Science & Technology, UK (Commonwealth Union) – Astronauts aboard the International Space Station (ISS) encounter elevated levels of potentially hazardous chemical compounds, surpassing those commonly found in households on Earth.
A recent study has unveiled that the concentrations of potentially harmful chemical compounds present in dust collected from air filtration systems on the ISS exceed those discovered in the floor dust of numerous American homes.
This pioneering research, featured in this month’s edition of Environmental Science and Technology Letters, was conducted by scientists from the University of Birmingham, UK, and the NASA Glenn Research Center, USA. They suggest that these findings could offer valuable insights for the design and construction of forthcoming spacecraft.
The assortment of contaminants detected in the ‘space dust’ encompasses polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), newly developed brominated flame retardants (BFRs), organophosphate esters (OPEs), polycyclic aromatic hydrocarbons (PAH), perfluoroalkyl substances (PFAS), and polychlorinated biphenyls (PCBs).
BFRs and OPEs, commonly employed to adhere to fire safety regulations in both consumer and commercial products such as electronics, building insulation, furniture fabrics, and foams, were among the substances identified.
PAH, originating from hydrocarbon fuels and released during combustion processes, along with PCBs, once utilized in building and window sealants as well as electrical equipment, were also detected. PFAS, once utilized in stain-resistant treatments for textiles and garments, have faced limitations due to potential health risks.
Certain variants of PBDEs such as Penta-, Octa-, and Deca-BDE commercial formulations, in addition to some PFAS, HBCDD, and PCBs, fall within the classification of persistent organic pollutants (POPs) under the UNEP Stockholm Convention. Meanwhile, specific PAH are identified as human carcinogens, and certain OPEs are being considered for regulatory restrictions by the European Chemicals Agency, according to researchers.
Co-author Professor Stuart Harrad, of the University of Birmingham, says “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.
“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.”
According to researchers, the levels of PBDEs detected in the dust sample, which fall within the range of concentrations found in household dust in the US, could potentially stem from the use of inorganic flame retardants (FRs) like ammonium dihydrogen phosphate on the ISS. These FRs are often employed to render fabrics and webbing fire-resistant. The researchers suggest that commercially available items, such as cameras, MP3 players, tablet computers, medical devices, and clothing, brought onto the ISS for astronauts’ personal use, could be sources of many of the identified chemicals.
The air within the ISS undergoes continuous recirculation at a rate of 8-10 changes per hour. While this process eliminates carbon dioxide and gaseous trace contaminants, its efficacy in removing chemicals like BFRs remains uncertain. Notably, the ISS environment is exposed to substantial ionizing radiation, which can hasten the deterioration of materials, including the breakdown of plastic items into micro and nanoplastics. These particles can become airborne in the microgravity setting. Consequently, this phenomenon might lead to variations in the concentrations and relative presence of PBDEs, HBCDD, NBFRs, OPEs, PAH, PFAS, and PCBs in dust on the ISS compared to indoor dust in terrestrial environments.
The scientists conducted measurements of various target chemicals in dust collected from the ISS. In the microgravity conditions of the environment, particles move in accordance with the flow patterns of the ventilation system, ultimately settling on surfaces and air intake points.
The analysis of these particle together with the previous findings of the study, is likely to be crucial for future safety considerations at space stations.
