How Many Credit Cards of Plastic Will You Eat in Your Lifetime?

In June 2019, the WWF published a report called “No Plastic in Nature.” One sentence from that report swept the global news cycle: “People could be ingesting approximately 5 grams of plastic every week — the equivalent of a credit card.” That single line ran in thousands of articles. You have almost certainly read it somewhere. What most of those articles left out is the thicket of assumptions behind it.

This is Part 3 of a 4-part series on plastic. This installment takes on the headline question directly: how many credit cards’ worth of plastic will you eat over a lifetime? And then it shows you how that answer swings from 76 cards to 4,300 depending on one critical assumption.

In the United States, the story landed hard. The EPA has flagged microplastics as an emerging contaminant of concern, and the FDA has said it is “continuing to evaluate the science” on dietary exposure — but as of 2025, no enforceable intake limit for plastics in food exists (FDA, 2022). Americans also drink more bottled water per capita than most high-income countries, which happens to be one of the better-studied microplastic intake pathways. That context matters: the 5 g/week figure originates from a study conducted in Australia, synthesized from global literature, and then applied as a universal headline. Whether it holds for a US diet — heavy on packaged food, lighter on fresh seafood relative to East Asian diets — is a question the original paper does not attempt to answer.

This article is for calculation purposes only and is not medical advice. If you have concerns about health effects of microplastic ingestion, consult a qualified healthcare professional.

INPUT

Variable 1: Weight of one credit card $M_{\text{card}}$

$$M_{\text{card}} = 5\ \text{g/card}$$

A standard plastic credit card (PVC material) conforms to ISO/IEC 7810 ID-1 specifications.^[1] That standard defines card dimensions as 85.60 × 53.98 mm with a thickness of 0.76 mm. The resulting volume is 3.51 cm³; applying PVC density (1.35–1.45 g/cm³) gives a mass of 4.74–5.09 g. Measured values reported in the literature also cluster around 5 g.^[11] This figure is used as a fixed constant throughout the calculation. It is the only variable in this article that nobody seriously disputes.

Variable 2: Weekly microplastic intake $W_{\text{week}}$ — the most contested number in this calculation

Microplastics are plastic fragments smaller than 5 mm in diameter. They enter the body through food, drinking water, and air. The problem is that estimates of how much vary enormously across studies.

Intake pathways (methodological summary)

The relative contributions of each pathway differ across studies, and the aggregation methodology drives large differences in final estimates. This article treats all three pathways as a single combined figure ($W_{\text{week}}$).

Three scenarios

Aggressive scenario — $W_{\text{week}} = 5.0\ \text{g/week}$ (upper bound, contested)

The WWF/Dalberg 2019 report is the source of this figure.^[5] A team at the University of Newcastle, Australia, synthesized over 50 studies and estimated weekly intake at roughly 5 g — the now-famous credit-card equivalent. Senathirajah et al. 2021 recited this estimate in the Journal of Hazardous Materials, cementing it in the scientific literature.^[2] However, the 5 g figure aggregates food, water, and inhalation pathways using aggressive assumptions. Within the scientific community, the methodology behind this number has drawn substantial criticism.

Central scenario — $W_{\text{week}} = 1.0\ \text{g/week}$ (this article’s baseline)

A realistic middle estimate reached by aggregating the mid-range values for food and water pathways. No single study pins down exactly this number — it represents a multi-pathway median synthesis and is the default value in the calculator below.

Conservative scenario — $W_{\text{week}} = 0.1\ \text{g/week}$ (lower bound)

This aligns with the lower-bound estimates from Toussaint et al. 2019’s review paper^[6] and the EFSA 2016 report.^[3] Toussaint et al. argue that the 5 g/week figure may overstate dietary-pathway intake by a factor of 10–50.

Bottom line: $W_{\text{week}}$ spans 0.1–5.0 g/week, and this single variable controls the final answer by a factor of 50. That fact is the real story of this calculation.

Variable 3: Life expectancy $L$

The [FORMULA] section uses the global average of 73 years as its primary baseline — the figure most relevant to a worldwide readership. Results for the US (~77 years) and South Korea (83 years) are included alongside for comparison.

Variable 4: Bodily retention rate $R_{\text{retain}}$ — the data-gap variable

$$R_{\text{retain}} = 0.05\ \text{(provisional central estimate)}$$

Most ingested microplastics are believed to pass through and exit via stool. However, a fraction can cross intestinal membranes and accumulate in blood and tissue.

• Leslie et al. 2022 detected microplastics in the blood of 80% of 22 healthy adult volunteers (mean 1.6 µg/mL).^[8]
• Ragusa et al. 2021 reported the first detection of microplastics in a human placenta.^[9]

There is currently no direct measurement in the literature of long-term bodily retention rate as a fraction of total intake. The fact that microplastics appear in blood and placentas is established; the percentage of intake that stays there is a separate question that has not yet been quantified. The 0.05 (5%) figure is a reasonable but poorly-constrained provisional estimate. Readers can adjust it freely in the calculator. Health effects are an active area of research; this article does not draw conclusions in either direction.

FORMULA

Step 1: Define the credit-card reference mass

$$M_{\text{card}} = 5\ \text{g/card}$$

ISO/IEC 7810 ID-1 standard PVC card weight.

Step 2: Lifetime cumulative intake

$$W_{\text{life}} = W_{\text{week}} \times 52\ \frac{\text{weeks}}{\text{year}} \times L\ \text{years}$$

Unit check:

$$\left[\text{g/week}\right] \times \left[\text{weeks/year}\right] \times \left[\text{years}\right] = \left[\text{g}\right]\ \checkmark$$

Three-scenario substitution (global average life expectancy 73 years)

Conservative scenario ($W_{\text{week}} = 0.1\ \text{g/week}$):

$$W_{\text{life}}^{\text{conservative}} = 0.1 \times 52 \times 73 = 379.6\ \text{g} \approx 380\ \text{g}$$

$$N_{\text{cards}}^{\text{conservative}} = \frac{379.6\ \text{g}}{5\ \text{g/card}} = 75.9\ \text{cards} \approx \mathbf{76\ \text{cards}}$$

Central scenario ($W_{\text{week}} = 1.0\ \text{g/week}$, baseline):

$$W_{\text{life}}^{\text{central}} = 1.0 \times 52 \times 73 = 3{,}796\ \text{g}$$

$$N_{\text{cards}}^{\text{central}} = \frac{3{,}796\ \text{g}}{5\ \text{g/card}} = 759.2\ \text{cards} \approx \mathbf{759\ \text{cards}}$$

Aggressive scenario ($W_{\text{week}} = 5.0\ \text{g/week}$):

$$W_{\text{life}}^{\text{aggressive}} = 5.0 \times 52 \times 73 = 18{,}980\ \text{g} \approx 19.0\ \text{kg}$$

$$N_{\text{cards}}^{\text{aggressive}} = \frac{18{,}980\ \text{g}}{5\ \text{g/card}} = 3{,}796\ \text{cards} \approx \mathbf{3{,}796\ \text{cards}}$$

Comparison at US life expectancy (~77 years) and South Korea (83 years)

At 77 years (US baseline):

$$W_{\text{life}}^{\text{central, US}} = 1.0 \times 52 \times 77 = 4{,}004\ \text{g},\qquad N_{\text{cards}}^{\text{US}} = \frac{4{,}004}{5} = \mathbf{801\ \text{cards}}$$

$$W_{\text{life}}^{\text{aggressive, US}} = 5.0 \times 52 \times 77 = 20{,}020\ \text{g},\qquad N_{\text{cards}}^{\text{US}} = \frac{20{,}020}{5} = \mathbf{4{,}004\ \text{cards}}$$

At 83 years (South Korea):

$$W_{\text{life}}^{\text{central, KR}} = 1.0 \times 52 \times 83 = 4{,}316\ \text{g},\qquad N_{\text{cards}}^{\text{KR}} = \frac{4{,}316}{5} = \mathbf{863\ \text{cards}}$$

$$W_{\text{life}}^{\text{aggressive, KR}} = 5.0 \times 52 \times 83 = 21{,}580\ \text{g},\qquad N_{\text{cards}}^{\text{KR}} = \frac{21{,}580}{5} = \mathbf{4{,}316\ \text{cards}}$$

The “~4,300 credit cards” figure that circulates in media headlines is not arbitrary: it comes from combining South Korea’s life expectancy of 83 years with the aggressive 5 g/week scenario. That combination yields exactly the headline number.

Step 3: Scenario comparison table

Step 4: Cross-check via Cox et al. particle-count pathway

Cox et al. 2019 estimated annual microplastic intake for US adults at 39,000–52,000 particles/year from food and water combined.^[4] Using the midpoint of 45,000 particles/year, we can back-calculate the implied average particle mass and see whether it is consistent with the central scenario.

$$m_{\text{particle}} = \frac{W_{\text{week}}^{\text{central}} \times 52\ \text{weeks/year}}{P_{\text{year}}} = \frac{1.0\ \text{g/week} \times 52\ \text{weeks/year}}{45{,}000\ \text{particles/year}}$$

$$m_{\text{particle}} = \frac{52\ \text{g/year}}{45{,}000\ \text{particles/year}} \approx 1.16 \times 10^{-3}\ \text{g/particle} = 1.16\ \mu\text{g/particle}$$

Unit check:

$$\left[\frac{\text{g/year}}{\text{particles/year}}\right] = \left[\text{g/particle}\right]\ \checkmark$$

A back-calculated particle mass of 1.16 µg corresponds to a spherical polypropylene particle (PP, density 0.9 g/cm³) with a diameter of roughly 100–150 µm. That falls within particle-size distributions commonly reported in microplastic research — which means two independent estimation routes (mass-based and particle-count-based) converge on roughly the same range. That internal consistency supports the plausibility of the central scenario.^[10]

Step 5: Estimating bodily retention

$$W_{\text{retain}} = W_{\text{life}} \times R_{\text{retain}}$$

Unit check:

$$\left[\text{g}\right] \times \left[\text{dimensionless}\right] = \left[\text{g}\right]\ \checkmark$$

Substituting the central scenario with the provisional retention rate of 0.05:

$$W_{\text{retain}}^{\text{central}} = 3{,}796\ \text{g} \times 0.05 = 189.8\ \text{g} \approx \mathbf{190\ \text{g}}$$

190 g is roughly enough to half-fill a standard 500 mL water bottle — or, in more tangible American terms, about the weight of a medium apple sitting in your palm. Results across the retention-rate range:

To repeat the caveat: these are estimates in a region with no direct measurement data. Detection in blood and placental tissue is an established finding. What fraction of total intake those detections represent has not yet been directly measured.

Step 6: Sensitivity summary

The uncertainty in this calculation lives entirely in the inputs, not in the math. Depending on which $W_{\text{week}}$ estimate you trust, “76 cards” and “4,300 cards” are both arithmetically correct answers to the same question.

OUTPUT

Under the central scenario (1.0 g/week, global average life expectancy of 73 years), lifetime cumulative intake comes to roughly 3,796 g — about 759 credit cards. Stretch that to a US lifespan of ~77 years and the number rises to about 801 cards. Apply South Korea’s life expectancy of 83 years and you reach about 863 cards. The provisional bodily retention estimate (5% retention rate) lands at around 190 g — enough to half-fill a standard water bottle.

But the genuinely interesting part of this calculation is not the numbers themselves. It is the fact that the “one credit card per week” framing already has the aggressive 5.0 g/week assumption baked in. Shake that assumption and the headline shakes with it. The conservative reading gives you 76 cards over a lifetime; the aggressive one gives you 4,300. A 50-fold spread from a single variable. The real answer to “how many credit cards will you eat in your lifetime?” turns out to be: ask what assumption you’re starting from first. What does not change across any scenario is that we are eating plastic. How much remains, for now, genuinely uncertain.