The demise of diesel in the US for forklifts started a little over 30 years ago. The US seems to be a very significant market for forklifts in the world wide picture - add in the demand in Canada & Mexico - N. America seems to be the top dog.
All the major US motor freight companies used to buy nothing but diesel 4000 & 5000 lift capacity press on solid tire for lifts - people like Road Way, Yellow Freight, Consolidated, ABF, etc. But turned to LPG fuel in the early to mid 1980s. Primary reason NOX poisoning - couldn't spell global warming back then and didn't hear out of Al Gore then he was in his mid/late 30s. Also many stevedoring operations turned away from diesel powered 6 k to 8k lb. lifts used in the ships hold and dock side warehousing operations for the same reason - the NOX issue. Diesel powered lift in Mexico is very small - mainly in large l capacity lift but no existent in 5K-6K lb. capacity pneumatic - poor quality diesel fuel.
Guess the switch over in other countries were slower to react - main reason fuel prices and mileage - was amazed when I visited the UK in the late 70s on how many diesel autos were in use & the price per liter vs. US prices ( the exchange rate then was 1 BP = ~$2.50 USD - today 1BP = $1.27 USD big difference).
Some how the world largest polluter doesn't seem to care very much about air quality.
"Top 5 most polluting countries
China (30%) The world's most populated country has an enormous export market, which has seen its industry grow to become a serious danger to the planet....
United States (15%) The world's biggest industrial and commercial power....
India (7%)...
Russia (5%)...
Japan (4%)
United States is historically responsible for more emissions than any other country, it is no longer the world's largest single emitter of greenhouse gases. China surpassed the United States a decade ago, and its emissions today are about double the American figure.