information on air quality refers to the air quality index. The index colour
refers to air quality in five classes shown in different colours and classified
from good to very poor. The air quality index illustrates the relation of these
classes to the health effects and norms.
quality is very bad, health effects are possible in sensitive individuals. If
air quality is good or satisfactory, health effects, in light of research data,
are very unlikely.
quality index is calculated for each monitoring site on an hourly basis. The index covers all the pollutants measured at
the monitoring site. The calculation rules in:
Table: Relation of the air quality index to effects.
|Very poor||Possible in sensitive population groups||Clear long-term impacts on vegetation and materials|
|Poor||Possible in sensitive individuals||Clear long-term impacts on vegetation and materials|
|Fair||Unlikely||Clear long-term impacts on vegetation and materials|
|Satisfactory||Very unlikely||Clear long-term impacts on vegetation and materials|
|Good||Not found||Mild long-term impacts on the nature|
index is defined for each pollutant and the highest pollutant-specific index
measured is the actual air quality index of that monitoring site. Therefore,
the indexes of different monitoring sites aren’t completely comparable because
the measured compounds may vary. For instance, if the index value rises to 51,
the air quality class will change from good to satisfactory.
The reference,limit and threshold values of air quality, as well as the estimate, provided by
THL's experts (National Institute of Health and Welfare), of the relation of
concentrations to health risks underlie the index.
quality index used nowadays in Finland has been developed by YTV (i.e. the
present HSY). The index was introduced in 1988. The index calculated by the
present method has been used for information communication since 1993. The calculation methods were revised in 2002
and in 2007. The index differs from indexes applied
in other countries because it works on an hourly basis. Elsewhere the value is
influenced by 24-hour, 8-hour and 1-hour averages.
Table: Definition of index classes according to the concentrations.
|Very poor (>151)||>201||>351||>181||>201||>76|
The unit is
a microgram per cubic metre (µg/m3).