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What is an Acceptable Ambient Level?
North Carolina's air toxics program is based upon protection of public health. Concentration levels of toxic air pollutants below which that toxic air pollutant may be considered to have very low risk of adverse effects on human health have been determined. These concentration levels are known as Acceptable Ambient Levels or AALs. AALs are expressed in units of mass of toxic air pollutant per unit volume of air, milligrams per cubic meter (mg/m3)). There is one exception, asbestos. AALs for 97 toxic air pollutants have been established and are found at http://www.ncair.org/rules/rules/D1104.pdf. AALs are distinctly different than measured air concentrations, and understanding the difference is necessary to prevent misapplication of AALs.
For more information regarding how AAL's are determined see: http://www.ncair.org/toxics/aaldisc.pdf
Currently the following list of AALs do not have risk background documentation. For more information regarding this list please contact Dr. Reginald Jordan at (919) 707-8444 or reginald.jordan@ncdenr.gov.
ammonia
aziridine
benzidine and salts
benzo(a)pyrene
bis-chloromethyl ether
carbon tetrachloride
chloroform
di(2-ethylhexyl)phthalate
dimethyl sulfate
1,4-dioxane
epichlorohydrin
ethylene dibromide
ethylene dichloride
formaldehyde
hexachlorodibenzo-p-dioxin
hydrazine
n-nitrosodimethylamine
perchloroethylene
polychlorinated biphenyls
1,1,2,2-tetrachloroethane
vinyl chloride
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