Wherever possible, estimates have been computed using standardized categories and methods in order to enhance cross-national comparability. This approach may result in some cases in differences between the estimates presented here and the official national statistics prepared and endorsed by individual WHO Member States. These differences between WHO and national statistics may be larger for countries with small cities and settlements which may not be fully represented by the resolution of the WHO model. This may be compounded for isolated regions where air pollution is primarily from local sources and is experienced at very local levels. It is important to stress that these estimates are also subject to considerable uncertainty, especially for countries with weak statistical information systems.


WHO Guideline values (annual mean) PM2.5: 10 μg/m3 , PM10: 20 μg/m3

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Alex E

Ecoclimax is defined by Odum (1969) as the culmination state after a succession in a stabilized ecosystem in which maximum biomass (or high information content) and symbiotic function among organisms is kept per unit of available energy flow.