Concentrations of probably harmful chemical contaminants on the International Space Station (ISS) could exceed those present in dust on floors in homes across america and Western Europe.
That was the conclusion reached in a first-of-its-kind latest study that checked out dust collected by the air filtration system on the orbiting space station. At some point, this investigation’s results could help engineers design and construct spacecraft for long-term human jaunts to space.
“Our findings have implications for future space stations and habitats, where it might be possible to exclude many contaminant sources by careful material decisions within the early stages of design and construction,” Stuart Harrad, a professor on the University of Birmingham in the UK and co-author of the study, said in an announcement.
The team behind the research included other scientists from the University of Birmingham in addition to some affiliated with NASA’s Glenn Research Center. Together, these experts identified that levels of organic contaminants in ISS dust were noticeably higher than average median levels of such contaminants in house dust across the U.S. and Western Europe.
As for what sorts of contaminants were found, there was a fairly wide selection.
For instance, the team identified polybrominated diphenyl ethers (PBDEs), that are commonly used as a flame retardant in electrical equipment. The researchers think this chemical’s presence may very well be the results of using inorganic flame retardants on the space station, similar to ammonium dihydrogen phosphate, to make fabrics and webbing flame retardant.
Nonetheless, Harrad identified that PBDE concentrations in ISS dust samples technically fall inside the range of concentrations in U.S. house dust.
“While concentrations of organic contaminants discovered in dust from the ISS often exceeded median values present in homes and other indoor environments across the US and western Europe, levels of those compounds were generally inside the range found on Earth,” Harrad said.
Other flame retardants called novel brominated flame retardants (BFRs) and organophosphate esters (OPEs) were present in ISS dust samples too. These are utilized in electrical and electronic equipment, constructing insulation, furniture fabrics and foams. Some OPEs are currently into consideration for limitation by the European Chemicals Agency because they may potentially be toxic to human health at high levels.
The team also detected polycyclic fragrant hydrocarbons (PAHs), that are present in hydrocarbon fuels and released when these fuels are burned, polychlorinated biphenyls (PCBs), that are utilized in constructing and window sealants, and perfluoroalkyl substances (PFAS), that are used for stain proofing in fabrics. PFAs have been limited, and even banned, in some regions due to their potential negative effects on human health — certain PFAs are literally considered human carcinogens.
Further, some contaminants found on the ISS are classed as “persistent organic pollutants (POPs),” that are compounds that may accumulate in living tissues. POPs are also known to pose health risks to humans.
Lots of these chemicals detected may very well be coming from commercially available items, the team suggested, including MP3 players, tablet computers, medical devices and clothing the ISS crew brought from Earth.
Air circulating through the ISS gets modified by the space station’s filtration system between eight and 10 times an hour. But while scientists know this process removes carbon dioxide and gaseous contaminants, it is not as clear how efficient it’s at removing other chemicals.
Scientists also aren’t sure how high levels of ionizing radiation in space, which causes accelerated aging of materials and breakdown of plastics to airborne microplastics, can affect the abundances of PBDEs, HBCDD, NBFRs, OPEs, PAH, PFAS, and PCBs in space-based dust relative to abundances in Earth dust — particularly in indoor environments.
Within the microgravity environment of the ISS, the flow of contaminant particles is primarily driven by ventilation systems. Eventually, these particles either find their ways to surfaces where they’re deposited or to air intakes where they collect as debris on filters. That debris should be vacuumed to make sure filters keep operating at maximum efficiency. (Other debris that finds its method to the filters comes from spacecraft cabins that bring crew and cargo between the ISS and Earth).
But importantly, what this implies is used vacuum bags on the ISS are full of previously airborne contaminant particles alongside other materials, similar to hair and lint. And it was these vacuum bags where the team found their dust samples for evaluation on Earth, which ultimately offered us a complete latest understanding of what chemicals contaminants are bunching up on the ISS.
The team’s research was published this month within the journal Environmental Science and Technology Letters.