SHELL OIL PIPELINE SPILL
LIMESTONE TOWNSHIP, KANKAKEE COUNTY, ILLINOIS
The Illinois Department of Public Health (IDPH) prepared this health consultation for the Shell Oil Pipeline Spill at the request of the Illinois Environmental Protection Agency (Illinois EPA). This consultation was accomplished as part of our review and evaluation of data generated from spill response actions in order to determine whether the site poses a public health hazard.
In November 1988, corrosion of a 14-inch underground pipeline owned and operated by the Shell Oil Company, a predecessor of Shell Pipeline Corporation (Shell), resulted in the release of an estimated 120,000 gallons of gasoline. A pool of gasoline about 450 feet by 50 feet appeared among fields of corn and soybeans. The site of the release was in Limestone Township in Kankakee County, about 4 miles west of Kankakee, Illinois. Approximately 2,100 people live within a 1 mile radius of the November 1988 release point (Attachment 1). Although much of the surrounding land is agricultural fields, this area is experiencing rapid development of new homes.
Bedrock in this area is highly fractured, permitting contaminants to seep into the aquifer that provides drinking water for many homes in the area. It is very difficult to predict how chemicals will move in the water when there is fractured bedrock. Groundwater in this area generally moves northeast toward the Kankakee River.
Following the release, Shell installed trenches to recover gasoline. They also conducted site investigations to characterize the nature and extent of contamination in soil and groundwater. Information from these investigations helped to define the affected area, and also provided geologic and hydrogeologic information required for determining appropriate remediation. Twenty-one monitoring wells were installed during the initial investigation. In addition, more than 400 private wells were also sampled. Several wells are still being sampled quarterly for benzene, toluene, ethylbenzene and xylene (BTEX) and methyl tert-butyl ether (MTBE).
As part of the remediation effort at the spill site, Shell excavated 16,000 cubic yards of contaminated soil and installed a local pump-and-treat system for contaminated groundwater. The system pumps groundwater through an air-stripper and then injects the water into soil upgradient of the spill to flush more contaminants to collection wells. This treatment system has been operating since l993.
In February 1994, MTBE was detected in the public water supply wells serving the Oakdale Acres and Village Green subdivisions. In March 1994, the water company installed activated carbon adsorption equipment to remove the MTBE. On April 7, 1994, about 400 people attended a public meeting at the Limestone Grade School gymnasium to learn about the groundwater contamination. IDPH staff answered questions from the audience about MTBE exposures and health. By 1995, a new water line was extended to the impacted subdivisions and the impacted public water supply wells were taken out of service.
Between 1994 and 2001, MTBE was discovered in several residential wells. The location of the wells where MTBE was detected shows that the contaminants are migrating away from the initial release point. Because of the fractured bedrock in the area, it is difficult to determine whether contaminants not recovered by the remediation efforts or by the pump-and-treat system are still migrating from the spill site. Periodic monitoring of the wells in the area provides information on where the contamination plume is located.
BTEX chemicals were reportedly found in residential wells sampled in August 2001. The validity of these results was questioned because benzene was also detected in the "trip blanks" used to ensure quality control measures during sampling and transport. Resampling of wells occurred in November 2001 using two independent laboratories and strict quality control measures. No benzene was detected in the November sampling. Based on these results, the Kankakee County Health Department and Illinois EPA concluded that the August 2001 data was in error and that no BTEX chemicals were present in residential wells.
Chemicals of Interest
IDPH compared the results of each sample collected in November 2001 with the appropriate comparison values to select chemicals for further evaluation for exposure and possible carcinogenic and non-carcinogenic health effects. Chemicals found at levels greater than comparison values or those for which no comparison value exists were selected for further evaluation. IDPH assumed that the November 2001 samples were collected and handled properly, and that appropriate analytic techniques were used.
Although MTBE did not exceed current comparison values for non-cancer health effects, residents in the community were concerned that MTBE may cause cancer. Because the carcinogenicity of MTBE is under review, it was selected as a chemical of interest.
IDPH evaluated the surrounding environmental conditions and local activities that may lead to exposure to determine whether residents living near the site have been, are being, or might be exposed to MTBE in groundwater. The information is evaluated for five components that comprise an exposure pathway. The five elements include:
- a contaminant source,
- an environmental transport pathway (such as groundwater),
- a point of potential exposure (such as a water spigot),
- a route of exposure (such as ingestion of contaminated groundwater), and
- a receptor population or people who are exposed.
An exposure pathway is considered complete, potential, or incomplete based on the status of the five elements. If all five elements exist, then exposure is complete and people have contacted contaminants, either currently or in the past. A potential exposure pathway is one in which at least one of the five elements is missing but could exist. Past exposure might have occurred, exposure could be occurring, or exposure could occur in the future. An exposure pathway can be eliminated if at least one of the five elements is missing and will never be present.
Residents who use private well water containing MTBE can be exposed by drinking the water, inhaling vapors during showering or bathing, and by skin contact with the water. The potential for exposed persons to experience adverse health effects depends on:
- the specific chemical to which a person is exposed,
- how much of each chemical to which a person is exposed,
- the duration of a person's exposure, and
- the condition of the exposed person's health.
The highest level of MTBE found in residential wells was 50 parts per billion (ppb) in the mid-1990s. Sampling performed from 2000 to 2002 found that MTBE levels in all groundwater samples were less than 10 ppb. Most people can detect MTBE in groundwater by taste and smell at levels much less than those that would be expected to cause adverse health effects. According to Ahmed (2001), a small segment of the population (e.g. asthmatic children, the elderly, and those with immune deficiencies) may be at increased risk for toxicity, however, no studies have been conducted to investigate this hypothesis. The Illinois Pollution Control Board has set a standard of 70 parts per billion of MTBE in groundwater used for drinking, agricultural, industrial, recreational, or other beneficial uses.
IDPH assumed that children would drink 1 liter of water per day and adults in the community would drink 2 liters of water per day. Also, residents would be exposed by breathing some MTBE vapors released during showering or other indoor water uses. Based on exposure to MTBE in private well water, the estimated exposure doses are below concentrations that would be expected to result in increased risks of non-cancer adverse health effects. The Illinois Pollution Control Board standard of 70 ppb was based on studies that caused increased cholesterol and diarrhea in animals. Because the levels of MTBE found in residential wells are lower than the 70 ppb standard, no adverse non-cancer health effects would be expected.
Whether MTBE poses a cancer risk to humans is still being reviewed at this time. Based on information from past animal studies, the amount of MTBE in private wells would not be expected to cause an increased risk of cancer.
On April 7, 1994, about 400 people attended a public meeting at the Limestone Grade School gymnasium. More recently, a public availability session was held on February 27, 2002, at the Limestone School in unincorporated Limestone Township, Kankakee County. IDPH was present to answer health-related questions and gather information about the community health concerns discussed below.
What are the health problems associated with MTBE?
Breathing high amounts of MTBE for short periods may cause nose and throat irritation. Some people exposed to MTBE while pumping gasoline, driving their cars, or working in gas stations have reported having headaches, nausea, dizziness, and mental confusion. However, the actual levels of exposure in these cases are unknown. In addition, these symptoms may have been caused by exposure to other chemicals. The Illinois Pollution Control Board standard of 70 ppb was based on studies that caused increased cholesterol and diarrhea in animals. Because the levels of MTBE found in residential wells are lower than the 70 ppb standard, no adverse non-cancer health effects would be expected.
Does MTBE cause cancer?
We know more about how MTBE affects animals than we do about how it affects the health of humans. When rats were given extremely high levels of MTBE (more than 100,000 times the levels found in residential wells) by mouth for 2 years, some developed cancer. It is unknown whether humans could have an increased incidence of cancer from exposure to MTBE; however, based on previous animal studies, the low levels found in residential wells near the Shell Pipeline would not be expected to cause an increased risk of cancer.
How can I reduce my exposure to MTBE?
Although exposure to MTBE in groundwater is not expected to cause adverse health effects, steps can be taken to reduce exposure. Using bottled water for drinking and cooking, and using an exhaust fan when taking a bath or shower can reduce your exposure to MTBE in groundwater. Another option is to install and properly maintain a water treatment unit approved by the National Sanitation Foundation (NSF).
Children are a sensitive sub-population so special consideration is given to potential exposures to children in the toxicological evaluation. Given the exposure scenario stated previously, IDPH does not expect children to experience adverse health effects from drinking the water.
Based on the current information reviewed from recent sampling activities, IDPH concludes that no apparent public health hazard exists from exposure to groundwater in the residential wells near the Shell Oil release site at this time. If additional sampling is conducted, the data will be reviewed to determine whether there is a potential for adverse health effects.
IDPH recommends that Illinois EPA continue to review groundwater data from sampling of private wells in the spill area.
Illinois Department of Public Health
Agency for Toxic Substances and Disease Registry. Toxicological profile for methyl t-butyl ether. Atlanta: U.S. Department of Health and Human Services; 1996 August.
Ahmed, FE. Toxicology and human health effects following exposure to oxygenated or reformulated gasoline, 2001. Toxicology Letters 123; 2-3 pp. 89-113.
Illinois Environmental Protection Agency. Investigation file for Kankakee Shell Oil Pipeline Spill. 2002.
This Shell Pipeline Spill health consultation was prepared by the Illinois Department of Public Health under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was begun.
W. Allen Robison
Technical Project Officer
Superfund Site Assessment Branch (SAAB)
Division of Health Assessment and Consultation (DAC)
The Division of Health Assessment and Consultation, ATSDR, has reviewed this health consultation and concurs with its findings.
Chief, State Programs Section
SSAB, DHAC, ATSDR