AAt this time of year, agricultural burning adds to the problem of air pollution across northern India and Pakistan. The region has 16 of the 20 most polluted cities in the World Health Organization’s PM2.5 global database. But are these the most polluted places ever recorded? Lack of metrics makes it difficult to compare history, but we do have some clues.
More than 200 years ago, Benjamin Franklin was famous among the first scientists to study electricity in the atmosphere. Lightning is the most obvious manifestation, but air pollution also changes the electrical properties of our air.
Electrical measurements near Hyde Park circa 1790 show that the level of particle pollution in 18th century London is probably only half the annual average in the most polluted cities in modern India.
By 1900, things got worse. Atmospheric electricity measurements at Kew show air pollution on the edge of London similar to the worst Indian cities today.
When the first conventional particle pollution measurements began in the 1920s, central London was approximately twice as polluted as contemporary India. Stoke-on-Trent is four times greater.
However, in the 1920s, the UK was home to 44 million people. About 400 million people are exposed to poor air exposure in the Ganges basin in northern India, making it a much larger air pollution crisis.