Monday, 26 December 2016

Importance of National Ambient Air Quality Standards

Importance of National Ambient Air Quality Standards

Air Pollutant includes any substance in solid, liquid or gaseous form present in the atmosphere in concentrations which may tend to be injurious to all living creatures, property and environment. Various contaminants in different forms from both man-made and natural sources perpetually enter our environment and contaminate it causing toxicity, diseases and environmental decay. Recent industrialization and increased number of potent air polluting sources like automobiles, landfills, etc. has gushed into the atmosphere toxic materials which not only harm human health but are also a threat to the ecosystem in general. In order to arrest the deteriorating air quality, Government of India enacted Environment (Protection) Act, 1986, which was an umbrella act for the protection of all aspects of the environment. The government had also enacted the Air (Prevention and Control of Pollution) Act, 1981 with the aim of ensuring moderated pollution concentrations and hence safe ambient air quality.
Also read- Vehicular Pollution and Emission Standards in India
Air pollution is a global concern. One can not merely abstain themselves from pollution at an individual level because unlike water whose purity can be ensured before consumption, air has to be taken up in the form that it is present. Air pollution is known to cause a lot of premature deaths, chronic asthma, decreased fertility, deteriorated property and may lead to the hazardous acid rains too. It is hence imperative that the air pollutant concentrations are regularly monitored and a proper inventory is maintained so that one can predict unforeseen disasters like The Great Smog of 1952 in London. With the aim of proper monitoring of the pollutant concentrations, the Central Pollution Control Board (CPCB) in1984-1985 launched the National Ambient Air Quality Monitoring network which was later renamed as National Air Monitoring Programme (N.A.M.P.). The objectives of N.A.M.P. can be enlisted as follows-
  • To determine the trend and status of the ambient air quality.
  • To ascertain that the prescribed levels are being met or not
  • To identify the cities where the pollution concentration is higher than the prescribed levels.
  • To understand and obtain knowledge for the development of preventive and corrective measures.
  • To understand the ongoing natural processes of cleansing like dispersion, dilution, dry deposition, wind-based movements, chemical transformation and precipitation.
The objective of National Ambient Air Quality Standards (NAAQS) is-
  • To indicate necessary air quality levels and appropriate margins required to ensure the protection of vegetation, health and property.
  • To provide assistance in the establishment of priorities for abatement and control of pollution.
  • To provide a uniform yardstick for assessment of air quality at the national level.
  • To indicate the extent and need of monitoring programme.
The NAAQS notified as on November 2009 is tabulated below-
Sr. NoPollutantsTime Weighted AverageConcentration in Ambient AirMethods of Measurement
Industrial, Residential, Rural and other Areas Ecologically Sensitive Area (notified by Central Government)
1Sulphur Dioxide (SO2 ), µg/m3Annual*50201.     Improved West and Gaeke2.      Ultraviolet Fluorescence
24 Hours**8080
2Nitrogen Dioxide (NO2 ), µg/m3Annual*40301.     Modified Jacob & Hochheiser (Na-Arsenite)2.     Chemiluminescence
24 Hours**8080
3Particulate Matter (Size <10 µm) or PM10 µg/m3Annual*60601.     Gravimetric2.     TEOM
3.     Beta attenuation
24 Hours**100100
4Particulate Matter (Size<2.5 µm) or PM2.5 µg/m3Annual*40401.     Gravimetric2.     TEOM
3.     Beta attenuation
24 Hours**6060
5Ozone (O3 ), µg/m38 hours**1001001.     UV photometric2.     Chemiluminescence
3.     Chemical Method
1 hours **180180
6Lead (Pb), µg/m3Annual*0.500.501.     AAS/ICP Method after sampling using EPM 2000 or equivalent filter paper2.     ED-XRF using Teflon filter
24 Hours**1.01.0
7Carbon Monoxide (CO), mg/m38 hours**0202Non dispersive Infra Red (NDIR) Spectroscopy
1 hours **0404
8Ammonia (NH3 ), µg/m3Annual*1001001. Chemiluminescence2. Indophernol blue method
24 Hours**400400
9Benzene (C6 H6 ) , µg/m3Annual*05051. Gas chromatography based continuous analyzer2. Adsorption and Desorption followed by GC analysis
10Benzo(a)Pyrene (BaP)- particulate phase only, ng/m3Annual*0101Solvent extraction followed by HPLC/GC analysis
11Arsenic (As), ng/m3Annual*0606AAS/ICP method after sampling on EPM 2000 or equivalent filter paper
12Nickel (Ni), ng/m3Annual*2020AAS/ICP method after sampling on EPM 2000 or equivalent filter paper
*Annual Arithmetic mean of minimum 104 measurements in a year at a particular site taken twice a week 24 hourly at a uniform interval.
** 24 hourly 08 hourly or 01 hourly monitored values, as applicable shall be complied with 98% of the time in a year. 2% of the time, they may exceed the limits but not on two consecutive days of monitoring.
The air quality is categorized under 4 broad categories based on Exceedance Factor.
Exceedance Factor
The four air quality categories are:
  • Critical pollution (C): when EF is > 1.5;
  • High pollution (H): when the EF is between 1.0 – < 0.5;
  • Moderate pollution (M) : when the EF between 0.5 – <1.0;
  • Low pollution (L): when the EF is < 0.5.
Pollution levelAnnual Mean Concentration Range (µg/m3 )
Industrial, Residential, Rural & others areas Ecologically Sensitive Area
Low (L)0-250-200-300-100-150-30
Moderate (M)26-5021-4031-6011-2016-3031-60
High (H)51-7541-6061-9021-3031-4561-90
Critical (C)>75>60>90>30>45>90
Percentage of locations exceeding NAAQS in residential industrial rural areasPercentage of locations exceeding NAAQS in sensitive areas
The US EPA identifies two types of NAAQS as per The Clean Air Act, namely, the primary standards for the protection of public health and that of sensitive populations such as children, elderly people and asthmatics. Secondary standards provide for the public welfare protection which includes a safeguard against reduced visibility and damage to crops, animals, vegetation and buildings.
[links to historical tables of NAAQS reviews]
Averaging TimeLevelForm
Carbon Monoxide (CO)primary8 hours9 ppmNot to be exceeded more than once per year
1-hour35 ppm
Lead (Pb)primary and
Rolling 3 month period0.15 μg/m3Not to be exceeded
Nitrogen Dioxide (NO2)primary1-hour100 ppb98th percentile of 1-hour daily maximum concentrations, averaged over 3 years
primary and
1 year53 ppbAnnual Mean
Ozone (O3)primary and
8 hours0.070 ppmAnnual fourth-highest daily maximum 8-hour concentration, averaged over 3 years
PM2.5primary1 year12.0 μg/m3annual mean, averaged over 3 years
secondary1 year15.0 μg/m3annual mean, averaged over 3 years
primary and
24 hours35 μg/m398th percentile, averaged over 3 years
PM10primary and
24 hours150 μg/m3Not to be exceeded more than once per year on average over 3 years
Sulfur Dioxide (SO2)primary1-hour75 ppb99th percentile of 1-hour daily maximum concentrations, averaged over 3 years
secondary3 hours0.5 ppmNot to be exceeded more than once per year
The European Union set Air Quality Limit Values (AQLVs) in 1980 and guide values for SO2 and suspended particulates. They later incorporated lead, nitrogen dioxide and ozone. The Air Quality Framework Directive (AQFD) of 1996 and its progenies aim for the establishment of harmonized structure for the assessment and management of air quality throughout the European Union. International comparison of Ambient Air Quality Standards in compared to WHO recommendations-
PollutantWHOEuropean UnionAustraliaUnited StatesCanada
Ozone8 hour, ppb5060808065
Fine particulate24 hour, μg/m32550256530
SO224 hour, ppb84880140115
NO2annual, ppb2121305353
CO8 hour, ppm999913
It is hence evident that all countries have a proper inventory of air pollutant monitored concentrations and also yardsticks that need to be met. It is important to ensure sustainable development and also to figure out the loopholes in the system as to why the criteria are not being met. Each country has their own norms and standards and it is imperative for the state to manage and work in a way to ascertain that the air pollutant concentrations are way below the maximum level and hence safe to breathe because we don’t have an alternative option to supply us with oxygen which is of essence in ensuring our survival on this planet.

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