Higher Levels of Toxic Substances Found in International Space Station: Study

The landmark study was conducted by researchers from the University of Birmingham in the UK and NASA Glenn Research Center in the US and recently published in the journal Environmental Science and Technology Letters.

They analyzed dust samples from the air filters of the International Space Station (ISS) and found higher levels of toxic pollutants than the average levels found in house dust found by US and Western European households.

What are these toxic substances?

The concentrations of potentially harmful chemical compounds in dust from ISS air filtration systems were measured. Pollutants found include: polybrominated diphenyl ethers (PBDE), hexabromocyclododecane (HBCDD), brominated flame retardants (BFR), organophosphorus esters (OPE), polycyclic aromatic hydrocarbons (PAH), perfluoroalkyls (PFAS) and polychlorinated biphenyls (PCB).

Perfluorooctanoic acid (PFOA) levels on the ISS were about 3.3 parts per million. For comparison, the highest level of this pollutant found in US homes and childcare facilities was about 2.0 parts per million, according to a 2008 survey.

BFR and OPE are used to meet fire safety regulations in commercial and residential applications such as electrical and electronic equipment, building insulation, upholstery fabrics and foams are used. PAHs are a component of hydrocarbon fuels and are released during combustion. PCBs are used in sealants for buildings and windows, and in electrical equipment. PFAS are used in stain resists for textiles and clothing, but their adverse health effects have led to some of them being banned or restricted in their use.

Most of them are classified as persistent organic pollutants (POP), which can accumulate in living tissues. Some types of PAH are known to be human carcinogens. The European Chemicals Agency (ECHA) is considering restricting some OPEs as they can be potentially toxic to human health at high concentrations.

And the source for all of this?

The authors believe that the items carried on board by the astronauts, such as cameras, MP3 players, tablets, medical devices and clothing are potential sources of many of the harmful chemicals identified.

The air inside the ISS is constantly being circulated, with air exchange taking place 8-10 times per hour. While this removes CO₂ and traces of gaseous contaminants, it is not known to what extent chemicals are also removed in the process. But first, the high levels of chemicals on the ISS could be related to the higher levels of ionizing radiation in orbit. Radiation causes materials in the ISS to age faster, breaking down plastic products into micro- and nano-plastics that float through the air in the microgravity environment.

What is the significance of this study?

The researchers believe that these findings will inform the design and construction of future spacecraft could be useful for space missions. Stuart Harrad, one of the co-authors, said: “Our findings have implications for future space stations and habitats, where it might be possible to eliminate many sources of pollution through careful selection of materials in the early stages of planning and construction.

However, Harrad says that “the concentrations of organic contaminants detected in the ISS dust while generally exceeding the average levels found in homes and other indoor environments in the United States and Western Europe, the levels of these compounds are generally within the range found on Earth”.