Environmental Protection Agency's Reference Concentrations (RfCs)

This ranking is based on EPA's Reference Concentration (RfC). A RfC is an estimate of a continuous inhalation exposure concentration to people (including sensitive subgroups) that is likely to be without risk of deleterious effects during a lifetime. An RfC is reported in milligrams of pollutant per cubic meter of air (mg/m³ ).

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 ten lowest reference concentrations:

Rank	Chemical Name	RfC mg/m³	Comments
1	Chromium VI chromic acid mists and dissolved Cr (VI) aerosols (PDF)	0.000008	N/A
2	Cadmium compounds (PDF)	0.00001	RfC from California Environmental Protection Agency
2	Hexamethylene-1,6-Diisocyanate (PDF)	0.00001	N/A
3	Acrolein (PDF)	0.00002	N/A
3	Beryllium Compounds (PDF)	0.00002	N/A
4	2-Chloroacetophenone (PDF)	0.00003	N/A
4	Arsenic Compounds-inorganic including arsine (PDF)	0.00003	RfC from California Environmental Protection Agency
5	Arsine (PDF)	0.00005	N/A
5	Manganese Compounds (PDF)	0.00005	N/A
5	Nickel Compounds (PDF)	0.00005	RfC from California Environmental Protection Agency
6	Chlorine (PDF)	0.00006	RfC from California Environmental Protection Agency
7	2,4-Toluene Diisocyanate (PDF)	0.00007	RfC for mixture of Toluene 2,4- and 2,6-Diisocyanate
7	Phosphorus (PDF)	0.00007	RfC from California Environmental Protection Agency
8	Chromium VI Particulates (PDF)	0.0001	N/A
9	1,2-Dibromo-3-Chloropropane (PDF)	0.0002	N/A
9	Antimony Compounds (PDF)	0.0002	RfC for Antimony Trioxide
9	Ethylene Dibromide (Dibromoethane) (PDF)	0.0002	N/A
9	Hexachlorocyclopentadiene (PDF)	0.0002	N/A
9	Hydrazine (PDF)	0.0002	RfC from California Environmental Protection Agency
10	Lindane - all isomers (PDF)	0.0003	RfC from California Environmental Protection Agency
10	Elemental Mercury (PDF)	0.0003	N/A
10	Phosgene (PDF)	0.0003	RfC from California Environmental Protection Agency
10	Phosphine (PDF)	0.0003	N/A

The following pollutants in the 1999 Alaska Air Toxics Emission Inventory also have RfCs:: 1,1,2-Trichloroethane; 1,2,4-Trichlorobenzene; 1,2-Epoxybutane; 1,3-Butadiene; 1,3-Dichloropropene; 1,4-Dichlorobenzene(p); 1,4-Dioxane (1,4-Diethyleneoxide); 2,4-Dinitrotoluene; 2-Butoxyethanol; 2-Ethoxyethanol; 2-Methoxyethanol; 2-Nitropropane; 4,4'-Methylenedianiline; Acetaldehyde; Acetonitrile; Acrylamide; Acrylic Acid; Acrylonitrile; Allyl Chloride; Aniline; Benzene (including benzene from gasoline); Benzidine; Bis(2-ethylhexyl)phthalate (DEHP); Carbon Disulfide; Carbon Tetrachloride; Chlordane; Chlorobenzene; Chloroform; Chloroprene; Cresols/Cresylic Acid (isomers and mixture); Cumene; Cyanide Compounds; Dichlorvos; Diethanolamine; Dimethyl Formamide; Elemental Selenium; Epichlorohydrin (1-Chloro-2,3-epoxypropane); Ethyl Benzene; Ethyl Chloride (Chloroethane); Ethylene dichloride (1,2-Dichloroethane); Ethylene Glycol; Ethylene Oxide; Ethylene Thiourea; Ethylidene dichloride (1,1-Dichloroethane); Hexachlorobenzene; Hexachlorobutadiene; Hexachloroethane; Hexane; Hydrochloric Acid; Hydrogen Fluoride (Hydrofluoric acid); Isophorone; Maleic Anhydride; Methanol; Methyl Bromide(Bromomethane); Methyl Chloroform (1,1,1-Trichloroethane); Methyl Ethyl Ketone (2-Butanone); Methyl Isobutyl Ketone (Hexone); Methyl Isocyanate; Methyl Methacrylate; Methyl Tert Butyl Ether; Methylchloride (Chloromethane); Methylene; Methylene chloride (Dichloromethane); Methylene diphenyl diisocyante (MDI); Naphthalene; Nitrobenzene; Pentachlorophenol; Phenol; Phthalic Anhydride; Propylene Dichloride (1,2-Dichloropropane); Propylene Oxide; Styrene; Styrene Oxide; Toluene; Trichloroethylene; Triethylamine; Vinyl acetate; Vinyl Bromide; Vinyl Chloride; Vinylidene Chloride (1,1-Dichloroethylene)

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

↑