Industrial plants in the Vietnamese capital of Hanoi have come under renewed pressure to scale back their operations as authorities respond to a week of heavy and hazardous smog in the city.Vietnam’s Ministry of Health earlier this week urged power, steel and chemical plants to cut output when the air quality index exceeds 200. The index gauges the volumes of hazardous small particles known as PM2.5 that are in the air.The air quality index (AQI) hit 243 midday on Thursday, putting Hanoi...