Kolkata gasped through another night of toxic air as unabated firecracker bursting on Monday pushed the PM2.5 pollution index into the ‘very poor’ category at all seven monitoring stations between 2 am and 4 am on Tuesday. The fresh onslaught, coming barely 24 hours after Kali Puja night witnessed an unprecedented pollution spike, prolonged the city’s exposure to hazardous firecracker emissions before showers brought some respite.