Air Pollution Impact Assessment
    1. Background on Assessment and Framework
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: Air quality impact assessment (AQIA) is a mechanism, which aids the efficient use of air resources. It is used in the following ways: 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: 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.

Step One:

Knowledge of existing air quality conditions of area under consideration.

The area under consideration requires following information:

Step Two: Determination of the Incremental Concentration of Pollutants.

This steps looks into the following aspects:

Step Three: Air Quality Impact Assessment.

The impact assessment is generally based upon:

      1. Baseline Information
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.
    1. Source location map showing location with respect to
    1. Information on urban/rural characteristics
    1. Emission inventory and operating/design parameters for major sources within region of significant impact of the project site
    1. Air quality monitoring data
    1. On-site/local and National Weather Service Meteorological Data
    1. Air quality modeling analysis
      1. Determination of Concentration
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.

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:

        1. Proposed Air Quality Modeling Methods
The various mathematical modeling techniques used in many countries are grouped in following classes: Statistical Models Emission models Dispersion models Since no such models are practiced in Nepal, two simple dispersion models and one Air Pollution Index Modeling are proposed here to start with.
        1. Simple Box Model

        2. 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 ?y and ?z 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 rate® 0):

          (Source: Gerard Kiely, Environmental Engineering, ISBN 0-07-709127-2)

        3. Gaussian Modeling
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:

'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, ISBN 0-07-709127-2)
        1. Modeling of Air Pollution Indices
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.

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
PSI Description Concentration (ppm)







Good quality






Hazardous-serious harm

< 0.07







(Source: Gerard Kiely, Environmental Engineering, ISBN 0-07-709127-2)

      1. Regional Assessment Models
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.

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.

    1. Air Pollution Impact Assessment

    2. 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.

      1. Development of National Standards
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:
        1. Ambient Air Quality Standards
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:
    1. WHO guidelines for Ambient Air Quality
    2. Ambient Air Quality Standards in neighboring countries
    3. Ambient Air Quality Standards in industrialized countries
    4. Recent Ambient Air Quality monitoring data produced by various project specific studies.
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 Valley.

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.

        1. Emission Standards
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.
        1. Technology Standards
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: 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).

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 needed. Step 4: Summarize and present the evaluation 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 option 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 option 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.
        1. Emission Standards for Mobile Sources
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.

Table 2.1 Nepal Vehicle Mass Emission Standard 2056
For passenger car upto six seats
grams per kilometer
Type Approval

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 fuels.
      1. Effects of Air Pollution

      2. 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.

        1. Effects on Human Being

        2. 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
          Concentration Measurement time Effects
          75µg/m3 Annual mean Ambient air quality standard
          80-100µg/m3 With sulfation levels of 30 mg/cm2/month Increased death of persons over 50 may occur
          100-130µg/m3 With SO2>120 µg/m3 Children likely to experience increased incidence of respiratory disease
          200µg/m3 24-hour average and SO2 > 250 µg/m3 Illness of industrial workers may cause an increase in absences from work
          260µg/m3 Maximum once in 24 hour Ambient air quality standard
          300µg/m3 24-hour maximum and SO2>630µg/m3 Chronic bronchitis patients will be likely to suffer acute worsening of symptoms
          750µg/m3 24-hour average and SO2>715µg/m3 Excessive number of deaths and considerable increase in illness occur
          Source: Wark, 1981

          Table 2.3 Health Effects of CO
          Environmental condition Effects
          9 ppm 8 hour exposure Ambient air quality standard
          50 ppm 6 week exposure Structural changes in heart and brain of animals
          50 ppm 50 minute exposure Changes in relative brightness threshold and visual acuity
          50 ppm 8 to 12 hour exposure Impaired performance on psychomotor

          source: Wark, 1981

          Table 2.4 Health Effects of SO2
          Concentration Effects
          0.037-0.092 ppm annual mean Accompanied by smoke at a concentration of 185µg/m3, increased frequency of respiratory symptoms and lung disease may occur
          0.11-0.19 ppm, 24 hour mean With low particulate level, increased hospital admission of older persons for respiratory diseases may occur. Increased metal corrosion rate.
          0.19 ppm, 24 hour mean With low particulate level, increased mortality may occur
          0.25 ppm, 24 hour mean Accompanied by smoke at a concentration of 750µg/m3, increased daily death rate may occur with sharp rise in illness rates
          0.52 ppm 24 hour average Accompanied by particulate, increased mortality may occur.

          Source: Wark, 1981

          Table 2.5 Health Effects of O3
          Concentration Exposure Effects
          ppm µg/m3    
          0.02 40 1 hour Cracked, stretched rubber
          0.03 60 8 hour Vegetation damage
          0.10 200 1 hour Increased airway resistance
          0.30 590 continuous working hours Nose and throat irritation, chest constriction
          2 3900 2 hour Severe cough

          source: Wark, 1981

        3. Effects on Plants
Phytotoxicants cause several forms of damages to leaves and some of them are listed here: Normally, on plants three different types of effects of air pollution have been observed:

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.

        1. Other Effects of Air Pollution

        2. 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.

        3. The Problem of Acid Rain
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

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 5

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 deposition pathways,
which are more acidic than pH 5.0.

Acid rain causes a number of adverse implications:
      1. Pollution Prevention and Control

      2. 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 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 chapter three.

        • 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:

          FLOW CHART


        #   Pollution Abatement Assessment

        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.

      3. Reporting
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 significant.

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.