Microplastics, these tiny bits of plastics of less than five millimeters, have contaminated almost every corner of the planet, including our homes — where we spend much of our time. However, not everyone is equally exposed, with those living in low-income countries and young children at greater risk, according to a new study.

Researchers from Macquarie University in Australia looked at microplastic exposure inside homes across 29 countries (covering all continents) and big disparities between different houses. They also analyzed the chemical composition of microplastics in the home and found the specific health risk was surprisingly low.

“We can’t escape exposure to these tiny bits of plastic in the environment, which includes the homes where people spend most of their time,” study authors Mark Patrick Taylor, Neda Sharifi Soltani and Scott Wilson wrote in a blog post in The Conversation. “However, the question of harm to humans remains unresolved.”

Microplastics at home

The study explored three big questions related to microplastic exposure inside homes: what’s the impact on different continents, who is most at risk, and what the health risks associated with microplastics are. The team collected indoor atmospheric dust over one month as well as information about households and behaviors to identify microplastic sources.

This included how often the floors were cleaned, the types of floors, the presence or absence of children, the number of people living in the home, and the percentage of full-time workers. They then measured the level of microplastics in the dust and used infrared spectroscopy to establish the chemical composition of these microplastics.

The household dust contained a wide variety of synthetic polymer fibers. The most common, in order according to their relevance, were polyester and polyamide (used in clothing fabrics), polyvinyls (used in floor varnishes), polyurethane (used in surface coatings of furniture), and polyethylene (used in food containers and bags), the researchers found.

They also looked at the prevalence of microplastics according to the gross national income of each country. Overall, lower-income countries were found to have higher loads of microplastics, deposited at an average daily rate of 3,518 fibers per square meter. Rates in medium and high-income countries were 1,268 and 1,257 respectively– more than two times less.

However, they found that overall, the risk of microplastic exposure was low. They used toxicity information on polymers to calculate health risks. Low-income countries had a larger lifetime risk of cancers due to microplastic exposure at 4.7 people per million. High-income and middle-income were next at 1.9 and 1.2 per million, respectively.

Children were found to be at a larger risk, no matter the income. This is because of their smaller size and weight and due to their tendency to have more contact with the floor, the researchers said.

The researchers also found that the microplastics in the house came mainly from sources inside the home, such as synthetic polymer-based materials, used widely in products such as carpets.

Study authors also have some advice for people looking to reduce the number of microplastics inside their homes: vacuum regularly instead of sweeping (or not doing anything); choose natural fibers for clothing, carpets, and furnishing instead of polymer fibers; in general, try to use less plastic products inside the home.

However, we still don’t fully understand the risks and potential health threats that these plastic pieces bring. For that, further research is necessary.

The study was published in the journal Environmental Pollution.