Block 8: Environmental Issues and Public Health - Air Pollution Chapter 12: Air Quality Management, the Environmental Impact Assessment, Life Cycle Assessment

An Air Quality (AQI) (or Air Pollution Indices, API):

The task of communicating the likely health impacts of ambient air pollutant concentrations to the general public in a manner that is both accurate and meaningful is difficult. In many countries and cities, air pollution indices are used. These indices are attempts to compare overall air quality in an area against a standard or guideline value by calculating an index that is indicative of the degree to which the air concentration values meet or exceed the guideline/ standards value(s). The index value may be used to advise vulnerable groups (such as asthmatics) to avoid exposure that might result in adverse health effects. However, there is no internationally accepted standard method for constructing these index systems. Two widely used approaches (with variants on the basic system), those of the US and UK, differ substantially from each other.

The WHO Guidelines and Risk Factors:

The World Health Organisation periodically reviews the data on the health (and to a lesser extent, environmental) impacts of air pollutants, and publishes a set of guideline values for the commonly occurring air pollutants, and risk factors for those compounds known or suspected to cause one or other form of cancer. (1)

The following table lists the WHO guideline values for the classical or common air pollutants.

Table 12.1: WHO Guidelines for the "classical" air pollutants
Compound Annual
ambient air
concentration		 Health
endpoint		 Observed
effect level		 Uncertainty
factor		 Guideline
Value		 Averaging
time
  µg/m3   µg/m3   µg/m3  
Carbon monoxide 500-7000 Critical level of COHb < 2..5% n.a. n.a. 100 000 15 min
          60 000 30 min
          30 000 1 hr
          10 000 8 hrs
Lead 0.01 - 2 Critical level of Pb in blood < 100-150 µg Pb/l n.a. n.a. 0.5 1 yr
Nitrogen dioxide 10 - 150 Slight changes in lung function in asthmatics 365 - 565 0.5 200 1 hr
          40 1 yr
Ozone 10 - 100 Respiratory function responses n.a. n.a. 120 8 hr
Sulphur dioxide 5 - 400 Changes in lung function in asthmatics 1000 2 500 10 min
    Exacerbations of respiratory symptoms in sensitive individuals 250 2 125 24 hr
    Exacerbations of respiratory symptoms in sensitive individuals 100 2 50 1 yr
Interpreting the WHO Guidelines:

The WHO guideline values may be used as the basis for setting ambient air quality standards. However, the WHO Guidelines have to be interpreted with care. Air pollutant concentrations that are below the guideline values may not be assumed to be 100% ‘safe’. The guideline values are periodically reviewed against ongoing research into the relationship between air pollution and health impacts.

References:

(1) (UPDATE AND REVISION OF WHO AIR QUALITY GUIDELINES FOR EUROPE, WHO (1997).