HP4: Irritant: skin irritation or eye damage
Waste that irritates the skin or damages the eyes on contact.
What HP4 means
HP4 covers waste that can irritate the skin or damage the eyes on contact. It's decided by adding up the substances in the waste that carry skin or eye hazard statements.
It sits one step below HP8, corrosive. Skin-corrosive substances in category 1A (H314) make a waste HP4 from 1% and HP8 at 5%.
The HP4 thresholds
| Hazard statement | Makes the waste HP |
|---|---|
| H314 (skin corrosion, category 1A) | 1% or more in total, and below 5% |
| H318 (serious eye damage) | 10% or more in total |
| H315 (skin irritation) and H319 (eye irritation) | 20% or more, added together |
Any one substance below 1% is left out of these totals. If substances with H314 (categories 1A, 1B or 1C) reach 5% together, the waste is HP8 instead of HP4.
Where not every component is known, a waste with a pH of 2 or lower, or 11.5 or higher, is treated as HP8 corrosive. It can only come down from there if an acid or alkali reserve test and an in vitro test both support it. Itchiness from fibres such as mineral wool doesn't count towards HP4.
Where you're likely to meet it
- Unleaded petrol, typically HP4 among other properties.
- Filter cake from waste treatment holding metal hydroxides, at pH 11.6 to 13.1. In WM3's worked example the in vitro test result was irritant.
What it changes when the waste moves
A waste needs only one hazardous property to be hazardous waste. In England and Wales it then moves on a hazardous waste consignment note in place of a waste transfer note, and the note goes with the load to the site that receives it.
On Digital Waste Tracking, the site that receives a hazardous load records its HP codes alongside the EWC code (the six-digit code from the List of Wastes that says what a waste is).
Sources
- WM3: Waste classification technical guidance (v1.2.GB): Appendix C4, pages C16 to C19; oils, page 28
- Annex III to the Waste Framework Directive (HP1 to HP15)
- GOV.UK: Hazardous waste consignment notes
- The Digital Waste Tracking (England) Regulations 2026: the paragraphs on hazardous properties and POPs, 15 and 16
This page explains the rules. Check the waste itself against WM3 before it moves.
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CarrierNote is on the GOV.UK software provider list, connected to DEFRA's Digital Waste Tracking service. Receiving sites are in scope from October 2026 and carriers from October 2027, and you can be recording to DEFRA's standard from your first load, whenever you start.