What a Transboundary Pollution Hazard Is

In one line

A transboundary pollution hazard is a risk created in one State that will fall on another, and the four routes it travels are air, water, the sea and the movement of the substance itself.

In exam wording: transboundary pollution is pollution originating within the territory or under the jurisdiction or control of one State which causes or is likely to cause damage in the territory of another State or in areas beyond national jurisdiction; a transboundary pollution hazard is the risk of such damage, and the governing rule is the customary obligation of prevention, requiring each State to use due diligence to ensure that activities within its jurisdiction and control do not cause significant harm beyond its borders, stated in Principle 21 of the Stockholm Declaration 1972 and Principle 2 of the Rio Declaration 1992.

The four routes, and why the law differs for each

One: through the air. The plume from a smelter, a power station or a fire, and the long-range transport of acidifying and persistent substances. Instruments: the Convention on Long-range Transboundary Air Pollution 1979, the Vienna Convention and Montreal Protocol for the ozone layer, and the climate regime.

Two: through water. A river carrying effluent across a border, an aquifer, a lake. Instruments: bilateral treaties, the Watercourses Convention 1997, and the customary rule of equitable and reasonable utilisation.

Three: through the sea. Dealt with in Module III, and its distinguishing feature is that a large part of the route lies in nobody's territory.

Four: by carrying the substance across the border. This is the route that makes Module IV different from Module I. Nobody's plume drifts; a ship, a lorry or a container takes the hazard across deliberately, under a contract, for a price. Instruments: the Basel Convention 1989, the Bamako Convention 1991, the Rotterdam Convention 1998, and the Stockholm and Minamata Conventions.

The legal consequence of the fourth route is decisive. Where a hazard drifts, the law can only impose a duty of prevention on the State of origin. Where it is carried, the law can require a permit, a consent, a notification and a return, because there is a transaction to attach them to. That is why the waste conventions are so much more detailed than the air conventions, and it is the organising idea of this module.

The elements of the customary rule

1. An activity within the jurisdiction or control of a State. Jurisdiction covers its territory; control covers a ship or an installation elsewhere.
2. A risk of harm crossing a border or reaching areas beyond national jurisdiction. Stockholm Principle 21 covers both.
3. Significance. Trivial harm is outside the rule. Trail Smelter required the case to be of serious consequence; the modern formulation is significant harm.
4. Due diligence. The obligation is one of conduct, so the question is what the State did, not what happened.
5. Proof. Trail Smelter required clear and convincing evidence, and the causation problem is the practical reason so few claims succeed.