Pollution Impact Assessment
Air is a resource not confined by political or geographical
boundaries. Air as a resource carries many social, economic and environmental
significance and air pollution creates the following problems:
Background on Assessment and Framework
Air quality impact assessment (AQIA) is a mechanism,
which aids the efficient use of air resources. It is used in the following
a public health and environmental quality problems
an economic problem, intimately and directly affecting
industry and agriculture
a social problem, creating constraints on the nature
and direction of urban and regional development and patterns of land use.
In the beginning the Air Pollution System was defined
and here a systematic approach for AQIA using a conceptual framework is
proposed in figure 2.1. As presented in the air pollution system, AQIA
must focus on the following three elements:
In the identification, prediction, and evaluation
of critical variables
To identify the potential changes of air quality
as a result of emissions from new proposed projects
As a screening device for settling priorities for
As a tool to test alternative project design at an
early stage and aid the identification of the most suitable site in terms
of benefit maximization and reduction of harmful effects
To identify the type of industry which can be accommodated
in an area while maintaining good air quality
To show the commitment in terms of compliance with
all the air pollution control regulations
In formulating new environmentally sound air resource
policies and plans.
At the moment, Nepal does not have prescribed any
approach to be used in the air quality impact assessment. The first step
is to determine the approach and select the methods to be used. The proposed
approach is provided in figure 2 and the various methods to be followed
are grouped in three steps and briefly highlighted.
Receptors and detectors
Knowledge of existing air quality conditions of
area under consideration.
The area under consideration requires following
Step Two: Determination
of the Incremental Concentration of Pollutants.
ambient pollutant concentrations
pollution sources and their locations
meteorology and climatology
local topographical and physical conditions affecting
This steps looks into the following aspects:
Step Three: Air
Quality Impact Assessment.
Types and quantities of pollutants that will be released
from the project sources, i.e. the emission rates of all pollutants.
Use of air quality modeling techniques to determine
the incremental ground level concentration of pollutant under consideration.
The impact assessment is generally based upon:
Comparison of the combined concentration (background
and incremental concentrations) of the pollutant and the acceptable or
allowable ambient air quality standards of that pollutant.
Identification of the mitigation measures to bring
the pollutants within the acceptable level.
AQIA first requires the knowledge of the baseline
conditions. In the first chapter, various air quality-monitoring networks
and national emission inventory procedures have been proposed and these
form the basis for the collection of baseline information. In addition
to these, AQIA requires other information too. The best approach is to
develop a checklist and collect information as per. The following is a
checklist showing the information and actions that are required for the
assessment of air quality impacts.
Source location map showing location with respect to
Urban areas within 50 km or distance to which source
has a significant impact, whichever is less
Prevention of significant deterioration (PSD) areas
or non-attainment area
Other major existing sources
Other major sources subject to PSD requirements
Regional/local/on-site air quality monitoring locations.
Plant layout on a topographical map covering 1-km
radius of the source.
Information on urban/rural characteristics
Land use within 3 km of source
Total population and population density
Using urban or rural modeling methodology
Emission inventory and operating/design parameters for major sources within
region of significant impact of the project site
Actual and allowable emission rates (g/s) and operating
Maximum design load short-term emission rate (g/s)
Associated emission characteristics as a function
of load for maximum, average, and normal operating conditions
Associated stack characteristics such as location,
stack height, stack diameter, exit velocity, and stack gas temperature.
Area source emissions (rates, size of area, height
of area source)
Location and dimensions of buildings to determine
potential building downwash considerations.
Associated variables such as boiler size, boiler
parameters, operating conditions, and pollution control equipment
Anticipated growth changes
Air quality monitoring data
Summary of existing observations for latest five
years from the responsible authority or private organizations
Comparison with standard
Discussion of background due to an inventory area
and description of the method used for determination of the background.
On-site/local and National Weather Service Meteorological Data
One or more years of hourly sequential on-site data,
or five consecutive years of the most recent representative sequential
hourly National Weather Service Data.
Discussion of meteorological conditions observed
Discussion of topographic/land use influences
Air quality modeling analysis
Model each individual year for which data are available
with a recommended model
Define worst case meteorology
Determine long-term and short-term background and
As outlined above, the second step in the impact
assessment process is the determination of qualitative and quantitative
aspects of pollutants released on the atmosphere and predicts their impacts
on the atmosphere. Air quality modeling is required for major sources of
new development projects. At the moment, only the subjective methods are
practiced in Nepal and no mathematical models are used.
Determination of Concentration
Air quality modeling is used to predict air quality
and assist with policy and planning decisions with respect to industrial
and infrastructure development and management. Air quality as a systems
analysis is represented in figure 2.1.
The science of modeling of air quality and specific
constituents is extremely sophisticated, particularly where adequate input
data on meteorological, topographical and chemistry constituents is available.
Modeling is mainly used to:
to demonstrate that emissions (in attainment areas)
from the proposed source will not exceed either the PSD increments or national
air quality standards
to demonstrate (in non-attainment areas) that offsets
will result in air quality improvement even with the addition of proposed
to ascertain the need for monitoring and then, when
necessary, to select monitoring sites.
The various mathematical modeling techniques used
in many countries are grouped in following classes:
Proposed Air Quality Modeling Methods
The statistical models relate to air quality based
on analysis of ambient air quality monitoring data. The simplest statistical
model assumes that the present air quality can be linearly scaled in direct
proportion to emissions.
Emission models have been developed and used in recent
years to predict emission rate from hazardous waste treatment and disposal
sites. The models are based on diffusion theory and emission rates are
calculated by determining the mass transfer coefficient of the pollutant.
Since no such models are practiced in Nepal, two
simple dispersion models and one Air Pollution Index Modeling are proposed
here to start with.
There are various dispersion model techniques most
commonly used in many countries. Most dispersion models produce estimates
of pollutant concentrations at selected locations. These points of location
are called receptors, and the network of points is the receptor grid. Some
models allow the user to choose the receptor locations. Usually, a uniform
pattern, either rectangular or circular, is chosen. Some models also allow
the inclusion of terrain features by allowing the user to specify the height
of each receptor above or below the source elevation.
The Gaussian plume models for single and multiple
sources are the most common air pollutant models. The equation that describes
the three-dimensional concentration field generated by point source(s)
under stationary meteorological and emission conditions is:
Simple Box Model
This is a common simple model used to get
an initial estimate of concentration values. It is based on the mass conservation
of a pollutant in a box. The reference frame is Eulerian, i.e. fixed frame,
rather than Lagrangrian, i.e. reference frame moving with the velocity
of the pollutant. The box or volume may represent a city or region. The
plan area over a city is represented by ?x
in the vertical dimension of the air shed.
Consider the wind entering the air shed with a
velocity U and a concentration Cin. Assume no pollutants leave
the sidewalls of the box and full mixing occurs within the box. The pollutants
for simplicity are assumed to be conservative (i.e. the generation/ decay
(Source: Gerard Kiely, Environmental Engineering, ISBN 0-07-709127-2)
'Gaussian' modeling is the more widely used technique
for estimating the impact of non-reactive pollutants (USEPA, 1986). Gaussian
modeling is far from being exact, as some of the model assumptions compromise
accuracy. These assumptions include:
(Source: Gerard Kiely, Environmental Engineering,
There is no variation in wind speed and direction
between the source and the receptor.
All effluent remains in the atmosphere and no provision
is made for wet or dry deposition or chemical conversion. Any plume impacting
on the ground is totally reflected.
Dispersion does not occur in the downwind direction.
It only occurs in the vertical and cross wind directions. The dispersion
is stochastic and is described exactly by the Gaussian distribution.
Emission rates are assumed constant and continuous.
It is typically based on a function
where ? is
ascribed a number indicating good quality, satisfactory quality, unhealthy
quality and hazardous quality. This index is used sometimes in the United
States at a level understandable by the public and is called the PSI, or
Pollution Standard Index. The function ?
may be related to a specific parameter like CO, smog or SO2
or any other parameter that is listed in the Air Quality Standard or a
group of parameters. This modeling method takes the weighted values of
individual pollutant parameters measured at spatial points and then compares
this to single number in the air quality standard.
Modeling of Air Pollution Indices
The attraction of this model is that the number
is a non-dimensional number and a value of, say, 400 for CO or SO2
may be deemed hazardous for both, even though the corresponding concentrations
may be, say 400 ppm (CO) and 1 ppm (SO2).
An example of PSI is given in following
table 2.1 for SO2 concentration in ppm. Similar PSI can be used
for other pollutants also.
Table 2.1 PSI Index for SO2
(Source: Gerard Kiely, Environmental
Engineering, ISBN 0-07-709127-2)
As stated in the very beginning, Nepal
is still to use models in assessing the air pollutant concentration. The
above-mentioned models are proposed for the local air quality assessment
purposes. However, the Gaussian modeling can be used for transboundary
air quality assessment in border areas with defined grid system. Therefore
regional specific model development and identification of characteristics
of such models is an area of investigation in Nepal. And this is the area
where mutual cooperation is needed so that similar model are developed
and used in all the member countries to facilitate the comparisons based
on the same models.
Regional Assessment Models
Primarily the main objective behind
the use of such air quality modeling is to estimate the transfer of pollutants,
particularly the oxides of sulfur and nitrogen across the political borders.
The formation of ozone in the transfer media also carries significance.
Once the national monitoring networks
are established in every member countries, the data collected can be transferred
to the regional network. Thus every country will have the knowledge how
much they individually produced the pollutants monitored and how much they
received from others or they transferred to others. In this fashion, the
national targets as well as the joint targets to reduce or abate such pollutants
can be developed.
The environmental protection act and
regulation requires environmental impact assessment study prior to start
of major development works. However, these requirements do not have the
national emission standards and therefore the first work is to make these
legislative requirements complete. The various standards required include:
Air Pollution Impact Assessment
Air quality impact assessment
primarily relies on comparing the limit values, i.e. the legislative requirements.
And then the impacts on various receptors are analyzed. Nepal still is
in the early stage of assessing the air quality impacts. The ambient air
quality standards and emission standards are yet to be made the part of
the prevailing legislative framework. Therefore, the first step is to develop
national air emission standards. The second step is to provide information
on the effects of air pollutants on various receptors so that the rate
of emission can be assessed with its effect on the receptors.
Development of National Standards
Ambient air quality standards
Emission standards for various stationary
Emission standards for mobile sources
Ministry of Population anf Environment
with technical assistance from Asian Development Bank has undertaken study
to develop ambient air quality standards. This study has recommended the
basis for ambient air quality standard settings. Basis used in setting
the values for ambient air quality parameters were:
Ambient Air Quality Standards
After analyzing the above basis, the
project has recommended the standard for Kathmandu Valley. It is divided
into two area- commercial area and non- commercial area. Only six parameters
are included in the standard. Further, MOPE as its annual program has worked
in developing ambient air quality standards. These proposed standard is
already presented in the baseline chapter and hence this standard must
be immediately implemented as the ambient air quality standard for Kathmandu
WHO guidelines for Ambient Air Quality
Ambient Air Quality Standards in neighboring countries
Ambient Air Quality Standards in industrialized countries
Recent Ambient Air Quality monitoring
data produced by various project specific studies.
The above mentioned standard need
to be followed by the commitment of the Government that the objectives
of this standard is to bring down the air quality to the WHO prescribed
limits in next few years. Further study is proposed in incorporating all
the criteria pollutants in the standard. The study should also look into
the possibility of incorporating other toxic air pollutants into the standard.
So far Nepal does not have introduced
the standards of performance for the stationary sources. Various industry
specific standards for both the existing and forthcoming industries are
required. This is because there is some maximum possible (or practical)
degree of emission control. This degree varies between various classes
of emitters. MOPE is currently working in developing the industry specific
emission standards. As per the work schedule of Institutional Strengthening
Project (DANIDA assisted), the standards for following sources are expected
to come into force by 2001.
Brick-Kiln Industries (traditional
as well as the modern one)
Industries using industrial boilers
(textile, wool dying, food processing, distillery and brewery, etc)
Industrial Furnaces (iron and steel)
Sugar (boilers with bagasse as fuel)
Paper and pulp
Power plants (diesel)
Nitric and Sulfuric Acid plants (for
Large Incinerators (for new projects)
Nepalese industry sector is dominant
of small and medium sized industries. The effectiveness of the emission
standards relies on the cost-benefit analysis of the control measures to
be taken to achieve the limits. In parallel to the emission standards following
basic technology issues need to be taken into account prior to enforcing
the emission standards.
MOI is currently working in promoting
pollution prevention programs in industries. In choosing the best practicable
environmental options following elements need to be taken into account:
Evaluation of the technologies currently
in use in the country.
Collection of information on various
technology options available in the sub region
Develop the national technology standards
(best environmental options)
Make these standards the part of the
national legislative requirements.
The judgement for the best environmental
options can be different for new projects and the existing projects. The
benefits of adopting this technique in existing plant will be less due
to its remaining life and likely utilization. In many countries, a systematic
approach is followed and in Nepalese context also following steps is recommended
in choosing the ‘Best Practicable Environmental Options’ (BPEO).
Available techniques for an operation
at the appropriate scale and commercial availability
The benefits gained by using such techniques
should be at a reasonable relationship to the cost of obtaining them.
It is as required by the carrying capacity
of the atmosphere.
Step 1: Define the objective
State the objective of the project
or proposal at the outset, in terms, which do not prejudge the means by
which that objective is to be achieved.
Step 2: Generate Options
Identify all feasible options
for achieving the objective. The aim is to find those, which are both practicable
and environmentally acceptable.
Step 3: Evaluate the options
Analyze these options, particularly
to expose advantages and disadvantages for the environment. Use quantitative
methods when these are appropriate. Qualitative evaluation will also be
Step 4: Summarize and present
Present the results of the evaluation
concisely and objectively, and in a format, which can highlight the advantages
and disadvantages of each option. Do not combine the results of different
measurements and forecasts if this would obscure information, which is
important to the decision.
Step 5: Select the preferred
Select the BPEO from the feasible
options. The choice will depend on the weight given to environmental impacts
and associated risks, and to the costs involved. Decision-makers should
be able to demonstrate that the preferred option does not involve unacceptable
consequences for the environment.
Step 6: Review the preferred
Scrutinize closely the proposed
detailed design and the operating procedures to ensure that no pollution
risks or hazards have been overlooked. It is good practice to have the
scrutiny done by individuals who are independent of the original team.
Step 7: Implement and monitor
Monitor the achieved performance
against the desired targets especially those for environmental quality.
Do this to establish whether the assumptions in the design are correct
and to provide feedback for future developments of proposals and designs.
Throughout Steps 1 to 7: Maintain
an audit trail
Record the basis for any choices
or decisions through all of these stages, i.e. the assumptions used, details
of evaluation procedures, the reliability and origins of the data, the
affiliations of those involved in the analytical work and a record of those
who have taken the decisions.
Nepal recently introduced Nepal Vehicle
Mass Emission Standard 2056 (table 2.1) for new vehicles. This standard
basically is a technology standard. The vehicles to be imported in the
country need to comply the following standard.
Emission Standards for Mobile Sources
Table 2.1 Nepal Vehicle Mass
Emission Standard 2056
For passenger car upto six seats
||grams per kilometer
||HC + NOx
Conformity of Production
* only for diesel vehicles
In addition to the above emissions requirement, the standard also
includes following requirements:
Nepal vehicle mass emission standard 2056 also includes limits for light
commercial vehicles and heavy-duty vehicles for both fueled with diesel
and gasoline. The standards for 2 and 3 wheelers are also in use. Nepal
also had standards for in-use vehicles- petrol driven vehicles (3% for
vehicles 1984 model year and later; 4.5 % for vehicles before 1984 model
year) and diesel vehicles (65 HSU for 1994 model years and later; 75 HSU
for before 1994 model year). As Nepal has initiate to works towards promoting
vehicles fueled with compressed natural gas and liquefied petroleum gas,
it is also required to bring standards for those vehicles fueled with these
CO at idling must not exceed 3.5%
No crankcase emission
Evaporative emission should not exceed 2 g/test`
Durability test of pollution control devices
Phytotoxicants cause several forms
of damages to leaves and some of them are listed here:
Effects of Air Pollution
Another method of air quality
assessment is the knowledge of pollution effects on human health, property,
aesthetics, and the global climate. Nepal does not have adequate data on
the effects of air pollutants on these receptors. Therefore it is recommended
to have the concentration level of various pollutants that will have minimum
effects in these receptors. First as a baseline the effects of various
pollutants on different receptors are outlined here.
Effects on Human Being
Major health effects from different
air pollutants are briefed in the following tables 2.2; 2.3; 2.4 and 2.5.
Table 2.2 Effects of Particulate
on Human Health
Source: Wark, 1981
air quality standard
levels of 30 mg/cm2/month
death of persons over 50 may occur
likely to experience increased incidence of respiratory disease
average and SO2 > 250 µg/m3
of industrial workers may cause an increase in absences from work
once in 24 hour
air quality standard
maximum and SO2>630µg/m3
bronchitis patients will be likely to suffer acute worsening of symptoms
average and SO2>715µg/m3
number of deaths and considerable increase in illness occur
Table 2.3 Health Effects of CO
|9 ppm 8
air quality standard
|50 ppm 6
changes in heart and brain of animals
|50 ppm 50
in relative brightness threshold and visual acuity
|50 ppm 8
to 12 hour exposure
performance on psychomotor
source: Wark, 1981
Table 2.4 Health Effects of SO2
ppm annual mean
by smoke at a concentration of 185µg/m3, increased frequency of respiratory
symptoms and lung disease may occur
ppm, 24 hour mean
particulate level, increased hospital admission of older persons for respiratory
diseases may occur. Increased metal corrosion rate.
24 hour mean
particulate level, increased mortality may occur
24 hour mean
by smoke at a concentration of 750µg/m3, increased daily death rate
may occur with sharp rise in illness rates
24 hour average
by particulate, increased mortality may occur.
Source: Wark, 1981
Table 2.5 Health Effects of O3
||Increased airway resistance
||continuous working hours
||Nose and throat irritation, chest
source: Wark, 1981
Effects on Plants
Normally, on plants three different
types of effects of air pollution have been observed:
Necrosis- killing tissue (dead tissue)
Chlorosis- loss or reduction of chlorophyll
thus causing yellow leaves
Abscission- dropping of leaves
Epinasty – downward curvature of leaves
due to higher growth rate of upper surface.
Acute Injury: experienced
due to short exposure (a few hours to few days) of high concentration,
visible making of necrotic patterns of dead tissues have been observed
Chronic Injury: this is long
term exposure at lower concentration following chlorosis and leaf abscission,
Effects on growth: suppression
of growth and yield observed which however is difficult to diagnose because
of several other factors not related to air pollution alone.
Carbon dioxide in the atmosphere dissolves
in rain reducing its pH to 5.6 and naturally occurring oxides of sulfur
and nitrogen are responsible for unpolluted rain having a pH of about 5.0.
Lower values of pH may result from strong acids produced from fuel use.
An alternative unit of acidity is the 'microequivalent of hydrogen ion
per liter', written as µeq H+/l, as defined by
pH = - log10 (µeq
H+/l * 10-6)
Hence, a value of 10µeq H+/l
equates to pH = - log10 10-5) = 5
Other Effects of Air Pollution
Moreover, air pollution has
direct visible effects on materials such as metals, building materials,
and textiles causing corrosion and fading. It has also visible effects
on art treasures. Air pollution has significant effect on atmosphere, e.g.,
reduction of visibility due to absorption and scattering of light by particulate
matters both solid and liquids. It has also effect on radiation flux as
high concentrations of PM can block sunshine from reaching the earth.
The Problem of Acid Rain
In assessing the impact of acidity,
the following definitions are in use:
Acid precipitation : rainfall
or snow with acidity greater than 10µeq
H+/l or pH lower than
Acid mists : fog, mist or low cloud
in which water has an acidity
greater than 10µeq H+/l
or pH lower than 5
Acid Deposition : total deposition
of acid (hydrogen ions) or acid
forming compounds e.g. SO2
and NOx by both wet and dry deposition.
Acid rain : precipitation and other
Acid rain causes a number of adverse
which are more acidic than pH 5.0.
Increase acidity in the soil, threatens
human life and aquatic life, destroys forests and crops reducing agricultural
Corrode buildings, monuments, statues,
bridges, fences and railings.
Serious threat to human health contaminating
breathing air, drinking water and even food.
Pollution Prevention and Control
As per the nature of Nepalese
industry sector, the dominance of small and medium enterprises, pollution
prevention activities are the more focused area. Nepal has launched the
cleaner production and energy efficiency improvement programs in Nepalese
industries. Little work has been done in the pollution control aspect.
# Pollution Abatement Assessment
Pollution Prevention Assessment
Majority of industries in South
Asian countries are small and medium scale industries. National efforts
are more focused on prevention of pollution aspect. Following the experiences
of DESIRE project in India, Ministry of industry has developed the cleaner
production assessment methodology as well as the criteria for analyzing
cleaner production options. Here only the adopted methodology and criteria
for analyzing CP options are presented and the identified barriers and
measures to be taken to overcome such barriers are dealt in details in
CP Assessment Methodology
Working in an unorganized and
piecemeal manner might produce the short-term immediate gains but for an
effective and sustaining CP program it is essential to have a structured
approach applicable to targeted sector or units. An organized approach
means assigning responsibility, setting targets and goals, developing implementation
plans, reviewing progress and timely implementation of techno-economically
feasible and agreed solutions as a continuos improvement program. The prevailing
industry culture, type of technology, and availability of trained manpower
all determine the methodology to be followed in a country like Nepal where
SMEs constitute the major industrial sector. The six-step methodology applied
in the CP demonstration program is presented in the flow chart:
As already explained earlier, Nepal
has not initiated many programs on pollution control field. Nepal has recently
brought the environmental protection act and regulation and now is in the
process of developing emission standards and monitoring mechanism.
Ministry of Population anf Environment
is the responsible body in Nepal, which has to provide information to general
public and others on various environmental issues relating with the pollution
load and its impacts on various detectors and receptors. Since 1997, MOPE
has started to publish the State of Environment Nepal with the objective
of informing all the environmental conditions over the years in the country.
ICIMOD's active participation in publishing this report is continuing and
Ministry is now working in opening
the hope page in the Internet for easy access to all about the environmental
situations of county, the initiatives taken and effectiveness of such measures.
However, the lack of networking system between different line ministries
and other institutions to MOPE is felt biggest hurdle in reporting in time
the actual national environmental picture.
MOPE is working towards establishing
the national environmental data bank, a prioritized program in the ninth
five-year plan. The upgrading of the existing MERCURE system of the Ministry
is on going and during this year it is expected that the system will began
to provide service.
Further, it is felt that a networking
between different line ministries, institutions and MOPE in collecting
various works, the impact on environment and related impacts on various
receptors is necessary. The experiences of ICIMOD in various countries
have to be exploited in Nepal too. A donor-assisted project in the establishment
of National Environmental Data Bank is the need at the time.