Carbon monoxide pollution has decreased (or been stable) in the countries I've bothered to check over the last decades (while the Flynn effect was in full swing

Carbon monoxide pollution has decreased (or been stable) in the countries I've bothered to check over the last decades (while the Flynn effect was in full swing): https://www.epa.gov/air-trends/carbon-monoxide-trends https://www.epa.gov/air-trends/carbon-monoxide-trends https://www.epd.gov.hk/epd/english/environmentinhk/air/data/emission_inve_co_C.html https://www.epd.gov.hk/epd/english/environmentinhk/air/data/... https://iir-de.wikidot.com/emission-trends-carbon-monoxide https://iir-de.wikidot.com/emission-trends-carbon-monoxide