A fleet of drones sprayed water over Bangkok last week after unprecedented levels of pollution forced schools to close and left residents reportedly sneezing blood.

Thailand's public health ministry advised residents to avoid outdoor activities as the health crisis continues to escalate.

People who did venture outdoors frequently wore masks.

Asawin Kwanmuang, the city's governor, accepted that drones were not a long term solution to Bangkok's pollution levels but invited academics and private sector workers to contribute ideas to end the crisis.

"Those who are knowledgeable on this issue, don't give opinions to others, tell me. I am the one who is working on the issue, please give me advice," he said.

The worst countries in the world for air pollution deaths Show all 10 1 /10 The worst countries in the world for air pollution deaths The worst countries in the world for air pollution deaths Ukraine A radioactive sign hangs on barbed wire outside a café in Pripyat. The worst countries in the world for air pollution deaths Bulgaria Mandatory Credit: Photo by NUKARI/REX (407890f) A power plant outside Sofia STOCK OF BULGARIA - FEB 2003 Rex Features The worst countries in the world for air pollution deaths Belarus The worst countries in the world for air pollution deaths Russia The worst countries in the world for air pollution deaths Armenia The worst countries in the world for air pollution deaths Bosnia and Herzegovina Women wearing masks walk in front of academy of fine arts as smog blankets Sarajevo, Bosnia and Herzegovina December 23, 2015. With severe air pollution affecting the city nestled among the mountains, the authorities have declared the first level of preparedness, advising the segment of the population that is at health risk to reduce movement in the mornings and evenings, appealing to drivers to use motor vehicles less and ordering heating utilities to lower the emission of harmful gases. REUTERS/Dado Ruvic REUTERS The worst countries in the world for air pollution deaths Georgia The worst countries in the world for air pollution deaths Hungary TOXIC SPILL, AJKA, HUNGARY-OCTOBER 9, 2010: This is an image of the toxic spill in Ajka, Hungary affecting the villages of Kolontar and Devecsar Hungary. (credit: DigitalGlobe) DigitalGlobe The worst countries in the world for air pollution deaths China The worst countries in the world for air pollution deaths Moldova

Critics have said that the water will not reduce air pollution levels.

"Do I know everything? No, I don't," the politician said.

"Because I do not know everything, that's why I will hold a meeting. Please join us in brainstorming."

The governor has declared the city a "pollution control zone", enforcing road closures and limits on outdoor burning, construction and diesel exhaust.

The proposed measures tackle the perceived causes of Bangkok's pollution, particularly in the form of vehicle emissions.

Some Bangkok residents took to social media to share photographs of the pollution's apparent physical impact.

Nutthawut Sirichainarumit, an office worker in the Thai capital, shared a photo of what appears to be blood in his hand.

“I was totally shocked because I never sneezed blood before in my entire life," he wrote on Facebook.

Meteorological events that trap noxious pollution in Bangkok have exacerbated the pollution crisis.

Support free-thinking journalism and attend Independent events

These include a thermal inversion, which traps particles close to the ground, combined with weak winds which fail to blow them away.

Thailand's prime minister, Prayuth Chan-ocha, ordered inspections of factories to measure how much pollution they were emitting.