Nitrogen dioxide (NO 2 ) Standards in Asia

Transcription

1 Nitrogen dioxide (NO 2 ) Standards in Asia Nitrogen dioxide (NO 2 ) is part of the general set of pollutants of Nitrogen oxides (NOx) along with Nitric oxide (NO), Nitrous acid (HNO 2 ) and Nitric acid (HNO 3 ). While the all members of the group NOx are considered to be pollutants, NO 2 is the component of greatest interest and the indicator for the larger group of nitrogen oxides. The majority of NOx emissions are in the form of nitrogen oxide (NO), which is subsequently oxidized by O 3 in the atmosphere to the secondary pollutant NO 2. NO 2 is the main source of tropospheric ozone in the presence of hydrocarbons and ultraviolet light, thus playing an important role in determining ambient O 3 concentrations. NO 2 is also a key precursor of nitrate particles which form an important fraction of the air particulates with diameter of 25microns or less (PM 2.5 ). World Health Organization (WHO) Ambient Air Quality Guidelines Unlike the usual 24-hr and annual mean levels, NO 2 follows a 1-hr and annual averaging periods based from recommendations of epidemiological and toxicological studies. The existing WHO AQG short-term NO 2 guideline value of 200 μg/m 3 (1-hour) and 40 μg/m 3 (annual) have both been retained as they have not been contested by more recent epidemiological or exposure studies. Table 1. WHO Air Quality Guideline (AQG) and Interim Targets: Basis of Selected Level for 1-hr and Annual Mean Level Standard µg/m 3 Category 1-hr Annual IT-1 (µg/-m 3 ) - IT IT WHO AQG Recent indoor studies have provided evidence of effects on respiratory symptoms among infants at NO 2 concentrations below 40 μg/m 3. Source: WHO, Higher Spatial Variation of NO 2 and the US EPA s Response Studies have shown that NO 2 can have a higher spatial variation than other traffic-related air pollutants like particulate matter. These studies demonstrated that metropolitan areas with higher levels of NO 2 had adverse effects on children s health even though the overall city-wide NO 2 level was quite low. As a traffic-related air pollutant, the United States Environmental Protection Agency (US-EPA) is establishing new monitoring requirements for NO 2 around major roads with large populations. CAI-Asia Factsheet No. 14

2 2 NO 2 Standards in Asia Most developing countries in Asia either use the 24-hr standard and/or the annual standard for NO 2. Though some countries have 1-hr guidelines, they are not comparable to the US EPA or even the European Union (EU) Air Quality Standards (AQS) except for very few countries (Table 2 and Figures 1 to 3). Table 2. Summary of NO 2 Standards in Select Asian countries (µg/m 3 ) Countries NO 2 1-hr NO 2 24-hr NO 2 Annual Afghanistan Bangladesh Bhutan (Industrial) Bhutan (Mixed) Bhutan (Sensitive) Cambodia China: Grade I China: Grade II China: Grade III Hong Kong SAR Hong Kong SAR India India Indonesia Lao PDR Malaysia Mongolia Myanmar Nepal Pakistan Pakistan Philippines Republic of Korea Singapore Sri Lanka Thailand Viet Nam areas, mixed commercial/residential areas, cultural, industrial, and rural areas; China: Grade III = special industrial areas; SAR = Special Administrative Region; PDR = People s Democratic Republic Nitrogen dioxide (NO 2) Conversion factor for ppb to µg/m 3 : 2.616

3 3 Figure 1. 1-hr NO 2 Standards in Asian countries vs. US EPA, WHO AQG and EU NAAQS. Notes for Figure 1. areas, mixed commercial/residential areas, cultural, industrial, and rural areas; China: Grade III = special industrial areas; SAR = Special Administrative Region; PDR = People s Democratic Republic; WHO = World Health Organization; IT = interim target; AQG = air quality guidelines; US EPA = United States Environmental Protection Agency; EU = European Union. Nitrogen dioxide (NO 2) Conversion factor for ppb to µg/m 3 : 1.880

4 4 Figure hr NO 2 Standards in Asian countries vs. US EPA, WHO AQG and EU NAAQS. Notes for Figure 2. areas, mixed commercial/residential areas, cultural, industrial, and rural areas; China: Grade III = special industrial areas; SAR = Special Administrative Region; PDR = People s Democratic Republic; WHO = World Health Organization; IT = interim target; AQG = air quality guidelines; US EPA = United States Environmental Protection Agency; EU = European Union. Nitrogen dioxide (NO 2) Conversion factor for ppb to µg/m 3 : 1.880

5 5 Figure 3. Annual NO 2 Standards in Asian countries vs. WHO AQG and EU NAAQS. Notes for Figure 3. areas, mixed commercial/residential areas, cultural, industrial, and rural areas; China: Grade III = special industrial areas; SAR = Special Administrative Region; PDR = People s Democratic Republic; WHO = World Health Organization; IT = interim target; AQG = air quality guidelines; US EPA = United States Environmental Protection Agency; EU = European Union. Nitrogen dioxide (NO 2) Conversion factor for ppb to µg/m 3 : References Clean Air Initiative for Asian Cities (CAI-Asia) Center, Air Quality in Asia: Status and Trends 2010 US EPA Nitrogen dioxide. Schwela, Dieter, Haq, Gary, Huizenga, Cornie, Han, Wha-Jin, Fabian Herbert, Ajero, May, Urban Air Pollution in Asian Cities. United Kingdom SEI, Foundation Course on Air Quality Management. WHO, WHO Air Quality Guidelines Global Update 2005 Particulate matter, ozone, nitrogen dioxide and sulphur dioxide. World Health Organization, Regional Office for Europe, Copenhagen.

6 Clean Air Initiative for Asian Cities Center. All rights reserved. CAI-Asia, Factsheet No. 13 Nitrogen dioxide (NO 2 ) Standards in Asia. Pasig City, Philippines. CAI-Asia Center Robinsons-Equitable Tower, ADB Avenue, Pasig City 1605 Metro Manila, Philippines Tel /Fax , center@cai-asia.org