A filter used to clear excess fats from the blood of people with cardiovascular disease may also trap much smaller stowaways: some persistent synthetic chemicals and microplastics.

The treatment, known as therapeutic apheresis, passes a patient’s blood through a machine, filters out targeted substances, and returns the blood to the body.

It was not developed to remove environmental pollutants. It is generally used in severe cases where medication alone cannot sufficiently remove cholesterol – fat-carrying particles linked to cardiovascular disease risk.