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Agency for Toxic Substances & Disease Registry Minimum Risk Levels (MRLs)

An MRL is an estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse non cancer health effects over a specified duration of exposure. MRLs are developed by the Agency for Toxic Substances and Disease Registry under the Centers for Disease Control and Prevention.

The following are the pollutants in the 1999 Alaska Air Toxics Emission Inventory considered to be some of the most toxic for non-cancer effects as they correspond to the the ten lowest minimum risk levels:

Rank Chemical Name Inhalation risk - mg/m3 Oral risk - mg/kg/day Comments
1 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (PDF) N/A 0.000000001 N/A
2 Cobalt Compounds (PDF) 0.00003 N/A N/A
3 Titanium Tetrachloride (PDF) 0.0001 N/A N/A
4 Nickel Compounds (PDF) 0.0002 N/A N/A
5 Radionuclides-including uranium, radium, and radon (PDF) 0.0003 N/A MRL determined for uranium
6 1,1-Dimethyl Hydrazine (PDF) 0.0005 N/A N/A
7 Toxaphene (Chlorinated Camphene) (PDF) N/A 0.001 N/A
8 Bis(chloromethyl)ether (PDF) 0.0014 N/A N/A
9 1,2-Dibromo-3-Chloropropane (PDF) N/A 0.002 N/A
10 Formaldehyde (PDF) 0.004 N/A N/A
11 4,6-Dinitro-o-Cresol, and Salts (PDF) N/A 0.004 N/A
The following pollutants in the 1999 Alaska Air Toxics Emission Inventory also have MRLs:
1,1,2,2-Tetrachloroethane
1,4-Dichlorobenzene(p)
4,4'-Methylenedianiline
Benzene (including benzene from gasoline)
Chloroform
Dichloroethyl ether (Bis[2-chloroethyl]ether)
Ethylene dichloride (1,2-Dichloroethane)
Ethylene oxide
Hexachloroethane
Hydrazine
Phosphorus
Propylene dichloride (1,2-Dichloropropane)
Tetrachloroethylene (Perchloroethylene)
Trichloroethylene
Xylenes (mixture)
To explore the possible health effects of these and other pollutants, please visit the following internet sites:
The Environmental Protection Agency's Integrated Risk Information System - list of non-cancer and cancer risk values for many pollutants
The Agency for Toxic Substances and Disease Registry - list of pollutants and corresponding minimum risk levels
The National Institutes of Health, National Library of Medicine's Hazardous Substances Data Bank (HSDB)
The Environmental Protection Agency's Health Effects Notebook for Hazardous Air Pollutants
The Agency for Toxic Substances and Disease Registry's Frequently Asked Questions about contaminants found at Hazardous Waste Sites