taken at 2.5 FBG in allthe borings and sampling continued to 60 FBG in SB 4, 13, and 14, and to 70 FBG in SB 3, 5,and 6. The highest concentrations of these compounds were detected in soil samples taken from2.5 to 20 FBG, and were generally detected throughout the depth of all the borings. Phenol wasdetected (range 0.2 mg/kg-soil to 209 mg/kg-soil) in 56/82 soil samples. The highestconcentrations of phenol were detected in soil samples taken from 2.5 to 10 FBG, and weregenerally detected throughout the depth of the borings.
A Petroleum Tank Release Investigation performed from 1988 to 1990 characterized thechemical contamination of soils and fill in the SE portion of the Site (east of LouisianaAvenue)(12). Six soil borings (drilled to depths of 11 to 41 feet) and six test trenches (excavatedto a depth of less than 10 feet) were completed as part of this study. Soil samples collected fromthe borings and test trenches were analyzed for petroleum products. The analytical results fromsamples taken from borings (S1, S2, S3) and trenches (T1, T2) are given below:
|Soil Sample Number||S1||S2||S3||T1|
|Sample Depth (FBG)||7-8||15-20||10-11||6.0||5.5|
|as fuel oil||33000||120||490||25000||33000|
- 2. Sediment
Sediment in the on-Site storm water retention pond has not been sampled for the presence ofeither organic or inorganic contaminants.
- 3. Surface Water
The National Pollutant Discharge Elimination System (NPDES) program is the national programfor issuing, monitoring and enforcing permits for direct discharges of pollutants to surfacewaters. The NPDES permit program was established under the federal Clean Water Act (CWA)which has as it's objective to restore and maintain the chemical, physical, and biological integrityof the nation's waters. Thus, NPDES permits are not issued to be protective of human health. An NPDES permit has been issued for the discharge of water from the on-Site storm waterretention pond (Oak Lake)(13,14). The concentrations of PAHs and phenolics released underthis permit have not exceeded the NPDES permit limits given below:
|Chemical||Daily Maximum Concentration||30-Day Average Concentration|
|Carcinogenic PAHs||--||311 ng/L*|
|Other PAHs||34 ug/L||17 ng/L|
|Phenanthrene||2 ug/L||1 ug/L|
- 4. Groundwater
On-Site groundwater monitoring data is discussed by aquifer:
One on-Site Drift well (W-6) and two on-Site Platteville wells (W-22, W-27) were sampledduring the RI of the Drift-Platteville aquifer Northern Area (13). Groundwater samples wereanalyzed for carcinogenic PAHs (cPAHs), other PAHs (oPAHs), and phenolics (P). Samplingtook place during 7/88 and 10/88. The analytical results are presented below:
|Chemical Concentrations (ug/L)|
No monitoring data are available for wells W-6, W-22, and W-27 for either 1989 or 1990.
- Prairie du Chien-Jordan
|Sampling Date||Total PAH (ng/L)|
|First Quarter 1989||120,200|
|Second Quarter 1989||117,600|
|Third Quarter 1989||106,300|
|Fourth Quarter 1989||No Data Available|
|First Quarter 1990||129,100|
|Second Quarter 1990||No Data Available|
|Third Quarter 1990||114,700|
|Fourth Quarter 1990||68*|
|First Half of 1990|
|Total Carcinogenic PAH = 0 ng/L|
|Total Other PAH = 2347 ng/L|
|Total Phenolics = 0 ug/L|
|Second Half of 1990|
|Total Carcinogenic PAH = 0 ng/L|
|Total Other PAH = 2600 ng/L|
|Total Phenolics = 0 ug/L|
There are no St. Peter or Mt. Simon-Hinckley wells on-Site.
- 5. Ambient Air
Air monitoring for organic vapors (using an HNu meter) took place from June through October,1991 at the perimeter of the Louisiana Avenue/Highway 7 construction zone. There were noreported organic vapor measurements above background at any sampling point during thatsampling period. On July 2, 1991, one upwind and two downwind 10-hour air samples werecollected in an area south of Walker St. and north of Highway 7 using personal air samplers Thesamples were analyzed for semivolatile organic compounds listed on the U.S. EPA TargetCompound List; chemicals on this list include phenolics, carcinogenic PAHs, andnoncarcinogenic PAHs. None of these chemicals was found above the reportable detection limit.
- 1. Subsurface Soil
In 1975/1976 six soil borings were made to depths ranging down to 45 to 75 FBG to collect soilsamples for analysis of benzene-extractable compounds and phenol (11). Typically, a total of 7to 14 soil samples were collected from each boring (one at each five-foot interval) beginning at 5FBG. Two borings (SB 8, SB 12) were placed in the lowland area directly south of the Site; theother four borings (SB 7,9,10,11) were specifically placed in areas south of the Site where wastedrainage was thought to have occurred. All borings were made within 1250 feet of the Site.
- Soil Borings 8 and 12 (Lowland area south of the Site)
Benzene-extractable compounds were detected (range: 65 mg/kg-soil to 140,000 mg/kg-soil) in30/31 soil samples obtained from SB 8 (boring depth = 71 feet) and SB 12 (depth = 65 feet). Thehighest concentrations were generally detected in samples taken from 2 to 20 FBG. Phenol wasdetected (range: 0.2 mg/kg-soil to 171 mg/kg-soil) in 25/31 soil samples. Concentrations ofphenol were highest in samples taken from 2 to 9 FBG.
- Soil Borings 7,9,10 and 11 (Drainage area south of the Site)
Benzene-extractable compounds were detected (range: 55 mg/kg-soil to 307,000 mg/kg-soil) in51/57 soil samples obtained from these four borings. The first samples were taken at 2 FBG inborings SB 9 and SB 11 and at 5.0 FBG in SB 7 and SB 10. Sampling continued to 45 FBG inSB 7, and to 60-70 FBG in SB 9-11. The highest concentrations of these compounds weredetected in soil samples taken from 2 to 30 FBG, and were generally detected throughout thedepth of all the borings. Phenol was detected (range 0.2 mg/kg-soil to 1500 mg/kg-soil) in 41/57soil samples. The highest concentrations of phenol were detected in soil samples taken from 2 to8 FBG.
In response to a reported petroleum release, an investigation of off-Site near surface soilcontamination was conducted in 1988 (17). A total of 15 shallow soil borings were made in anarea south-southeast of the Site (ranging from 500 to 2500 feet from the Site) along the formerpath of waste water drainage to Minnehaha Creek. One soil sample from each boring, along withten other obviously contaminated (smell and/or visual inspection) samples, were analyzed forbenzene-extractable compounds and phenolics. The vast majority of samples selected forchemical analysis were obtained from depths of greater than 9 FBG.
The concentration of benzene-extractable compounds ranged from < 50 mg/kg-soil to 14,000 mg/kg-soil, with typical concentrations in the range of 50 to 500mg/kg-soil. Eleven of the twenty-five samples has concentrations of benzene-extractables of <100 mg/kg-soil; nine had concentrations between 100 and 1000 mg/kg-soil. The concentrationsof phenolics ranged from < 0.2 mg/kg-soil to 0.50 mg/kg-soil; twenty samples had concentrationsof phenolics below the limit of detection (0.2 mg/kg-soil).
- 2. Sediment
- 3. Surface Water
An NPDES permit has been issued for the discharge of water from the off-Site storm waterretention pond (South Oak Lake)(13, 14). The concentrations of PAHs and phenolics releasedunder this permit have not exceeded the NPDES permit limits given below:
|Chemical||Daily Maximum Concentration||30-Day Average Concentration|
|Carcinogenic PAHs||--||311 ng/L*|
|Other PAHs||34 ug/L||17 ng/L|
|Phenanthrene||2 ug/L||1 ug/L|
- 4. Groundwater
Off-Site groundwater monitoring data is discussed by aquifer:
|Total PAH (ug/L)||3949||2430||3143||3027|
|Total PAH (ug/L)||74||59||88||61|
|Total PAH (ug/L)||1416||714||1409||1142|
The concentrations of total PAHs and phenolics in individual Drift and Platteville wells remainedrelatively constant in 1990.
- St. Peter Aquifer
|Total PAH (ng/L)|
|Round 1||Round 2|
|Sum of benzo(a)pyrene + dibenz(ah)anthracene (ng/L)||0||0|
|Sum of other Carcinogenic PAHs (ng/L)||4.5||1.3|
|Sum of Other PAHs (ng/L)||28.9||17.7|
- Prairie du Chien-Jordan
b Concentration sum of carcinogenic PAHs (ng/L)
c Concentration sum of other PAHs (ng/L)
d (-) = Not sampled for this particular group of PAH(s)
|Sampling Date||Carcinogenic PAH |
ND = Not Detected
NS = Not Sampled
Treated water obtained from SLP 10 and 15 on 12/27/90 was also analyzed for an extended listof PAHs (seven compounds including 3-methylcholanthrene, 7,12-dimethylbenz(a)anthracene,and dibenzo(a,e)pyrene). None of the seven PAHs was detected.
As a result of the detection of increased levels of other PAH in the discharge water on 12/27/90,the activated carbon of the GAC treatment unit was replaced.
The only Ironton-Galesville well sampled for Site-related contaminants is located on-Site andwas discussed in the previous section.
- Mt. Simon-Hinckley
|Sum of B[a]P |
|Concentration Sum of Conc. |
Carcinogenic PAH (ng/L)
|Sum of Other|
|SLP 11||Not Sampled||Not Sampled||Not Sampled|
Groundwater samples taken for PAH analysis are obtained directly from the individual sourcewell(s); there is no analysis for PAHs after the water from the source wells is routed to the St.Louis Park municipal water supply and distribution system. Thus, the actual concentration ofPAHs in the water obtained from residential taps is not known.
The data supplied are adequate to conduct a Public Health Assessment for the Reilly Tar andChemical Corporation site. Sample collection, chain-of-custody, laboratory analytical methods,calibration and preventive maintenance of instruments, internal quality control, data reductionand validation, audits, and data-precision assessment were reviewed by MPCA QA/QC staff andfound to be in accordance with procedures outlined in the CD-RAP and associated work plans.
The only potential physical hazard observed at the Site is the exposed debris (rocks, rotted wood,and pieces of bricks, cement and asphalt) on the hill in the SW portion of the Site. This situationmay be hazardous to children if they play on the hill since the Site is now used as a park, and thehill is totally accessible.
A completed exposure pathway consists of the following five elements: 1) a source ofcontamination (that is, a source that is releasing contaminants into the environment, 2)environmental media (groundwater, surface water, air, soil, etc.), 3) a point of exposure (a pointof human contact with the contaminated environmental medium such as a well or playground), 4)a route of exposure (ingestion, inhalation, skin contact), and 5) a receptor population (peoplebeing exposed at a point of exposure).
Data have been presented showing that the Drift, Platteville, St. Peter, Prairie du Chien-Jordan,Ironton-Galesville, and Mt. Simon-Hinckley aquifers are contaminated to varying degrees withPAHs and/or phenolic compounds.
Contaminants present in both on- and off-Site subsurface soils have leached, and may still beleaching into the underlying aquifers. Downward migration of chemical contaminants fromshallow to deeper aquifers is facilitated by hydrogeological connections between aquifers, buriedbedrock valleys, and unknown multi-aquifer wells. However, the St. Lawrence-Franconia andEau Claire confining layers effectively prevent the downward movement of contaminants into thetwo deepest regional aquifers (Ironton-Galesville and Mt. Simon-Hinckley).
There is the potential for the contaminants to move further away from the Site along the path ofregional groundwater flow (which is generally east-southeast). The installation of source andgradient control wells both on- and off-Site should, however, significantly limit this movement.
The city of St. Louis Park obtains its potable water from wells finished in the St. Peter, Prairie duChien-Jordan, and Mt. Simon-Hinckley aquifers (7). The Prairie du Chien-Jordan and Mt.Simon Hinckley aquifers are the primary sources, while the St. Peter is used only during periodsof peak demand. Municipal wells were first sampled for PAHs in 1978; at that time,carcinogenic and non-carcinogenic PAHs were detected in four Prairie du Chien-Jordan wells. Because sampling did not take place prior to 1978, neither the length of time the wells had beencontaminated nor the level of contamination can be determined. Thus, MDH can't evaluate theextent of past exposures to PAHs in drinking water or potential health impacts resulting fromexposure. Because certain wells which are currently used to supply the municipal drinking watersystem contain detectable levels of PAHs, it can be inferred that local residents are being exposedto very low levels of PAHs via water ingestion (for further discussion, please see Public HealthImplications). However, the extent of exposure is not known since finished water is not analyzedfor PAHs.
Historical information regarding PAH contamination of private wells is not available.
Results of studies performed at the Site by the U.S. Geological Survey in the early 1980's showedthat the concentrations of phenolics in the groundwater dramatically decreased downgradient ofthe Site (19, 20). They determined that this decrease was largely due to their degradation bybacteria under both anaerobic and aerobic conditions (4, 19, 20).
- Surface/Subsurface Soil of the On-Site Hill
A potential route of human exposure to Site-related contaminants currently exists becausegullying and erosion of the hill (observed during site visits) on the southwestern portion of theSite may be exposing previously inaccessible, contaminated soil. It should be recalled that thishill was formed when visibly contaminated soil and some demolition debris wereexcavated/moved from other parts of the Site in the 1970's. Neighborhood children playing onthe hill and disrupting the cover soil (this portion of the Site is designated as a park) would be themost likely population to be exposed to chemical contaminants by ingestion or dermal contactwith the exposed soils. This hill represents only a small portion of the total on- and off-Site areathat may contain contaminated subsurface soils.
Exposure to non-chemical hazards such as exposed demolition debris on the hill may alsopotentially occur.
- On-Site Subsurface Soil (Excluding the Hill)
The results of very limited sampling efforts have shown that on-Site subsurface soils arecontaminated with Site-related chemicals. A large portion of the Site to the west of LouisianaAvenue is currently used as a park; there are also three rental apartment/town home complexes inthis area of the Site. The contaminated subsurface soil in these areas may be made accessible tocontact during normal, everyday activities such as during soccer games, or other sportingactivities at the park and children digging in the soil both at the park and in the yards of the rentalproperties. Thus, there is the potential for persons (most likely children) to be exposed tocontaminants in the subsurface soil, primarily via skin contact and incidental ingestion ofcontaminated soil on hands/fingers, etc.
- Off-Site Subsurface Soil
Site-related chemicals have been detected in off-Site subsurface soils in areas south of the Sitewhere contaminated waste water pooled after being discharged from the Site, and along theformer drainage pathways leading from these discharge points to the area near Minnehaha Creek. The possibility of significant human exposure to Site-related chemicals either by ingestion orinhalation of contaminated subsurface soil, or dermal contact with the off-Site subsurface soils isconsidered to be small because this area is occupied by established light industrial facilities andbusinesses having limited access (for example, fences) and access to subsurface soil itself wouldbe limited because of the buildings, parking lots, and roads associated with these industrialfacilities and businesses. In addition, under certain environmental conditions, microbialmetabolism of PAHs and phenolics may play a major role in decreasing their concentrations insoil.
Exposure to contaminated subsurface soils excavated during the construction of the LouisianaAvenue/Highway 7 interchange is also estimated to be minimal. The excavated soils from thisconstruction were kept in this area; however, they were placed on a liner, covered, and a fenceput around them to minimize contact with them.
Sediment in the on-Site pond (Oak Pond) has not been sampled for contaminants. Off-Sitesediments in the vicinity of the Site have not been shown to contain elevated levels of chemicalcontaminants.
Neither ingestion nor dermal contact with sediment are considered to be routes of humanexposure to Site-related contaminants because: 1) of the inaccessibility of the on-Site sediment(slope of the banks of the pond and tall grasses), 2) the on-Site storm water retention pond is notused for swimming or wading, thus eliminating the potential for dermal contact and 3) samplingdata have not shown sediments in off-Site surface waters in the vicinity of the Site to becontaminated. In addition, biological and non-biological degradative processes occurring insediments, and their associated aquatic environments (prior to adsorbing to sediments), willreduce concentrations of certain PAHs and phenolics, if present (22, 23, 19, 20, 4). For example,microbial degradation within sediment may be an important route of degradation for two- andthree-ringed PAHs (naphthalenes, phenanthrene, anthracene), and for phenolics such as phenol,2-methylphenol, and 3-methylphenol.
- Surface Water
The concentrations of PAHs and phenolics in water discharged to on- and off-Site surface watershave been below NPDES surface water discharge limits outlined in the CD-RAP. Depending onenvironmental conditions, PAHs and phenolics are degraded in aquatic environments bymicrobial and algal metabolism, and by chemical processes such as photooxidation and chemicaloxidation (22, 23, 25, 27).
Neither ingestion nor dermal contact with surface water are considered to be routes of humanexposure to Site-related contaminants because: 1) sampling data have not shown either on- oroff-Site surface waters to be contaminated at levels at or above surface water discharge criteria,2) the off-Site retention pond is relatively inaccessible and unappealing, 3) the on-Site stormwater retention pond is not used for swimming or wading, 4) the waters are not used as drinkingwater supplies, and 5) PAHs and phenolics are degraded in aquatic environments by microbialand algal metabolism and chemical processes such as photooxidation and chemical oxidation.
Ambient air was sampled during phases of the construction of the Louisiana Avenue/Highway 7interchange in 1991. No volatile organic compounds, phenolics, carcinogenic PAHs, ornoncarcinogenic PAHs were detected at the perimeter of the construction zone.
Site-related chemicals such as PAHs or phenolics are not expected to volatilize (becomeairborne) from the subsurface soil to a significant degree. However, if limited volatilization wereto occur (possible for the low molecular weight PAHs such as anthracene, fluorene, andphenanthrene), degradation via photooxidative occurs fairly readily (atmospheric half-lives ofPAHs are generally less than 30 days) (22). In addition, the concentrations of volatilizedcontaminants would be significantly reduced because of dilution with ambient air.
Thus, inhalation of ambient air in the vicinity of the Site is not considered to be a route ofexposure to Site-related contaminants.
The Site is surrounded by residential areas, light industrial/business areas, and park areas. Site-related contaminants (PAHs and phenolics) can be taken up from water, sediment, and food byaquatic organisms and by terrestrial animals through the food chain or ingestion of sediment andsoil (22). However, the metabolism of PAHs and phenolics in biota renders them more watersoluble and more excretable; accumulation in tissues may occur to a limited degree but is notconsidered to be a significant process. Because of this, it is very unlikely that there would be anysignificant exposures to humans ingesting these biota (for example, geese or ducks). Ingestion ofbackyard-grown fruits and vegetables watered with municipal water is also considered to be aninsignificant route of exposure to Site contaminants because of: 1) the very low levels ofcontaminants (especially PAHs) in the water, 2) the generally low solubility of PAHs in water, 3)the dilution and possible degradation of PAHs within the St. Louis Park water supply anddistribution system prior to household use, 4) degradation of both phenolics and PAHs in theaquatic environment, 5) the insignificant amount of water that would come into contact with theplants in comparison to the amount of contaminants taken in via ingestion of water, and 6) thegenerally low level of plant uptake of PAHs (PAHs which bind fairly strongly to soils) (22). Inaddition, any PAHs that accumulate on the surface of the produce will be removed during normalfood washing prior to preparation.
As discussed earlier, there is the potential for anyone (for example, children) either playing oncertain parts of the hill or disrupting the surface soil of the hill in the SW portion of the Site to beexposed Site-related chemicals. At this time, one may presume that chemical contaminants arepresent in the subsurface soil since visibly contaminated soil excavated from other portions of theSite make up a very large portion of this hill. Exposure could now presumably occur becauseparts of the hill have gullied and eroded (observed on site visits), and exposed subsurface soil. These processes have also exposed various potential physical hazards (wood, bricks, etc.). Localresidents are also exposed to very low levels of PAHs via ingestion of and possibly dermalcontact with municipal drinking water. Exact PAH exposure concentrations can't, however, beestimated because residential water sampling (at the tap) is not done. Persons playing on the hillmay also come into contact with the physical hazards.
Human exposure to very low levels of PAHs via drinking water requires further discussion. Oneprovision of the CD-RAP requires that each well that may be affected by contaminants from theSite, and which is used to supply area residents with drinking water, be monitored for thepresence of PAHs. Monitoring is performed, depending on which aquifer the well draws waterfrom, either annually, twice yearly, or quarterly. The results of this PAH monitoring are dividedinto three categories in the CD-RAP: (1) the concentration sum of benzo(a)pyrene anddibenz(a,h)anthracene (both are known to produce cancer in animals following ingestion of highdoses), (2) the concentration sum of nine additional carcinogenic PAHs (listed in Appendix 3),and (3) the concentration sum of twenty-three other PAHs (listed in Appendix 3). Theconcentration sum from each of the three categories is then compared to a pre-set Drinking WaterCriterion value established for each of the three categories. These Drinking Water Criteria werederived through a joint effort between the MDH, MPCA, and EPA. The Criteria are defined asthe recommended maximum permissible concentrations of PAHs in drinking water whichprovide for the protection of human health.
However, for maximum protection of human health from potential carcinogenic effects due toexposure to PAHs by ingestion of contaminated drinking water, the Drinking Water Criteria forPAHs in categories (1) and (2) should be equal to 0 ng/L based on the non-threshold assumptionfor carcinogens. Under the non-threshold assumption, zero risk for a carcinogenic response onlyoccurs only at zero dose. Because reaching the zero concentration level may not be attainable orfeasible, the Drinking Water Criteria for the carcinogenic PAHs (categories 1 and 2) were set tocorrespond to an incremental lifetime cancer risk level of 1 in 100,000 (10-5). The cancer risklevel provides an estimate of the additional incidence of cancer that may be expected in anexposed population. For example, if exposure to a chemical at a certain concentration isassociated with an estimated risk level of 10-5, there exists the probability that one additionalcancer case will occur for every 100,000 persons exposed to the chemical at this concentration.
|Category||Drinking Water Criterion|
|(1)||Sum of benzo[a]pyrene and |
|(2)||Sum of carcinogenic PAH||28 ng/L|
|(3)||Sum of other PAH||280 ng/L|
The Drinking Water Criteria for categories (1) and (2) correspond to an estimated lifetime cancerrisk of 10-5 if 2 liters of water (containing PAHs at the Criterion level) are ingested daily for 70years. The Drinking Water Criterion value for category (3) was not based on potentialcarcinogenic effects of PAHs, but rather for their potential to: 1) modify the toxicity of the PAHsin categories (1) and (2), 2) interfere with the analytical detection of the PAHs in categories (1)and (2), and 3) cause non-cancerous toxic effects.
Compliance with the Drinking Water Criteria are determined at the point at which the water inquestion is introduced into the water supply distribution system (before dilution with water fromany other supply source well). The Commissioner of the MDH may require that the use of anydrinking water supply well whose water exceeds any of the three Drinking Water Criteria, asdetermined by provisions of the CD-RAP, be discontinued until such time as the Drinking WaterCriteria are met by treatment or other means. At present, two of the drinking water supply wells(SLP 10 and SLP 15) have GAC treatment systems to remove PAHs.
As noted earlier, groundwater samples taken for PAH analysis are obtained directly from theindividual source wells; there is no analysis for PAHs after the water from the source wells isrouted to the St. Louis Park municipal water supply and distribution system. Prior to its arrival atthe tap, the water in the supply and distribution system may undergo chemical and physicaltreatment (for example aeration, chlorination, fluoridation), remain in storage (tanks and/or watermains) for variable periods of time, and be mixed with water from other source wells which donot contain PAHs (this will lower the concentration of the contaminants in the water supplybecause of dilution). Each of these steps may have an impact on the concentration of PAH(s) towhich an individual may be exposed.
The purpose of the following toxicological summary is to provide information about potentialhuman health effects that may result from exposure to PAHs. However, it is important to realizethat several factors determine whether or not harmful effects will occur and their severity if theyoccur. These factors include: the dose of the chemical (that is, the amount taken into the body),the length of exposure to the chemical, the route of intake of the chemical (for example, ingestionor inhalation), simultaneous exposure to other chemicals (for example drugs, environmentalpollutants, or chemicals in the workplace), and individual characteristics such as age, sex,nutritional status, family traits (genetics/heredity), and general state of health.
- Polycyclic Aromatic Hydrocarbons (PAHs)
PAHs are found everywhere in the environment (22). The primary source of many PAHs in air isthe incomplete combustion of wood and fuels; thus, PAHs are products of such common sourcesas motor vehicles (exhaust), wood burning stoves and furnaces, cigarette smoke, industrialsmoke and soot, and charcoal-broiled foods (22). PAHs found in the wood preservative creosoteinclude chrysene, naphthalene, phenanthrene, fluoranthene, pyrene methylnaphthalenes,acenaphthene, and anthracene (21). Most human exposure is to a mixture of PAHs, as opposedto a single PAH compound.
There are essentially no experimental or clinical data that provide evidence for a directassociation between human exposure (ingestion, inhalation, or skin contact) to individual PAHsand adverse health effects (22). Therefore, in order to try to predict adverse responses in humansfollowing exposure to PAHs, toxicologists must rely on reported effects in humans (primarilycancer) after exposure to complex mixtures of PAHs and on information derived from animalstudies in which high doses of PAHs were administered. However, even when animal studies arereviewed, it is evident that there are very little data on the potential non-carcinogenic andcarcinogenic effects of many PAHs (22, 26-29). The carcinogenic PAH benzo[a]pyrene (B[a]P)has been the most-studied PAH in animals, and the toxicity of it and other PAHs in humans isoften inferred from its toxicity (22,30). The following profile on PAHs discusses thecarcinogenic and non-carcinogenic effects of PAHs when data are available.
PAHs are absorbed following ingestion, inhalation, and skin contact in both humans andlaboratory animals (22, 31). Orally administered B[a]P, benz[a]anthracene, chrysene, anddibenz[a,h]anthracene primarily distribute to blood, liver, lung, and kidney (22, 26-28, 30).
The non-carcinogenic PAH naphthalene has produced nausea, vomiting, abdominal pain,diarrhea, and even death when ingested in large doses following suicide attempts and accidentalingestion of naphthalene-containing mothballs by children (33).
Orally administered B[a]P at 120 mg/kg-day for 180 days produced adverse effects on the bonemarrow of mice (30). These effects included a decrease in all types of blood cells and aplasticanemia. B[a]P has also been shown to cause allergic reactions when applied to the skin of mice(30). Oral administration of certain PAHs has been shown to cause changes in liver function inlaboratory animals; these changes are not considered to be serious (22, 30). Naphthalene has notbeen shown to cause liver toxicity in rats following ingestion (33). PAHs have not been shownto be toxic to the kidneys of laboratory animals following ingestion (33).
There are no studies available on either the reproductive or developmental effects (that is, theproduction of birth defects) of either B[a]P or any other PAH in humans (22, 30, 33). The resultsof two ingestion studies using experimental animals suggest that exposure during pregnancy tovery large doses of B[a]P is associated with an impairment of reproductive ability and theproduction of birth defects (30). No birth defects were observed in offspring of mice or rabbitsfollowing oral administration of naphthalene during pregnancy (33).
The vast majority of the research on the health effects of PAHs has focused on their ability tocause cancer. When ingested by mice and rats, the PAHs benzo[a]pyrene benz[a]anthracene,dibenz[a,h]anthracene, and 7H-dibenzo[c,g]carbazole induced liver, lung, forestomach and breasttumors (32). Naphthalene has not been shown to be carcinogenic in humans or experimentalanimals (33).
Dermal exposure to shale oils and coal tar (which contain PAHs in addition to other carcinogens)has been associated with an increased incidence of skin tumors in workers (34, 35). Workersexposed by skin contact to creosote (composed primarily of PAHs) have also developed skintumors (32). When applied to the skin, all fifteen PAHs listed below induced skin tumors infemale mice or in mice of both sexes.
Not all these PAHs have been detected at the Site.
In 1979, the MDH Division of Disease Prevention and Control compared the cancer incidencerates in St. Louis Park with those of three other areas (the cities of Edina and Richfield and theMinneapolis-St. Paul SMSA). The incidence rates for 45 types or sites of cancer were calculatedfor the three cities and the SMSA using data from the Third National Cancer Survey for the years1969 to 1971. Incidence rates were age-adjusted to the SMSA populations of white males andfemales. Calculations were done of average and annual age- and sex-specific cancer incidencerates, age-adjusted incidence rates, standard incidence ratios (SIR). Chi-square and Z-statisticswere used to assess the significance of rate differences.
For males, cancer rates in St. Louis Park were not significantly different from those in the threecomparison areas. For St. Louis Park females, the age-adjusted rates for all cancers combinedand breast cancer were significantly higher (P < 0.0005), and that for cancer of the gastrointestinal tract only slightly increased (P < 0.05)when compared to each of the other three areas.
Following the completion of this 1979 epidemiological study, attention was focused on thestatistically significant increase in the incidence of breast cancer in St. Louis Park females. Possible reasons for this observed increase were outlined by MDH (6). For example, it is knownthat breast cancer rates vary considerably both with geographic location and populationcharacteristics. In addition, risk factors known to be associated with an increase breast cancerrates are: having a first degree relative with breast cancer, history of fibrocystic disease of thebreast, upper socio-economic class, obesity, early age at menarche, and late age at menopause.
Because PAH exposure doses were not known, and the contribution of various risk factors to thedifference in breast cancer rates between St. Louis Park and the comparison areas couldn't beevaluated without further information about the individual cases, the increased incidence ofcancer could not be attributed to ingestion of PAH-contaminated water (36). However, thelimited information available at that time did not rule out an association between water ingestionand subsequent breast cancer development.
In early 1984, the Minnesota Legislature authorized funding to evaluate the feasibility ofconducting a community-based epidemiologic study to address adverse health outcomes (such asbreast cancer) which might be related to ingestion of contaminated drinking water in St. LouisPark (36). The 18-month MDH evaluation, which was conducted in conjunction with theUniversity of Minnesota School of Public Health, concluded such an epidemiological study wasnot feasible or scientifically defensible because of the following issues: 1) no valid assessment ofindividual exposure was possible due to considerable uncertainty about historical distribution ofcontaminants and no reliable measure of cumulative exposure to PAHs, 2) the continuous non-water exposures to PAHs could not be measured reliably, and their effects could not bedistinguished from possible exposure via water, and 3) there existed no means to identify andcontrol the wide variety of factors which could confound or modify any association (apparent orreal) between the presumed PAH exposure of interest and particular health outcomes. These andother considerations led MDH to conclude that it was very unlikely that any type of study wouldbe able to directly address the impact of ingestion of PAH-contaminated water and subsequentcancer development.
The local community has had various complaints regarding the Site since the 1930's. However,specific concerns regarding human health effects of contaminants from the Site arose in the late1970's and early 1980's when six St. Louis Park municipal wells had to be closed down becauseof contamination with PAHs. In addition, an epidemiological study performed during this timereported that the rates for breast cancer were higher in St. Louis Park females when compared tofemales in each of three other study areas.
Municipal wells that are used to supply residents with drinking water are closely monitored forPAHs in accordance with the 1986 Consent Decree-Remedial Action Plan instituted for the Site. Under this monitoring program, the concentrations of both carcinogenic and non-carcinogenicPAHs are compared to pre-set Drinking Water Criteria which were established through a jointeffort between MDH, MPCA, and EPA. These criteria are defined as the recommendedmaximum permissible concentrations of PAHs in drinking water which provide for theprotection of human health. As long as the concentrations of PAHs in these wells remain belowthe Criteria, exposure to them via drinking water use is not of public health concern. Ifconcentrations of PAHs in any well exceed these Criteria, the Commissioner of the MDH canrequire that its use be discontinued until the Criteria can be met (for example by treatment orother means). In addition, there are "Advisory" levels for the PAHs that are set below theDrinking Water Criteria (thus, they are more strict than the Criteria Levels). If PAHconcentrations reach these Advisory levels, the well(s) is more closely monitored for PAHs toassure that levels do not approach the Criteria levels.
In a 1985 report to the Minnesota Legislature entitled "Feasibility of Community-WideEpidemiologic Studies of Drinking Water and Health: St. Louis Park & New Brighton", theMDH concluded that it was unlikely that the observed excess of breast cancers in St. Louis Parkin 1969-1971 (see reference 6) could be related to [ingestion of] water contaminants. The MDHreached this conclusion after critical analysis of a number of findings/factors including: 1) thespecific PAHs that had been shown to induce mammary tumors in rodents were either not presentin contaminated wells, or were detected very rarely even in the most highly contaminated wells,2) published epidemiologic studies had not demonstrated clear evidence of an associationbetween breast cancer and smoking (a substantial exposure to many PAHs occurs duringsmoking), 3) epidemiologic studies of breast cancer had identified a number of risk factors thatcould account for some of the observed variations in cancer rates among different groups ofwomen, and 4) there is a latency period, usually anywhere from 10 to 30-40 years, between onsetof exposure and diagnosis of cancer; thus, cancer cases observed during 1969-1971 may havebeen related to events that occurred decades earlier.
More recently, epidemiological data have shown a rise in the incidence of breast cancer in theU.S. from the late 1970's through the decade of the 1980's (37). While this increase may beassociated with occupational and/or environmental exposures to chemicals, again, otherexplanations put forward such as an increase in the prevalence of suspected risk factors and/orincreased detection of cancer cases.
A fact sheet summarizing the available information about the Reilly Tar & Chemical Corporationsite was written by the Minnesota Department of Health in March, 1992 and mailed to interestedparties. A copy of this fact sheet is included in this Public Health Assessment as Appendix 4.
Lastly, the Site is still being cleaned-up under provisions put forward in the Remedial ActionPlan of the Consent Decree. This is important because these measures are intended tosignificantly reduce or prevent further contamination of area groundwater with Site-relatedcontaminants such as PAHs.