Accra Top the list of the most polluted Cities on Earth

Ghana's capital city, Accra has turned out to be the most polluted city on earth followed by Lebanon's Beirut.

Accra led with a pollution index of 102.13 whilst Beirut followed closely with 97.71.

The ranking was published by numbeo.com, a website that tracks several countries with respect to pollution, health, crime, among others.

The ranking is based on surveys from visitors of the website. Each entry in the survey is saved as the number in the range [-2, +2], with -2 having meaning of strongly negative and +2 meaning of strongly positive.
Surveys were filtered to eliminate potential spam, like people entering the large amount of data which are differentiating from the median value.

In presenting its survey result, the website used the scale [0, 100] for values since it is easier to read for users.
Most of the data are based on perceptions (opinions) from visitors of this website. For pollution section, the survey included some relevant data from World Health Organization and other institutions.

Pollution Index is an estimation of the overall pollution in the city. The biggest weight is given to air pollution, than to water pollution or accessibility, which are two main pollution factors.