Validation of Blood Microplastics Measurement: Polyethylene and PVC Raise Concerns About False Positives

A validation study published in Environmental Science & Technology found that pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), widely used to analyse micro- and nanoplastics in human samples, is not yet suitable for accurately measuring polyethylene (PE) and polyvinyl chloride (PVC) in blood. It was carried out by researchers at the Queensland Alliance for Environmental Health Sciences (QAEHS) at the University of Queensland in Australia and the Minderoo Foundation.

The researchers developed and validated an extraction method that reduces interference, in which blood components produce signals that look like plastics. However, recovery varied widely from 7 to 109% depending on the polymer type, and the 'realistic limit of detection,' which accounts for signal suppression by the blood matrix and for recovery, was up to 20 times higher than the nominal limit of detection calculated in pure water. In a preliminary analysis of Australians, PE interference was reduced but not eliminated, and all other polymers were below the limit of detection.

How to read a 'detected' number

The researchers concluded that PE and PVC in biological samples are affected by interfering substances and nonspecific pyrolysis products, so the method is not suitable at this stage. Detection of some polymers in blood may be possible, they noted, but the expected exposure concentrations are close to the instrument's limit of detection. Because a good share of the studies that reported high plastic concentrations in human tissue rely on PE values from the same technique, this means the findings need to be cross-checked with different analytical methods. However, this does not mean there are no plastics in the human body; it shows that the uncertainty in the measured values is large.