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The Armour Road site soil is contaminated with several contaminants at levels significantly above the Agency for Toxic Substances and Disease Registry's (ATSDR's) Environmental Media Evaluation Guides (EMEG) and/or the Missouri Department of Health's (DOH's) Any-Use Soil Levels (ASLs) (see Table 1). EMEGs are guidelines used to determine if there is a need to further investigate exposure to these chemicals for their possible health effects. Levels below the EMEG are unlikely to pose a health threat. An ASL is a health-based value that represents the maximum concentration of a chemical that will always be acceptable in the soil, regardless of future land use.

In the past, workers were probably exposed to site contaminants through direct contact with the chemicals, possibly through direct contact with the chemicals in soil, and possibly through inhalation or incidental ingestion of contaminated soil particles.

Although the site has a security fence surrounding it, there is evidence of trespassing on the site. During the most recent DOH site visit, there was a gap in the fence and the gate was unlocked. The contaminated on-site soil has become exposed in some areas through movement of the gravel cap and deterioration of the polypropylene geo-fabric. The exposed soil is mostly unvegetated. Therefore, people can gain access to the site and become exposed to contaminated soil through direct contact with, and/or inhalation or ingestion of soil particles. There is evidence that people are using the site, although the type and duration of use is unknown.

To determine possible health effects, a trespasser exposure scenario was considered. The scenario included a teenager (weighing 43 kilograms) visits the site two days per week during the warmest three months of the year for five years. The scenario assumed the teenager to ingest, conservatively, 100 milligrams of soil per day. This resulted in an acute dose of .28 milligrams of arsenic per kilogram of body weight per day (mg/kg/day), and an intermediate dose of .019 mg/kg/day, both of which are above the ATSDR Minimal Risk Level (MRL) of 0.0003 mg/kg/day, based on a chronic exposure. No MRL is available for acute or intermediate exposure. An MRL is an estimate of daily exposure of a human being to a chemical that is likely to be without an appreciable risk of deleterious effects (noncarcinogenic) over a specified duration of exposure. MRLs are based on human and animal studies. Based on these numbers, this scenario could results in adverse effects to the following human body systems: gastrointestinal, dermal/ocular, neurological, and possibly the cardiovascular, hematological, and hepatic systems. The toxicity of arsenic is discussed further below.

To evaluate the risk of cancer, the ingested dose was averaged over a 70 year life time. Using EPA's oral slope factor, there is a slight increase in the lifetime risk of developing cancer (Appendix C).

There is also a slight potential for off-site migration of contaminated dust from the soil. Using an exposure scenario assuming an adult worker (weigh 70 kilograms) drives past the site en-route to work five days per week, 50 weeks per year for 30 years results in an inhaled dose less than the MRL. There is no expected adverse health effects from this exposure pathway.

Reportedly, the on-site building floor is layered with pigeon droppings. If there are droppings in the building, they represent another possible health hazard to people entering the site. Through inhalation of aerosolized agents people could become ill with histoplasmosis or psittacosis.

Future potential exposure pathways would continue to include dermal contact and inhalation or ingestion of soil particles by trespassers and possible off-site migration of contaminated dust, unless the site is made secure and the polypropylene geo-fabric and gravel cover are repaired. As long as the polypropylene geo-fabric, its gravel cover and the security fence are maintained, exposure to on-site contaminated soil and dust would not be expected.

Future exposure receptors include remedial workers who could be exposed to contaminants from the building and soil due to direct contact with the substances, and/or inhalation and incidental ingestion of dust/soil.


Contaminants from the soil are entering the groundwater at this site. Arsenic, along with other site contaminants, has been found in the groundwater at concentrations above ATSDR EMEGs and the Environmental Protection Agency's (EPA's) Maximum Contaminant Level (MCL) (see Table 2). An MCL is the maximum permissible level of a contaminant in water which is delivered to any user of a public water system. DOH considers concentrations above the MCL to be of health concern.

The only wells downgradient of the site that are currently in use are monitoring wells. Therefore, no current exposure to contaminants from groundwater should be occurring. Future exposure to groundwater could occur to remedial workers, primarily through dermal contact and incidental ingestion. In addition, any drinking water wells installed within the contaminated plume would lead to exposure through ingestion and dermal contact. Also, industrial wells installed within the contaminated plume could lead to dermal exposure. Assuming an adult would ingest two liters of water per day over a lifetime, and using the highest arsenic concentration from on-site groundwater as an upper-bound estimate of exposure concentration, an ingested dose of 58.9 mg/kg/day is determined. This is clearly above the MRL for arsenic and is of concern for health effects.

Arsenic toxicity

Although this site is contaminated with a variety of chemicals at concentrations significantly above levels of health concern, arsenic is the chemical of primary concern due to its extremely high levels in soil and groundwater.

Long-term oral exposure to inorganic arsenic can cause a pattern of skin changes including darkening of the skin, and the appearance of small "corns" or "warts" on the palms, soles, and torso. Although these changes are not considered to be a health concern, a small number of the corns may ultimately develop into skin cancer. The Environmental Protection Agency (EPA) has classified arsenic as a Class A or known human carcinogen. Other possible health effects from ingesting inorganic arsenic include a decreased production of red and white blood cells, abnormal heart rhythm, blood-vessel damage, and impaired nerve function causing a "pins and needles" sensation in the hands and feet. Inhalation of high levels of inorganic arsenic can result in a sore throat, irritated lungs, skin effects mentioned above, and an increased risk of lung cancer. Dermal contact with inorganic arsenic may cause some redness and swelling of the skin (8).


Although it isn't likely that young children would be trespassing on this site, if they were to gain access and become exposed, the health effects mentioned above could be more severe. Due to children's smaller body weight, the amount of exposure per unit body weight would be greater than seen in teenagers and adults, thus resulting in a greater exposure.


There are no known public health concerns about the Armour Road site. As part of the Armour Road Public Health Assessment's release (Public Comment version), DOH/ATSDR held a public availability session on July 16, 1998, to gather more information on community health concerns. Three community members attended the session; however, none of them had public health concerns.

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