Toyota pitches its new Mirai hydrogen fuel cell car as a godsend for the planet. Heat and water are its only byproducts, not climate-altering carbon dioxide.
But just how clean is that exhaust water vapor? After all, there is artesian spring, pristine mountain stream water; then, there's bottom-of-the-barrel Love Canal water.
Turns out, the Mirai's exhaust water is safer than milk, Toyota says.
"We tested the health impact of drinking the water in a special lab," said Seiji Mizuno, who is in charge of designing the car's fuel stack power generator. "They said that compared to drinking milk, this drainage water has much fewer organic impurities."
Still, the company doesn't recommend drinking it. That's because the water is created by sucking in oxygen from the surrounding air and bonding it to hydrogen from the fuel tank.
"Depending on the place you are driving, some parts of the world might have certain issues, such as organisms like E. coli, which could be hazardous to your health," Mizuno said. "You never know what the quality of the air intake is."
Despite the stack's high-tech chemical process, it neither sterilizes nor distills the water. Still, if you were daring or desperate enough, what would the water taste like?
No one at Toyota has tried it. But the water is slightly acidic, with a pH around 5 or 6. That's less acidic than acid rain and even beer. But still just tangier than good old milk.