DISCUSSION
The only locations at or near the Eastern Michaud Flats NPL site that used contaminated shallow groundwater for human consumption (i.e., drinking water) are the Old Pilot Cafe well, the Frontier well, and the Batiste Spring. Currently, no one is drinking water containing any site-related contaminants. The public health implication of the past exposures to contaminated drinking water from these three locations will be discussed separately.
From the early 1950's through 1994, the Pilot Cafe was a family run restaurant which could serve about 25 people at a time. The only source of water for the Cafe was either the Old Pilot Cafe well (early 1950's through 1976) or the New Pilot Cafe well (1977 until the Cafe moved in 1994) (2,4). Analysis of samples from the New Pilot Cafe well found no contaminants in the water above comparison values (the New Pilot Cafe well was not contaminated).
Historical (1972 forward) analytical results of samples taken from the Old Pilot Cafe well indicate that arsenic, boron, and nitrate/nitrite have been found in the well consistently above comparison values (4). In addition, recent sampling results indicate that radiological parameters (gross alpha and gross beta) were at levels above comparison levels (2). It is not known when these contaminants entered the Old Pilot Cafe well. No sampling data are available prior to 1972. However, the levels of contamination were not high enough in the Old Pilot Cafe well to cause any adverse health effects to the patrons of the Cafe. This is because the occasional glass of water or cup of coffee at the Cafe would not provide enough of the contaminants (dose) to result in any adverse health effects (the contaminants were not present at levels where acute exposures would lead to adverse health effects).
Long-term (greater than a year) employees of the Pilot Cafe may have been exposed to enough contaminants such that adverse health effects could have occurred. This is assuming that the employees drank a significant amount of their daily water at the Cafe (2 liters per day). At the levels detected, arsenic (0 - 7.48 milligrams of arsenic per liter of water [mg/L] with an average of about 0.7 mg/L) has been shown in humans to cause changes in the skin (darkening of the skin and the appearance of small "corns" or "warts" on the palms, soles, and torso) (7). While these skin changes are not considered to be a health concern in their own right, a small number of the corns may ultimately develop into skin cancer (arsenic is a known human carcinogen). In addition, a number of human studies indicate that people who drink water containing arsenic, as low as 0.6 to 0.8 mg/L over a significant portion of a lifetime (>20 years), may develop decreased production of red and white blood cells, abnormal heart rhythm, and blood-vessel damage (e.g., Raynaud's disease and cyanosis of fingers and toes) (7). There is also some evidence that longer term (a significant portion of a lifetime, > 20 years) ingestion of arsenic contaminated water may increase a person's risk of developing liver, bladder, and kidney cancer (7).
Although boron was detected at levels above comparison values, it is unlikely that any boron-related adverse health effects would occur in people who ingested the water from the Old Pilot Cafe well (even long term employees of the Cafe). The actual amount (dose) of site-related boron that a person may have ingested from the Old Pilot Cafe well is below that which has been observed to cause adverse health effects in humans or animals (0.91 mg/L is a dose of 0.026 milligrams of boron per kilogram body weight per day [mg/kg/day -- assuming a 70 kilogram person drank 2 liters of water per day] vs. the 0.6 mg/kg/day observed level that did not result in any adverse health effects in laboratory animals [No Observed Adverse Effect Level {NOAEL}]) (8).
The nitrate/nitrite levels detected in the Old Pilot Cafe well were sometimes found at levels above the comparison value of 10 mg/L. At that level, scientific literature indicates that adverse health effects could occur in infants even after a short period of exposure (several days) (9,10). Infants less than four months of age who are fed formula diluted with nitrate/nitrite contaminated water are prone to develop acute acquired methemoglobinemia ("blue babies"). The gut pH of infants less than four months of age is normally higher than that in older children and adults. The higher pH permits a greater abundance of certain bacteria that convert nitrate to nitrite in infants, resulting in increased toxicity from oral nitrate exposure (9,10). There is little evidence that breast-fed infants develop methemoglobinemia from exposure to nitrate/nitrite ingested by the nursing mother. Pregnant women may be more sensitive to the toxic effects of nitrates/nitrites. Therefore, water from wells with nitrate/nitrite levels above 10 mg/L should not be used to make baby formula or as the primary drinking water supply for pregnant women.
Elevated levels of radiation (gross alpha and beta) have been detected in the Old Pilot Cafe well. Depending upon how much water the long term employees drank at the Pilot Cafe (prior to 1976), they may have an increased risk of developing cancer (11,12).
From 1943 to the late 1980's, the Frontier Well provided drinking water to the Frontier Building and the Simplot softball/baseball field (6). Analytical results of samples taken from this well indicate that arsenic (maximum of 3.01 mg/L with an average of about 1 mg/L) was detected above comparison values (2). It is not known when arsenic entered the Frontier well. No sampling data is available prior to 1970. However, the levels of arsenic were not high enough in the well to cause any adverse health effects to any visitors to the Frontier Building or the Simplot softball/baseball field. This is because the occasional glass of water or cup of coffee would not provide enough of the contaminant (dose) to result in any adverse health effects (the contaminant was not present levels where acute exposures would lead to adverse health effects).
Long-term (greater than a year) employees at the Frontier Building may have been exposed to enough arsenic that could have resulted in adverse health effects. This is assuming that the employees drank a significant amount of their daily water at the Frontier Building and the Simplot softball/baseball field (2 liters per day). At the levels detected, arsenic has been shown to cause changes in the skin (darkening of the skin and the appearance of small "corns" or "warts" on the palms, soles, and torso) in humans (7). While these skin changes are not considered to be a health concern in their own right, a small number of the "corns" may ultimately develop into skin cancer (arsenic is a known human carcinogen). In addition, a number of human studies indicate that people who drink water containing arsenic, as low as 0.6 to 0.8 mg/L over a significant portion of a lifetime (>20 years), may develop decreased production of red and white blood cells, abnormal heart rhythm, and blood-vessel damage (e.g., Raynaud's disease and cyanosis of fingers and toes) (7). There is also some evidence that longer term (a significant portion of a lifetime, > 20 years) ingestion of arsenic contaminated water may increase a person's risk of developing liver, bladder, and kidney cancer (7).
The Batiste Spring was used by the Union Pacific Railroad as process waters and drinking water for the railroad workers (3). In addition, 30 residences of Pocatello were also provided water from the spring (approximately 120 people) (3).
Analytical results of samples taken from the Batiste Spring by the U.S. Geological Survey, 1982-7, indicate that arsenic (maximum of 0.094 mg/L and a mean of 0.036 mg/L) and nitrates/nitrites (maximum of 15 mg/L and a mean of 7.9 mg/L) were detected above comparison values (4). However, the average amount of arsenic detected in the Batiste Spring is not at levels that have been shown to cause adverse health effects in humans (please see the discussion above concerning the Old Pilot Cafe well).
The nitrate/nitrite levels detected in the Batiste Spring were sometimes found at levels above the comparison value of 10 mg/L (4). At that level, the scientific literature indicates that adverse health effects could occur in infants even after a short period of exposure (several days) (9,10). Infants less than four months of age who are fed formula diluted with nitrate/nitrite contaminated water are prone to develop acute acquired methemoglobinemia "blue babies". The gut pH of infants less than four months of age is normally higher than that in older children and adults. The higher pH permits a greater abundance of certain bacteria that convert nitrate to nitrite in infants, resulting in increased toxicity from oral nitrate exposure (9,10). There is little evidence that breast-fed infants develop methemoglobinemia from exposure to nitrate/nitrite ingested by the nursing mother. Pregnant women may be more sensitive to the toxic effects of nitrates/nitrites. Therefore, water from wells with nitrate/nitrite levels above 10 mg/L should not be used to make baby formula or as the primary drinking water supply for pregnant women (9,10).
As part of the ATSDR Child Health Initiative, ATSDR Public Health Assessment and Health Consultations must indicate whether any site-related exposures are of particular concern for children. As discussed above, the nitrate/nitrite levels detected in the Old Pilot Cafe well and the Batiste Spring were at levels that could result in adverse health effects in infants less than four months of age and possibly pregnant women (acute acquired methemoglobinemia) (9,10). These adverse health effects may have occurred in the past if nitrate/nitrite contaminated water from either the Old Pilot Cafe well or the Batiste Spring was used for several days to make baby formula or as the primary drinking water supply for pregnant women.
Based upon the data and information reviewed, the Agency for Toxic Substances and Disease Registry (ATSDR) has drawn the following conclusions:
