Fossil fuels have reduced disease

reports David Henderson:

After having taken George Hilton's transportation economics at UCLA in 1973, I never thought the same of horses again. Hilton pointed out that horses in New York and other cities were responsible for flies and disease because they dumped 10.5 pounds of manure and urine on a typical day. Hilton pointed out that when people over 100 years ago talked about pollution, they had in mind the pollution created by horses. That's when I started to see the absurdity of bumper stickers I saw in L.A. that said, "Fight pollution: ride a horse." When I go on one of my favorite walks in Monterey, I refer to the horse mess on the trail as pollution. That's due to what Hilton taught me.

[SuperFreakonomics authors] Levitt and Dubner tell a similar story, with more data and an even bigger estimate of the amount of manure dumped by horses. They point out that electric street cars and cars were a huge improvement.