The world’s most polluted cities have been found in the South African capital of Pretoria and a number of cities in northern Africa and eastern Europe.

    In Pretoria, the city’s main harbour, there were more than a million tons of pollutants per square kilometre in 2013, with an average concentration of 4.5 ppb, according to the WHO.

    The city of Pretori, the capital of South Africa, has the third highest average pollution levels in the continent, according a report by the UN Environment Programme (UNEP) released on Thursday.

    According to the report, the average daily PM2.5 level in Pretoria in 2013 was 1,095 micrograms per cubic metre, or more than 10 times the World Health Organization’s limit of 30 microgram per cubic meter.

    The city also had the highest annual air pollution levels.

    “In terms of particulate matter (PM2.6), there are almost 3,000,000 tonnes of pollutants in the city,” Dr Hlaudi Motsoeneng, a scientist at UNEP told Reuters news agency.

    It is the fourth worst pollution city in Africa.

    This is the first time that Pretoria has been ranked as the most pollutant city in a ranking by the WHO, which is based on pollution levels and population.

    The UNEP also revealed that South Africa is one of only two African cities with the lowest levels of ozone.

    Ozone is a harmful pollutant that causes smog.

    It is a key ingredient of the ozone layer.

    The WHO recommends that South Africans should have adequate air quality by 2025.

    UNEP said it is very important that the WHO provides better air quality data to the public in order to monitor and improve air quality in cities around the world.

    The United Nations Environment Programme has been working to improve the monitoring of air quality across the world, as part of its ‘Air in 2030’ initiative.

    It has also launched the Global Air Quality Index, a global ranking of the global health impacts of air pollution.