MARPOL on board

Make three shipboard decisions to prevent pollution at sea.

A container ship at sea

Aerial photograph of a real container ship under way
Photograph by Robert So. The oil discharge scenario is fictional.

Oil · Faulty separator

Illustrative assessment · Likelihood: possible. Severity: major.

Likelihood. Bilge water builds up and a faulty alarm can leave the watchkeeper unsure whether discharge is safe.

Consequence. Oil can spread at the surface and harm wildlife and shorelines.

Control. Stop the overboard discharge. If it has already stopped, keep it stopped. Tell the duty engineer and retain the bilge water safely for approved handling.

Garbage · Bag of mixed waste on deck

Illustrative assessment · Likelihood: likely. Severity: moderate.

Likelihood. If the crew skips sorting or checks, they may mistake a bag of mixed waste for food waste.

Consequence. Plastic can persist in the sea, where animals can become entangled in it or swallow it.

Control. Keep the bag on board, sort its contents according to the ship’s garbage procedures and arrange proper disposal.

Air · Entry into an emission control area

Illustrative assessment · Likelihood: possible. Severity: major.

Likelihood. Incomplete fuel records or a missed changeover check can leave compliance unconfirmed at the boundary.

Consequence. Sulphur emissions can affect respiratory health and air quality, especially near ports.

Control. Verify the fuel records and approved compliance method. Tell the responsible officer about any discrepancy before entry.

Compare the three risks

Likelihood describes how probable an event is in the scenario. Severity describes how serious its consequences could be. These ratings are illustrative and depend on the vessel and circumstances.

Illustrative likelihood and severity matrix
SeverityUnlikelyPossibleLikely
Major—Oil, air—
Moderate——Garbage
Minor———

Keep the controls working

Sources & references

  1. IMO · MARPOL convention overview
  2. IMO · Prevention of pollution by oil
  3. IMO · Prevention of pollution by garbage
  4. IMO · Annex V implementation guidelines (PDF)
  5. IMO · Sulphur oxides and particulate matter, Regulation 14
  6. IMO · IMO 2020 sulphur limit

Visual credits

The annex photo credits appear with each image. The 3D reef and harbour were created for this voyage.

Still image: Robert So, An Aerial Shot of a Cargo Ship · Pexels licence

3D vessel: Container Ship, 1DesignTool. The scene was built with Three.js · MIT licence.

Oil appearance reference: NOAA Open Water Oil Identification Job Aid.

Design inspiration: The Sea We Breathe, Blue Marine Foundation.