from 2022 shows that the primary cause of pollution in Lahore is from traffic-related PM (both exhausts and non exhaust sources) Doctors advised residents to stay indoors and wear facemasks outside. Pollution index The severity of smog is often measured using automated optical instruments such as nephelometers, as haze is associated with visibility and traffic control in ports. Haze, however, can also be an indication of poor air quality, though this is often better reflected using accurate purpose-built air indexes such as the American Air Quality Index, the Malaysian API (Air Pollution Index), and the Singaporean Pollutant Standards Index. In hazy conditions, it is likely that the index will report the suspended particulate level. The disclosure of the responsible pollutant is mandated in some jurisdictions. The Malaysian API does not have a capped value. Hence, its most hazardous readings can go above 500. When the reading goes above 500, a state of emergency is declared in the affected area. Usually, this means that non-essential government services are suspended, and all ports in the affected area are closed. There may also be prohibitions on private sector commercial and industrial activities in the affected area excluding the food sector. So far, the state of emergency rulings due to hazardous API levels was applied to the Malaysian towns of Port Klang, Kuala Selangor, and the state of Sarawak during 1997 Southeast Asian haze and the 2005 Malaysian haze. Cultural references The London "pea-soupers" earned the capital the nickname of "The Smoke". Similarly, Edinburgh was known as "Auld Reekie". The smogs feature in many London novels as a motif indicating hidden danger or a mystery, perhaps most overtly in Margery Allingham's The Tiger in the Smoke (1952), but also in Dickens's Bleak House (1852) and T.S. Eliot's "The Love Song of J. Alfred Prufrock". The 1970 made-for-TV movie A Clear and Present Danger was one of the first American television network entertainment programs to warn about the problem of smog and air pollution, as it dramatized a man's efforts toward clean air after emphysema killed his friend. The history of smog in LA is detailed in Smogtown by Chip Jacobs and William J. Kelly. See also Smog tower Asian brown cloud 1997 Southeast Asian haze 2005 Malaysian haze 2006 Southeast Asian haze 2013 Eastern China smog 2013 Northeastern China smog 2013 Southeast Asian haze 2015 Southeast Asian haze Atmospheric chemistry Contrail Criteria air contaminants