Microplastics in Arterial Plaque: The 2024 NEJM Heart Study

What the study actually did

Marfella and colleagues enrolled 304 patients undergoing carotid endarterectomy, a routine surgery to remove fatty plaque from neck arteries. Of these, 257 completed the 34-month follow-up. The team analysed the excised plaque using pyrolysis–gas chromatography–mass spectrometry, the same technique used in the 2022 Leslie blood study, plus electron microscopy to visualise individual particles.

They then tracked which patients suffered a major adverse cardiovascular event (non-fatal heart attack, non-fatal stroke, or all-cause death) over the following ~3 years.

The headline number: 4.53× higher risk

Of the 150 patients whose plaque contained polyethylene or PVC, 30 (20%) had a heart attack, stroke, or died. Of the 107 patients with no detectable plastic, only 8 (7.5%) did.

After adjusting for the standard cardiovascular risk factors (age, sex, smoking, BMI, hypertension, diabetes, statin therapy, prior cardiovascular disease), the hazard ratio for the plastic-positive group was 4.53 (95% confidence interval 2.00–10.27). That confidence interval does not cross 1, meaning the result is statistically significant, and the effect size dwarfs many traditional risk factors.

Why this study mattered scientifically

1. It is prospective, not retrospective. The plaque samples were taken first and the patients were followed forward in time, the gold standard for causal-inference epidemiology.
2. It is in humans, not rodents. Most microplastic toxicology before 2024 was either in vitro or in laboratory animals at unrealistic doses. This is real patients at real exposure levels.
3. It links physical particles to clinical events. Not a biomarker, not an animal-model proxy, actual heart attacks, strokes, and deaths.
4. It found a biological mechanism. Plaque containing plastic also showed elevated levels of the inflammatory markers IL-6, IL-18, and TNF-α, plus macrophage infiltration, a plausible chain from plastic to inflammation to plaque instability to clinical event.

Important limitations

The NEJM editorial accompanying the paper was unusually direct in its praise but also explicit about what this trial does not show:

• Single-centre. All patients were treated at one Italian hospital. Replication in other populations is essential.
• No exposure measurement. The study measured plastic in plaque but did not measure each patient's historical plastic intake. We cannot say which lifestyle behaviours led to which plaque content.
• Association, not causation. Patients who accumulate plastic may also have other unmeasured risk factors. Randomising humans to plastic exposure is obviously impossible.
• Endarterectomy patients aren't representative of the general population, these were people already sick enough to need surgery.

How did the plastic get into their arteries?

The dominant polymers (polyethylene and PVC) match the materials we ingest and inhale most. Polyethylene is everywhere: plastic bags, milk jugs, water pipes, food packaging films. PVC is in pipes, food wrap, vinyl flooring, and some medical tubing. From gut and lung absorption, particles small enough to cross epithelial barriers reach the bloodstream and can embed in inflammatory tissue like atherosclerotic plaque, where they accumulate over years.

See our explainer on microplastics in human blood for the upstream evidence on circulation.

What this means for everyday decisions

A 4.5× hazard ratio is large enough that it would change clinical guidelines if it were a drug. Until the result is replicated and quantified into a per-particle exposure relationship, no health authority will issue formal guidance. But the precautionary case for individual action is now stronger than at any prior point in the field.

The exposure reductions that do the most, supported across the entire peer-reviewed literature, remain:

1. Filter your tap water (RO or carbon block) and stop drinking bottled water
2. Replace plastic food storage and water bottles with glass or stainless steel
3. Never heat food or water in plastic, microwaving releases millions of particles per container per cycle
4. Choose natural fibres and HEPA-filter indoor air
5. Reduce ultra-processed and heavily packaged food

For a full action plan, see how to avoid microplastics and how to reduce kitchen microplastics.