As New Delhi grappled with its worst smog in 17 years, the head of India’s largest mobile payment firm got on a plane and left, one of thousands of professionals escaping pollution that could cost the capital and the broader economy dear. Vijay Shekhar Sharma, founder of PayTM payment start-up, left last Sunday for a temporary stay in Mumbai, worried about the impact of hazardous clouds of dust, smoke and fumes that hang over Delhi during the winter months. “It became very visibly clear that it is going to be tough in Delhi, especially with young kids,” Sharma said in Mumbai. “We were worried that it could create long-term (health) problems.” His company, which has considered moving from its base outside Delhi, has installed air purifiers, brought in plants and masks and offered extra health assistance. […]