Freakonomics Radio

Snapshot · Freakonomics Radio

This Is Your Brain on Pollution (Update)

Explore episode Jun 10, 2026

Where this was said

The Peppered Moth and the East Side Story

At 17:57 · chapter starts 13:10

In cities of the Western Hemisphere, prevailing winds blow west to east, and east sides are disproportionately poorer — a pattern Hiblik suspected was no coincidence. His team hunted down the locations of 5,000 Victorian industrial chimneys across 70 English cities using historical maps of astonishing detail, then modeled how coal smoke dispersed eastward on the wind. To validate the model, they used the peppered moth: the ratio of dark-to-light moths in a given area served as a biological pollution proxy, since darker moths thrived where coal smoke had blackened trees. Census records from 1817 — before heavy coal use — showed no systematic east-west poverty gap. By 1881, at the height of industrialization, east sides across England had a significantly higher share of low-skilled workers. The mechanism: pollution made the east side undesirable, wealthy residents sorted away, and the socioeconomic divide was born.

History
East Side Story: How Coal Smoke Sorted England's Rich and Poor for Centuries

This Is Your Brain on Pollution (Update) · Jun 10, 2026 History

Industrial chimneys in England's Victorian cities spewed coal smoke eastward on prevailing winds, pushing poor workers to the east sides of cities. Stefan Hiblik tracked 5,000 chimney locations and census data across 70 English cities and found the sorting effect has only deepened — even after the coal is long gone.

Similar snapshots

Society & Culture
Private adoption costs $40,000–$70,000

Tortilla Face · Aug 10, 2026

Private domestic infant and international adoptions typically cost $40,000 to $70,000, while foster care adoption is the most affordable route at $0 to $2,000.