Overview of Air Pollutants and Management Strategies – Env 247 –
February 24, 2011
Classification of Air Pollutants
Air Pollutants
Criteria Pollutants
NOx, Sox, PM, CO,
Ozone, Lead
Mobile Pollutants
CO, VOCs, NOx,
Sox, Lead
Health Effects
Irritant, Edema, Emphysema
Acid Rain Precursors
Sox, NOx
Emission Cap and Trade
Program
Air Toxics
NESHAPS, HAPs,
TAPs,
112r Substances
Ozone Depleters
CFCs, HCFCs,
Halogenated VOCs
Health Effects –
Toxics, Mutagens,
Carcinogens
Permits - Title V, NSPS,
NSR
Standards –
Threshold Emission
Limits
Standards - NAAQS
Permits –
Major Source =
10/25 tons
Title V
Control –
Attainment, SIPs
Control –
MACT, RMPs
Source control
LAER
BACT
Criteria Pollutants
Pollutants for which National Ambient Air Quality
Standards (NAAQS) have been established:
1.
2.
3.
4.
5.
6.
Particulates (PM10)
Sulfur Oxides (SOx)
Nitrogen Oxides (NOx)
Carbon Monoxide (CO)
Photochemical Oxidants (Ozone)
Lead
Toxic Pollutants
Pollutants hazardous to health or the environment
but not regulated as criteria pollutants:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Mercury
Asbestos
Arsenic
Benzene
Radon
Vinyl Chloride
Beryllium
Coke Oven Emissions
188 compounds designated by EPA as “Hazardous Air
Pollutants” or HAPs.
10. North Carolina has identified 105 “Toxic Air Pollutants” with
acceptable ambient levels or AALs.
Global Pollutants
Pollutants that because of their persistence or
distribution have a global impact on air quality:
• Chlorofluorocarbons – Stable “freons” that once
in the stratosphere breakdown Ozone.
• Carbon dioxide – Major substance related to the
global “greenhouse effect”.
Regulation of Air Pollution
Hazardous Air Pollutants - HAPs:
 188 Specific compounds

Definition = A substance when released to the
atmosphere can cause significant harm to
human health or the environment; includes
 Particularly or extremely toxic substances
 Carcinogens
 Mutagens
Regulation of Air Pollution
Hazardous Air Pollutants – Sources

Major Source = Any stationary source that
emits 10 tons or more per year of any single
HAPs or 25 tons or more per years of all HAPs.

Area Source = Any stationary source of HAPs
that is not a major source.
Regulation of Air Pollution
Hazardous Air Pollutants – Emission Control

US EPA required to list:
 categories of major sources,
 categories of area sources warranting regulations, and
 national emission standards.

Maximum Achievable Control Technology or MACT =
 For a major source in a particular category – The average emission
limitations achieved by the best performing 12% of existing sources
or
 The average emission limitation achieved by the best performing 5
sources if there are fewer than 30 sources in a given category
HOW HAPS AND TAPS ARE REGULATED

Emission limits for major or area sources are established and regulated
by air permitting process
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Sources (major and area) of HAPs must install MACT to meet HAP
emission reduction requirements
All sources of NC TAPs must comply with NC TAP regulations
CONTROL OF HAZARDOUS AND TOXIC AIR
POLLUTANTS
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NC Toxic Air Pollutants TAPS Program Compliments the Clean Air Act
Program for Hazardous Air Pollutants (HAPs)
Federal HAP Program is technology-based and requires Maximum
Achievable Control Technology (MACT)
NC TAP Program is health-based and has an acceptable ambient
concentration
Regulation of Air Pollution
North Carolina – Toxic Air Program
A health-based toxic air pollutant control program that regulates 105 air
pollutants emitted from stationary sources.
Emissions of toxic air pollutants must be reduced such that the resulting
modeled ambient air levels are below health-based acceptable ambient
air levels at the property line.
Regulated facilities must submit a complete air toxic emissions report
once every 3 years.

NC TAP REGULATORY PROGRAM


The Science Advisory Board sets an exposure limit – the Acceptable
Ambient Limit (AAL)
The NC Division of Air Quality (DAQ) is responsible for enforcing the
AAL through air permits:


The NCDAQ sets an emission limit from emission sources above which the
ambient concentration will be exceeded
This emission limit (rate) is called the Toxic Permitting Exemption Rate, or
TPER
NC TOXIC AIR POLLUTANTS
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Each TAP has an AAL-Acceptable Ambient Level established by a State
Science Advisory Board (SAB)
SAB composed of physicians, toxicologist and other scientists
The AAL is the concentration limit for exposure of the public
Some pollutants have hourly limits, others have daily or annual
Examples
HCl: Hourly Limit
Carbon disulfide: 24-hour limit
EtO: Annual limit
Hourly = Acute irritant
24-hour = Chronic irritant
Annual = Cancer causing
EXAMPLE OF STEPS INVOLVED
ETHYLENE OXIDE
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Identify all possible sources of EtO
Determine the emission rate of each source. In this case – 7 EtO sterilizers
- number of cycles per year
- emission of EtO per cycle
Obtain precise emission parameters
- stack height, location
- exhaust temperature, velocity, etc.
Build the computer dispersion model
- topography
- all buildings, structures, etc.
- all emission information
Obtain NCDAQ approval of all modeling information
Run the emission model (Aeromod) for 5 consecutive years of meteorological
data. Use results of the worst-case year and must be below Acceptable Ambient
Limit.
Apply for air permit with emission limits
AIR PERMITTING OF TOXIC AIR POLLUTANTS
If facility’s emissions of any TAP are above the TPER, facility must:



Perform dispersion modeling to demonstrate that the off-site
concentration due to the facility emissions will be below the Acceptable
Ambient Limit
Submit application for air permit
Maintain records to demonstrate it always operates within the emission
limits of its air permit
Modeling Air Toxics – Ethylene Oxide
Meteorological Data
Stack Parameters
Temperature
Exit velocity
Stack diameter
Stack height
Constituent Emission Rate
Modeled air
concentration –
Air model
(Aeromod)
expressed as a
single point of
maximum impact
or as an isopleth
EXAMPLE OF MODEL RESULTS
ETHYLENE OXIDE EXAMPLE
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The TPER for EtO is 1.8 lbs/yr
The EtO potential emissions (assumes every sterilizer runs 24/7) were estimated at 18.02
lbs/yr – Therefore:
Constructed and ran computer model and applied for air permit
Modeling results:
- Allowable Ambient Limit (AAL) = 2.7 x 10-5 milligrams/m3
- Highest concentration = 8.47 x 10-6 milligrams/m3
- Highest concentration ~ 31% of AAL at one spot
- Vast majority of area is less than 10% of the AAL
Figure shows modeling results in micrograms/m3 (µg/m3)
e.g. kellygreen = 0.003 µg/m3 = 0.000003 milligrams/m3 = 11% of AAL
Release Prevention and Control
Regulatory Actions Aimed towards Emergency Preparedness
to Prevent and Mitigate Releases
.
Release Prevention and Control –
SARA Title III

Section 302 – Identification of Extremely Hazardous Substances stored,
processed or otherwise used above threshold planning quantities

Section 304 – Notification of reportable releases of CERCLA hazardous
substances or Section 302 Extremely Hazardous Substances above
reportable quantities.

Section 311 – Initial report to local fire department, LERC, and SERC of
hazardous substances used or stored on site.
Section 312 – Annual report on the presence of hazardous substances
used or stored on site


Section 313 – Toxic Release Inventory:
Facilities with SIC codes 20-39 who manufacture or process more than
25,00 lbs/yr or use more than 10,000 lbs/hr of listed toxic chemicals must
report annual releases to the environment .
Release Prevention and Control
Prevention of Accidental Releases –
Hazardous Substances Defined as:
Any chemical listed under Section 112(r) or any other chemical which
may, as a result of short-term exposures, cause death, injury, or
property damage due to their toxicity, reactivity, or corrosivity.
Release Prevention and Control
Prevention of Accidental Releases – Section
112(r) Risk Management Planning
Owners/operators of stationary sources subject to Section 112 (r) that
use, store or process listed hazardous chemicals at or above designated
thresholds must implement a Risk Management Program the includes 
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An off-site consequence analysis to evaluate:
 A worst-case scenario and
 Other alternative release scenarios.
Develop and maintain a 5 year release history.
A Release Prevention Program.
An Emergency Response Plan
Release Prevention and Control
Prevention of Accidental Releases – Section 112(r) General
Duty Clause
Owners/operators of stationary sources that produce, process, handle or
store any listed substance or other extremely hazardous substance
below the threshold quantity must develop and implement plans to –
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Identify hazards which may result for releases using appropriate hazard
assessment techniques.
Design and maintain a safe facility, taking steps as necessary to prevent
releases, and
Minimize the consequences of accidental releases.