Vietnam’s capital, Hanoi, enjoyed little more than one month of clean air last year as pollution levels rose to match China’s smog-prone capital, Beijing, preliminary findings of a new report showed. The US Embassy and Consulate in Vietnam publishes daily report on the air quality in Hanoi. On Tuesday, the embassy says its Air Quality Index reached 164, indicating that citizens may begin to experience health effects, with some sensitive groups possibly experiencing more serious health effects. Hanoi has a population of 7 million, and if counting current visitors, the figure would be 10 million. There are about 6 million motorbikes in the city, including 2.5 million old ones which cannot meet requirements for use on the roads.