Microplastics Research note 03 Confidence: contested

A credit card a week?

You've seen the stat: we each swallow about 5 grams of plastic a week, the weight of a credit card. It's striking, it's everywhere, and it's the one number on our homepage we flag as under debate. Here's why.

By the Vorus desk ~6 min read Last read: 2026

When a number goes viral, the first job is to find where it actually came from. This one traces to a 2019 analysis commissioned by WWF and carried out at the University of Newcastle, which pooled existing studies to estimate human microplastic intake from food and water.1 The headline that travelled: up to ~5 grams a week — "a credit card."

Why we don't repeat it as fact

We quote it on the homepage and we label it contested, because being evidence-led means flagging weak evidence too, not just citing the convenient stuff. The reasons for caution:

  • It's an estimate built on estimates. The figure aggregates studies that measured very different things in very different ways, then extrapolates. Small methodological choices swing the answer enormously.2
  • Measurement is genuinely hard. Detecting and counting particles a few micrometres wide, without your own lab plastics contaminating the sample, is a real challenge the field is still standardising.2
  • Intake is not the same as harm. Swallowing a particle and it doing damage are different questions. Much of what's ingested passes through; what's absorbed, and what it does, is still being worked out.3
Our rule here A contested number isn't a lie — it's a number doing its best with thin data. We'll cite it, attribute it, and tell you it's shaky. What we won't do is build a fear campaign on a figure we'd flag in a footnote.

What we'd actually stand behind

Strip out the viral headline and the careful, defensible statements are quieter:

  • Microplastics are genuinely widespread — found in drinking water, food, air, and human tissue samples including blood and placenta.3
  • The exact quantity any individual takes in is uncertain by at least an order of magnitude.
  • The health effects in humans are an open research question, not a settled finding — which is a reason to reduce avoidable exposure sensibly, not to panic.

The bottom line

"A credit card a week" is a memorable estimate resting on shaky foundations — real enough to take seriously, soft enough that we won't sell off the back of it. The defensible takeaway is duller and more useful: microplastics are everywhere, the dose is uncertain, the harm is unproven, and cutting the exposure you can control is a reasonable hedge. That's the spirit behind our material choices — a hedge, honestly labelled, not a scare.

Sources

  1. Senathirajah K, Palanisami T (Univ. of Newcastle) for WWF. No Plastic in Nature: Assessing Plastic Ingestion from Nature to People. 2019.
  2. Critiques and commentary on microplastic intake methodology and measurement standardisation, peer-reviewed literature 2019–2023.
  3. Reviews on microplastic detection in human tissue and current state of human health-effects evidence, 2021–2024.

This note describes a contested estimate, deliberately. Citations to be finalised before launch.

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