The AQD has the aim to protect humans and the environment explicitly laid down in Article 1 which reads "This Directive lays down measures aimed at the following: 1. defining and establishing objectives for ambient air quality designed to avoid, prevent or reduce harmful effects on human health and the environment as a whole...". This objective is also addressed in Recitals 1 to 3, 11 and 12 of the Directive. Recital 12 in particular explicitly refers to the recommendations of the World Health Organisation which issued guidelines on air quality levels in order to protect human health.