Madam,
The photo of smoking chimneys (Shuttle, 28 October 2021) reminded me of when coal was the main fuel and also used to make gas for domestic consumption.
The North Sea Gas we switched to in the late 1960s and early 1970s wasn’t toxic, unlike coal gas and there was a major reduction in air pollution for most of the population, resulting both a major reduction in infant mortality rates and also a surge in life expectancy. 
The report “Geographical trends in infant mortality: England and Wales, 1970–2006” (Health Statistics Quarterly 40 Winter 2008) starts: “At national level in England and Wales, infant mortality rates fell rapidly from the early 1970s and into the 1980s.”
The first and last sentences in the first paragraph of the Introduction are: 
“The level of infant mortality can be seen as a major indicator of the health of a nation with the focus on infant mortality rates (deaths at ages under one year, per 1,000 live births) remaining high on academic and public health and policy agendas within the UK and throughout the world.” 
“The reduction in infant mortality has been cited as the single greatest factor contributing to increased life expectancy over the past 100 years.”
Canaries used to be taken into mines to give early warning of polluted air, whereas today the rate of baby deaths is one accurate indicator of exposure to toxic air pollution, whilst another is the percentage of children in primary schools bringing inhalers to school for asthma (Airborne pollutants and acute health effects, The Lancet, 8 April 1995).

Michael Ryan