| Mean yearly values of nitrogen dioxide
range from 7-58 µg/m3. The highest concentrations are
recorded in periods of dense automobile traffic.
The concentrations in the Rîga centre, at the observation
station to assess the impact of transport, exceed the limit value
for human health protection. In the year 2001, a 50% margin of
tolerance is made for the limit value. In other words, the limit
value of 40 µg/m3 can be exceeded by 50%, up to a
value of 60 µg/m3. However, this margin of tolerance
will gradually be phased out until the year 2010.
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