Asbestos is a pretty fantastically useful material. A naturally-occuring silicate material that forms in hollow rock formations deep underground, asbestos is a great sound insulator, is terrifically fire resistant, and is relatively affordable to produce. Also it will probably give you lung cancer and kill you.
You'll see a lot about the good parts and nothing about the bad parts in this retroactively chilling 1942 video from British Pathé:
By the 1940s when this film was made, the dangerous qualities of asbestos were starting to be understood. The death of a factory worker from asbestos-related illness in the UK in 1924 sparked research which lead to the regulation of its use in the UK by the early 1930s. The United States didn't follow suit until years later, .
Asbestos is dangerous when its it is friable, meaning that its natural fibers can be broken apart into tiny strands and inhaled causing mesothelioma. Asbestos garments are not particularly friable, so wearing an asbestos suit like our friend in the video is not necessarily a death sentence.
Producing asbestos cloth on the other hand would definitely expose workers to friable asbestos. In general, folks who are involved in the production of asbestos-related material are most at risk of health problems. Roughly 100,000 people have died due to asbestos exposure in the U.S., mostly thanks to exposure during ship-making.
But as deadly as it is, the stuff sure works: