The Russian rocket that exploded during lift-off on Tuesday morning has already cost the country's government more than $200 million — the estimated value of the three GLONASS satellites that the Proton-M was carrying. But the crash might also be accompanied by significant ecological tolls and human health problems due to the toxic nature of the outdated fuel combination the rocket relies on.

"These propellants are carcinogenic, toxic, and highly reactive," said Mike Gruntman, a professor of aerospace engineering at the University of Southern California. "As the explosion occurred near the launch site, it would cause a major contamination of the area."

An ominous chemical cloud

To be specific, the Proton-M — a booster rocket used for decades to carry commercial and military payloads — relies on a combination of unsymmetrical dimethylhydrazine (better known as heptyl fuel) and nitrogen tetroxide. Used together, the components combust to yield huge quantities of energy, necessary to propel the massive, 17-story rocket and its load. During Tuesday's accident, the rocket was carrying 600 tons of fuel, which blanketed the crash site in an ominous chemical cloud for hours following the explosion.

It might be toxic, but the propellant is also the necessary go-to for the Proton-M: the Proton family of rockets were initially designed as dual-use vehicles, to serve as space launchers and intercontinental ballistic missiles during the Cold War. As a result, the Proton-M still needs propellants that can be stored "for ICBM readiness [over] several years," Gruntman explained. The requirement rules out commonly used cryogenic propellants, like liquid hydrogen, which are significantly cleaner. The US once used a similar rocket to the Proton-M, called the Titan, but it was retired in 2005 and replaced with rockets that rely on these cleaner substances.

"Carcinogenic, mutagenic, convulsant, teratogenic..."

Unfortunately, Russia's struggling space program simply hasn't kept up. "Development of a space launcher is extremely expensive," Gruntman said. "So it often makes economic sense to use what is already there, rather than developing new — though better — vehicles." Russia's technological lag, however, has already been blamed for health and environmental problems in the vicinity of the Baikonur Cosmodrome in Kazakhstan. In one 2008 analysis of heptyl's regional impact, researchers described the compound as "carcinogenic, mutagenic, convulsant, teratogenic and embryotoxic." They also noted that remnants of burned heptyl were "persistent in the soil environment ... and remain in the environment for a significantly longer time than originally anticipated."

As this research points out, even remnants of heptyl burned during a successful launch can stick around and yield undesirable side effects. That's been a point of contention for years between the Russian and Kazakh governments, the latter having pushed several times for more comprehensive environmental cleanup following launches. Earlier this year, Kazakhstan — which rents the Baikonur Cosmodrome to Russia for $115 million per year — threatened to curb the number of yearly Proton launches due to concerns over health problems and acid rain, among other ecological woes.

"There is no way to prevent contamination."

Russia does have plans to replace the Proton-M with the Angara 5 rocket, a launcher that'll rely on cryogenics rather than toxic alternatives. Though development of the Angara family of rockets is now years behind, the Angara 5 is likely to be ready for deployment by 2020. When it is, the rocket will be launched at a new cosmodrome, Vostochny, which is being built to facilitate launches over the Pacific Ocean — rather than populated land masses vulnerable to the environmental effects of space missions.

Still, Russian officials have consistently denied that Proton-M launches — and failures, of which there have been several — cause any problems. Following Tuesday's explosion, leaders at the Russian space agency quickly announced that most of the heptyl aboard the Proton-M had burned up completely, and that heavy rains had dissipated the fuel cloud, mitigating any potential risks. Gruntman, for one, disagrees. "There is no way to prevent contamination," he said. "When something goes wrong, everything will be spread all over the place."