Every time Mithilesh turns on her stove to cook, her eyes begin to burn. The small home the 29-year-old housewife shares with her husband, daughter, son and elderly in-laws in the slums of the Indian capital Delhi quickly fills up with smoke, making it hard for anyone to see.

Mithilesh has cooked over a traditional chulha – a metal coated combustor stove that uses firewood as fuel – since she was 13 years old. She often has difficulty breathing and experiences uncontrolled bouts of coughing.

But even when she steps outside her home, there is little respite. Delhi, the world’s second largest megacity, has some of the worst outdoor air quality in the world. Although the authorities in India have been making strides to improve air quality in the city, levels of multiple pollutants regularly exceed World Health Organization (WHO) limits. One recent study published by the Energy Policy Institute at the University of Chicago warned that the lives of residents in India’s capital are being cut short by up to 11.9 years compared to if air pollution was reduced to levels recommended by the WHO.

Mithilesh and her family are an extreme example of something happening globally. Although almost everyone in the world now breathes air that is polluted in some way, those who are worst hit are also the least able to protect themselves or escape from it. The story of air pollution is one of environmental inequality.