[darkwizard42]

Not being exact, but at least 150+ AQI seems to generate a significant impact on sunlight coming through creating that "smoky"/"faded" look. I can't comment on how to get the orange exactly as I think it also requires specific particulate matter to get that.

[Tade0]

Not particulate matter, but photochemical smog, so nitrogen and sulfur oxides, volatile organic compounds and of course ozone.

Add sodium lamps for lighting and you get a rich, orange hue.