Heavy smog in Tehran, captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite on November 9, 2016. Tehran is the pale gray smog patch in the center, just south of the Alborz Mountains. More than 400 people died due to the recent air pollution, according to news reports. Emissions standards for cars are weak, and the mountains around the city prevent smog from leaving the valley.