Air quality standards are emission rates or concentrations or deposition rates that are designed to protect people and the environment from harm. The Earth's atmosphere is one of the global commons – those regions, which also include Antarctica, the ocean floor and outer space, over which no one nation has individual control. Emissions to the atmosphere may also be considered within a wider regulatory process involving planning permission from Local Authorities, environmental impact assessment, environmental management systems and environmental auditing. The European Union (EU) requires its member states to divide their territory into specified zones and agglomerations and to undertake assessments of air pollution levels using measurements and modelling and other empirical techniques. Acid deposition has been a major environmental concern in the EU since the 1970s, and legislation has been passed to reduce deposition levels. EU standards for petrol-engine vehicles are divided by engine capacity categories into small, medium and large.