NEW DELHI (Reuters) -- Primary schools will reopen in India’s capital New Delhi this week and curbs will be lifted on certain construction activities, authorities said on Monday, after pollution levels improved to the ‘very poor’ category from ‘severe’. Residents in the capital have been waking up in recent weeks to hazy mornings with the sky a shade of grey. A thick layer of smog envelops the city in winter as cold, heavy air traps construction dust, vehicle emissions and smoke from crop stubble burning in neighboring states, causing a surge in respiratory illnesses among its 20 million people.