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PETITIONED PUBLIC HEALTH ASSESSMENT

AMOCO OIL COMPANY
(a/k/a AMOCO OIL COMPANY - SUGAR CREEK (FINDS) SS#0716)
SUGAR CREEK, JACKSON COUNTY, MISSOURI


1. SUMMARY

In June 1998, the Agency for Toxic Substances and Disease Registry (ATSDR) received a petition to conduct a public health assessment of a former petroleum refinery, the Amoco Oil Company site, in Sugar Creek, Missouri. The petitioner believes the incidences of various types of cancers, Alzheimer's, multiple sclerosis, and nervous disorders are directly related to contaminants migrating from the site. The Norledge area, adjacent to the southern boundary of the site, was described as an area at particular risk for off-site migration of contaminants. The Norledge area of Sugar Creek encompasses approximately 100 residences.

ATSDR reviewed off-site groundwater, soil, soil gas, and air data from the Norledge area. ATSDR evaluated pathways of human exposure to determine whether nearby residents are exposed to contamination. From this evaluation, ATSDR determined that past, current, and future completed exposure pathways to indoor air exist for residents who live in the Norledge area. A potential exposure pathway was identified for subsurface soil in the Norledge area. No direct exposures to groundwater or soil gas were identified in the Norledge area.

On the basis of available environmental and toxicologic information, ATSDR concluded that the Norledge area, adjacent to the Amoco Oil Company site in Sugar Creek, Missouri, poses no apparent public health hazard. Short-term exposures to the contaminant levels detected during indoor air sampling events are not likely to be associated with adverse health effects. Potential intermittent exposures to subsurface soils in the Norledge area during drilling, building, and excavating would be unlikely to result in adverse health effects, although workers should avoid contact with free product (crude oil) that may be encountered during these types of activities.

The maximum (highest) concentrations of contaminants detected in groundwater and soil gas exceeded health-based comparison values. However, as far as ATSDR has been able to determine, no residents are using this contaminated groundwater as a drinking water source. Furthermore, no residents are experiencing direct exposures to soil gas.

Based on the information reviewed for this public health assessment, ATSDR recommends the following:

  • prevent potential future exposures to contaminated groundwater, including the placement of institutional controls on the installation of wells in areas of known groundwater contamination;
  • continue to remediate contaminated groundwater in the Norledge area; and
  • take precautionary measures to prevent worker and resident exposures to free product that may be encountered during drilling, building, and excavating subsurface soil in the Norledge area.

Summary update:

ATSDR previously concluded in a May 1999 public comment version of this public health assessment that the Amoco Oil Company site in Sugar Creek, Missouri, posed an Indeterminate public health hazard 1. This determination was made, at that time, because insufficient air data were available to evaluate chronic (long-term) indoor air exposures and because no surface soil data (top 0-3 inches) were available to evaluate off-site conditions for public health significance. ATSDR recommended sampling indoor air and surface soil in the Norledge area. The Environmental Protection Agency (EPA) immediately collected the requested data and ATSDR evaluated the data in two subsequent ATSDR documents. Because the agency's evaluations of the additional data concluded that no adverse health effects would be likely to result from chronic exposure to indoor air or surface soil, ATSDR removed the recommendations to sample indoor air and surface soil from this public health assessment (see Section 5.1 and 5.3).


2. PURPOSE AND HEALTH ISSUES

The Agency for Toxic Substances and Disease Registry (ATSDR) was petitioned on June 13, 1998, to produce a public health assessment of the Amoco Oil Company (Amoco) site in Sugar Creek, Missouri. The petitioner believes the incidences of various types of cancers, Alzheimer's, multiple sclerosis, and nervous disorders are directly related to contaminants migrating from the site.

As an initial step in the public health assessment process, ATSDR typically visits a site to gather information from area residents about their health concerns. For the Amoco site, ATSDR collected this information from about 12 residents during a meeting held in Sugar Creek in July 1998. Additionally, ATSDR received numerous telephone calls from residents reporting health concerns. Residents reported having high stress levels in their community from worrying about environmental contamination. The Norledge area, adjacent to the southern boundary of the site, was described as an area at particular risk for off-site migration of contaminants.

Residents are also concerned about past air exposures from when the facility was operating. No air data exist from this time frame; however, ATSDR was informed in October 2000 that there may be some limited groundwater data from the 1960s and 1970s that could be used to model past indoor air concentrations. If modeling is feasible, the information it provides may assist in addressing community concern about past indoor air exposures.

Based on the information currently available to the agency, this public health assessment focuses on the following:

  • a review of off-site groundwater, soil, soil gas, and air data from the Norledge area to determine if current exposures are of potential health concern for local residents;
  • a review of information on chemicals associated with this site to determine whether there is any known association between these contaminants and risk to human health; and,
  • a plan identifying future ATSDR activities and any need for additional information.

3. BACKGROUND

3.1 Site Description and History

The Amoco Oil Company (Amoco) began petroleum refinery operations in Sugar Creek, Missouri, in 1904. Crude oil was brought in by pipeline from several states to produce gasoline, distillate fuels, jet fuels, residual fuels, asphalt, petroleum coke, liquified petroleum gases (LPG), sulfur, and polymers (TriTechnics Corporation, 1995b). Although petroleum refinery operations ceased in 1982, Amoco has continued to use portions of the site as a light oil petroleum product marketing terminal, a pipeline facility, and an asphalt receiving and processing center (TriTechnics Corporation, 1995b).

While the refinery was operational, the site consisted of numerous process units. In addition to these process units, several storage tank areas existed. Active and inactive underground pipelines currently run throughout many portions of the site. Starting in the 1970s, Amoco began to replace underground pipelines with above-ground pipelines to reduce the potential for undetected releases (TriTechnics Corporation, 1995b). Landfarming occurred and there were sludge pits, sludge lagoons, and sludge ponds. Numerous spills and leaks of crude oil occurred throughout the site.

Refinery operations were regulated under the Resource Conservation and Recovery Act (RCRA). When refinery operations ceased, a RCRA Facility Investigation (RFI) identified potential sources, areas, and characteristics of contamination to be investigated (TriTechnics Corporation, 1995b). Remedial activities occurred and are still occurring on-site.

3.2 Land and Natural Resource Use

The Amoco site occupies approximately 500 acres on both sides of Sugar Creek (see Figure 1, Appendix A). The Missouri River bounds the site to the north, wooded areas are on the East Bluff and West Bluff, and residential areas are to the south (TriTechnics Corporation, 1995b). The Norledge area is located adjacent to the south side of the site. The Atchison Topeka & Santa Fe and Missouri Pacific railroad lines run through the northern portion of the site.

Most of the former refinery is situated on the bluffs of the Missouri River approximately 100 to 200 feet higher in elevation than the river basin (TriTechnics Corporation, 1995b). Much of the site has become overgrown with vegetation and many areas are covered with dense trees, shrubs, and grasses; however, a few sparsely vegetated areas exist.

Sugar Creek was incorporated in the 1920s. Initially, residents were provided with municipal water through the Kansas City water system (ATSDR, 1999a). In 1956, the city of Independence built a water treatment plant and assumed the responsibility of supplying Sugar Creek with municipal water. A groundwater well survey was conducted in the Norledge area to determine the potential for possible residential ingestion of groundwater by residents (TriTechnics Corporation, 1995b). Results indicated that residents in the Norledge area were not using groundwater as a source of drinking water (TriTechnics Corporation, 1995b).

3.3 Physical Hazards

Access restrictions to the site include a fence and natural barriers (like water and steep cliffs). ATSDR identified numerous physical hazards on the site including rusty pipes sticking out of the ground, rusty barrel fragments, old manholes, drainage lines, drains, old construction debris, steep inclines, small springs, and heavy vegetation. Amoco recently reviewed the issue of site access, with specific focus on the risk of unlawful entry, and is currently making further improvements to site access control.

3.4 Demographics

According to the 1990 U.S. Census of Population and Housing (U.S. Bureau of the Census, 1991), the demographic statistics for locations within 1 mile of the Amoco site indicated there were 10,148 persons residing in 4,468 households. Of these, 97% were white; 0.4% were black; 0.7% were American Indian, Eskimo, Aleut; 0.9% were Asian or Pacific Islander; and 1% were members of other races. There were 1,119 children 6 years of age or younger, and 1,338 adults 65 years of age and older. Please refer to Figure 2, Appendix A, for additional demographic statistics.


4. DISCUSSION

ATSDR evaluates contaminants detected in environmental media at hazardous waste sites and determines whether an exposure to the contamination has public health significance. ATSDR begins this evaluation process by gathering reports that contain relevant environmental data for the site. These data are reviewed to determine if the levels of contaminants are above health-based comparison values. Health-based comparison values are media-specific concentrations of chemicals that are not likely to result in adverse health effects under default conditions of exposure. Please refer to Appendix C for further information on health-based comparison values.

Once the environmental data have been obtained and evaluated, ATSDR staff determine whether people were, or continue to be, exposed to the contaminants. ATSDR evaluates the factors that lead to human exposure. These factors, called elements, include (1) a source of contamination, (2) a transport through an environmental medium, (3) a point of exposure, (4) a route of human exposure, and (5) an exposed population. Exposure pathways fall into one of three categories:

  • Completed Exposure Pathway. ATSDR calls an exposure pathway "complete" if it is certain that people are exposed to contaminated media. Completed exposure pathways must include all five elements and indicate that human exposure to the contaminant has occurred, is occurring, or will occur.

  • Potential Exposure Pathway. Potential exposure pathways are those in which at least one of the five elements is missing but could exist. Potential exposure pathways indicate that exposure to a contaminant could have occurred, could be occurring, or could occur in the future. Potential exposure pathways are those that have (1) documented exposure, but there is insufficient information available to determine whether the environmental medium is contaminated, or (2) a documented environmental medium that is contaminated, but it is unknown whether people have been, or may be, exposed to the medium.

  • Eliminated Exposure Pathway. An eliminated exposure pathway is one in which at least one of the five elements is missing and will never be present. From a human health perspective, pathways can be eliminated from further consideration if ATSDR is able to show that (1) an environmental medium is not contaminated, or (2) no one is exposed to contaminated media.

Numerous environmental investigations have occurred both on and off the Amoco site. For the purpose of this public health assessment, ATSDR's evaluation focused on off-site air, the environmental pathway most likely to lead to human exposure. Off-site soil gas also was evaluated to determine the extent to which contaminated groundwater may affect the air pathway. ATSDR reviewed recently collected environmental data on groundwater and soil from the Norledge area to address community concern about environmental contamination of this area. An evaluation of on-site data is not included in this public health assessment. Table 1, Appendix B, contains a description of the off-site exposure pathways for this site. The following text provides ATSDR's evaluation of off-site groundwater, soil, soil gas, and air data.

4.1 Groundwater

Area groundwater investigations at the site have identified 11 on-site areas of benzene contamination encompassing 68 acres. Additionally, 13 on-site, free product plumes are estimated to encompass 73 acres of the former refinery (TriTechnics Corporation, 1995b). One off-site area of benzene contamination and two off-site areas of free product contamination were identified in the Norledge area. The RCRA Facility Investigation Report (RFI) concluded that it appears the plume migration in the Norledge area is the result of transport, at least in part, via a migration pathway other than groundwater (i.e., underground utility corridors) (TriTechnics Corporation, 1995b). Amoco began efforts to recover free product in the late 1950s and to control the migration of hydrocarbons dissolved in groundwater in the 1960s through construction of interceptor drain systems and trenches (TriTechnics Corporation, 1995b). This program was expanded in the 1970s and 1980s with the construction and expansion of the Norledge Interceptor Trench Recovery Network.

In March and April 1996, groundwater samples were collected primarily in the Norledge area to determine the presence of contaminants in the subsurface and to conceptualize the extent and magnitude of hydrocarbon contamination in the area (EnviroRemedy International, Inc., 1996). Split groundwater samples were also obtained during this sampling event (TriTechnics Corporation, 1996). The groundwater samples were analyzed by separate laboratories for volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs). Please refer to Table 2, Appendix B, for the groundwater sampling results.

From May 5 to May 27, 1997, groundwater data were collected in the Norledge area to support the evaluation of potential corrective measures (Amoco Oil Company, 1997). Samples were collected from 15 newly installed wells and from 17 previously existing wells throughout the Norledge area (both on-site and off-site), the Norledge Interceptor Trench (near the sump), and the fire station (see Figure 3, Appendix A). These groundwater samples were analyzed for benzene, toluene, ethyl benzene, xylene (BTEX); diesel range organics (DRO); and gasoline range organics (GRO). Benzene levels ranged from non-detect to a high of 931 micrograms per liter (µg/L) in monitoring well MW-106 in the off-site Norledge area. Of note, the maximum level detected at the Norledge Interceptor Trench was 18,800 µg/L and at the fire station was 308 µg/L. Please refer to Table 2, Appendix B, for the results of the off-site Norledge area groundwater data.

A Limited Subsurface Investigation was performed in July 1998 at selected properties (primarily in the Norledge area) to determine whether petroleum hydrocarbons had impacted the area. During the July 1998 Limited Subsurface Investigation, groundwater samples were collected from test holes P-1 and P-2 (see Figure 4, Appendix A) and analyzed for BTEX; total petroleum hydrocarbons (TPH) for both gasoline and diesel range organics; and chlorinated hydrocarbons (Hydro-LOGIC, Inc., 1998a). Benzene was detected at a maximum concentration of 2,560 µg/L (sample location P-2). Please refer to Table 2, Appendix B, for the results of this sampling event.

During the July 1998 Limited Subsurface Investigation, groundwater samples were collected from two private wells and analyzed for BTEX and TPH (for both gasoline and diesel range organics). No residents currently use private groundwater wells for household purposes. Please refer to Table 3, Appendix B, for the results of this sampling event.

On December 15 and 16, 1998, groundwater samples were collected from test holes P-8A, P-11 and P-13 and analyzed for BTEX and TPH (for both gasoline and diesel range organics) (Hydro-LOGIC, Inc., 1998b). Split groundwater samples collected from locations P-8A and P-13 were sent to a different laboratory and analyzed for BTEX , TPH (for both gasoline and diesel range organics), methyl-tert-butyl-ether (MTBE), and naphthalene (Pace Analytical, 1998c). Amoco contractors also collected groundwater samples from locations P-8A, P-11, and P-13 at this time and analyzed them for BTEX, TPH, and MTBE (Southwest Laboratory of Oklahoma, Inc., 1999). Please refer to Table 2, Appendix B, for the results of the December 1998 sampling events.

In March 1999, groundwater samples were collected from locations designated as "Trench" and "LB". These locations were analyzed for BTEX and TPH (Pace Analytical, 1999a). On April 15, 1999, groundwater samples were collected from three test holes and analyzed for BTEX, TPH (for both gasoline and diesel range organics), and MTBE (Hydro-LOGIC, Inc., 1999). Amoco contractors also collected groundwater samples on April 15, 1999, and analyzed them for BTEX and TPH (ThermoRetec, 1999). One additional groundwater split sample was collected on April 15, 1999, and analyzed for BTEX , TPH (for both gasoline and diesel range organics), MTBE, and naphthalene (Pace Analytical, 1999b). Please refer to Table 2, Appendix B, for the results of these sampling events.

The site and surrounding area have been provided with municipal drinking water since the 1920s; therefore, past and current exposures to Norledge area groundwater constitute an eliminated exposure pathway. ATSDR is not aware of any restrictions on the installation of private wells in the Norledge area. ATSDR defines future exposure to off-site groundwater in the Norledge area as a potential exposure pathway. Potential routes of exposure include dermal contact, inhalation, and ingestion.

4.2 Soil

Soil investigations have occurred on-site from randomly selected locations in process and storage tank areas, and specific locations in focused investigation areas at the former refinery (TriTechnics Corporation, 1995b). The RFI identified lead and benzo(a)pyrene as primary contaminants of concern in surface soil and lead, benzene, and benzo(a)pyrene as primary contaminants of concern in subsurface soil. Off-site subsurface soil samples collected and analyzed for these contaminants of concern in the Norledge area are described in the following paragraphs.

In March and April 1996, subsurface soil samples were collected primarily in the Norledge area to determine the presence of contaminants in the subsurface and to conceptualize the extent and magnitude of hydrocarbon contamination in the area (EnviroRemedy International, Inc., 1996). The subsurface soil samples were analyzed by separate laboratories for VOCs and SVOCs. Please refer to Table 4, Appendix B, for the soil sampling results.

During a July 1998 Limited Subsurface Investigation, subsurface soil samples were collected from ten test holes labeled P-1 through P-10 (see Figure 4, Appendix A) and analyzed for BTEX and TPH (for both gasoline and diesel range organics). Three of the soil samples were also analyzed for chlorinated hydrocarbons and four of the soil samples were analyzed for polynuclear aromatic hydrocarbons (PAHs). No compounds were detected above ATSDR comparison values. Please refer to Table 4, Appendix B, for the results of this sampling event.

During a December 1998 Limited Subsurface Investigation, subsurface soil samples were collected from four test holes and analyzed for BTEX and TPH (Hydro-LOGIC, Inc., 1998b). Amoco contractors also collected subsurface samples from several locations at this time and analyzed them for BTEX, TPH, and MTBE (Southwest Laboratory of Oklahoma, Inc., 1999). BTEX and MTBE were not detected above ATSDR's comparison values in these sampling events. Please refer to Table 4, Appendix B, for the results of these sampling events.

Also in December 1998, three test pits were excavated to assess subsurface conditions in the vicinity of a proposed sanitary sewer excavation planned along Willow Street and Burton Street (Amoco, 1998). Two soil samples were collected and analyzed for TPH and benzene. One of the samples indicated TPH at 127 milligrams per kilogram (mg/kg) which was above the State of Missouri Cleanup Standards for Hydrocarbon Contaminated Soil. Soil that exceeds this standard (50 mg/kg) will be managed by Amoco as a special waste and taken to a licensed landfill (Amoco, 1998). Table 4, Appendix B, contains the results of this sampling event.

In January 1999, a subsurface soil sample was collected from location P-13A and analyzed for BTEX, TPH, and MTBE (Analytical Report, 1999). BTEX and MTBE were not detected above ATSDR's comparison values. Table 4, Appendix B, contains the results of this soil sample.

During an April 1999 Limited Subsurface Investigation, subsurface soil samples were collected from test holes in the Norledge area and analyzed for BTEX and TPH (Hydro-LOGIC, Inc., 1999). Benzene was detected above ATSDR's CREG comparison value. Amoco contractors also collected subsurface samples at this time and analyzed them for BTEX and TPH (ThermoRetec, 1999). Toluene, ethyl benzene, and xylenes were not detected above ATSDR's comparison values during these sampling events. Please refer to Table 4, Appendix B, for the results of these sampling events.

Present and future potential exposures to subsurface soil by residents and workers could exist because of soil-disturbing activities (e.g., drilling, building, or excavation). These potential exposures to subsurface soil in the Norledge area are likely to be infrequent and primarily limited to dermal contact.

4.3 Soil Gas

As part of the RFI, a subsurface gas sampling program was implemented. Off-site samples were collected from 35 locations primarily in the Norledge area (see Figure 5, Appendix A). The locations were aligned in a grid corresponding to the area of groundwater contamination (TriTechnics Corporation, 1995b). Samples were analyzed for BTEX. Please refer to Table 5, Appendix B, for the results of this sampling event.

Soil gas concentrations do not generally reflect concentrations in the breathing zone because soil gas measurements are obtained by mechanically evacuating volatiles from the soil in order to generate a concentrated sample. During the RFI, soil gas samples were collected from five feet below ground surface; therefore, residents living near the Amoco site are not directly exposed to soil gas. ATSDR defines exposure to soil gas as an eliminated exposure pathway. However, soil gas data does help identify the contaminants that would be important to evaluate in air.

4.4 Air

Sampling of indoor air in the Norledge area was conducted in June 1998 for BTEX and VOCs. Seven residential houses were chosen for sampling on the basis of their location relative to the area where the groundwater and soil gas plumes overlapped (ThermoRetec, 1998). Samples were collected from basements and from ground floor rooms (that were not located above a basement). Indoor (basement) air sampling was also conducted in two control houses located outside the groundwater and soil gas plume area (see Figure 6, Appendix A). Please refer to Table 6, Appendix B, for the results of this sampling event.

In November 1998, sampling of indoor and outdoor air was conducted at two residences in the Norledge area (Pace Analytical, 1998a). The samples were analyzed for BTEX. Split samples were also obtained during this sampling event and analyzed for BTEX as well as other VOCs (Pace Analytical, 1998b). Results of this sampling event are in Table 7, Appendix B.

Sampling of indoor air was conducted on October 21 and 22, 1999, in the basements of eight Amoco-owned homes. The samples were analyzed for benzene, VOCs, total volatile petroleum hydrocarbons, methane, hexane, and ethane (ThermoRetec, 2000). Results of this sampling event are in Table 7, Appendix B.

A past, current, and future completed exposure pathway to indoor air was identified for residential homes in the Norledge area. Benzene, chloroform, 1,4-dichlorobenzene, methylene chloride, tetrachloroethene, and trichloroethene were detected in residential homes at levels above comparison values. People who reside or work in these homes are exposed to these contaminants through inhalation.


5.0 TOXICOLOGIC EVALUATION

In public health assessments, ATSDR addresses the likelihood that exposure to contaminants at the maximum concentrations detected would result in adverse health effects. Although the relative toxicity of a chemical is important, the response of the human body to chemical exposure is determined by several additional factors, including the concentration (how much); the duration of exposure (how long); and the route of exposure (breathing, eating, drinking, or skin contact). Lifestyle factors (e.g., occupation and personal habits) have a major impact on the likelihood, magnitude, and duration of exposure. Individual characteristics (e.g., age, sex, nutritional status, overall health, and genetic constitution) affect how a human body absorbs, distributes, metabolizes, and eliminates a contaminant. A unique combination of all these factors will determine the individual's physiological response to a chemical contaminant and any adverse health effects the individual may suffer as a result of the chemical exposure.

In this section, ATSDR provides a review of information on the chemicals associated with this site to determine whether there is any known association between these contaminants and risk to human health. Because a contaminant generally must first enter the body before it can produce an effect, this evaluation will focus on chemicals of concern in completed pathways of exposure. Please refer to Appendix D for information on ATSDR methodology.

5.1 Air

A past, current, and future completed exposure pathway to indoor air was identified for residential homes in the Norledge area. In the following text, an evaluation of the chemicals benzene; 1,4-dichlorobenzene; chloroform; methylene chloride; tetrachloroethene; and trichloroethene is provided.

5.1.1 Benzene

Benzene was detected in indoor air at several residences above ATSDR's comparison values (see Tables 6 and 7, Appendix B). The highest levels (62 micrograms per cubic meter (µg/m3) and 120 µg/m3), were detected in basements. The highest concentration of 120 µg/m3 was detected in a control home outside the area of groundwater and soil gas contamination (see Figure 6, Appendix A). Endogenous sources (e.g., second-hand tobacco smoke, auto exhaust from attached garages, glues, paints, and other domestic materials containing benzene) may have contributed to the benzene levels detected in these homes.

The highest concentrations of benzene detected in the Norledge area (62 µg/m3) and in a control home (120 µg/m3) exceeded ATSDR's intermediate environmental media evaluation guide (EMEG) of 4 parts per billion (ppb) or 13 µg/m3. This health-based comparison value represents the concentration of benzene in air that is not likely to result in adverse health effects for short-term exposures. However, exceeding a comparison value does not necessarily mean that the contaminant represents a public health threat. This particular intermediate EMEG is based on a behavioral effect (i.e., a facilitated aversion response) observed in male Kunming mice exposed to 780 ppb (2,496 ug/m3) benzene for 2 hours a day, 6 days a week, for 30 days (Li et al., 1992). To avoid an electrical shock, mice exposed to 780 ppb benzene found their way to a safe area at the end of a "Y" maze more quickly, on average, than did untreated control mice. The intermediate EMEG based on this observed effect includes a safety factor (also known as an uncertainty factor) of 90, an adjustment for intermittent exposure, and a human equivalent concentration adjustment. The maximum concentration of benzene detected in indoor air of residents' homes (120 µg/m3 or 37.5 ppb) was significantly below this 780 ppb level and was well below levels that have been associated with central nervous system effects in humans (ATSDR, 1997a). The air data indicate that the residents are not constantly exposed to the highest levels of benzene that were found in their homes, but to benzene levels that fluctuate within their homes. Therefore, none of the benzene exposures in the Norledge area would be expected to produce adverse health effects.

The highest concentrations of benzene detected in the Norledge area exceeded ATSDR's cancer risk evaluation guide (CREG) which is based on long-term (i.e., chronic) exposures. At the time this public health assessment was released for public comment in May 1999, ATSDR was only able to provide some perspective concerning benzene exposures because the air sampling data were insufficient to make a public health determination for chronic exposure. Additional indoor air data have since been collected and evaluated in a March 2000 public health assessment. The median of the indoor air values for samples collected in June and July 1999, was 2.45 µg/m3 (or 0.77 ppb) benzene. This median indoor air value is consistent with typical indoor background air levels of 10 µg/m3 (or 3.1 ppb). Based on a review of the literature, there are no known adverse health effects in humans associated with benzene exposures in the low parts per billion range (see Appendix E). Considering the levels of chemicals found in indoor air to date and a review of available toxicologic and epidemiologic data, chronic (long-term) exposures to indoor air would not be expected to produce any adverse health effects in Sugar Creek residents. Groundwater and subsurface soil remedial activities in the Norledge area should result in decreasing contaminant concentrations in the future. Therefore, any potential contribution from these media to indoor air levels should decrease as well.

5.1.2 1,4-dichlorobenzene

No adverse health effects would be expected at the maximum level of 1,4-dichlorobenzene detected indoors (3,400 µg/m3). The latter concentration exceeds ATSDR's intermediate EMEG (200 ppb or 1,200 µg/m3) by less than 3% of the incorporated safety factor and it exceeds ATSDR's chronic EMEG (100 ppb or 600 µg/m3) by less than 6% of the incorporated safety factor. The safety factor for both the intermediate and chronic EMEG is 100 which means the EMEG is 100 times lower than the corresponding no effect level in exposed rats. All known effect levels (including those for "less serious effects") exceeded 50,000 ppb or 300,000 µg/m3 of 1,4-dichlorobenzene. Humans may experience nose and eye irritation at 80,000 ppb. The current OSHA permissible exposure limit is 75,000 ppb. Space deodorants for toilets and fumigants for moths, molds and mildews are common sources of 1,4-dichlorobenzene in the home (ATSDR, 1998b).

5.1.3 Other Chemicals

The highest levels of chloroform, methylene chloride, tetrachloroethene (PCE), and trichloroethene (TCE) detected in indoor air were below all comparison values for non-cancer effects, but they did exceed ATSDR's CREGs. ATSDR provides cancer classifications in Appendix I. However, the CREGs for these compounds have limited relevance to humans because all are based primarily on rodent liver tumors produced by species-specific mechanisms that are dependent on unusually high doses. The induction of cancers in mice and rats by these compounds required doses in excess of anything humans might reasonably be expected to encounter, and involved certain elements of rodent biology that are not likely to be shared by humans. The Environmental Protection Agency's (EPA) cancer risk assessments for PCE and TCE have been withdrawn for the better part of a decade, now, and the cancer risk assessment for chloroform by inhalation is based on an oral study. None of the available epidemiological data suggests that any of these four chemicals represents a realistic cancer hazard at the levels detected.

For example, the highest detected concentration of methylene chloride (6.7 µg/m3) exceeded by a factor of 2 the CREG of 3 µg/m3, which is ultimately based on inhalation studies in mice exposed 6-hours a day, 5 days a week, for life (104 weeks) to 2,000,000 ppb or 7,000,000 µg/m3 methylene chloride. Several more-relevant, epidemiological studies have not detected excess risk of cancer deaths in workers exposed to methylene chloride at levels up to 475,000 ppb or 1,650,000 µg/m3 (ATSDR, 1998a).

5.2 Groundwater

Groundwater contamination exists in the Norledge area. The maximum concentrations of some of the compounds detected in this groundwater exceeded EPA's maximum contaminant levels (MCLs) and/or ATSDR's comparison values. These compounds are benzene, bis(2-ethylhexyl)phthalate, ethyl benzene, MTBE, methylene chloride, naphthalene, toluene, and xylenes. However, where there is no exposure, there can be no exposure-related health effects, regardless of the level of environmental contamination. As far as ATSDR has been able to determine, no one is using this contaminated groundwater as a source of drinking water, and no groundwater wells (other than monitoring wells) are located down gradient of the facility. Measures should be taken to assure that this remains the condition, at least until current remediation efforts are effectively completed.

5.3 Soil

To date, subsurface soil sampling in the Norledge area indicated one contaminant, benzene, which was above a health-based comparison value. All other contaminants were below health-based comparison values. In one sample collected at 12 to 14 feet below the ground surface, benzene exceeded ATSDR's CREG comparison value. However, the CREG comparison value is based on chronic (i.e., lifelong) exposure. It is unlikely that chronic exposure occurs because 1) the soil sample was taken at a depth of 12 to 14 feet and 2) only one sample exceeded the CREG value (all other samples were below this health-based comparison value). Therefore, potential intermittent exposures to these subsurface soils during drilling, building, or excavation would be unlikely to result in adverse health effects.

Although exposures to subsurface soil have not indicated contamination at levels of health concern, ATSDR received verbal reports during March 1999 that the city workers had encountered free product (crude oil) when excavating soil. They were installing new sanitary sewer lines in the Norledge area (ATSDR, 1999b). Precautionary measures should be taken to prevent workers from being exposed to free product during these types of activities.

In the initial public comment version of this public health assessment, ATSDR recommended that samples of surface soil (top 0-3 inches) be collected in the Norledge area to determine if current levels of contaminants are of public health concern. The EPA collected surface soil samples in February 2000. In a May 2000 health consultation, ATSDR determined that the contaminants detected during the surface soil sampling event are not at levels of health concern. No adverse health effects would be expected from exposure to this soil during activities such as gardening or playing.

5.4 Soil Gas

Soil gas contamination exists in the Norledge area; however, concentrations of contaminants contained in soil gas collected from five feet below ground surface generally do not reflect concentrations in the breathing zone. Soil gas measurements are obtained by mechanically evacuating volatiles from the soil using negative pressure and concentrating them in a small, enclosed space for later analysis. Such artificial air concentrations cannot be used for determining the levels that people might actually be exposed to via inhalation of the ambient air. Only measurements in air are directly useful in the assessment of inhalation exposures (see Section 5.1 of this public health assessment).

5.5 Chemical Mixtures

Communities are often concerned about harmful effects that might occur as a result of the combined exposures to more than one chemical present in their environment. Although adverse interactions following exposures to multiple chemicals in our environment are theoretically possible, such effects have been difficult to demonstrate even in well controlled animal experiments, except under conditions where the dose levels of the individual chemicals in the mixture were at or above their respective no-observed effect levels (NOAELs) (Feron et al., 1993; Jonker at el., 1990; Jonker at el., 1993; Groton at el., 1991). Typically, human exposures to most environmental chemicals result in dose levels considerably below their respective NOAELs. For example, at this site, even assuming that the maximum concentrations were always present, the indoor air values are 1 to 5 orders of magnitude (or 10 to 100,000 times) below the lowest known effects levels established in humans or animals. Additionally, the air data indicate that the residents are not constantly exposed to the highest levels of benzene that were found in their homes, but to benzene levels that fluctuate within their homes. Because the individual contaminants detected in media that the residents are directly exposed to have consistently been present at levels below their respective NOAELs, ATSDR considers that the combined effect of all these contaminants is not likely to be of public health concern (see Appendix G for additional information on chemical mixtures). Nevertheless, ATSDR considers it prudent public health policy to reduce or eliminate, wherever possible, excess exposure to substances which at higher concentrations can be toxic.


6. COMMUNITY HEALTH CONCERNS

As part of the petition process, ATSDR staff have gathered health concerns from the petitioner and local community. ATSDR addresses each of the community concerns as follows:

Concern: Residents are concerned about an increased incidence of cancer in their community, particularly brain cancer, leukemia, and lymphoma.

Response: At this time, ATSDR is not able to state whether there is increased incidence of brain cancer, leukemia, and lymphoma in Sugar Creek; however, the Missouri Department of Health (MDOH) is conducting an investigation of these cancers in this area. Recently, MDOH added breast cancer to their investigations. For each phase of their investigation, MDOH releases a report which ATSDR reviews. For information on brain cancer, leukemia, and lymphoma, please refer to Appendix F.

Concern: Residents are concerned about an increased incidence of Alzheimer's in their community.

Response: ATSDR was not able to determine whether the incidence of Alzheimer's is higher than expected in Sugar Creek since data regarding this disease are not routinely collected by public health agencies. However, current medical and toxicological literature have not established an association between the types of contaminants identified off-site in the Norledge area and Alzheimer's. For information on Alzheimer's, please refer to Appendix F.

Concern: Residents are concerned about an increased incidence of multiple sclerosis in their community.

Response: Data on multiple sclerosis (MS) are not routinely collected by public health agencies. However, MS has not been linked with any of the identified chemicals of concern in the Norledge area. To address this community concern, ATSDR's Division of Health Studies (DHS) is funding a multiple sclerosis (MS) prevalence study through the Jackson County Health Department to determine if higher rates of MS exist in Sugar Creek and Independence. For information on MS, please refer to Appendix F.

Concern: Residents are concerned about an increased incidence of nervous disorders in their community.

Response: The term "nervous disorders" has a broad definition that may include a number of different conditions; thus, it is difficult to comment further at this time. However, at the maximum concentrations measured off-site thus far, none of the contaminants detected in the Norledge area would be expected to increase the incidence of conditions affecting the central or peripheral nervous systems.

Concern: Residents are concerned about high levels of stress among community members from worrying about environmental contamination which they believe has negatively affected their health and has decreased property values.

Response: Many stressors are associated with living near an area of potential contamination including the specific stressors mentioned in this comment. ATSDR had considered conducting a stress workshop with the residents of the Norledge area. However, based on conversations and meetings with the residents, it appears that a stress workshop would not appropriately address the community's needs at this time.

Concern: Residents are concerned about past exposures from when the facility was operating.

Response: ATSDR determined a completed exposure pathway to air existed when the facility was operating. Although no air data exist to determine the extent to which nearby residents were exposed to air contaminants, ATSDR is evaluating the possibility of modeling. In October 2000, the EPA reported to ATSDR there may be groundwater data from the 1960s and 1970s. Although no past exposure to groundwater was identified, ATSDR has requested this data to evaluate its use in modeling past indoor air concentrations. If modeling is feasible, the information it provides may assist in addressing community concern about past indoor air exposures.


7. ATSDR CHILD HEALTH INITIATIVE

ATSDR recognizes that infants and children may be more vulnerable to exposures than adults in communities faced with contamination of their air, water, soil, or food. This vulnerability is a result of the following factors:

  • Children are more likely to play outdoors and bring food into contaminated areas.

  • Children are shorter, resulting in a greater likelihood of breathing dust, soil, and heavy vapors that are close to the ground.

  • Children are smaller, resulting in higher doses of chemical exposure per body weight.

  • Children's developing body systems can sustain permanent damage to organs if toxic exposures occur during critical growth stages.

Because children depend completely on adults for risk identification and management decisions, ATSDR is committed to evaluating their special interests at the Amoco Oil Company site, as part of the ATSDR Child Health Initiative.

Children who are the most likely to be exposed to environmental media at the site are those living in nearby homes and attending nearby schools. Indoor air and subsurface soil sampling data do not indicate contaminants at levels of health concern for area children. No exposures to groundwater or soil gas have been identified.


8. CONCLUSIONS

On the basis of available environmental and toxicologic information, ATSDR concludes that the Norledge area, adjacent to the Amoco Oil Company site in Sugar Creek, Missouri, poses a No Apparent Public Health Hazard. This determination was made because the levels of contaminants detected during indoor air sampling events are not likely to be associated with adverse health effects for short-term exposures. Potential intermittent exposures to subsurface soils in the Norledge area during drilling, building, and excavating would also be unlikely to result in adverse health effects, although precautionary measures should be taken to prevent worker exposures to free product that may be encountered during these types of activities.

As far as ATSDR has been able to determine, no one is using contaminated groundwater as a source of drinking water. Since the 1920s, Sugar Creek residents have been provided with municipal water. Measures should be taken to assure that residents do not install wells or use contaminated groundwater in the Norledge area for drinking water purposes until current remediation efforts are effectively completed.

Conclusion Update: ATSDR previously concluded in the initial public comment version of this public health assessment that the Amoco Oil Company site in Sugar Creek, Missouri, posed an Indeterminate Public Health Hazard2. This determination was made because insufficient air data were available to determine whether nearby residents in the Norledge area are chronically exposed to elevated levels of benzene in their homes and no surface soil data (top 0 to 3 inches) were available to determine if surface soil contains contaminants at levels of health concern. However, since this public health assessment was released in May 1999 for public comment, additional indoor air and surface soil sampling data were collected and evaluated. ATSDR determined in subsequent documents that no adverse health effects would be expected from chronic exposure to the levels of contaminants detected in indoor air or surface soil (see Section 5.1 and 5.3).


9. RECOMMENDATIONS

  • Prevent potential future exposures to contaminated groundwater, including the placement of institutional controls on the installation of wells in areas of known groundwater contamination.

  • Continue remediating contaminated groundwater in the Norledge area.

  • Take precautionary measures to prevent worker and resident exposures to free product that may be encountered during drilling, building, and excavating subsurface soil in the Norledge area.

Recommendation Update: ATSDR previously recommended additional indoor air sampling and surface soil sampling in the May 1999 public comment version of this public health assessment. EPA immediately collected the requested data and ATSDR evaluated the data in a March 2000 public health assessment and a May 2000 health consultation. Because the agency's evaluations of the additional data concluded that no adverse health effects would be likely to result from chronic exposure to indoor air or surface soil, ATSDR removed the recommendations to sample indoor air and surface soil from this public health assessment (see Section 5.1 and 5.3).


10. PUBLIC HEALTH ACTION PLAN

The actions described in this section are designed to ensure that this public health assessment identifies public health hazards and provides a plan of action to mitigate and prevent adverse health effects resulting from exposure to hazardous substances in the environment. ATSDR includes a commitment to follow up on this plan and ensure that it is implemented where applicable.

Actions Completed:

  • May 3, 1999: ATSDR reviewed and provided comments to the Missouri Department of Health regarding their report entitled, "The Sugar Creek Cancer Inquiry Report - Level 2 Investigation, March 23, 1999."

  • May 7, 1999: ATSDR released this public health assessment for public review and comment. ATSDR concluded in the initial public comment version that the Norledge area of Sugar Creek posed an Indeterminate Public Health Hazard(3) because only limited data for indoor air was available and no data for surface soil was available.

  • May 1999: ATSDR released an easy-to-understand fact sheet summarizing our findings from this public health assessment document. This fact sheet was included as an insert in the Sweet Talk Newsletter released in June1999.

  • June 2, 1999: ATSDR conducted a public meeting and public availability sessions during the comment period of this public health assessment to address questions regarding this document and to collect additional community concerns.

  • September 1999: ATSDR published an article in the Sweet Talk Newsletter to provide residents with an update on our activities in the Sugar Creek Community.

  • March 29, 2000: ATSDR released a public health assessment addendum for public review and comment which evaluated additional air data collected in 1999 in Norledge area homes and health concerns from community members. ATSDR determined that current, chronic exposures to contaminants in indoor air in Norledge area homes pose No Apparent Public Health Hazard to Sugar Creek residents. Current, chronic exposures to the contaminant levels detected are not likely to be associated with adverse health effects.

  • April 2000: ATSDR released an easy-to-understand fact sheet summarizing our findings from the March 2000 public health assessment addendum. This fact sheet was included as an insert in the Sweet Talk Newsletter released in May 2000.

  • April 12, 2000: ATSDR released a health consultation, "Review of January 2000 Air Data", for public review and comment. ATSDR had received a request on March 10, 2000, from Amoco to review January 2000 indoor air sampling results from eight Amoco-owned homes in the Norledge area. ATSDR determined that the contaminant levels detected during this indoor air sampling event pose No Apparent Public Health Hazard.


  • May 1, 2000: ATSDR released a health consultation, "Review of February 2000 Soil Data", for public review and comment which evaluated Norledge area surface soil data provided by the EPA. ATSDR determined that the contaminant levels detected during this surface soil sampling event pose No Apparent Public Health Hazard. No adverse health effects would be from exposure to this soil during activities such as gardening or playing.

  • June 27, 2000: ATSDR reviewed and provided comments to the Missouri Department of Health regarding their report entitled, "The Sugar Creek Cancer Inquiry Report - Level 3 Investigation, March 3, 2000".

  • August 28, 2000: ATSDR released a health consultation, "Surface Water and Sediment Data Review", for public review and comment which evaluated surface water and sediment data provided by the Missouri Department of Natural Resources. Based on the limited data provided, ATSDR determined that surface water and sediment contaminants are not a public health threat to residents in the Norledge neighborhood.

Actions Planned:

  • ATSDR will continue to assess the health educational needs of the community related to site issues.


  • ATSDR will continue to evaluate additional environmental data for the Norledge area for public health significance, upon request. Results of these evaluations will be provided to the public in subsequent ATSDR documents.

  • ATSDR will review groundwater data from the 1960s and 1970s to determine the feasibility of modeling indoor air chemical concentrations from this data.

  • ATSDR will respond to additional community concerns reported to the agency.

  • ATSDR will provide the community with updates about our activities by 1) publishing articles in the Sweet Talk Newsletter for Sugar Creek, 2) developing fact sheets when needed, and 3) providing information to the local television stations, newspapers, and radio stations in the Sugar Creek area.

11. PUBLIC COMMENT

ATSDR released this Amoco Oil Company public health assessment for public review and comment from May 7 through June 20, 1999. Appendix J contains both the comments received during the public comment period and ATSDR's responses to those comments.


12. SITE/TEAM AUTHORS

Environmental Health Scientist:

Danielle M. Langmann, MS
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation

Toxicologist:

Frank C. Schnell, PhD, DABT
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation

Medical Officer:

David Hewitt, MD, MPH
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation

Community Involvement Specialist:

PerStephanie Thompson
Community Involvement Branch
Division of Health Assessment and Consultation

Health Educator:

Teresa Nastoff, RN
Health Education Branch
Division of Health Education and Promotion

Epidemiologist:

Dhelia Williamson, MS
Health Investigation Branch
Division of Health Studies

Regional Representative:

Denise Jordan-Izaguirre
Office of Regional Operations

Writer/Editor:

Kathryn D. Harmsen, MPH
Office of Policy and External Affairs


13. REFERENCES AND DOCUMENTS REVIEWED

ACGIH, 1998. American Conference of Governmental Industrial Hygienists. 1995-1996 Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. Cincinnati, OH. 1998.

Amoco Oil Company, 1994a. Assessment of Impacts Associated with the Change of Condition Reported in Monitoring Well MW-62 at the Amoco Oil Company Sugar Creek Former Refinery, Docket No. VII-89-H-0028. Amoco Oil Company letter to Mr. Alan K. Hancock, Corrective Action Officer, US EPA, Region VII. March 11, 1994.

Amoco Oil Company, 1994b. Assessment of Impacts Associated with the Change of Condition Reported in Monitoring Well MW-62 at the Amoco Sugar Creek Former Refinery, Docket No. VII-89-H-0028. Letter containing attachments from Mr. Raymond D Stoelting, Amoco Oil Company, to Mr. Alan K. Hancock, Corrective Action Officer, US EPA, Region VII. April 29, 1994.

Amoco Oil Company, 1997. RE: May 1997 Additional Investigation, Amoco Former Refinery, Sugar Creek, Missouri. Report submitted by Joseph E. Casebolt, Amoco Site Manager, to JoAnn M. Heiman, Chief, RCRA Permits and Compliance Branch (EPA Region VII). August 21, 1997.

Amoco, 1998. Sampling Protocol and Sampling Results, Burton Street and Willow Street Sewer Excavation, Amoco, Sugar Creek, Missouri. Sampling protocol (dated November 30, 1998) and sampling results (conducted on December 23, 1998) provided to ATSDR by Ron Martinovich, City Administrator. 1998.

Amoco, 2000. RE: Comments to Petitioned Public Health Consultation, Amoco Oil Company. Letter submitted by Joseph E. Casebolt, Amoco Site Manager, to Chief, Program Evaluation, Records, and Information Services Branch, ATSDR. June 12, 2000.

Analytical Report, 1999. Analytical Report, Sugar Creek, Missouri. Data sheet containing soil sample results for Client: Arthur Benson and Associates, Sample ID: P-13A 32.0-34.0', Date Sampled: 1/22/99, Dante Analyzed: 1/22/99. January 22, 1999.

ATSDR, 1992. Agency for Toxic Substances and Disease Registry. Public Health Assessment Guidance Manual. Lewis Publishers, Chelsea, Michigan. 1992.

ATSDR, 1994. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Toluene (Update), Atlanta, Georgia. Report No. TP-93-14. May 1994.

ATSDR, 1997a. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Benzene (Update), Atlanta, Georgia. September 1997.

ATSDR, 1997b. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Chloroform (Update), Atlanta, Georgia. September 1997.

ATSDR, 1997c. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Tetrachloroethylene (Update), Atlanta, Georgia. September 1997.

ATSDR, 1997d. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Trichloroethylene (Update), Atlanta, Georgia. September 1997.

ATSDR, 1998a. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Methylene Chloride (Update), Atlanta, Georgia. September 1998.

ATSDR, 1998b. Agency for Toxic Substances and Disease Registry. Toxicological Profile for 1,4-Dichlorobenzene (Update), Atlanta, Georgia. December 1998.

ATSDR, 1999a. Agency for Toxic Substances and Disease Registry. ATSDR Record of Activity. Record of telephone conversation between Charles E. Dumsky, Mayor of Sugar Creek, and Danielle Langmann, ATSDR. February 25, 1999.

ATSDR, 1999b. Agency for Toxic Substances and Disease Registry. ATSDR Record of Activity. Record of ATSDR conference call with Denise Jordan-Izaguirre, Dhelia Williamson, and Danielle Langmann. March 15, 1999.

Bond GG, McLaren EA, Baldwin CL, et al., 1986. "An update of mortality among chemical workers exposed to benzene", Br. J. Ind. Med. 43: 685-691. 1986.

Casciato, Dennis A. and Lowitz, Barry B., 1988. Manual of Oncology. Third Edition, Little, Brown and Company, New York, N.Y. 1988.

Chang, LW and Dyer RS, 1995. Handbook of Neurotoxicology. Marcel Dekker, Inc., New York, NY, pp. 123-7.

Cunningham, M.L., Elwell, M.R., and Matthews, H.B, 1994. Relationship of carcinogenicity and cellular proliferation induced by mutagenic noncarcinogens vs carcinogens. Fundamental and Applied Toxicology, 23: 363-369.

Drouet B, Pincon-Raymond M, Chambaz J, Pillot T, 2000. "Molecular basis of Alzheimer's disease". Cell Mol Life Sci 57(5):705-15.

EnviroRemedy International, Inc., 1996. Affidavit of Mohammed Aboudah, P.E., (Known as Marco Odah, P.E.) Prepared for Humphrey, Farrington & McClain, P.C. June 26, 1996.

EPA, 1986. Environmental Protection Agency. Guidelines for Carcinogenic Risk Assessment. Fed. Reg., 51: 33997-33998, September 24, 1986.

Feron VJ, Jonker D, Groten JP, Horbach GJMJ, Cassee FR, Schoen ED, Opdam JJG., 1993. Combination technology: From challenge to reality. Toxicology Tribune 1993; 14: 1-3.

Groton JP, Sinkeldam EJ, Luten JB, Van Bladern PJ., 1991. Interaction of dietary calcium, potassium, magnesium, manganese, copper, iron, zinc, and selenium with the accumulation and oral toxicity of cadmium in rats. Food and Chemical Toxicology 1991; 4: 249-258.

Hasegawa, R, Miyata, E, Futakuchi, M, Hagiwara, A, Nagao, M, Sugimura, T and Ito, N, 1994. Synergistic enhancement of hepatic foci development by combined treatment of rats with 10 heterocyclic amines at low doses. Carcinogenesis 15: 1037-1041.

Hydro-LOGIC, Inc., 1998a. RE: Limited Subsurface Investigation Results for your Selected Residential Properties in Sugar Creek and Independence, Missouri, Letter containing attachments from Mr. Don W. Dulaney, Hydro-LOGIC, Inc., to Ms. Jamie Kathryn Lansford, Arthur Benson & Associates. July 14, 1998.

Hydro-LOGIC, Inc., 1998b. RE: Addendum to the Limited Subsurface Investigation Results for your Selected Residential Properties in Sugar Creek and Independence, Missouri, Letter containing attachments from Mr. Don W. Dulaney, Hydro-LOGIC, Inc., to Ms. Jamie Kathryn Lansford, Arthur Benson & Associates. December 23, 1998.

Hydro-LOGIC, Inc., 1999. RE: Limited Subsurface Investigation Results for Selected Residential Properties in Sugar Creek, Missouri, Letter containing attachments from Mr. Don W. Dulaney, Hydro-LOGIC, Inc., to Ms. Jamie Kathryn Lansford, Arthur Benson & Associates. April 26, 1999.

IARC, 1982. International Agency for Research on Cancer. "Benzene." pp. 99-106 in IARC Monographs, Volume 29, Some Industrial Chemicals and Dyestuffs, Lyons, France, 1982.

Inskip, Peter D., Linet, Martha S., and Heineman, Ellen F., 1995. "Etiology of brain tumors in adults", Epidemiologic Reviews 17(2): 382-414. 1995.

Jonker D, Woustern RA, Van Bladern PJ, Til HP, Feron VJ., 1990. Four week oral toxicity study of a combination of eight chemicals in rats: comparison with the toxicity of the individual compounds: Food and Chemical Toxicology 1990; 28: 623-631.

Jonker D, Jones MA, Van Bladern PJ, Woustern RA, Til HP, Feron VJ., 1993. Acute 24 hour toxicity of a combination of four nephrotoxicants in rats compared with the toxicity of the individual compounds: Food and Chemical Toxicology 1993; 31: 45-52.

Lamm, S.H., Walters, A..S., Wilson, R., Byrd, D.M., and Grunwald, H., 1989. "Consistencies and Inconsistencies underlying the Quantitative Assessment of Leukemia Risk from Benzene Exposure," Environmental Health Perspectives 82: 289-297. 1989.

Li L., Sun W., Gong Z., et al., 1992. "Effect of low benzene exposure on neurobehavioral function, AChe in blood and brain and bone marrow picture in mice," Biomed Environ Sci 5(4): 349-354. 1992.

Merck, 1992a. The Merck Manual of Diagnosis and Therapy, Vol. I, General Medicine, pp. 1075-82.

Merck, 1992b. The Merck Manual of Diagnosis and Therapy, Vol. I, General Medicine, pp. 1287-89.

Ott M.G., Towsend J.C., Fishbeck W.A., et al., 1978. "Mortality among workers occupationally exposed to benzene," Arch Environ Health 33: 3-10. 1978.

Pace Analytical, 1998a. RE: Pace Project Number:1010945, Client Project ID: 110.98. Letter from Mr. Will Elcoate, Project Manager, Pace Analytical, to Mr. Gil Zemansky, Compass Environmental Services, containing attached data sheets. November 20, 1998.

Pace Analytical, 1998b. RE: Pace Project Number:1010937, Client Project ID: Litigation Support. Letter from Ms. Carolynne Trout, Project Manager, Pace Analytical, to Mr. Bill Solberg, Remediation Technologies, Inc., containing attached data sheets. November 24, 1998.

Pace Analytical, 1998c. RE: Pace Project Number: 6026487, Client Project ID: 110.98. Letter from Mr. Mark Gudnason, Project Manager, Pace Analytical, to Mr. Zemansky, Compass Environmental Inc., containing attached data sheets. December 30, 1998.

Pace Analytical, 1999a. RE: Pace Project Number: 6028366, Client Project ID: 110.98. Letter from Mr. Mark Gudnason, Project Manager, Pace Analytical, to Mr. Zemansky, Compass Environmental Inc., containing attached data sheets. March 19, 1999.

Pace Analytical, 1999b. RE: Pace Project Number: 6029570, Client Project ID: 110.98. Letter from Mr. Mark Gudnason, Project Manager, Pace Analytical, to Mr. Zemansky, Compass Environmental Inc., containing attached data sheets. May 4, 1999.

Paustenbach, D.J., Price, P.S., Ollison, W., Jernigan, J.D., Bass, R.D., and Peterson, H.D., 1992. Reevaluation of benzene exposure for the Pliofilm (rubberworker) cohort (1936-1976). J. Toxicol. Environ Health 36; 177-231. 1992.

Paxton, M.B., 1996. "Leukemia Risk Associated with Benzene Exposure in the Pliofilm Cohort," Environmental Health Perspectives 104 (Suppl 6): 1431-1436. 1996.

Petition Letter, 1998. RE: Proposed Epidemiological Study in Sugar Creek, Missouri, Petition letter addressed to Dr. Barry Johnson, Assistant Administrator, ATSDR. June 13, 1998.

Raabe, Gerhard and Wong, Otto, 1996. "Leukemia Mortality by Cell Type in Petroleum Workers with Potential Exposure to Benzene," Environmental Health Perspectives 104 (Suppl 6): 1381-1392. 1996.

Rinsky, R.A., Smith, A.B., Hornung, R., Filloon, T., Young, R., Okun, A., and Landrigan, P., 1987. Benzene and Leukemia: An epidemiological risk assessment. N. Eng. J. Med. 316: 1044-50. 1987.

SOT, 1981. Society of Toxicology. Re-evaluation of the ED01 Study. Fundamental and Applied Toxicology 1:27-128.

Southwest Laboratory of Oklahoma, Inc., 1999. Project: LIT SUPPORT, SWLO ID: 36834.01-36834.08. Letter from Mr. Randy Staggs, Project Officer, Southwest Laboratory of Oklahoma, Inc., to Mr. Bill Solberg, ThermoRetec, containing attached data sheets. January 8, 1999.

Takayama, S, Hasagawa, H and Ohgaki, O, 1989. Combination effects of forty carcinogens administered at low doses to male rats. Jpn. J. Cancer Res. 80: 732-736.

ThermoRetec, 1998. ThermoRetec Consulting Corporation. Basement Air Sampling Report, Amoco Oil Company, Sugar Creek, Missouri, Prepared by ThermoRetec Consulting Corporation, Golden, Colorado, for Amoco Oil Company, Sugar Creek, Missouri. ThermoRetec Project No.: 3-3080-503. November 12, 1998.

ThermoRetec, 1999. RE: Split Sampling Results. Letter from Mr. William A. Solberg, ThermoRetec, to Mr. Benson, Arthur Benson & Associates, containing attached data sheets. May 14, 1999.

ThermoRetec, 2000. RE: Indoor Air Study Results, October 1999. Memorandum letter from Ms. Jenny Phillips, ThermoRetec, to Mr. Bill Solberg, ThermoRetec, containing both a description of an air sampling event and the air sampling data. January 11, 2000.

TriTechnics Corporation, 1995a. Memorandum from Sher Long to Mike Paules concerning a private water well in Sugar Creek. November 17, 1995.

TriTechnics Corporation, 1995b. RCRA Facility Investigation Report, AMOCO Sugar Creek Former Refinery, Volume 1: Sections 1-9, Volume 2: Sections 10-12, Volume 3: Section 14, Volume 4: Appendix 8A and 8C, Volume 11: Appendix 12B, Volume 12: Appendix 15A. Prepared by TriTechnics Corporation, Air, Water and Soil Management, Golden, Colorado. Submitted by Amoco Corporation to the U.S. Environmental Protection Agency. December 18, 1995.

TriTechnics Corporation, 1996. Analytical Summary for Split Sampling Results, Amoco Sugar Creek Former Refinery, Sugar Creek, Missouri. Data sheets for split groundwater sampling provided. August 30, 1996.

U.S. Bureau of the Census, 1991. 1990 Census of Population and Housing, Summary Tape File 1A [machine-readable data files]. Washington: The Bureau.

Wallace, Lance, 1996. "Environmental Exposure to Benzene: An Update," Environmental Health Perspectives 104 (Suppl 6): 1129-1136. 1996.

Williams, Gary M., and Weisburger, John H, 1991. "Chemical Carcinogenesis". pp.153-154 in Chapter 5 of: Casarett and Doull's TOXICOLOGY: The Basic Science of Poisons. (Mary O Amdur, John Doull, and Curtis Klaassen, Editors.) Pergamon Press pp 127-200.

Wong, Otto, 1995. "Risk of Acute Myeloid Leukemia and Multiple Myeloma in Workers Exposed to Benzene," Occupational and Environmental Medicine 52: 380-384. 1995.

Xia Z-L, Xi-Peng J, Pei-Lian L, et al., 1995. "Ascertainment corrected prevalence rate (ACPR) of leukopenia in workers exposed to benzene in small-scale industries calculated with capture-recapture methods," Biomed Environ Sci. m8: 30-34. 1995.

Yin, Song-Nian, Hayes, Richard B, Linet, Martha S., Li, Gui-Lan, Dosemeci, Mustafa, Travis, Lois B, Zhang, Zhi-Nan, Li, De-Gao, Chow, Wong-Ho, Wacholder, Sholom, Blott, William J, and the Benzene Study Group, 1996. "An expanded cohort study of cancer among benzene-exposed workers in China", Environmental Health Perspectives 104 (Suppl 6): 1339-1341. 1996.


1The phrase "Indeterminate Public Health Hazard" is a formal conclusion category that ATSDR reserves for sites at which, due to the unavailability of critical information, no determination can be made regarding the existence or non-existence of a potential threat to health in the community.
2 The phrase "Indeterminate Public Health Hazard" is a formal conclusion category that ATSDR reserves for sites at which, due to the unavailability of critical information, no determination can be made regarding the existence or non-existence of a potential threat to health in the community.
3 The phrase "Indeterminate Public Health Hazard" is a formal conclusion category that ATSDR reserves for sites at which, due to the unavailability of critical information, no determination can be made regarding the existence or non-existence of a potential threat to health in the community.


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