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ping process to remove the organic contaminants, which would result in a potential
cross-media problem if air emissions created by this process were not controlled. The
cleanup process (removal and remediation) is also required to comply with applicable
rules and requirements (ARARs). Additionally, for some cleanup operations under the
Superfund, Phase I RCRA air standards may be ARARs.
Another important tool used to address air toxics is toxic release inventory, required
by SARA Title 313. Generally, this inventory assists in improving US EPA’s knowledge
of the sources of air toxics. Recently, the US EPA reviewed this inventory to identify
sources of the 190 toxic pollutants listed under the CAA of 1990.
Figure 20 shows the overlap of statutory coverage of air emission sources with various
laws. This overlap may in some instances result in the same source being subject to
regulations with different control requirements. This conflict is the result of regula-
tions being developed under laws with different mandates. For example, CAA
requires technology-based standards for NSPS, whereas RCRA 3004(n) air standards
are risk based. Compliance under this circumstance must be demonstrated with all
applicable rules. The US EPA will try to make consistent and complementary control
requirements of rules that apply to the same sources. This overlap is illustrated in
Fig. 20 for the coverage of air emissions from storage tanks in waste management.
For example, three separate rules may cover storage tanks containing benzene waste
located at chemical plants, petroleum refineries, coke byproduct plants, and certain
TSDFs. First, NESHAP regulations, as described in 40 CFR 61 Part FF, would apply.
Second, NSPS regulations, as described in 40 CFR Part 60, Subpart Kb, would apply
to new, modified, or reconstructed tanks containing volatile organic liquids (VOLs)
and tanks above a certain size limits. Third, Phase II air standards, as described in
RCRA, would apply to tanks in which organic hazardous waste is managed.
Therefore, depending on the particular physical characteristics of the tank, these stan-
dards could be covered by the benzene waste NESHAP, the VOL storage NSPS, and
RCRA Phase II air standards. This overlap would have minimal ramifications on
owner/operators because control requirements would be the same for all three.
Readers are referred to the literature for the additional discussions on the US Clean
Air Act compliance (47,48,56,66).

10. CONTROL
In the subsequent chapters of this volume, the ways in which emissions diffuse and
become diluted in the atmosphere and methods for controlling air pollution emissions
are discussed. Once the basic diffusion mechanisms and their theory of control are
mastered, it is important to understand how to implement this information effectively in
real situations (23,24). When determining the control option to meet a specific regula-
tion, there will always be several available alternatives. One must consider factors
such as adverse environmental impact, economics, and effect on the process
(27,33,34,63,64). The following discussion illustrates how these factors may influence
the choice of control devices.
One must remember that the improper control of air pollutants can result in other
environmental problems. For example, the byproduct discharge from a control system
can create odors and other varieties of air pollution, water pollution, or solid-waste