Marine Pollutant

A marine pollutant is a substance designated under MARPOL Annex III as harmful to the marine environment if released from a ship. The designation is parallel to the IMDG hazard class, a substance can be Class 6.1 (toxic) AND a marine pollutant, or Class 9 (miscellaneous) AND a marine pollutant, or just a marine pollutant on its own under UN 3077 or UN 3082. The designation drives additional marking, stowage, and documentation requirements that apply on top of whatever else the substance triggers.

What makes a substance a marine pollutant

The MARPOL Annex III criteria are based on aquatic toxicity test data (LC50 to fish, EC50 to crustaceans, EC50 to algae) and on persistence and bioaccumulation. A substance qualifies as a marine pollutant if it meets specified thresholds in those tests. The IMDG Code lists named marine-pollutant substances in its Marine Pollutant Index in Chapter 2.10.

Two tiers exist:

Most cargoes the typical chemical buyer sees are standard marine pollutants. Severe marine pollutants are rarer and often subject to additional national restrictions on top of MARPOL.

The marking requirement

A package of marine-pollutant cargo must carry the marine pollutant symbol, a fish and a tree inside a triangle. The symbol must appear on the outside of every package, on each side of every container or transport unit, and (for bulk shipments) on the bulk container or tank.

The marking is in addition to the IMDG hazard placard, not a replacement for it. A package of TDI (Class 6.1) that is also a marine pollutant carries both the Class 6.1 placard AND the fish-and-tree mark. A package of UN 3082 environmentally hazardous substance solution carries the Class 9 placard AND the fish-and-tree mark.

Containers of bulk marine-pollutant cargo without correct marking are routinely held at destination for re-marking. The cost is the demurrage clock plus the labour to apply the marking at the port, typically USD 200 to USD 400 per container at a US west coast terminal.

Stowage restrictions

Marine-pollutant cargo cannot be stowed:

• On deck where it could be washed overboard if not in a closed cargo transport unit
• In a position where leakage would discharge directly to the bilges or overboard
• Adjacent to certain other cargoes per the segregation table

For containerised cargo this usually means the carrier places the container in an under-deck stowage with secondary containment monitoring. The buyer rarely interacts with this directly, but it does affect carrier vessel utilisation and can drive freight rate or surcharge differences for cargoes with marine pollutant flags.

Documentation requirements

The marine pollutant designation must be declared on:

• The DG declaration, the declaration includes a “Marine Pollutant” line item where applicable
• The bill of lading
• The SDS section 14, transport classification
• The container booking with the carrier

A common failure mode is the SDS being silent on marine-pollutant status when the substance qualifies. The factory’s SDS may not have been updated to reflect the IMDG amendment that added the substance to the Marine Pollutant Index. The buyer should cross-check the substance against the current IMDG Marine Pollutant Index before booking, not rely solely on the factory SDS.

Confirming marine pollutant status before booking

Three reliable cross-references:

1. The IMDG Code Marine Pollutant Index (Chapter 2.10), the authoritative list. The current edition is IMDG Amendment 41-22.
2. The substance entry in the IMDG Dangerous Goods List, column 4 carries marine-pollutant status indicators.
3. The ECHA C&L Inventory for substances marketed in the EU, the H400/H410/H411 hazard statements correlate strongly with marine pollutant designation.

If the substance is on any of these three lists with marine-pollutant flags, treat it as a marine pollutant and require the marking and declaration.

Common Chinese-export marine pollutants

A non-exhaustive list of substances routinely shipped from China that carry marine pollutant designation:

• Many copper-based pesticide and antifouling formulations (UN 3077, UN 3082)
• Certain organic solvents at higher purity grades (some halogenated solvents, some PFAS-related formulations)
• Pyrethroid pesticide active ingredients (UN 3077, UN 3082)
• Some surfactant formulations at concentrated grade
• Tributyltin-containing antifoulants (severe marine pollutant; phasing out under separate IMO regimes)

For pesticide active ingredient buyers especially, marine-pollutant designation is the rule rather than the exception. Build the marking and stowage requirement into the purchase order standard terms.

Operator note: the FOB factory mistake

Buyers sometimes accept FOB Shanghai pricing on a marine-pollutant cargo without checking that the factory has correctly marked the packaging. The cargo arrives at the load terminal without the fish-and-tree mark. The terminal refuses loading until marking is applied, which the buyer’s freight forwarder must arrange at the port at premium rates. Pre-load marking inspection at the factory (a standard part of pre-shipment inspection) catches this. Specify it on the PO for any marine-pollutant cargo.

Related terms

IMDG umbrella code. MARPOL Annex II covers chemical pollution from bulk liquid cargoes (different regime, related framework). IMDG Class 9. UN 3077 and UN 3082 sit in Class 9 specifically for environmentally hazardous substances. IMDG Class 6.1, many toxic substances are also marine pollutants.