Ultrafine plastic particles cause lung inflammation

A new study on laboratory mice has revealed that ultrafine plastic particles cause inflammation in the lungs that can last for several weeks. These findings come amid growing concerns about the prevalence of microplastics in the air and their potential to reach deep into the lungs whilst breathing.

The study was conducted by researchers from the Korean Institute of Bioscience and Biotechnology at Dong-A University in South Korea. The researchers tested two common types of plastic: polyethylene (PE) and polypropylene (PP). These are used in the manufacture of plastic bottles, cups and packaging materials. The researchers injected the particles directly into the trachea of mice at doses of 50, 150 and 300 micrograms per mouse. They then compared their effects with those of diesel exhaust particles. The average particle size was 357 nanometres for polyethylene and 473 nanometres for polypropylene.

The results showed clear signs of inflammation in the lungs 24 hours after exposure to both types. The effect of polyethylene was equivalent to or stronger than that of diesel exhaust particles when the sizes were comparable. However, when compared in terms of particle surface area, both types of plastic caused more severe inflammation than diesel particles.

The inflammation subsided over time. However, its effects persisted to a mild degree even after 28 days. The researchers found that plastic particles stimulate the immune cells responsible for clearing the lungs to produce greater quantities of highly reactive molecules called reactive oxygen species (ROS). These molecules can damage cells when they accumulate in large quantities, increase inflammation and attract additional immune cells to the area.

The study reveals that the weight of plastic particles alone is not sufficient to assess their potential harm, as their surface area and ability to interact with cells also influence the severity of inflammation. However, the findings do not mean that breathing air containing these particles necessarily causes the same damage in humans. The experiments were carried out on mice, and the particles were injected directly into the trachea rather than being inhaled naturally from the air. We therefore do not yet know the extent of the risk posed by the levels of nanoplastics present in the air we breathe, or the effects of long-term exposure on human health.