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ATSDR's comparison values are based on chemical-specific toxicologic
information derived from human and animal studies, and on the conservative
assumption that a person will come in contact with the chemical every
day throughout the exposure period.
ATSDR has developed an environmental media evaluation guide, called the EMEG, and a cancer risk evaluation guide, the CREG.
Comparison values available from EPA include maximum contaminant levels, MCLs; reference dose media evaluation guides, RMEGs; health advisories for drinking water; EPA Region 3 Risk-Based Concentration Tables; soil screening levels; and national ambient air quality standards.
Other comparison values have been developed by the Food and Drug Administration (advisories), and state and local agencies have established state and local standards.
To calculate the environmental media evaluation guide, you must multiply the minimum risk level by the body weight and divide the product by the intake rate.
In this case, multiply 0.00002 milligrams of chemical per kilogram per day by seventy kilograms (which is the assumed body weight for an adult) and divide the number by the intake rate.
The intake rate is the soil ingestion rate in kilograms per day. Often
the intake rate is provided in milligrams per day. You must convert milligrams
per day to kilograms per day. To do this, multiply one hundred milligrams
of soil per day by 0.000001 kilograms of soil per milligram of soil. Then
divide the numerator by the denominator to calculate the environmental
media evaluation guide for Aroclor 1254 for an adult exposed to the soil
containing the chemical.
The answer is fourteen milligrams of chemical per kilogram of soil.
Round to one significant figure. The final answer is ten milligrams of
chemical per kilogram of soil.
February 20, 2008
EPH Training Coordinator