By Laurence Mathieu-Léger, Source: Guardian (Wednesday 25 February 2015 01.39 GMT) 

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London (left): Renowned for centuries for its infamous smog and severe pollution, the city today has the cleanest air that it has had since the Middle Ages. In virtually every developed country, the air is more breathable and the water is more drinkable than they were 40 years ago. Shanghai (right): Some of the most polluted places are the megacities of the developing world, such as Shanghai, New Delhi, and Mexico City. In the 1930s and 1940s, however, London was more polluted than any of these cities are today. Photos: Johannes Mann / Corbis (left); Michael Prince / Gallery Stock NEWSWEEK. June 20, 2011, p. 24-27

From the 18th through the mid-19th century, whale oil provided light to much of the Western world. At its peak, whaling employed 70,000 people and was the United States’ fifth-largest industry. The U.S. stood as the world’s foremost whale slayer. Producing millions of gallons of oil each year, the industry was widely seen as unassailable, with advocates scoffing at would-be illumination substitutes like lard oil and camphene. Without whale oil, so the thinking went, the world would slide backward toward darkness.

By today’s standard, of course, slaughtering whales is considered barbaric.

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