The top ten countries by air pollution listed in another comment hardly produce anything the developed world uses, they mostly export natural resources.
That top 10 was for childhood deaths from air pollution per capita and included mostly poor nations with less healthcare.
When you look at consumption based accounting for e.g. CO2, the list is very different, namely for 2022:
!. Singapore 2. United Arab Emirates 3. Qatar 4. Saudi Arabia 5. Kuwait 6. Brunei 7. Malta 8. Belgium 9. United States 10. Oman
source: https://ourworldindata.org/grapher/consumption-co2-per-capit...
Very surprised to see Belgium in that list. What gives? Our electricity mix isn't too bad. We don't have much heavy industry. We're not heavy A/C users. Is it our meat consumption?
What is worse, our real consumption based per capita emission is still rising (+8%)! We love importing stuff that polluted elsewhere.
Local reasons:
Belgium has a highly industrialized economy, with significant sectors like chemicals, steel, cement, and refining which are energy-intensive and heavily reliant on fossil fuels. Antwerp’s port, with very high and very dirty maritime transport, hosts Europe’s largest petrochemical cluster.
Belgium's car culture, company cars as a tax benefit, and a well-developed fossil-fueled freight transport sector. One of the most dense road networks in the world leading to heavy road traffic and congestion.
Belgium also hosts the capital of Europe. The diplomat and CxO consultant class flies in and out of Zaventem almost daily.