National Ambient Air Quality Standards
Section 108 of the amended CAA specifies the
development of scientific criteria for certain air
pollutants. It specifies that the Administrator publish a list for pollutants: (a) which have an adverse
effect on public health or welfare, and (b) which
are derived from numerous or diverse mobile or
stationary sources. It explicitly states – “the
criteria shall accurately reflect the latest scientific
knowledge on the kind and extent of all identifiable effects on public health and welfare which
may be expected from the presence of the pollutant in ambient air, in varying quantities” [15].
Section 109 of the CAA [15] directs the
Administrator to propose and promulgate “primary” and “secondary” NAAQSs for criteria pollutants identified under Section 108. The primary
Standards are to be set to protect public health;
secondary Standards are to be set to protect the
public welfare such as effects on soils, water,
crops, visibility, and deterioration of property. In
this entry, I focus on the setting of the primary
Standards and on the specific NAAQS. However,
the issues discussed are also broadly applicable to
the setting of secondary Standards.
Section 109(b)(1) defines a primary NAAQS
as one that “the attainment and maintenance of
which in the judgment of the Administrator, based
on the criteria and allowing an adequate margin of
safety, is requisite to protect the public health.”
The margin of safety, as interpreted by the EPA, is
intended to address uncertainties associated with
inconclusive scientific and technical information
at the time the Standard is set and to account for
hazards that research has not yet identified.
The primary Standards are intended to protect
against “adverse effects, not necessarily against
all identifiable effects of changes produced by a
pollutant.” Although the US Congress did not
rigorously define an adverse effect, it did provide
general guidance in the legislative history of the
debate on the CAA [30]. Congress was concerned
with effects ranging from cancer, metabolic and
respiratory disease, and impairment of mental
processes to headaches, dizziness, and nausea.
Congress also noted concern for sensitive population groups in setting the NAAQSs. In
particular, Congress noted that the Standards
should protect “particularly sensitive citizens
such as bronchial asthmatics and those with
emphysema who in the normal course of daily
activity are exposed to the ambient environment.”
This has been interpreted to exclude individuals
who are not performing normal activities, such as
individuals who are hospitalized. Further guidance was given noting that the Standard is statutorily sufficient whenever there is “an absence of
adverse effect on the health of a statistically
related sample of persons in sensitive groups
from exposure to the ambient air.”
The challenge of interpreting the “adequate
margin of safety” language of the CAA was noted
in an editorial by Donald Kennedy on Risk versus
Risk published when he served as Editor-in-Chief
of Science [27]. He wrote – “In the United States
and some other industrial democracies, where people and their governments tend to be risk averse,
legislatures, courts, and administrative entities usually create a presumption favoring more safety
rather than less. The definitions of risk in law are
often vague (‘reasonable certainty of no harm’ or
‘adequate margin of safety’) and are likely to
encourage an unrealistic belief that risks can be
minimized or even eliminated altogether.” I think
Kennedy has captured the conundrum posed by the
language of the CAA, a conundrum that has been
addressed by US Supreme Court Justice Stephen
Breyer as I will relate later.
In 1977, several key amendments were made
to the CAA [16]. Concern about slow action of the
EPA in preparing criteria documents and
reassessing NAAQSs prompted a legislated
requirement that the NAAQSs be reevaluated not
later than January 1, 1980, and at 5-year intervals
thereafter. Reevaluation was not intended to automatically result in changes in the NAAQSs for a
pollutant; rather, reevaluation was intended to
ensure that the scientific database was reviewed
and that the NAAQSs were consistent with current knowledge. To my knowledge, this requirement for mandatory review every 5 years is
unique to the setting of the NAAQS in the United
States. Indeed, I know of no other statute calling
for an updating of the science and reconsideration
of the Standard every 5 years.
18
Air Quality Guidelines and Standards
Section 108 of the amended CAA specifies the
development of scientific criteria for certain air
pollutants. It specifies that the Administrator publish a list for pollutants: (a) which have an adverse
effect on public health or welfare, and (b) which
are derived from numerous or diverse mobile or
stationary sources. It explicitly states – “the
criteria shall accurately reflect the latest scientific
knowledge on the kind and extent of all identifiable effects on public health and welfare which
may be expected from the presence of the pollutant in ambient air, in varying quantities” [15].
Section 109 of the CAA [15] directs the
Administrator to propose and promulgate “primary” and “secondary” NAAQSs for criteria pollutants identified under Section 108. The primary
Standards are to be set to protect public health;
secondary Standards are to be set to protect the
public welfare such as effects on soils, water,
crops, visibility, and deterioration of property. In
this entry, I focus on the setting of the primary
Standards and on the specific NAAQS. However,
the issues discussed are also broadly applicable to
the setting of secondary Standards.
Section 109(b)(1) defines a primary NAAQS
as one that “the attainment and maintenance of
which in the judgment of the Administrator, based
on the criteria and allowing an adequate margin of
safety, is requisite to protect the public health.”
The margin of safety, as interpreted by the EPA, is
intended to address uncertainties associated with
inconclusive scientific and technical information
at the time the Standard is set and to account for
hazards that research has not yet identified.
The primary Standards are intended to protect
against “adverse effects, not necessarily against
all identifiable effects of changes produced by a
pollutant.” Although the US Congress did not
rigorously define an adverse effect, it did provide
general guidance in the legislative history of the
debate on the CAA [30]. Congress was concerned
with effects ranging from cancer, metabolic and
respiratory disease, and impairment of mental
processes to headaches, dizziness, and nausea.
Congress also noted concern for sensitive population groups in setting the NAAQSs. In
particular, Congress noted that the Standards
should protect “particularly sensitive citizens
such as bronchial asthmatics and those with
emphysema who in the normal course of daily
activity are exposed to the ambient environment.”
This has been interpreted to exclude individuals
who are not performing normal activities, such as
individuals who are hospitalized. Further guidance was given noting that the Standard is statutorily sufficient whenever there is “an absence of
adverse effect on the health of a statistically
related sample of persons in sensitive groups
from exposure to the ambient air.”
The challenge of interpreting the “adequate
margin of safety” language of the CAA was noted
in an editorial by Donald Kennedy on Risk versus
Risk published when he served as Editor-in-Chief
of Science [27]. He wrote – “In the United States
and some other industrial democracies, where people and their governments tend to be risk averse,
legislatures, courts, and administrative entities usually create a presumption favoring more safety
rather than less. The definitions of risk in law are
often vague (‘reasonable certainty of no harm’ or
‘adequate margin of safety’) and are likely to
encourage an unrealistic belief that risks can be
minimized or even eliminated altogether.” I think
Kennedy has captured the conundrum posed by the
language of the CAA, a conundrum that has been
addressed by US Supreme Court Justice Stephen
Breyer as I will relate later.
In 1977, several key amendments were made
to the CAA [16]. Concern about slow action of the
EPA in preparing criteria documents and
reassessing NAAQSs prompted a legislated
requirement that the NAAQSs be reevaluated not
later than January 1, 1980, and at 5-year intervals
thereafter. Reevaluation was not intended to automatically result in changes in the NAAQSs for a
pollutant; rather, reevaluation was intended to
ensure that the scientific database was reviewed
and that the NAAQSs were consistent with current knowledge. To my knowledge, this requirement for mandatory review every 5 years is
unique to the setting of the NAAQS in the United
States. Indeed, I know of no other statute calling
for an updating of the science and reconsideration
of the Standard every 5 years.
18
Air Quality Guidelines and Standards