The Secretary of State must ensure that levels of sulphur dioxide, nitrogen dioxide, benzene, carbon monoxide, lead and particulate matter do not exceed the limit values set out in Schedule 2.

In zones where levels of the pollutants mentioned in paragraph (1) are below the limit values set out in Schedule 2, the Secretary of State must ensure that levels are maintained below those limit values and must endeavour to maintain the best ambient air quality compatible with sustainable development.

Where the Secretary of State considers that a limit value has been exceeded for a reason attributable to natural sources, that limit value will not be considered to be exceeded for the purposes of these Regulations.

Where the Secretary of State considers that a limit value has been exceeded for a reason attributable to natural sources in accordance with paragraph (3), the Secretary of State must publish information, for the relevant zones and agglomerations, demonstrating that the exceedances are attributable to natural sources.