article_snippet: Air quality monitors showed concentrations of potentially dangerous particulates in the Pars air were above the recommended maximum.
article_snippet: The Airparif monitoring agency said smog density was still near alert levels Monday, but rain forecast for Tuesday was expected to clear the air.
article_snippet: Authorities measure the concentration of particulates with a diameter of less than 10 microns - so-called PM10 - in the air to determine pollution levels.
article_snippet: The safe limit for PM10 is set at 80 microgrammes per cubic metre (mcg/m3), with levels in Paris Monday expected to be somewhere between 40 and 55 mcg/m3.
article_snippet: Paris's alert level is fixed at 50 mcg/m3.
article_snippet: According to a 2011 World Health Organisation report, the planet's most polluted city was Ahvaz in Iran with an average of 372 mcg/m3.
article_snippet: Beijing had an average of 121 mcg/m3, while Paris was measured at 38 mcg/m3.