In the case of spatial planning, i.e. in particular for new construction and expansion measures, the law stipulates that harmful environmental impacts on residential and other areas in need of protection must be avoided.
The legal definition of when a harmful environmental impact exists is set out in the Ordinance on Air Quality Standards and Emission Ceilings (39th BImSchV), which is based on European directives.
Air pollution control plans contain measures that are meant to ensure compliance with the immission limits. In the case of spatial planning (development plan, planning approval procedures and feasibility studies), however, the issues related to of air pollutant loads must also be investigated and measures must be proposed that lead to compliance with the thresholds.
Air pollutants from traffic and agriculture also lead to nitrogen deposition (ammonia, nitrogen oxides, etc.), which can reduce species/plant diversity for nature reserves. In this case, the effects on protected areas (especially FFH areas) must be presented and evaluated when planning new roads or expansions.