Tool 28 - Some Technical Concepts and
Units and Abbreviations
Terms and Definitions
Units and Abbreviations
||benzo[a]pyrene, is the best known and most-measured
||Oxides of Nitrogen
||Policyclic aromatic hydrocarbons
||Particulate Matter of 10 microns or less
||Suspended Particulate Matter
||Total Suspended Particles
||Volatile Organic Compounds
||Non- Methane Volatile Organic Compounds
|| milligrams (10-3 grams)
||microgram (10-6 grams)
||parts per million (volume/volume)
||parts per billion (volume/volume)
||milligrams per cubic metres
||micrograms per cubic meter
* For descriptions of pollutants, see Tool 4.
|1 ppm = 2,860µg/m3
1mg/m3 = 0.35 ppm
|1 ppm = 1.145mg/m3
1mg/m3 = 0.873 ppm
|1ppm = 1,230 µg/m3
|1 ppm = 1,880µg/m3
1 µg/m3 = 0.000532 ppm
|1 ppm = 3.19mg/m3
1mg/m3 = 0.313 ppm
|1ppm = 1.5mg/m3
1mg/m3 = 0.670 ppm
|1ppm = 2.589mg/m3
1 mg/m3 = 0.386 ppm
||1ppm = 3.75 mg/m3
1 mg/m3 = 0.226 ppm
|1ppm = 5.4mg/m3
1mg/m3 = 0.18 ppm
|1ppm = 6.78mg/m3
1 mg/m3 = 0.14 ppm
|1 ppm = 4.2mg/m3
1mg/m3 = 0.24 ppm
|1 ppm = 1.2mg/m3
1mg/m3 = 0.833ppm
|1 ppm = 5mg/m3
|1 ppm = 3.13mg/m3
1mg/m3 = 0.32 ppm
|1ppm =4.12mg/m3 (at 20oC)
1mg/m3 = 0.242 ppm
|1 ppm = 3.47mg/m3
1 mg/m3 = 0.28 ppm
|1 ppm = 2mg/m3
*For conversions between ppm, ppb, mg/m3 and ug/m3:
MolWeight x PPM = 24.45 x mg/m3 or MolWeight x
PPB = 24.45 x ug/m3
For additional unit conversions see the attached Conversion
Acute Health Effects:
Those immediate health effects resulting from exposure to an episode of
air pollution e.g. asthma attack. In certain conditions, acute episodes
of air pollution are also associated with an overall increase in respiratory
and cardiovascular mortality.
Any effect that may affect the performance of the whole organism or that
reduces an organism's ability to respond to an additional pollutant.
The normal concentration of a particular air pollutant occures naturally
in the environment (also without any human activity). This is determined
by the natural characteristics of an area like the presence of deserts,
A substance that causes abnormal, uncontrolled growth of cells or cancer,
like lung cancer or leukaemia. This includes benzene, benzo-a pyrene (BaP)
and heavy metals like lead, arsenic, nickel, cadmium etc.
Carcinogenic and Toxic Health Effects:
Those health effects resulting from exposure to carcinogenic (cancer causing)
Heart related disease
Chronic Health Effects:
Those health effects owing to long term exposure to lower levels of pollution
e.g. bronchitis resulting from SO2 exposure,
or the increased respiratory and cardiovascular mortality observed in
a number of epidemiological studies due to exposure to particulate matter.
Cost Benefit Analysis (CBA):
An analysis of the costs of pollution abatement versus the benefits to
be derived from such abatement measure: both of which are expressed in
Cost Effective Analysis (CEA):
An analysis of the costs of abatement measures whose benefits are expressed
in physical terms such as reduced emissions or reduced concentrations.
A dispersion model is a software programme that assesses/calculates the
concentrations of a specific pollutant on the basis of the emissions of
the polluting activity sectors, at a certain point in time and space.
These models account for geographic factors such as wind speed, temperature
and direction. e.g. CAR International, IMMIS LUFT, BLB etc., Dispersion
models help to limit the complex and often expensive ambient air monitoring
since it calculates the ambient air quality in a given area and identifies
where the emissions are likely to have an impact. However, regular monitoring
will remain important to validate the models and determine the natural
Any measurable air contaminant, pollutant, gas stream, or unwanted sound
from a known source which is passed into the atmosphere
Emission Control Device:
Any device that is placed in a system to reduce the amount of air pollutants
released into the environment.
This is a constant which relates the emission of a certain compound to
the input or output of another compound by the same source, e.g. the emissions
of SO2 by a factory can be estimated from its
coal consumption. Emission factors are useful in cases where emissions
data are missing. They can be used to make a rough estimate of emissions,
based on economic activities, traffic and number of households, followed
by the use of dispersion models to assess concentrations.
(OR: a numerical estimate of the mass of one or more air contaminant
produced by a given amount of material processed by an industrial facility
or, in the case of transportation sources, per mile driven (by a given
vehicle using a particular fuel). It is important to note if the emission
factor is for an uncontrolled source or one with properly functioning
air pollution control equipment. This factor is used to arrive at a rough
estimate of the total air emissions for a facility or a geographical area.)
A compilation of estimated air emissions by pollutant from smokestacks,
cars and other emission sources in a given area.
Legal limits on the degree or quantities of pollutants that are permitted
to be discharged to the atmosphere from specific sources or process, e.g.
emissions from vehicles or from industrial sources.
Environmental Impact Assessment (EIA):
The process of analyzing the probable environmental effects, both positive
and negative, of a proposed project, programme or policy and suggesting
ways to mitigate the adverse effects, including the identification of
alternatives or other ways of implementing parts of it.
A series of short-term air pollution events that significantly alter the
ambient air quality of an affected area.
Lowest Achievable Emission Rate:
Any technology or combination of technologies and process controls that
result in the lowest possible emission of a given air pollutant. The technology
must be reasonably demonstrated to be appropriate and reliable for the
Lowest Observed Adverse-Effect Level (LOAEL):
The lowest experimental dose of a chemical at which there is statistically
or biologically significant increase in the severity or frequency of a
Those sources of pollution that emit pollutants along their path of movement
e.g. road transport and off road mobile sources.
A substance that causes mutation or the alteration of the basic genetic
structure of any living organism
No Observed Adverse Effect Level (NOAEL):
The highest experimental dose of a chemical at which there is no statistically
or biologically significant increase in the frequency or severity of a
toxicity effect between an exposed group and its appropriate control.
Air pollution problems related to the respiratory/ breathing difficulties,
sometimes resulting in acute effects like asthma and fatal heart attacks.
Those sources of air pollution that emit the pollutants from a fixed-point
e.g. industrial plants, power generation facilities, domestic cooking
and heating, agricultural activities etc.
The point below which the environment is not harmed by any pollutant.
Denotes the concentration of a pollutant below which no negative effects
The minimum dose of a toxic substance that causes harmful effects in any
Threshold Limit Value (TLV):
The concentration of an airborne contaminant to which workers may be exposed
regularly without adverse effect. The TLV recognizes that there are some
individual variations among workers and that maintaining exposures within
the limits may not prevent discomfort or aggravation of a pre-existing
condition in some individuals. Most TLVs represent average exposures and
some fluctuations during the day is possible without causing adverse effects.
The distance separating one wave crest from the next in any uniform succession
of traveling waves.