Air pollution across the airshed is transboundary.
Source
World Bank — https://www.worldbank.org/en/brief/2025/12/09/air-quality-management-in-the-indo-gangetic-plains-and-himalayan-foothills. Verified in source set / retroactive normalization pending.
What it proves
Environmental problems cross administrative borders; fragmented governance is inadequate.
What it does not prove: Transboundary means sources and exposure are shared across a common airshed; it attributes no share to any one country or province and therefore cannot be read as evidence that Pakistan's pollution is mostly imported. The same finding that dilutes exclusive provincial responsibility also rules out blaming a neighbour, since domestic transport, industry and energy sit inside the airshed.
Memory hook: One airshed → Lahore's air is partly decided outside Punjab's jurisdiction
Rebuts the claim: "Punjab's own enforcement can clean Lahore's air" — pollution moves across administrative borders, so a province acting alone cannot control its own exposure.