The precautionary principle

The precautionary principle states that protective action should be taken in any situation where there is a threat of severe or irreversible harm.

Furthermore, if there is no positive proof that harm would not result decisions should be taken to protect people from the worst-case scenario until there is positive proof that harm would not result.

The latest scenario where this principle was applied was the eruption of the Eyjafjallajökul volcano in Iceland on the 20th March, which was the first activity since the eruptions of 1821-23, followed by the major eruption on the 14 April. There were also fears that Eyjafjallajökul could trigger a similar eruption in the nearby Mount Katla which is much larger.

The Plume

Both eruptions sent clouds of volcanic ash into the atmosphere which at high concentrations definitely poses a hazard to aircraft. There have been previous incidents of aircraft being affected by volcanic ash, including probably the most dramatic incident when a British Airways flight from London to Auckland in 1982, lost all four engines after flying through the ash cloud from Mount Galunggung, a small volcano which had erupted on the island of Java. Fortunately the crew were able to restart the engines and land safely at Jakarta (but the plane was close to a write off). What’s not known is when the ash density is a threat and when it is not – aircraft happily fly through ice particles, birds and other airborne debris.

Based on an interpretation of the precautionary principle, European airspace was closed for eight days stranding about five million passengers across the globe and costing billions of dollars. Was this justified?

Dr. David Hillson, the ‘Risk Doctor’ thinks the decisions were appropriate despite being stranded in the USA for most of the 8 days; see:

My questions fall into several parts:

  • Assuming on day 1 applying the ‘precautionary principle’ was correct, why did it take authorities 8 days to decide the atmosphere was now ‘safe enough?
    • Clouds band at different levels in the atmosphere (including ash clouds) why not change flying levels?
    • What difference in pollution density occurred between day 8 and 9?
    • What tests were carried out on day 2, 3….???? We have satellites, observation balloons and a host of military and civilian aircraft that don’t carry commercial passengers.
    • How come all of Europe suddenly became ‘safe’ virtually overnight??
  • Why is a low level of risk from ash different to many other low level risks that occasionally cause air crashes?
    • The likely cost in lives caused by Americans choosing to drive rather than fly after 9/11 has been estimated at over 5000. The number of accidents and serious injuries dwarf the totals actually killed and injured in New York.
    • Why not ban all flights over the Atlantic until the cause of the A330-200 crash of Brazil is resolved? (see the BEA Report)
  • If the prospect of any fatal accident is unacceptable to authorities why not ban private cars? They kill massive numbers of people each year and applying the precautionary principle would demand this dangerous activity be stopped.

I believe in many situations public authorities hide behind the precautionary principle to avoid making decisions that may attract liability. Every decision and action has a degree of risk; the difference between allowing people to drive cars and banning flights over a vast area of Europe is very few effective legal challenges have been made against authorities for allowing people to drive. However, once a ban had been imposed on flying, the authorities would be potentially liable for a claim if they lifted it and any incident occurred. My feeling is the delay in re-opening airspace was not about passenger safety rather the responsible authorities attempting to avoid any possibility of liability regardless of the cost and damage caused by not making a balanced decision.

On a different aspect of the same issue, the lack of contingency planning and workarounds was appalling. Europe has a high density road and rail network why weren’t flights diverted on a priority basis to ‘safe’ airports and passengers, mail and freight moved on by land or sea? Everyone seemed to take the view if they could not operate business as usual they would simply stop operating!

Certainly when confronted with an unusual and potentially dangerous situation, applying the precautionary principle is a valid first step. However, it is then incumbent on the authorities that take this decision to urgently assess the problem, determine options and start allowing alternative workaround to happen to mitigate the damage caused by their imposition of the precautionary principle. The European authorities seem to have failed miserably in this second essential part of the response, preferring to avoid decisions rather than acting for the overall good of society. Proving a negative proposition is impossible, therefore it is impossible to prove harm would not result from reopening the airspace… so sooner or later the precautionary principle has to be ignored for the practical purposes of living.

I would like to know what happened on days 7 and 8 of the European air traffic shutdown to shift the balance of the decision from no flying to flying, my guess is pressure for airlines and politicians on the decision makers built to a level where there best option was to allow flying rather then apply the precautionary principle. The erupting ash was still in the atmosphere and as at 2nd May, the Institute of Earth Sciences reported changes to the eruption during the last 2 to 3 days. This included lava producing phase being larger than the explosive phase and the plume becoming darker, denser and wider than in the preceding week (see Wikipedia).

I may be wrong in this view – what do you think?


5 responses to “The precautionary principle

  1. Pat,

    Some engineering facts:
    1. Ash entering the turbine is known to cause problems. The quantities of ash that cause know caking on the compress blades is measurable.
    2. The density of ash varies and was not well documented in the early days of the eruption. Marshalling the sensor platforms takes time.
    3. The certification of the flights is a multi-level issue. The airframe manufacturer, the engine manufacturer are both involved. Not manufacturer is going to say OK without complete sensor data and testing of the impact on the flight worthiness.

    Regarding Air France, there is no know cause of the crash. All aircraft continue to fly as certified. Ash is a known cause.

    • All of your points are true, particularly point 3. The two issues I was raising in the post were the decisions of the authorities to play ultra safe based on the ‘precautionary principle’ and not allow proper risk management until after the airspace was reopened. And secondly, the inability of the overall transport system to work around the problem – Spain and Italy remained clear.

  2. The work around is interesting. I’d suspect that the positioning of flights, the airways routing systems impact, and the general impact on ATC system (radar and in-route systems) can not accommodate changes in rapid response.

    • Disaster management is always difficult (particularly the need to avoid making things worse) but after the tsunami, Katrina and other events one would hope disaster planning was starting to be high on every public authorities list of priorities.

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