Hydrogen Toyotas at Olympics irk scientists

The hydrogen fuel cell cars that Toyota Motor Corp. supplied to the Paris Olympics aren't green enough for a group of environmentalists.

The group — 120 scientists, engineers and academics — wrote an open letter this month urging organizers to replace the Toyota Mirai with a battery-electric alternative as the official vehicle of the Olympics, which officially kick off July 26.

"We are writing to express our concern that Toyota's promotion of a hydrogen car is scientifically misaligned with net-zero and will damage the reputation of the 2024 Games," the letter says.

Although fuel cell vehicles themselves don't produce greenhouse gases, the letter notes that nearly all hydrogen used today is made from fossil fuels. And while Toyota has said it would power the Olympic fleet of 500 Mirais with hydrogen from renewable sources, the environmentalists argue that consumers who buy a Mirai will not.

In addition to the Mirais, Toyota has provided the Olympics with 10 hydrogen buses and 1,150 battery-electric vehicles. A Toyota Crown fuel cell EV will be used for the marathon, and a prototype Hilux FCEV will support equestrian events.

"The mix of different vehicle technologies in the fleet reflects Toyota's global multi-path strategy that the right solution is needed for differing situations to decarbonize transportation dependent on diverse energy availability, infrastructure and customers' needs," Toyota Motor Europe said in a statement to CNN.

The Paris Olympics will mark the end of Toyota's contract — valued at $835 million in 2015 — with the International Olympic Committee. Japanese news agency Kyodo reported in May that Toyota didn't like how the committee was using its sponsorship money.

Toyota is promoting its involvement in the 2024 Olympics and Paralympics with an advertising campaign called "Start Your Impossible."