For weeks now, most of the friends and families I know have had a cough of some kind. The pollution in the dry season in Thailand has long been a problem. But recently, it's reached dangerous and deeply worrying levels. Bangkok was the fourth most polluted city in the world this month. Across 31 districts 352 schools were also closed because of pollution. Image: People wearing face masks because of poor air pollution in the Thai capital. Pic: Reuters/Athit Perawongmetha For weeks, I've had to rush my children into school with masks on, as the cheery teachers apologetically declare: "Pollution…