There are two separate groups of people who may come in contact with site-related contaminants (the general public including children and workers at the FMC and Simplot facilities). Each of these groups' potential for exposure to site-related contaminants and potential for adverse health effects will be discussed separately.
A. Children and the General Public
For the following reasons, it is very unlikely that children or the general public would come in contact with site-related surface soil contamination for a sufficient amount of time (a significant portion of a lifetime continuously -- 20 years) to result in any adverse health effects: no residences are located next to the two facilities, people rarely trespass onto the facilities, those people who do trespass are at the facilities for only short periods of time, and the analytical results of surface soil samples taken at some distance from the facilities indicate that there is no surface soil contamination at levels of health concern within residential areas. In addition, people who attend or participate in the drag racing and softball/baseball activities directly across the street from the two facilities are unlikely to come in contact with a significant amount of surface soil contaminants. None of the contaminants found at or near the drag strip or the ball field are high enough to cause acute health effects (health effects that may occur after only a brief contact with contaminated surface soil).
B. Workers at the FMC and Simplot Facilities
Workers at the two facilities are the only people who may come in contact with a significant amount of surface soil contamination. There is very little vegetation covering the soil at the facilities (this is not an uncommon situation for these type of facilities). Therefore, the surface soil contamination is mobile and available for people to inhale or ingest (wind blown dust and direct transfer to clothes and hands).
Although arsenic, beryllium, and lead were found above comparison values, it is unlikely that adverse health effects would occur because the highest levels of contamination were found at discrete areas (e.g., lead was only found in one sample above comparison values). It is unlikely that workers would ingest enough contaminated soil or inhale enough contaminated dust over the amount of time required to result in any adverse health effects (e.g., 50 grams of contaminated soil per day for several years) (4-6). It is important to note that the comparison values used to develop Tables 1, 2, and 3 assume that upon ingesting contaminated soil or inhaling contaminated dust, 100% of the contaminant is absorbed into the body. However, scientific literature clearly demonstrates that less than 50% of the ingested metal contaminants associated with soil (i.e., arsenic, beryllium, and lead) are absorbed into the body (4,5,6). In addition, comparison values have built-in safety factors which lower the values by 100 to 10,000 times below concentrations known to cause adverse health effects in animals or humans. The actual amount (dose) of site-related arsenic, beryllium, and lead (excluding any exposures directly related to job duties) that a worker may ingest or inhale is below that which has been observed to cause adverse health effects in humans or animals.
Fluoride was detected above the comparison value for surface soil (35,000 milligrams of fluoride per kilogram of soil [mg/kg]) at both facilities. The maximum concentration found at the FMC and Simplot facilities is 221,000 mg/kg and 123,000 mg/kg, respectively (2). According to the EPA Risk Assessment for this NPL site, the average fluoride surface soil concentration at the two facilities is 16,868 mg/kg (7). Assuming that a 70 kilogram (kg) adult ingests 50 milligrams (mg) of soil per day (incidental ingestion by hand to mouth activities and the clearing of contaminated dust particles from the respiratory tract) and that 100 percent of the fluoride is bio-available, the exposure dose to a worker ranges from 0.16 milligrams of fluoride per kilogram of body weight per day (mg/kg/day), worse case situation, to 0.012 mg/kg/day, an average situation. These doses are below the levels of exposure shown to have resulted in adverse human health effects (0.48 mg/kg/day -- increased non-vertebral fracture rate in osteoporotic women) (8). Therefore, it is unlikely that any adverse human health effects would occur because of exposure to site-related fluoride.
Cadmium was detected at very high levels at the facilities (particularly at the FMC facility -- upwards of 5,110 mg/kg with an average of approximately 740 mg/kg) (2). Although EPA has designated cadmium as a probable human carcinogen via inhalation (Group B1 --occupational and animal studies indicate that inhaling cadmium fumes or aerosols could result in an increased risk of lung cancer ), it is doubtful that workers exposed to cadmium contaminated surface soil would inhale a sufficient amount of cadmium into their lungs that would result in an increased risk of lung cancer. The particle sizes of surface soil are probably too large to be deposited into the lung (the inhaled soil dust would either not enter the lungs in the first place or would be removed from the lungs by the various filtering and clearing mechanisms that function in the human body).
However, workers may ingest a significant amount of cadmium contaminated surface soil (either by hand to mouth habits or via the clearing of inhaled soil dust from the respiratory tract). The worst case theoretical dose (assuming a 70 kg person ingests 50 mg of contaminated soil per day, 50% bio-availability, and 5,110 mg/kg of cadmium in the surface soil) indicates that a worker could receive as much as of 0.0018 mg/kg/day of cadmium. A worker exposure of 0.0003 mg/kg/day could occur if the average concentration of cadmium found at FMC is used. These theoretical doses are near the minimum risk level (MRL) of 0.0007 mg/kg/day established by ATSDR (9). The ATSDR MRL is based on a lifetime (greater than 20 years) threshold for proteinuria (proteins found in the urine because of damage to the kidneys) caused by dietary cadmium intake in residents of cadmium-polluted areas of Japan. The current average cadmium dietary intake of adult Americans is approximately 0.0004 mg/kg/day and smokers receive an additional 0.0004 mg/kg/day from cigarettes (9). Based upon these facts, workers who smoke may already exceed the threshold for chronic cadmium-related kidney damage without any environmental or occupational exposures. Therefore, smoking workers employed at FMC for 20 years or more and who ingest cadmium contaminated surface soil may be at increased risk. The workers of particular concern are those that perform most of their duties outside (i.e., slag and maintenance workers -- <50 workers) (2,7).
Elevated levels of radiation (gross alpha, beta, and gamma) have been detected in surface soil at both facilities (2). The highest levels of radiation are associated with the slag and gypsum. Usually only a few workers may come in contact with or near the slag and gypsum. These waste materials are generally handled via mechanical means (i.e., slurry pipeline and frontend loaders with enclosed cabs at Simplot, frontend loaders and haul trucks with enclosed cabs at FMC) (2,7). These material handling procedures tend to shield the worker from radiation and reduce the amount of radioisotopes that the worker may ingest or inhale. Gamma radiation exposure studies conducted at both facilities indicate that the workers are not being exposed to an excessive amount of gamma radiation (2). Depending upon work practices (e.g., amount of dust generated and personal protection devices used) and personal hygiene habits (e.g., how often hands are washed), slag or gypsum pile workers may inhale or ingest surface soil containing elevated gross alpha and beta radiation. This may increase the cancer risk of slag or gypsum pile workers (<50 workers) (10,11).
The surface soil contamination at the facilities is a potential reservoir of contaminants that could migrate into groundwater or surface water. Therefore, it may be prudent to remediate surface soil contamination in order to protect groundwater and surface water resources even though the surface soil contamination may not be at levels that pose a public health concern.