Focusing on PM pollution tends to reduce CO2 emissions. Most PM 2.5 comes from burning fossil fuels, so insisting on lower levels means burning fewer fossil fue

Focusing on PM pollution tends to reduce CO2 emissions. Most PM 2.5 comes from burning fossil fuels, so insisting on lower levels means burning fewer fossil fuels. PM studies are able to tie pollution directly to lives and thus dollars (through statistical lives). So, if reducing coal use costs $2.7B a year, but we extend enough lives, prevent asthma, etc., to equal at least $2.7B then as a country we should enact the regulation. The US starting doing exactly this from 1996-2003 and it reduced CO2 emissions by making coal plants, steel mills, etc., more expensive to operate. As a result, PM studies like the Harvard Six Cities study were highly controversial and fossil fuel companies lobbied hard against them. It is a lot harder to tie climate change to direct costs because the impacts are somewhat fuzzy and on a long timeframe. In this case, discovering brake pads and tires cause PM2.5 means we can invest in less-emitting brake pads. But this isn’t likely to produce tires/brakes that dramatically reduce emissions. A more likely approach is investing in mass transit, which would reduce CO2 output. I wouldn’t say greenhouse gasses are a larger problem but a rather a harder to coordinate long-term global problem. PM pollution caused 4.2 million premature deaths in 2016 [0]. It is hard to directly state how many deaths climate change caused in 2016 but conservative estimates [1] are for about 500,000 deaths a year by 2050. Most PM deaths stem from terrible industrial air in poorer countries which if combated would also dramatically cut CO2. [0] https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health https://www.who.int/news-room/fact-sheets/detail/ambient-(ou... [1] https://www.cnn.com/2019/01/16/health/climate-change-health-emergency-study/index.html https://www.cnn.com/2019/01/16/health/climate-change-health-...