Scientists analysed a sample of dust from air filters within the ISS and found levels of organic contaminants which were higher than the median values found in US and Western European homes.
Publishing their results in Environmental Science and Technology Letters, researchers from the University of Birmingham, UK, and the NASA Glenn Research Center, USA, say their findings could guide the design and construction of future spacecraft.
Contaminants found in the ISS dust included polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), ‘novel’ brominated flame retardants (BFRs), organophosphate esters (OPEs), polycyclic aromatic hydrocarbons (PAH), perfluoroalkyl substances (PFAS), and polychlorinated biphenyls (PCBs).
BFRs and OPEs are used in many countries to meet fire safety regulations in consumer and commercial applications like electrical and electronic equipment, building insulation, furniture fabrics and foams.
PAH are present in hydrocarbon fuels and emitted from combustion processes, PCBs were used in building and window sealants and in electrical equipment as dielectric fluids, while PFAS have been used in applications like stain proofing agents for fabrics and clothing.
“Our findings have implications for future space stations and habitats, where it may be possible to exclude many contaminant sources by careful material choices in the early stages of design and construction,” said co-author Professor Stuart Harrad from the University of Birmingham. “While concentrations of organic contaminants discovered in dust from the ISS often exceeded median values found in homes and other indoor environments across the US and western Europe, levels of these compounds were generally within the range found on earth.”
Researchers note that PBDE concentrations in the dust sample falling within the range of concentrations detected in US house dust may reflect use on the ISS of inorganic FRs like ammonium dihydrogen phosphate to make fabrics and webbing flame retardant. They believe that the use of commercially available ‘off-the-shelf’ items brought on board for the personal use of astronauts, such as cameras, MP3 players, tablet computers, medical devices, and clothing, are potential sources of many of the chemicals detected.
Air inside the ISS is constantly recirculated with 8–10 changes per hour. While CO2 and gaseous trace contaminant removal occurs, the degree to which this removes chemicals like BFRs is unknown. High levels of ionizing radiation can accelerate ageing of materials, including breakdown of plastic goods into micro and nanoplastics that become airborne in the microgravity environment. This may cause concentrations and relative abundance of PBDEs, HBCDD, NBFRs, OPEs, PAH, PFAS and PCBs in ISS dust to differ notably from those in dust from terrestrial indoor microenvironments.
The paper Persistent Organic Contaminants in Dust from the International Space Station by Stuart Harrad, Mohamed Abou-Elwafa Abdallah, Daniel Drage, and Marit Meyer, is published in Environmental Science and Technology Letters.