In the air quality directive (2008/EC/50) the EU has set two limit values for nitrogen dioxide (NO2) for the protection of human health: the NO2 hourly mean value may not exceed 200 micrograms per cubic metre (µg/m3) more than 18 times in a year and the NO2 annual mean value may not exceed 40 micrograms per cubic metre (µg/m3). These limit values come into force for concentrations measured from 1.1.2010 so during 2009 a margin of tolerance equal to an annual mean value of 42 micrograms per cubic metre (μg/m3) is still in place.
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Home gardens can add immensely to the biodiversity of cities and towns.
They provide cover, feeding and commuting routes for wildlife including hedgehogs, badgers, birds and butterflies. If you have a garden, increase its value by planting berry-bearing trees and flowering plants. Rowan, bird cherry and dandelion, among others, can serve as food and shelter to a wide range of invertebrates.
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