In early September, a riot of colour spilled through downtown Nairobi. Children, cyclists, artists and policy wonks marched to Uhuru Park — not for a carnival, but for survival. It was the International Day of Clean Air for Blue Skies, and the enemy was one they cannot see: pollution. Led by Nairobi City County and the Clean Air Fund, the campaign began in schools with art contests and student-led projects. It ended with a rallying cry against the toxic air suffocating Kenya’s capital. Follow The Standard channel on WhatsApp The data is damning: in August, Nairobi briefly became the second most polluted major city on Earth, according…