Assuming S. Trevor lives to 100 years.... he would be dead for a good 20 to 30 years in 2016

1. While it maybe possible for Ottoman (Turkish language) to have word representations for Hydrogen and it has to be very recent (just 138 years before WW1).... and would not be at all possible with the Sumerian language (long extinct language).... Sulphur Mustard (gas)was even more recent, 1915...So, the Amazons frequently visit the outside world update their diction....

2. The sticking/sore scientific failure in regards to hydrogen....
Many compound has hydrogen atoms (the most numerous element in the Universe)... it cannot serve as a "base"....even if it's a "base" it's bound, not free H2... Even if the "poison" compound needs hydrogen gas... hydrogen gas does not pass-though or destroy gas-mask....
detailed here: https://www.theverge.com/2017/6/6/15742378/...science-history

WB's failure: They don't employ scientific advisors....

Come to think of it Steve Trevor actually did not need to die.... He should have followed what Steve Rogers did (or what he did at the beginning of the movie) ..
Crash-land the plane in the English channel (like Sully) and allow the plane to sink, the bomb-gas will self-detonate... and then swim to shore...

While Steve Rogers had very limited choice... Steve Trevor made the wrong choice...