Editing Smog (section)

== Pollution index ==
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[[File:Pollution over São Paulo (Jardins).jpg|thumb|Smog in [[São Paulo]], [[Brazil]]]]

The severity of smog is often measured using automated optical instruments such as [[nephelometer]]s, 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|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]].{{needs update|date=July 2021}}