New Delhi, Dec. 16 -- Delhi woke to marginally cleaner air on Tuesday, but the improvement has done little to ease a growing public health dilemma: does exercising outdoors still make sense when pollution levels remain dangerously high? New international research suggests the answer is nuanced - exercise still helps, but toxic air can blunt its benefits.

On Tuesday morning (16 December), Delhi's air quality index (AQI) stood at 377, an improvement from 498 a day earlier, according to official data. Despite the drop, air quality remained firmly in the "very poor" category, with thick smog reducing visibility as temperatures dipped to 8.3degC. Several parts of the city continued to record "severe" pollution levels.

With many residents hea...