MercoPress. South Atlantic News Agency

Santiago in smog emergency.

Santiago de Chile declared this Thursday an environmental pre-emergency limiting vehicle circulation to 40% of the city's transport fleet (both cars and buses) and temporary shutting down 500 to 900 factories in the metropolitan area.

Toxic gases from vehicles and industrial chemical pollution are the main urban air contaminating agents that in the case of Santiago de Chile are worsened because of its geographical condition.

The Chilean capital is virtually in a "hole" boxed in by mountains that prevent air circulation particularly in autumn and winter months creating heavy smog that hinders breathing and seriously limits visibility.

Santiago's health authorities have mounted a special emergency program in public hospitals for caring children and elderly people the most affected by the respiratory consequences of contamination.

Callisthenics and open classes in schools have been temporarily suspended, smoking is banned and health officials have also suggested the ban be extensive to private homes.

If the situation continues primary and secondary schools, as has happened before, will be closed until the situation improves have warned authorities.

Some neighbourhoods of Santiago reported 300 micrograms of toxic particles per cubic centimetre of air which is considered "dangerous" by World Health Organization standards.

Together with Mexico City and Sao Paulo, Santiago with a six million population is among the most air contaminated cities in Latinamerica. Actually the three cities as well as Rio and Buenos Aires figure among the world's 21 most contaminated cities.

Besides, booming Santiago doubles its car fleet every five years.

Santiago residents are praying for rain, which has been forecasted for the weekend, and should help clear the smog from the air (and dump it into soil, rivers and sea).

Traffic authorities will then decide if, and it what numbers and conditions, can the 250,000 banned vehicles return to the streets of the city.