Methodology
The three Evidence Dials
Last updated 25 September 2026
Every swap and product on PlasticFreeHome carries three dials, each scored 0 to 4, so you can see how strong the evidence is — not just what we recommend.
Plastic advice online often mixes strong science with guesswork. The dials keep them apart. A swap can be easy and cheap but backed by thin evidence; the dials say so plainly.
Dial 1 — Exposure evidence
How strong is the evidence that the plastic version exposes you to microplastics or plastic chemicals?
| Level | Name | What it takes |
|---|---|---|
| 4 | Strong | Several independent peer-reviewed studies measure release or migration from this product type under realistic home use, with consistent results. |
| 3 | Moderate | Peer-reviewed studies agree on direction, but products, conditions or methods vary. |
| 2 | Emerging | A few studies, or lab conditions harsher than real use (for example, long boiling). |
| 1 | Weak | A plausible mechanism, but little direct measurement. |
| 0 | Not yet assessed | We have not reviewed the evidence yet. |
Exposure is not the same as harm. Research on the health effects of microplastics in people is young. We grade the evidence that exposure happens; we do not claim harm the evidence does not show.
Dial 2 — Environmental evidence
How strong is the evidence that this swap cuts environmental harm across the product's whole life?
We look at life-cycle assessments, including how many uses an alternative needs before it beats the plastic version. A cotton tote, for example, needs many uses to break even with a plastic bag on some measures, so a bag swap scores lower here than you might expect.
| Level | Name | What it takes |
|---|---|---|
| 4 | Strong | Consistent life-cycle evidence that the swap is better under typical UK use. |
| 3 | Moderate | Most evidence favours the swap; results depend on how long you keep the alternative. |
| 2 | Emerging | Limited or single-source evidence. |
| 1 | Weak or mixed | Evidence conflicts, or the swap only wins with unusually long use. |
| 0 | Not yet assessed | We have not reviewed the evidence yet. |
Dial 3 — Claim verification
How well has the alternative's plastic-free claim been verified? This dial belongs to each product. On a swap page it shows the best-verified product we list.
| Level | Name | What it takes |
|---|---|---|
| 4 | PFH Checked | Passed all six criteria of the PFH Checked standard and is within its 12-month window. |
| 3 | Lab-tested | We bought it at retail and an independent lab identified every component's material. |
| 2 | Documents reviewed | We have seen a full bill of materials or supplier declarations for every component. |
| 1 | Brand-declared | The brand says it is plastic-free; we have not seen supporting documents. |
| 0 | Unverified | No claim, or a claim we could not substantiate. |
How the dials feed the score
Dials 1 and 2 adjust Swap Priority: weak evidence pulls a swap down, but never below 60% of its raw score. Dial 3 never changes Swap Priority. It tells you how far to trust a specific product.
Who sets the dials
A named researcher sets each dial and cites the sources on the page. A second person reviews it before publication. No commercial team member sees or sets dials, and no brand can pay to change one. See our independence rules.