BANGKOK (Reuters) – The Thai capital fired water cannon into the hot tropical air and hosed down streets on Monday as authorities handed out masks in a bid to combat air pollution in one of the world’s most visited cities which has been blanketed by smog since Saturday.

The Agriculture Ministry was also preparing to seed clouds to try to clear the air.

The level of hazardous dust particles known as PM 2.5 has exceeded the safe level in 30 of 50 Bangkok’s districts for days, Bangkok Governor Aswin Kwanmuang told reporters.

PM 2.5 is a mixture of liquid droplets and solid particles that can include dust, soot and smoke. It is one of the main pollutants included in measuring the Air Quality Index (AQI).

Monday morning’s AQI in Bangkok was 180, according to the popular website airvisual.com, which measures levels in cities worldwide. The temperature was a sizzling 31 degrees Celsius.

Any level above 150 is considered unhealthy and Bangkok ranked in the top 10 of polluted cities worldwide on Monday. At the top was Tel Aviv in Israel, at 454 on the index.

Pollution in Bangkok has reached unhealthy levels before, usually during the dry season between January and March, but it doesn’t normally hang around too long.

Thai authorities vowed to keep fighting.

“The city will hand out N95 masks that can protect people against PM 2.5 dust… We will distribute the first 10,000 masks to people in various spots around the city,” Aswin said earlier in the day.

Many shops have ran out of masks because of high demand.

“We have been sold out since Saturday,” Supannee Boriwongse, 37, a drug store manager in Bangkok’s Silom district, told Reuters.

“We have ordered more but were told that there is a shortage.”

The Department of Pollution Control says diesel fumes from cars contribute 50-60 percent of the pollution while burning rubbish and crops attributed about 35 percent.

The government has banned large trucks from entering downtown Bangkok during the rush hours, while police have vowed to enforce the law on emission controls.