Chemical contamination on International Space Station is out of this world, study shows

A groundbreaking study reveals that dust collected from air filtration systems on the International Space Station (ISS) contains higher concentrations of potentially harmful chemical compounds than floor dust in many American homes.

In the first-of-its-kind study, scientists examined a sample of dust from the ISS air filters and discovered levels of organic contaminants that exceed the median values found in homes across the US and Western Europe.

The study, published in Environmental Science & Technology Letters, was conducted by researchers from the University of Birmingham, UK, and the NASA Glenn Research Center, US. They suggest that these findings could inform the design and construction of future spacecraft.

The contaminants found in the “space dust” include polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), “novel” brominated flame retardants (BFRs), organophosphate esters (OPEs), polycyclic aromatic hydrocarbons (PAH), perfluoralkyl substances (PFAS), and polychlorinated biphenyls (PCBs).

BFRs and OPEs are commonly used worldwide to meet fire safety regulations in consumer and commercial applications, such as electrical and electronic equipment, building insulation, furniture fabrics, and foams.

PAHs are present in hydrocarbon fuels and emitted during combustion processes, while PCBs were used in building and window sealants, as well as in electrical equipment. PFAS have been utilized as stain-proofing agents for fabrics and clothing. However, due to their potential adverse health effects, some of these compounds have been banned or restricted in use.

PCBs, certain PFAS, HBCDD, and Penta-, Octa-, and Deca-BDE commercial formulations of PBDEs are classified as persistent organic pollutants (POPs) under the UNEP Stockholm Convention. Additionally, some PAHs are classified as human carcinogens, and certain OPEs are being considered for restriction by the European Chemicals Agency.

Co-author Professor Stuart Harrad from the University of Birmingham stated, “Our findings have implications for future space stations and habitats, as it may be possible to minimize contaminant sources through careful material selection in the early stages of design and construction.

“Although concentrations of organic contaminants in ISS dust often surpass the median values found in homes and indoor environments across the US and Western Europe, the levels of these compounds generally fall within the range found on Earth.”

The researchers note that the presence of PBDE concentrations in the dust sample, within the range detected in US house dust, may indicate the use of inorganic flame retardants like ammonium dihydrogen phosphate on the ISS. This compound is used to make fabrics and webbing flame retardant. They believe that commercially available personal items brought aboard by astronauts, such as cameras, MP3 players, tablet computers, medical devices, and clothing, could be potential sources of many of the detected chemicals.

The ISS recirculates its air with eight to ten changes per hour. While carbon dioxide and gaseous trace contaminants are removed, the extent to which this process eliminates chemicals like BFRs is unknown. High levels of ionizing radiation can accelerate the aging of materials, leading to the breakdown of plastic goods into micro and nanoplastics, which become airborne in the microgravity environment. This may cause notable differences in the concentrations and relative abundance of PBDEs, HBCDD, NBFRs, OPEs, PAHs, PFAS, and PCBs in ISS dust compared to dust in terrestrial indoor environments.

Scientists measured the concentrations of various target chemicals in the dust collected from the ISS. In a microgravity environment, particles float around according to the ventilation system’s flow patterns, ultimately depositing on surfaces and air intakes.

Screens covering the ISS HEPA filters collect this debris, requiring weekly vacuuming to maintain efficient filtration. The material in the ISS vacuum bags consists of previously airborne particles, clothing lint, hair, and other debris commonly referred to as spacecraft cabin dust. Some of the vacuum bags were returned to Earth for further study of this unique dust, and a small sample was sent to the University of Birmingham for analysis in this study.

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