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You’ve probably seen the headline: humans eat a credit card’s worth of plastic every week. That number — 5 grams — comes from a single 2019 WWF-commissioned analysis that follow-up research has called an overestimate by 1–2 orders of magnitude. The real range, depending on your habits, is more like 0.05 to 5 grams per week — a 100× spread.

The calculator below uses per-unit coefficients from 2019–2025 peer-reviewed studies to estimate your weekly intake. Every number it uses is documented and sourced. The output is shown as a range because the underlying science is honestly that uncertain.

Estimate your weekly microplastic intake from the exposure routes with the strongest peer-reviewed data. Results are order-of-magnitude estimates — the underlying studies disagree by factors of 10–100×, so the calculator outputs a range, not a single number.

Drinking water
Food & drink
Air
Estimated weekly intake
— particles
— mg of plastic by mass
Where it's coming from
How this is calculated (methodology & caveats)

Each input is multiplied by a published per-unit coefficient. All coefficients are documented with primary citations in the article below the calculator. The output is shown as a wide range because:

  • Studies of the same exposure route disagree by 1–2 orders of magnitude depending on detection method (older methods missed nanoplastics entirely).
  • Particle-to-mass conversion depends on particle size, which varies by source.
  • Your actual exposure depends on local tap water quality, brands consumed, and household environment.

Don't read this as "you eat exactly X." Read it as "your dominant exposure routes are roughly Y and Z, and that's where reduction effort pays back."

How to read your result

The calculator outputs three things:

  • Particle count range — billions if you use plastic tea bags or microwave food in plastic; thousands if you don’t. The two orders of magnitude come from one fact: tea bags and microwaved containers release nanoplastics in the billions per cup or per session, while drinking water releases particles in the hundreds-to-thousands.
  • Mass estimate — milligrams or grams of plastic by weight per week. This is the more honest metric because particle counts are dominated by nanoplastics (huge counts, tiny individual mass).
  • The breakdown bar chart — sorted by mass contribution. The top bar is where your reduction effort matters most.

A typical reader who drinks mostly filtered tap water, never uses plastic tea bags, and rarely microwaves in plastic lands at 5–50 mg per week by mass. A reader who drinks bottled water daily and uses plastic tea bags lands at 500 mg – 5 g per week. The intervention that matters depends on which inputs are non-zero.

What the science actually supports

The “credit card per week” figure has been challenged in peer-reviewed follow-up. A 2022 critical analysis published in Environmental Science & Ecotechnology1 concluded the original 5g estimate “overestimates microplastic ingestion by several orders of magnitude” due to methodological errors in extrapolating from limited input data. A separate Korean intake study estimated adult microplastic ingestion at roughly 0.1–1 g per week — still substantial, but 5–50× lower than the credit-card figure.

What’s not in dispute:

  • Plastic tea bags release billions of particles per cup — the Hernandez et al. 2019 finding has been confirmed by 2025 follow-up work using independent detection methods.23
  • Heating accelerates plastic shedding — the Hussain et al. 2023 microwave study at the University of Nebraska found up to 4.22 million microplastic and 2.11 billion nanoplastic particles released from a single square centimeter of plastic container in 3 minutes of microwaving.4
  • Bottled water contains 10–100× more particles than tap when nanoplastics are counted — the Qian et al. 2024 PNAS study found 240,000 particles per liter on average in major bottled water brands using stimulated Raman scattering microscopy.5
  • Indoor air is a significant exposure route — a 2025 study found median concentrations of 528 microplastics/m³ in apartment air, rising to 2,238/m³ in car cabins.6

What to do about it

The calculator’s recommendation bar (under “Your highest-mass source”) points to the single change that would reduce your intake the most. The pattern across thousands of households is consistent:

  1. If you drink bottled water: the bottled column is almost always your biggest source. Switching to filtered tap eliminates it. See our breakdown of the best water filters for microplastics — reverse osmosis cuts ≥99% of particles across size ranges.
  2. If you use plastic tea bags: loose-leaf or paper-only bags eliminate the single highest-per-unit exposure in any kitchen. ~16 mg per cup is more plastic by mass than most people get from any other single source.
  3. If you microwave food in plastic: glass and ceramic eliminate this entirely. Heat is the dominant driver of shedding from plastic containers — the 2023 Nebraska study quantified billions of nanoparticles released per microwave session.
  4. If your indoor air is high-synthetic: swap synthetic carpets and curtains for natural fibers over time. This is a slow lever but a real one.

The remaining sources — tap water (already low), shellfish (small contribution), salt (negligible) — aren’t worth obsessing over until the top three are addressed. For a fuller exposure-reduction framework that includes routes beyond ingestion, see our microplastics in human blood deep dive.

Methodology and citations

The calculator uses these per-unit coefficients. Every one maps to a peer-reviewed source:

InputCoefficientMass (per week per unit)Source
Tap water4–6 particles/L~5 μg/L2024 Water Research meta-analysis; Mason 20187
Bottled water325–240,000 particles/L~1 mg/LMason 20187; Qian 2024 PNAS5
RO-filtered water0.1–1 particles/L~1 μg/Lderived from NSF/ANSI 58 removal rates
Plastic tea bag~14.7B particles/cup~16 mg/cupHernandez 20192
Microwaving in plastic2B–10B particles/session~4 mg/sessionHussain 20234
Shellfish serving (~100g)50–250 particles/serving~50 μg/serving2024 US West Coast survey; Thailand 20248
Sea salt~0.5 particles/g~10 μg/week2025 European salt review9
Car cabin air2,238 particles/m³~10 μg/m³Aslam 20256
Indoor air528 particles/m³ (medium)~5 μg/m³Aslam 20256

Key uncertainty: particle-to-mass conversion. A “particle” can be anything from a 100 μm fiber (weighing micrograms) to a 50 nm nanoplastic (weighing femtograms). The mass estimates in the calculator use median sizes reported in the source studies, but a 10× error in either direction is plausible. This is why the output is shown as a range.

Not included in the calculator (yet):

  • Food packaging migration (other than microwaving) — research too sparse to coefficient
  • Cosmetics and personal care — variable by product
  • Outdoor air — far lower than indoor in most settings
  • Cutting boards, plastic utensils — emerging data, not yet quantified per-use

Frequently Asked Questions

How much microplastic does the average person eat per week?
The honest answer is somewhere between 50 milligrams and 5 grams per week — a 100× range that depends almost entirely on your habits. The famous “credit card per week” (5 g) figure represents the high end of a 2019 WWF estimate that follow-up peer-reviewed analysis has criticized as an overestimate by 1–2 orders of magnitude. Most adults eating a mixed diet without plastic tea bags or daily bottled water consumption fall in the 0.05–0.5 g/week range.
What is the biggest source of microplastics in my diet?
For most people, in order of typical contribution: (1) bottled water, if consumed regularly — by mass it dwarfs every other dietary source; (2) plastic tea bags — single cups release ~16 mg of plastic by mass, the highest per-unit exposure of any food item; (3) microwaving food in plastic containers — heat dramatically accelerates shedding. Drinking water from the tap, salt, and shellfish contribute less by mass even though they may show up frequently.
Does drinking bottled water really mean that much more plastic?
Yes, particularly when nanoplastics are counted. The 2024 Qian et al. study in PNAS used advanced detection methods and found bottled water averages 240,000 particles per liter — 10–100× more than earlier studies that missed nanoplastics. By mass it’s still small (roughly 1 mg per liter), but for someone drinking 2 liters of bottled water a day, that’s ~14 mg/week — comparable to a single plastic tea bag.
How accurate is this calculator?
Order-of-magnitude accurate, not precise. The calculator uses coefficients from peer-reviewed studies, but those studies disagree by factors of 10–100× depending on detection method (newer techniques find more particles, particularly nanoplastics). The output is shown as a wide range to reflect that real uncertainty. Use it to compare your own habits against each other — “switching from bottled to filtered tap would cut my intake by X” is reliable; “I eat exactly Y particles” is not.
Should I worry about my result?
Worry is the wrong frame. The actionable question is: which exposure route can you reduce at low cost? For most people, switching from bottled to filtered tap water and from plastic to paper tea bags accounts for the majority of modifiable exposure. The health implications of chronic low-dose microplastic exposure are still being characterized — there’s no clinical cut-off above which harm is established. The precautionary case for reducing avoidable exposure is reasonable; the panic case is not supported by current evidence.
Where can I read the original studies?
Every coefficient in the calculator links to its peer-reviewed source in the methodology section above. Key papers: Mason et al. 2018 (tap and bottled water baseline), Hernandez et al. 2019 (tea bags), Hussain et al. 2023 (microwaved containers), Qian et al. 2024 PNAS (bottled water nanoplastics), Aslam et al. 2025 (indoor and car air).

For the broader context on where these particles end up after ingestion, see our microplastics in human blood deep dive and the environmental toxins hub.

This article is for informational purposes only and does not constitute medical advice.

  1. Vethaak, A.D. & Legler, J. “Microplastics and Human Health.” Science, 2021. See also: “Ingested Microplastics: Do humans eat one credit card per week?” Environmental Science & Ecotechnology, 2022. DOI ↩︎

  2. Hernandez, L.M., Xu, E.G., Larsson, H.C.E., Tahara, R., Maisuria, V.B., & Tufenkji, N. “Plastic Teabags Release Billions of Microparticles and Nanoparticles into Tea.” Environmental Science & Technology, 2019. DOI ↩︎ ↩︎

  3. “Evolution of Microplastics Released from Tea Bags into Water.” Polymers, 2025. DOI ↩︎

  4. Hussain, K.A., Romanova, S., Okur, I., et al. “Assessing the Release of Microplastics and Nanoplastics from Plastic Containers and Reusable Food Pouches: Implications for Human Health.” Environmental Science & Technology, 2023. DOI ↩︎ ↩︎

  5. Qian, N., Gao, X., Lang, X., Deng, H., Bratu, T.M., Chen, Q., Stapleton, P., Yan, B., & Min, W. “Rapid single-particle chemical imaging of nanoplastics by SRS microscopy.” PNAS, 2024. DOI ↩︎ ↩︎

  6. Aslam, M., et al. “Human exposure to PM10 microplastics in indoor air.” PLOS ONE, 2025. DOI ↩︎ ↩︎ ↩︎

  7. Kosuth, M., Mason, S.A., & Wattenberg, E.V. “Anthropogenic contamination of tap water, beer, and sea salt.” PLOS ONE, 2018; Mason, S.A., Welch, V.G., & Neratko, J. “Synthetic Polymer Contamination in Bottled Water.” Frontiers in Chemistry, 2018. ↩︎ ↩︎

  8. “Microplastics in retail shellfish from a seafood market in eastern Thailand.” Marine Pollution Bulletin, 2024. DOI ↩︎

  9. “Microplastics in salt: A critical review of contamination, analytical methodologies, and health implications.” ScienceDirect, 2025. DOI ↩︎