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 for further evaluation. Chemicals listed in this section will be discussed and further evaluated in subsequent parts of the public health assessment. It is important to note that the inclusion of chemicals in this section does not necessarily imply that they pose a threat to human health. This section focuses on those chemicals found either on-site or off-site that were selected as contaminants of concern based on the following considerations:
1) To assist in selecting contaminants which produce noncarcinogenic toxic effects, ATSDR developed environmental media evaluation guides (EMEGs). EMEGs are media-specific (for example, air, water and soil) and are derived from estimates of daily doses of a chemical that humans may take in, over a specified period of time, that are unlikely to produce adverse health effects. Briefly, the environmental concentration of each chemical is compared to the appropriate EMEG 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 environmental concentration is less than the EMEG, exposure to the contaminant in that medium (air, soil or water) is unlikely to pose a public health hazard. EMEGs for Site contaminants are given in Appendix 1.
2) Cancer risk evaluation guides (CREGs) are media-specific comparison values that are used to select chemicals which produce carcinogenic effects. CREGs are calculated using EPA-derived cancer potency factors. Media-specific CREG values are defined as the estimated contaminant concentration that will result in one excess cancer in a million persons continuously exposed over lifetime. CREGs are used in exactly the same way as are EMEGs. CREGs for Site contaminants are listed Appendix 1.
3) Chemicals found in groundwater are considered to be chemicals of concern and are included in this evaluation if their concentrations exceed health-based Recommended Allowable Limits (RALs) developed by MDH for contaminants in private drinking water supplies. RALs are derived for those chemicals which are most frequently found in Minnesota's groundwater. RALs for noncarcinogens are often taken from current Drinking Water Health Advisories published by EPA 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 an estimated lifetime excess cancer risk of 1 in 100,000. RALs for Site contaminants of concern are given 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 to derive RALs. HRLs will soon be adopted as Minnesota rules and will thus become enforceable by law.
4) Chemicals detected in other media (for example soil and air) are included as chemicals of concern for further evaluation if their concentrations exceed media-specific concentrations calculated using risk assessment methodology (for example, ATSDR-derived minimal risk levels (MRLs) or EPA-derived reference doses (RfDs). The concentration values for carcinogens will reflect an excess lifetime cancer risk of 1 in 100,000.
5) Chemicals which do not exceed the comparison values used for selecting contaminants of concern may also present a potential health hazard. These may also be included as chemicals of concern based on professional judgment. There may be a concern when there are low levels of many chemicals (mixtures) because of the unknown consequences of exposure to mixtures. Professional judgement may also indicate a concern exists when exposure may be occurring through more than on route of exposure (for example through inhalation and ingestion) or when there are extenuating circumstances related to known or suspected exposures. Examples of these behaviors include subsistence fishing and pica behavior in children (a craving to ingest soil, paint chips, and other non-food items).
6) Chemicals may also be included as contaminants of concern based upon site-specific information or low confidence in the adequacy and the representativeness of sampling data. For example, releases and movement of chemicals from hazardous waste sites may be unpredictable. Chemicals are often released in pulses and monitoring results may reflect peak concentrations found during pulses or they may reflect lower concentrations between pulses. Therefore, chemicals not found or detected at low concentrations may be detected at much higher concentrations in future sampling events. Additional uncertainty may be the result of geological variability which is typical in Minnesota and the imprecise nature of hydrogeologic characterization.
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 selecting contaminants of concern.
To identify nearby facilities that may currently contribute to the contamination of air, soil, and water near and/or on-Site, MDH searched the Toxic Release Inventory (TRI) for 1987 through 1991 (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 the neighboring city of Hopkins that could have contributed to the documented contamination (PAHs and phenolics) either on-Site or in investigated areas off-Site. Chemicals released by reporting facilities in these communities were: Freon 113, sodium hydroxide (solution), sulfuric acid, acetone, toluene, xylene, trichloroethylene, and 1,1,1-trichloroethane. All these releases were into the air.
Groundwater samples collected from on- and off-Site locations were/are routinely analyzed for carcinogenic PAHs and "other" PAHs. There are nine carcinogenic and twenty-three other PAHs listed in the CD-RAP. A listing of these PAHs can be found in Appendix 3 of this Public Health Assessment. Total PAH is the sum of carcinogenic PAH plus other PAH. The concentrations of benzene-extractable compounds and phenol(ics) were used as a gross indicator of the relative amount 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).
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-foot interval) beginning at 5 FBG. Two borings (SB 1, SB 2) were randomly placed in the northern portion of the Site; the other six borings (SB 3,4,5,6, and SB 13, SB 14) were specifically placed in areas suspected of being saturated with coal tar derivatives during the operation of the plant (generally in the south-central portion of the Site).
Benzene-extractable compounds were detected (range: 65 mg/kg-soil to 2865 mg/kg-soil) in 19/21 soil samples obtained from SB 1 (boring depth = 74 feet) and SB 2 (depth = 45 feet). The highest concentrations were generally detected in samples taken from 5 to 15 FBG. Phenol was detected (range: 0.2 mg/kg-soil to 1.3 mg/kg-soil) in 11/21 soil samples. Phenol was detected in all seven samples taken from SB 2.
Benzene-extractable compounds were detected (range: 60 mg/kg-soil to 188,400 mg/kg-soil) in 63/82 soil samples obtained from these borings. The first samples were taken at 2.5 FBG in all the 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 from 2.5 to 20 FBG, and were generally detected throughout the depth of all the borings. Phenol was detected (range 0.2 mg/kg-soil to 209 mg/kg-soil) in 56/82 soil samples. The highest concentrations of phenol were detected in soil samples taken from 2.5 to 10 FBG, and were generally detected throughout the depth of the borings.
A Petroleum Tank Release Investigation performed from 1988 to 1990 characterized the chemical contamination of soils and fill in the SE portion of the Site (east of Louisiana Avenue)(12). Six soil borings (drilled to depths of 11 to 41 feet) and six test trenches (excavated to a depth of less than 10 feet) were completed as part of this study. Soil samples collected from the borings and test trenches were analyzed for petroleum products. The analytical results from samples taken from borings (S1, S2, S3) and trenches (T1, T2) are given below:
| Soil Sample Number | S1 | S2 | S3 | T1 | T2 | |
| Sample Depth (FBG) | 7-8 | 15-20 | 10-11 | 6.0 | 5.5 | |
| Chemical | Chemical Concentration (mg/kg-soil) | |||||
| Phenol | 800 | 4.0 | <42 | 0.16 | 53 | |
| Benzene | 300 | <0.6 | 0.42 | NT | NT | |
| Toluene | 1400 | 0.91 | 17 | NT | NT | |
| Ethylbenzene | 160 | 3.4 | 41 | NT | NT | |
| Xylene (total) | 1600 | 13 | 93 | NT | NT | |
| Total Hydrocarbons: | ||||||
| as gasoline | 8400 | NT | NT | <2.4 | 5600 | |
| as fuel oil | 33000 | 120 | 490 | 25000 | 33000 | |
| Total PAHs | NT | NT | 1610 | 6600 | 44000 | |
Sediment in the on-Site storm water retention pond has not been sampled for the presence of either organic or inorganic contaminants.
The National Pollutant Discharge Elimination System (NPDES) program is the national program for issuing, monitoring and enforcing permits for direct discharges of pollutants to surface waters. 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 integrity of 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 water retention pond (Oak Lake)(13,14). The concentrations of PAHs and phenolics released under 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 |
| Phenolics | -- | 10 ug/L |
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 sampled during the RI of the Drift-Platteville aquifer Northern Area (13). Groundwater samples were analyzed for carcinogenic PAHs (cPAHs), other PAHs (oPAHs), and phenolics (P). Sampling took place during 7/88 and 10/88. The analytical results are presented below:
| Chemical Concentrations (ug/L) | ||||||
| 7/88 | 10/88 | |||||
| Well | cPAH | oPAH | P | cPAH | oPAH | P |
| W-6 | 610 | 10600 | 10.3 | 1.7 | 1882 | 11.1 |
| W-22 | ND | ND | 0 | NA | NA | NA |
| W-27 | NA | NA | NA | 0 | 678 | 62.5 |
No monitoring data are available for wells W-6, W-22, and W-27 for either 1989 or 1990.
One on-Site Prairie du Chien-Jordan well (W23) is sampled quarterly for PAHs. A summary of the analytical results for W23 from 1989 and 1990 is given below (15, 16):
| 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* |
One on-Site Ironton-Galesville well (W105) is sampled twice yearly for total carcinogenic PAH, total other PAH, and total phenolics. A summary of the analytical results for the 1990 sampling of W105 is given below (16):
| 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.
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 no reported organic vapor measurements above background at any sampling point during that sampling period. On July 2, 1991, one upwind and two downwind 10-hour air samples were collected in an area south of Walker St. and north of Highway 7 using personal air samplers The samples were analyzed for semivolatile organic compounds listed on the U.S. EPA Target Compound List; chemicals on this list include phenolics, carcinogenic PAHs, and noncarcinogenic PAHs. None of these chemicals was found above the reportable detection limit.
In 1975/1976 six soil borings were made to depths ranging down to 45 to 75 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-foot interval) beginning at 5 FBG. Two borings (SB 8, SB 12) were placed in the lowland area directly south of the Site; the other four borings (SB 7,9,10,11) were specifically placed in areas south of the Site where waste drainage was thought to have occurred. All borings were made within 1250 feet of the Site.
Benzene-extractable compounds were detected (range: 65 mg/kg-soil to 140,000 mg/kg-soil) in 30/31 soil samples obtained from SB 8 (boring depth = 71 feet) and SB 12 (depth = 65 feet). The highest concentrations were generally detected in samples taken from 2 to 20 FBG. Phenol was detected (range: 0.2 mg/kg-soil to 171 mg/kg-soil) in 25/31 soil samples. Concentrations of phenol were highest in samples taken from 2 to 9 FBG.
Benzene-extractable compounds were detected (range: 55 mg/kg-soil to 307,000 mg/kg-soil) in 51/57 soil samples obtained from these four borings. The first samples were taken at 2 FBG in borings SB 9 and SB 11 and at 5.0 FBG in SB 7 and SB 10. Sampling continued to 45 FBG in SB 7, and to 60-70 FBG in SB 9-11. The highest concentrations of these compounds were detected in soil samples taken from 2 to 30 FBG, and were generally detected throughout the depth of all the borings. Phenol was detected (range 0.2 mg/kg-soil to 1500 mg/kg-soil) in 41/57 soil samples. The highest concentrations of phenol were detected in soil samples taken from 2 to 8 FBG.
In response to a reported petroleum release, an investigation of off-Site near surface soil contamination was conducted in 1988 (17). A total of 15 shallow soil borings were made in an area south-southeast of the Site (ranging from 500 to 2500 feet from the Site) along the former path of waste water drainage to Minnehaha Creek. One soil sample from each boring, along with ten other obviously contaminated (smell and/or visual inspection) samples, were analyzed for benzene-extractable compounds and phenolics. The vast majority of samples selected for chemical 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 500 mg/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 concentrations of phenolics ranged from < 0.2 mg/kg-soil to 0.50 mg/kg-soil; twenty samples had concentrations of phenolics below the limit of detection (0.2 mg/kg-soil).
Past sampling events have not shown elevated concentrations of either PAHs or phenolics in the sediments of area surface waters (13, 14).
An NPDES permit has been issued for the discharge of water from the off-Site storm water retention pond (South Oak Lake)(13, 14). The concentrations of PAHs and phenolics released under this permit have not exceeded the NPDES permit limits given below:
| Chemical | Daily Maximum Concentration | 30-Day Average Concentration |
| Carcinogenic PAH | -- | 311 ng/L* |
| Other PAH | 34 ug/L | 17 ng/L |
| Phenanthrene | 2 ug/L | 1 ug/L |
| Phenolics | -- | 10 ug/L |
Off-Site groundwater monitoring data is discussed by aquifer:
Two Drift aquifer monitoring wells (W420 and W422) were sampled on a quarterly basis in 1990 for PAHs and phenolics. A summary of the analytical results from 1990 is given below (16):
| Well | Q1 | Q2 | Q3 | Q4 | |
| W420 | |||||
| Total PAH (ug/L) | 3949 | 2430 | 3143 | 3027 | |
| Phenolics (ug/L) | 239 | 231 | 244 | 228 | |
| W422 | |||||
| Total PAH (ug/L) | 74 | 59 | 88 | 61 | |
| Phenolics (ug/L) | 21 | 14 | 14 | 18 | |
One Platteville aquifer well (W421) was sampled on a quarterly basis in 1990 for PAHs and phenolics. A summary of the analytical results from 1990 is given below (16):
| Q1 | Q2 | Q3 | Q4 | |
| Total PAH (ug/L) | 1416 | 714 | 1409 | 1142 |
| Phenolics (ug/L) | 33 | 29 | 36 | 29 |
The concentrations of total PAHs and phenolics in individual Drift and Platteville wells remained relatively constant in 1990.
Eight St. Peter wells were monitored for PAHs in June and October, 1989 and June and August, 1990. The concentration of total PAHs in individual St. Peter wells remained relatively constant from 1989 through 1990. A summary of the analytical results from these two years is given below (16):
| Total PAH (ng/L) | ||||
| Well | 6/89 | 10/89 | 6/90 | 8/90 |
| W33 | NS | NS | NS | 290 |
| W129 | 601 | 40 | 143 | 96 |
| W133 | 37870 | 21370 | 19440 | 14030 |
| W408 | 150 | 110 | 24 | 158 |
| W409 | 630 | 830 | 141 | 243 |
| W411 | 208 | 460 | 466 | 336 |
| W412 | 226 | 130 | NS | 485 |
| P116 | 83 | 43 | NS | 22 |
St. Peter well SLP 3 is one of thirteen area wells used to supply potable water to the city of St. Louis Park. It was sampled twice during 1990 for PAHs. The analytical results from these two sampling rounds are given below (16):
| 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 |
Twenty-five Prairie du Chien-Jordan wells were sampled quarterly (if possible) during 1990 for PAHs. Eight of these wells supply potable water to St. Louis Park. Two (SLP 10 and SLP 15) of the eight wells have a GAC treatment system. The 1990 sampling results for municipal water supply wells without GAC treatment are given below (16):
| Wells without GAC Treatment | PAH (ng/L) | |||
| Q1 | Q2 | Q3 | Q4 | |
| SLP 6 | 0a | 0 | 0 | 0 |
| 0b | 2.6 | 0 | 0 | |
| 44.9c | 79.7 | 117 | 68 | |
| SLP 7 | 0 | 0 | 0 | 0 |
| 0 | 1.6 | 1.5 | 0 | |
| 43 | 47.6 | 91.4 | 48.5 | |
| SLP 8 | 0 | -d | - | - |
| 0 | - | - | - | |
| 15.3 | - | - | - | |
| SLP 9 | - | - | - | - |
| SLP 14 | 0 | - | 0 | - |
| 0 | - | 0 | - | |
| 98 | - | 145 | - | |
| SLP 16 | - | - | - | 0 |
| - | - | - | 0 | |
| - | - | - | 60 | |
As noted above, groundwater pumped from wells SLP 10 and SLP 15 undergoes GAC treatment. GAC-treated water was sampled six times in 1990 for carcinogenic PAHs and other PAHs. The sampling results are given below (18):
| Sampling Date | Carcinogenic PAH Total (ng/L) | Other PAH Total (ng/L) |
| 1/30/90 | 6.2/ND | 217/330 |
| 2/27/90 | NS | NS |
| 3/14/90 | ND/ND | 438/374 |
| 6/26/90 | 1.0/ND | 15/22.9 |
| 9/12/90 | 2.5/2.6 | 72.3/79.8 |
| 12/27/90 | ND/2.8 | 195/191 |
Treated water obtained from SLP 10 and 15 on 12/27/90 was also analyzed for an extended list of 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 and was discussed in the previous section.
Four Mt. Simon-Hinckley wells (SLP 11, 12, 13, and 17) are also among the thirteen wells used to supply potable water to the city of St. Louis Park. These four wells are sampled annually for PAHs. The sampling results from 1990 are given below (16):
| Sum of B[a]P + DB[a,h]Aa | Concentration Sum of Conc. Carcinogenic PAH (ng/L) | Sum of Other PAH(ng/L) | |
| Well | |||
| SLP 11 | Not Sampled | Not Sampled | Not Sampled |
| SLP 12 | 0 | 0 | 108.6 |
| SLP 13 | 0 | 0 | 13.9 |
| SLP 17 | 0 | 1.2 | 15.7 |
Groundwater samples taken for PAH analysis are obtained directly from the individual source well(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 of PAHs in the water obtained from residential taps is not known.
C. Quality Assurance and Quality Control
The data supplied are adequate to conduct a Public Health Assessment for the Reilly Tar and Chemical Corporation site. Sample collection, chain-of-custody, laboratory analytical methods, calibration and preventive maintenance of instruments, internal quality control, data reduction and validation, audits, and data-precision assessment were reviewed by MPCA QA/QC staff and found 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 situation may be hazardous to children if they play on the hill since the Site is now used as a park, and the hill is totally accessible.
A completed exposure pathway consists of the following five elements: 1) a source of contamination (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 point of 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 (people being exposed at a point of exposure).
A. Completed Exposure Pathways
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 with PAHs and/or phenolic compounds.
Contaminants present in both on- and off-Site subsurface soils have leached, and may still be leaching into the underlying aquifers. Downward migration of chemical contaminants from shallow to deeper aquifers is facilitated by hydrogeological connections between aquifers, buried bedrock valleys, and unknown multi-aquifer wells. However, the St. Lawrence-Franconia and Eau Claire confining layers effectively prevent the downward movement of contaminants into the two 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 of regional groundwater flow (which is generally east-southeast). The installation of source and gradient 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 du Chien-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 periods of 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 been contaminated nor the level of contamination can be determined. Thus, MDH can't evaluate the extent of past exposures to PAHs in drinking water or potential health impacts resulting from exposure. Because certain wells which are currently used to supply the municipal drinking water system contain detectable levels of PAHs, it can be inferred that local residents are being exposed to very low levels of PAHs via water ingestion (for further discussion, please see Public Health Implications). However, the extent of exposure is not known since finished water is not analyzed for 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 showed that the concentrations of phenolics in the groundwater dramatically decreased downgradient of the Site (19, 20). They determined that this decrease was largely due to their degradation by bacteria under both anaerobic and aerobic conditions (4, 19, 20).
B. Potential Exposure Pathways
A potential route of human exposure to Site-related contaminants currently exists because gullying and erosion of the hill (observed during site visits) on the southwestern portion of the Site may be exposing previously inaccessible, contaminated soil. It should be recalled that this hill was formed when visibly contaminated soil and some demolition debris were excavated/moved from other parts of the Site in the 1970's. Neighborhood children playing on the hill and disrupting the cover soil (this portion of the Site is designated as a park) would be the most likely population to be exposed to chemical contaminants by ingestion or dermal contact with the exposed soils. This hill represents only a small portion of the total on- and off-Site area that may contain contaminated subsurface soils.
Exposure to non-chemical hazards such as exposed demolition debris on the hill may also potentially occur.
The results of very limited sampling efforts have shown that on-Site subsurface soils are contaminated with Site-related chemicals. A large portion of the Site to the west of Louisiana Avenue is currently used as a park; there are also three rental apartment/town home complexes in this area of the Site. The contaminated subsurface soil in these areas may be made accessible to contact during normal, everyday activities such as during soccer games, or other sporting activities at the park and children digging in the soil both at the park and in the yards of the rental properties. Thus, there is the potential for persons (most likely children) to be exposed to contaminants in the subsurface soil, primarily via skin contact and incidental ingestion of contaminated soil on hands/fingers, etc.
C. Exposure Pathways Eliminated from Consideration
Site-related chemicals have been detected in off-Site subsurface soils in areas south of the Site where contaminated waste water pooled after being discharged from the Site, and along the former 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 or inhalation of contaminated subsurface soil, or dermal contact with the off-Site subsurface soils is considered to be small because this area is occupied by established light industrial facilities and businesses having limited access (for example, fences) and access to subsurface soil itself would be limited because of the buildings, parking lots, and roads associated with these industrial facilities and businesses. In addition, under certain environmental conditions, microbial metabolism of PAHs and phenolics may play a major role in decreasing their concentrations in soil.
Exposure to contaminated subsurface soils excavated during the construction of the Louisiana Avenue/Highway 7 interchange is also estimated to be minimal. The excavated soils from this construction were kept in this area; however, they were placed on a liner, covered, and a fence put around them to minimize contact with them.
Sediment in the on-Site pond (Oak Pond) has not been sampled for contaminants. Off-Site sediments in the vicinity of the Site have not been shown to contain elevated levels of chemical contaminants.
Neither ingestion nor dermal contact with sediment are considered to be routes of human exposure 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 not used for swimming or wading, thus eliminating the potential for dermal contact and 3) sampling data have not shown sediments in off-Site surface waters in the vicinity of the Site to be contaminated. In addition, biological and non-biological degradative processes occurring in sediments, and their associated aquatic environments (prior to adsorbing to sediments), will reduce 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- and three-ringed PAHs (naphthalenes, phenanthrene, anthracene), and for phenolics such as phenol, 2-methylphenol, and 3-methylphenol.
The concentrations of PAHs and phenolics in water discharged to on- and off-Site surface waters have been below NPDES surface water discharge limits outlined in the CD-RAP. Depending on environmental conditions, PAHs and phenolics are degraded in aquatic environments by microbial and algal metabolism, and by chemical processes such as photooxidation and chemical oxidation (22, 23, 25, 27).
Neither ingestion nor dermal contact with surface water are considered to be routes of human exposure to Site-related contaminants because: 1) sampling data have not shown either on- or off-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 storm water retention pond is not used for swimming or wading, 4) the waters are not used as drinking water supplies, and 5) PAHs and phenolics are degraded in aquatic environments by microbial and 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 7 interchange in 1991. No volatile organic compounds, phenolics, carcinogenic PAHs, or noncarcinogenic PAHs were detected at the perimeter of the construction zone.
Site-related chemicals such as PAHs or phenolics are not expected to volatilize (become airborne) from the subsurface soil to a significant degree. However, if limited volatilization were to occur (possible for the low molecular weight PAHs such as anthracene, fluorene, and phenanthrene), degradation via photooxidative occurs fairly readily (atmospheric half-lives of PAHs are generally less than 30 days) (22). In addition, the concentrations of volatilized contaminants 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 of exposure 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 by aquatic organisms and by terrestrial animals through the food chain or ingestion of sediment and soil (22). However, the metabolism of PAHs and phenolics in biota renders them more water soluble and more excretable; accumulation in tissues may occur to a limited degree but is not considered to be a significant process. Because of this, it is very unlikely that there would be any significant exposures to humans ingesting these biota (for example, geese or ducks). Ingestion of backyard-grown fruits and vegetables watered with municipal water is also considered to be an insignificant route of exposure to Site contaminants because of: 1) the very low levels of contaminants (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 and distribution system prior to household use, 4) degradation of both phenolics and PAHs in the aquatic environment, 5) the insignificant amount of water that would come into contact with the plants in comparison to the amount of contaminants taken in via ingestion of water, and 6) the generally low level of plant uptake of PAHs (PAHs which bind fairly strongly to soils) (22). In addition, any PAHs that accumulate on the surface of the produce will be removed during normal food washing prior to preparation.
As discussed earlier, there is the potential for anyone (for example, children) either playing on certain parts of the hill or disrupting the surface soil of the hill in the SW portion of the Site to be exposed Site-related chemicals. At this time, one may presume that chemical contaminants are present in the subsurface soil since visibly contaminated soil excavated from other portions of the Site make up a very large portion of this hill. Exposure could now presumably occur because parts 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.). Local residents are also exposed to very low levels of PAHs via ingestion of and possibly dermal contact with municipal drinking water. Exact PAH exposure concentrations can't, however, be estimated because residential water sampling (at the tap) is not done. Persons playing on the hill may also come into contact with the physical hazards.
Human exposure to very low levels of PAHs via drinking water requires further discussion. One provision of the CD-RAP requires that each well that may be affected by contaminants from the Site, and which is used to supply area residents with drinking water, be monitored for the presence of PAHs. Monitoring is performed, depending on which aquifer the well draws water from, either annually, twice yearly, or quarterly. The results of this PAH monitoring are divided into three categories in the CD-RAP: (1) the concentration sum of benzo(a)pyrene and dibenz(a,h)anthracene (both are known to produce cancer in animals following ingestion of high doses), (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). The concentration sum from each of the three categories is then compared to a pre-set Drinking Water Criterion value established for each of the three categories. These Drinking Water Criteria were derived through a joint effort between the MDH, MPCA, and EPA. The Criteria are defined as the recommended maximum permissible concentrations of PAHs in drinking water which provide for the protection of human health.
However, for maximum protection of human health from potential carcinogenic effects due to exposure to PAHs by ingestion of contaminated drinking water, the Drinking Water Criteria for PAHs in categories (1) and (2) should be equal to 0 ng/L based on the non-threshold assumption for carcinogens. Under the non-threshold assumption, zero risk for a carcinogenic response only occurs only at zero dose. Because reaching the zero concentration level may not be attainable or feasible, the Drinking Water Criteria for the carcinogenic PAHs (categories 1 and 2) were set to correspond to an incremental lifetime cancer risk level of 1 in 100,000 (10-5). The cancer risk level provides an estimate of the additional incidence of cancer that may be expected in an exposed population. For example, if exposure to a chemical at a certain concentration is associated with an estimated risk level of 10-5, there exists the probability that one additional cancer case will occur for every 100,000 persons exposed to the chemical at this concentration.
The Drinking Water Criterion value for each of the three categories of PAHs defined in the CD-RAP are given below:
| Category | Drinking Water Criterion | |
| (1) | Sum of benzo[a]pyrene and dibenz[a,h]anthracene | 5.6 ng/L |
| (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 cancer risk of 10-5 if 2 liters of water (containing PAHs at the Criterion level) are ingested daily for 70 years. The Drinking Water Criterion value for category (3) was not based on potential carcinogenic effects of PAHs, but rather for their potential to: 1) modify the toxicity of the PAHs in 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 in question is introduced into the water supply distribution system (before dilution with water from any other supply source well). The Commissioner of the MDH may require that the use of any drinking water supply well whose water exceeds any of the three Drinking Water Criteria, as determined by provisions of the CD-RAP, be discontinued until such time as the Drinking Water Criteria 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 the individual source wells; 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. Prior to its arrival at the tap, the water in the supply and distribution system may undergo chemical and physical treatment (for example aeration, chlorination, fluoridation), remain in storage (tanks and/or water mains) for variable periods of time, and be mixed with water from other source wells which do not contain PAHs (this will lower the concentration of the contaminants in the water supply because of dilution). Each of these steps may have an impact on the concentration of PAH(s) to which an individual may be exposed.
The purpose of the following toxicological summary is to provide information about potential human health effects that may result from exposure to PAHs. However, it is important to realize that several factors determine whether or not harmful effects will occur and their severity if they occur. 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, ingestion or inhalation), simultaneous exposure to other chemicals (for example drugs, environmental pollutants, or chemicals in the workplace), and individual characteristics such as age, sex, nutritional status, family traits (genetics/heredity), and general state of health.
PAHs are found everywhere in the environment (22). The primary source of many PAHs in air is the incomplete combustion of wood and fuels; thus, PAHs are products of such common sources as motor vehicles (exhaust), wood burning stoves and furnaces, cigarette smoke, industrial smoke and soot, and charcoal-broiled foods (22). PAHs found in the wood preservative creosote include chrysene, naphthalene, phenanthrene, fluoranthene, pyrene methylnaphthalenes, acenaphthene, and anthracene (21). Most human exposure is to a mixture of PAHs, as opposed to a single PAH compound.
There are essentially no experimental or clinical data that provide evidence for a direct association between human exposure (ingestion, inhalation, or skin contact) to individual PAHs and adverse health effects (22). Therefore, in order to try to predict adverse responses in humans following exposure to PAHs, toxicologists must rely on reported effects in humans (primarily cancer) after exposure to complex mixtures of PAHs and on information derived from animal studies in which high doses of PAHs were administered. However, even when animal studies are reviewed, it is evident that there are very little data on the potential non-carcinogenic and carcinogenic 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 is often inferred from its toxicity (22,30). The following profile on PAHs discusses the carcinogenic and non-carcinogenic effects of PAHs when data are available.
PAHs are absorbed following ingestion, inhalation, and skin contact in both humans and laboratory animals (22, 31). Orally administered B[a]P, benz[a]anthracene, chrysene, and dibenz[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 accidental ingestion 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 bone marrow of mice (30). These effects included a decrease in all types of blood cells and aplastic anemia. 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 in laboratory animals; these changes are not considered to be serious (22, 30). Naphthalene has not been shown to cause liver toxicity in rats following ingestion (33). PAHs have not been shown to 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, the production of birth defects) of either B[a]P or any other PAH in humans (22, 30, 33). The results of two ingestion studies using experimental animals suggest that exposure during pregnancy to very large doses of B[a]P is associated with an impairment of reproductive ability and the production of birth defects (30). No birth defects were observed in offspring of mice or rabbits following oral administration of naphthalene during pregnancy (33).
The vast majority of the research on the health effects of PAHs has focused on their ability to cause 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 breast tumors (32). Naphthalene has not been shown to be carcinogenic in humans or experimental animals (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). Workers exposed by skin contact to creosote (composed primarily of PAHs) have also developed skin tumors (32). When applied to the skin, all fifteen PAHs listed below induced skin tumors in female mice or in mice of both sexes.
The National Toxicology Program of the U.S. Department of Health and Human Services determined that the fifteen PAHs listed below may reasonably be anticipated to cause cancer in humans (32):
| Benzo[a]anthracene | Benzo[b]fluoranthene |
| Benzo[j]fluoranthene | Benzo[k]fluoranthene |
| Benzo[a]pyrene | Dibenz[a,h]acridine |
| Dibenz[a,j]acridine | Dibenz[a,h]anthracene |
| 7H-Dibenzo[c,g]carbazole | Dibenzo[a,e]pyrene |
| Dibenzo[a,h]pyrene | Dibenzo[a,i]pyrene |
| Dibenzo[a,l]pyrene | Indeno[1,2,3-cd]pyrene |
| 5-Methylchrysene | |
Not all these PAHs have been detected at the Site.
B. Health Outcome Data Evaluation
In 1979, the MDH Division of Disease Prevention and Control compared the cancer incidence rates in St. Louis Park with those of three other areas (the cities of Edina and Richfield and the Minneapolis-St. Paul SMSA). The incidence rates for 45 types or sites of cancer were calculated for the three cities and the SMSA using data from the Third National Cancer Survey for the years 1969 to 1971. Incidence rates were age-adjusted to the SMSA populations of white males and females. Calculations were done of average and annual age- and sex-specific cancer incidence rates, age-adjusted incidence rates, standard incidence ratios (SIR). Chi-square and Z-statistics were used to assess the significance of rate differences.
For males, cancer rates in St. Louis Park were not significantly different from those in the three comparison areas. For St. Louis Park females, the age-adjusted rates for all cancers combined and 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 the statistically 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 known that breast cancer rates vary considerably both with geographic location and population characteristics. In addition, risk factors known to be associated with an increase breast cancer rates are: having a first degree relative with breast cancer, history of fibrocystic disease of the breast, 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 the difference in breast cancer rates between St. Louis Park and the comparison areas couldn't be evaluated without further information about the individual cases, the increased incidence of cancer could not be attributed to ingestion of PAH-contaminated water (36). However, the limited information available at that time did not rule out an association between water ingestion and subsequent breast cancer development.
In early 1984, the Minnesota Legislature authorized funding to evaluate the feasibility of conducting a community-based epidemiologic study to address adverse health outcomes (such as breast cancer) which might be related to ingestion of contaminated drinking water in St. Louis Park (36). The 18-month MDH evaluation, which was conducted in conjunction with the University of Minnesota School of Public Health, concluded such an epidemiological study was not feasible or scientifically defensible because of the following issues: 1) no valid assessment of individual exposure was possible due to considerable uncertainty about historical distribution of contaminants 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 be distinguished from possible exposure via water, and 3) there existed no means to identify and control the wide variety of factors which could confound or modify any association (apparent or real) between the presumed PAH exposure of interest and particular health outcomes. These and other considerations led MDH to conclude that it was very unlikely that any type of study would be able to directly address the impact of ingestion of PAH-contaminated water and subsequent cancer development.
C. Community Health Concerns Evaluation
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 late 1970's and early 1980's when six St. Louis Park municipal wells had to be closed down because of contamination with PAHs. In addition, an epidemiological study performed during this time reported that the rates for breast cancer were higher in St. Louis Park females when compared to females in each of three other study areas.
Municipal wells that are used to supply residents with drinking water are closely monitored for PAHs 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-carcinogenic PAHs are compared to pre-set Drinking Water Criteria which were established through a joint effort between MDH, MPCA, and EPA. These criteria are defined as the recommended maximum permissible concentrations of PAHs in drinking water which provide for the protection of human health. As long as the concentrations of PAHs in these wells remain below the Criteria, exposure to them via drinking water use is not of public health concern. If concentrations of PAHs in any well exceed these Criteria, the Commissioner of the MDH can require that its use be discontinued until the Criteria can be met (for example by treatment or other means). In addition, there are "Advisory" levels for the PAHs that are set below the Drinking Water Criteria (thus, they are more strict than the Criteria Levels). If PAH concentrations reach these Advisory levels, the well(s) is more closely monitored for PAHs to assure that levels do not approach the Criteria levels.
In a 1985 report to the Minnesota Legislature entitled "Feasibility of Community-Wide Epidemiologic Studies of Drinking Water and Health: St. Louis Park & New Brighton", the MDH concluded that it was unlikely that the observed excess of breast cancers in St. Louis Park in 1969-1971 (see reference 6) could be related to [ingestion of] water contaminants. The MDH reached this conclusion after critical analysis of a number of findings/factors including: 1) the specific PAHs that had been shown to induce mammary tumors in rodents were either not present in 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 association between breast cancer and smoking (a substantial exposure to many PAHs occurs during smoking), 3) epidemiologic studies of breast cancer had identified a number of risk factors that could account for some of the observed variations in cancer rates among different groups of women, and 4) there is a latency period, usually anywhere from 10 to 30-40 years, between onset of exposure and diagnosis of cancer; thus, cancer cases observed during 1969-1971 may have been related to events that occurred decades earlier.
More recently, epidemiological data have shown a rise in the incidence of breast cancer in the U.S. from the late 1970's through the decade of the 1980's (37). While this increase may be associated with occupational and/or environmental exposures to chemicals, again, other explanations put forward such as an increase in the prevalence of suspected risk factors and/or increased detection of cancer cases.
A fact sheet summarizing the available information about the Reilly Tar & Chemical Corporation site was written by the Minnesota Department of Health in March, 1992 and mailed to interested parties. 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 Action
Plan of the Consent Decree. This is important because these measures are intended to
significantly reduce or prevent further contamination of area groundwater with Site-related
contaminants such as PAHs.
