University of Birmingham scientists have analysed dust samples and found levels of organic contaminants higher than the median values found in US and western European homes.
The team said the findings could help guide the design and construction of future spacecraft.
Contaminants found in the 'space dust' included those used in many countries to meet fire safety regulations in consumer and commercial applications such as electrical and electronic equipment, building insulation, furniture fabrics and foams.
They also found contaminants typically emitted from the combustion of hydrocarbon fuels, the likes of which are used in space travel.
Forever chemicals, or PFAS, were discovered in the dust that are typically used in applications like stain-proofing agents for fabrics and clothing. However, their potential human health effects have led to some of them being banned or limited in use.
Professor Stuart Harrad, co-author of the study, said: "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."
Researchers note that concentrations in the dust sample fall within the range of concentrations detected in US house dust. 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 some of the chemicals detected is unknown.
High levels of ionising radiation can accelerate the 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 the contaminants found to differ notably from those in dust from terrestrial indoor micro-environments.
Scientists measured concentrations of a range of target chemicals in dust collected from the ISS. In a microgravity environment, particles float around according to ventilation system flow patterns, eventually depositing on surfaces and air intakes.
Screens covering the ISS HEPA filters accumulate this debris, requiring weekly vacuuming to maintain efficient filtration. Material in ISS vacuum bags comprises previously airborne particles, clothing lint, hair and other debris generally identified as spacecraft cabin dust. Some vacuum bags were returned to Earth for studies of this unique dust, with a small sample shipped to the University of Birmingham for analysis.
