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

Air toxic image

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: