MaximumContaminant Level (MCL)

DOE-HDBK-1188-2006

110. MAXIMUM ACHIEVABLE CONTROL TECHNOLOGY (MACT). Technology for achieving

the maximum control of emissions from major sources of hazardous air pollutants, using particularly

stringent control devices, as prescribed in 40 CFR 63.41 for new sources and in 40 CFR 63.51 for

existing sources. [Derived from 40 CFR 63.41, 40 CFR 63.51]

111. MAXIMUM CONTAMINANT LEVEL (MCL). The designation for U.S. Environmental

Protection Agency standards for drinking water quality under the Safe Drinking Water Act. The

maximum contaminant level for a given substance is the maximum permissible concentration of that

substance in water delivered by a public water system. The primary MCLs (40 CFR Part 141) are

intended to protect public health and are federally enforceable. They are based on health factors, but

are also required by law to reflect the technological and economic feasibility of removing the

contaminant from the water supply. Secondary MCLs (40 CFR Part 143) are set by the U.S.

Environmental Protection Agency to protect the public welfare. The secondary drinking water

regulations control substances in drinking water that primarily affect aesthetic qualities (such as taste,

odor, and color) relating to the public acceptance of water. These regulations are not federally

enforceable, but are intended as guidelines for the states. [Derived from 40 CFR 141.2, 40 CFR

143.1, 40 CFR 143.2, EPA OPPT]

Related term:

Maximum contaminant level goal (MCLG) means the maximum level of a contaminant in drinking

water at which no known or anticipated adverse effect on the health of persons would occur, and

which allows an adequate margin of safety. Maximum contaminant level goals are non-enforceable

health goals. [40 CFR 141.2]

112. METRIC TONS OF HEAVY METAL (MTHM). Quantities of unirradiated and spent nuclear fuel

and targets are traditionally expressed in terms of the initial weight in metric tons of uranium,

plutonium, and thorium (collectively called "heavy metal") in the unirradiated fuel. Other fuel

components, such as cladding, alloy materials, and structural materials, are not included. A metric ton

is 1,000 kilograms, which is equal to about 2,200 pounds. [Derived from 40 CFR 191.12,

OCRWM MP]

113. MILLIREM (MREM). One-thousandth of a rem (0.001 rem). (See rem.)

114. MINORITY POPULATION. Minority populations exist where either: (a) the minority population of

the affected area exceeds 50 percent or (b) the minority population percentage of the affected area is

meaningfully greater than in the general population or other appropriate unit of geographic analysis

(such as a governing body's jurisdiction, a neighborhood, census tract, or other similar unit).

"Minority" refers to individuals who are members of the following population groups: American Indian

or Alaskan Native; Asian or Pacific Islander; Black, not of Hispanic origin; or Hispanic. "Minority

populations" include either a single minority group or the total of all minority persons in the affected

area. They may consist of groups of individuals living in geographic proximity to one another or a

geographically dispersed/transient set of individuals (such as migrant workers or Native Americans),

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