Abbreviations and Acronyms
|ALCOA||Aluminum Company of America|
|ATSDR||Agency for Toxic Substances and Disease Registry|
|CERCLA||Comprehensive Environmental Response, Compensation and Liability Act of 1980.|
|DOD||Department of Defense|
|EE/CA||Engineering Evaluation/Cost Analysis|
|EPA||U.S. Environmental Protection Agency|
|ft/yr||feet per year|
|HOD||health outcome data|
|IWTP||Industrial Wastewater Treatment Plant|
|MCL||maximum contaminant level|
|NPDES||National Pollutant Discharge Elimination System|
|NPL||National Priorities List|
|PHA||public health assessment|
|ppb||parts per billion|
|ppm||parts per million|
|PPWS||Permanent Potable Water Supply|
|RBAAP||Riverbank Army Ammunition Plant|
|RCRA||Resource Conservation and Recovery Act|
|SARA||Superfund Amendments and Reauthorization Act (1986)|
|STEL||Short Term Exposure Limit|
|VOC||volatile organic compound|
Toxicological Evaluation of Chromium in Plants
Using EPA estimates, we determined that the average consumption of fresh fruit is 65 grams/day for a child and 66 grams/day for an adult, and the average consumption of fresh vegetables is 118 grams/day for a child and 230 grams/day for an adult. The EPA estimate of the average percentage of homegrown produce consumed is 8% of fresh fruit and 21% of vegetables for both children and adults. Assuming the child consumed 8% of a 65 grams/day of a fresh fruit diet and 21% of a 118 grams/day of a fresh vegetable diet, the sum of the resulting chromium dosage would be 3x10-4 mg/kg/day for a child. An adult consuming 8% of 66 grams/day of fresh fruit and 21% of 230 grams/day of fresh vegetables would be exposed to 1x10-4 mg/kg/day chromium. Compared to the EPA RfD of 5x10-3 mg/kg/day for hexavalent chromium (the most toxic form of chromium), chromium from home grown produce would not be expected to be of concern in causing adverse health effects for children or adults.
Toxicological Evaluation of Chromium in Drinking Water
Chromium analysis was not speciated but assumed to be total chromium (hexavalent + trivalent). The estimated exposure dose by oral ingestion of the current maximum concentration reported (23 ug/L) would be 0.0007 mg/kg/day for a 70 kg adult ingesting 2 liters/day, which is below the chronic oral Reference Dose (RfD) for hexavalent chromium (the most toxic species) of 0.005 mg/kg/day. The chronic oral RfD for trivalent chromium is 1 mg/kg/day. The estimated exposure dosage for a 15 kg child would be 0.0015 mg/kg/day, also below the chronic oral RfD for hexavalent chromium. We should also make reference to the adequate dietary intake of 0.2 mg/total chromium/day, adopted by the National Research Council in 1989, to allow for the fact that reproductive toxicity has not been assessed in chronic duration studies. In addition, Longer Term Health Advisories for a child are orders of magnitude higher than the estimated dosage. Therefore, there is little concern for health effects from current oral ingestion of chromium in ground water when used as a drinking water source. We believe this is a conservative evaluation considering the adoption of the hexavalent form for total dosage, as the hexavalent form is better absorbed and more toxic than the trivalent form. In addition, the hexavalent form is a recognized human carcinogen, although the hexavalent form has not been evaluated for carcinogenicity in animal studies.
Past exposures may have included oral ingestion of drinking water, and inhalation and dermal contact while showering. Using the historical maximum concentration for chromium (117 ug/l) found in the domestic wells, the estimated exposure dose from oral ingestion of drinking water would be 0.0014 mg/kg/day for a 70 kg adult consuming 2 liters/day for 30 years. Compared to a chronic oral RfD of 0.005 mg/kg/day (hexavalent chromium), this past exposure to chromium in groundwater would not warrant concern.
Toxicological Evaluation of Cyanide in Plants
The use of groundwater for irrigation and bioaccumulation in plants was investigated. The likelihood of uptake in crops is influenced by the watering method, ie., if sprinklers are used, much of the cyanide would dissipate before it could be taken up by plants. Also, uptake of cyanide by plants is dependent on plant species, soil type, cyanide form and concentration, but highly volatile hydrogen cyanide would not be expected to be present in sediment or soil in any appreciable amounts. It would be unlikely that cyanide would bioaccumulate in this scenario; however, it may be possible if cyanide were constantly replenished, as in this case by contaminated groundwater.
Additionally, there is little specific information on the uptake of cyanide by individual plant types. Without this information and specific information about amounts and types of produce consumed, and lacking definitive information about the amount of cyanide dissipated during watering, it is not possible to accurately or precisely determine uptake by people eating produce watered with cyanide contaminated groundwater.
Harmful health effects of cyanide ingestion are believed to be primarily short term (or acute). Currently, there is no information available to suggest that consumption of produce contaminated with low levels of cyanide results in long term harmful health effects. There is a lack of scientific information available on long term effects of consumption of low doses of cyanide contaminated food. Studies of long term low dose effects are limited to inhalation, a much more sensitive pathway than consumption of contaminated food (meaning that much higher levels would have to be present in the food than in contaminated air inhaled by the subject to result in harmful health effects), so that it is not possible to generalize from inhalation studies to consumption of produce.
EPA's RfD for cyanide is 0.02 mg/kg/day. Cyanide was not generally speciated in the analyses performed on groundwater in the Study Area. As previously mentioned, hydrogen cyanide is assumed to be the species present. We assumed a scenario whereby residents substituted home grown products for 8% of a 65 grams/day fresh fruit diet and 21% of a 118 grams/day of a fresh vegetable diet for a child, and 8% of a 66 grams/day fresh fruit diet and 21% of a 230 grams/day fresh vegetable diet for an adult, edible product only. This exposure scenario could result in a daily consumption of 30 grams/day of home grown fresh fruit and vegetables for a child and 53.58 grams/day for an adult. This conservative scenario would limit the concentration of hydrogen cyanide to 10 ppm to protect the child and 26 ppm to protect the adult, when compared to the EPA chronic oral ingestion RfD of 0.02 mg/kg/day.
The primary cyanide source in food is cyanogenic glycosides. Plants containing cyanogenic glycosides can produce hydrogen cyanide by acid hydrolysis or by the action of the enzyme B-glucosidase. The potential toxicity of cyanogenic plants depends on their ability to release hydrogen cyanide at concentrations of concern for human health. Hydrogen cyanide release can occur either during maceration, which activates the intracellular B-glucosidase, or in the gut by the action of B-glucosidase produced by micro flora. The level of activity of B-glucosidase in the gut depends on the bacterial composition and the pH level. Those glycosides that are absorbed intact from the gut are not metabolized to hydrogen cyanide by mammalian enzymes.
Over 2650 plant species can produce hydrogen cyanide, but cyanogenic glycoside content varies widely and is affected by the conditions of heat processing.
Cyanide is not classified as to its carcinogenicity, meaning that there is no known human carcinogenicity.
Toxicological Evaluation of Cyanide in Drinking Water
Past exposure of individuals using ground water as a drinking water source was examined for potential non-cancer effects, assuming a 70 kg adult drinking 2 liters/day for 30 years (1963 to 1993) at the maximum concentration historically reported (169 ug/l at one residence during one sampling period). Results suggest an estimated exposure dose of 0.0015 mg/kg/day, which is below the EPA Reference Dose (RfD) of 0.02 mg/kg/day, for which no adverse health effects would be expected. Therefore, past exposure to contaminated ground water via oral ingestion as drinking water would not be expected to result in adverse health effects.
An estimate of the past exposure of individuals to cyanide via inhalation during showering was also examined, as hydrogen cyanide is volatile. This scenario involves numerous conservative assumptions including: (1) the maximum concentration of cyanide (113 ug/l) was assumed to be the exposure concentration, (2) all cyanide was assumed to be in the form of hydrogen cyanide and available for inhalation for 15 minutes, once per day for 30 years, and (3) absorption was assumed to be 100%. An estimated exposure dose of 0.003 mg/cu.m. is indicated, which is below the NIOSH Recommended Exposure Limit for Occupational Exposure (Ceiling) of 5 mg/ cu.m., at which no adverse health effects are expected. Dermal exposure by cyanide was not investigated as it is less toxic than exposure via inhalation at low levels, and considering all of the cyanide available for inhalation did not result in levels of concern for health effects.
The maximum concentration (16 ug/l) of cyanide detected in ground water results in an estimated exposure dose of 0.00046 mg/kg/day (assuming 2 liters/day consumed by a 70 kg adult) and is well below the EPA Reference Dose (RfD) of 0.02 mg/kg/day for oral ingestion, so present exposure to ground water would not be of concern due to ingestion as drinking water. Estimated exposure to a child would be 0.001 mg/kg/day, also below the RfD.
Analytical Results of Domestic Well Sampling in the Study Area 1985 - 1995
The following tables were not available in electronic format for conversion to HTML at the time of preparation of this document. To obtain a hard copy of the document, please contact:
- Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Attn: Chief, Program Evaluation, Records, and Information Services Branch,
1600 Clifton Road NE, Atlanta, Georgia 30333
1. In other words, unless someone experienced immediate effects within a short time of eating, it is very unlikely that consuming vegetables contaminated with low levels of cyanide would result in adverse health effects.
2. Information lacking includes: scientific information on whether there are long-term effects from ingestion of produce contaminated with low levels of cyanide; information on what types of produce accumulate cyanide and how much each type accumulates; information on how irrigation affects levels of cyanide in water; types and amounts of produce actually consumed by residents and the length of time individuals consumed homegrown produce from the Study Area.
3. Bioaccumulation is the process in which plants (or animals) can accumulate and retain levels of chemicals greater than the levels taken in, such as through irrigation with contaminated water.
4. This report concentrates on the extent of cyanide contamination plume because cyanide was determined to be the most likely to present a public health concern.
5. Although 200 ug/l is the EPA MCL for cyanide in drinking water, 10 ug/l is used to provide a
conservative estimate of maximum extent of the cyanide "plume" contamination in groundwater.