I read recently that the French were the first to have a go at building the Panama Canal (having gained considerable expetise with Suez). After many years, and over 20,000 deaths, they gave up and the project was eventually finished by the Americans. Of interest to me was that most of the 20,000 deaths were due to malaria, which the French believed came from the noxious air (hence, malaria). They were careful to wear masks but continued to drop like flies, as it were.