The risk of harm arising from asbestos left in soil is one which has only recently been identified. We do not yet have any legal cases arising from this type of exposure but asbestos itself has a very bad history in the workplace. There are reputed to be 4000 asbestos related deaths per year.

Consequently there are many civil cases, some appealed to the Supreme Court recently, which have given guidelines as to the way the courts view the assessment of that risk, and how they may evaluate the causal risks of asbestos in soil.

There will be two general types of claims (possibly group claims), those for property damage and those for damage to health. These will be assessed under the civil law of negligence, but there will be differences for each type of claim in proving the liabilities and the causal links between the damage and the negligence. For property claims, the process is the standard approach for negligence, but for the human health cases, the courts recognise the special circumstances of asbestos exposure and impose a lower burden of proof on the claimant.

Remember that the claimants have not only to have been exposed, but in England and Wales to have progressed to full blown mesothelioma, not just the pleural plaques which precede it (as is the case in Scotland). The claimants also have to prove that the exposure was negligent. This means that not all exposure victims will have legal claims.

Then the claimants have to prove that the negligent exposure caused their condition. This is  fundamental  to all claims in negligence; you have to prove that the negligence specifically caused the damage which you suffered. However this is so difficult in cases of asbestos exposure that the courts have made an exception for such cases.

The House of Lords decided the claimants did not have to prove which negligent source or which defendant caused the problem, only that the negligent exposure of the defendant had materially increased the risk of the disease for the claimant.

The Compensation Act 2006 amended the rule to provide that each negligent defendant would be independently and equally jointly liable, no matter how much exposure they were individually liable for. But the duty did not become a statutory duty; the process is still evaluated under the common law of tort.

In 2007, the Court of Appeal considered whether material exposure could be quantified as a doubling of the risk but decided that for mesothelioma, it could not, because it would contravene the Compensation Act which talked only of “material“ risk. So material means less than a doubling of the risk. But how much is “material”?

Cases so far have all been employers’ liability claims. This year, the Supreme Court heard two claims together, concerning different types of exposure, one low level long term at work at an increase of only 18%, and the other a single instance, when as a student, school buildings were being constructed. The court held that this test applies even here to these limited exposures.

How low can the risk be before it is not material? We do not know this as yet. But there will come a time when the exposure will be seen as too insignificant to be taken into account. Lord Phillips said in the Willmore case: “I doubt whether “material risk” is ever possible to define, in quantitative terms, what for the purposes of the application of any principle of law, is de minimis. This must be a question for the judge on the facts of the particular case. In the case of mesothelioma, a stage must be reached at which, even allowing for the possibility that exposure to asbestos can have a cumulative effect, a particular exposure is too insignificant to be taken into account, having regard to the overall exposure that has taken place.”

Scientific advances as to the cause of the disease might give us a clearer view, and the law will respond to this. Lord Phillips also said“(the 2006 act)does not preclude the common law from identifying exceptions to the “material increase of risk” test, nor from holding, as more is learned about mesothelioma, that the material increase of risk test no longer applies.”

Watch this space.