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Defining an 'acceptable' or 'unacceptable' intake of contamination by people is a complicated business, which may be why Defra is dragging its feet, says Phil Crowcroft.

Brownfield regeneration and Part IIA of the Environmental Protection Act have been in the public eye of late. The parliamentary debate in late November created a stir about the practical problems for members of the public whose properties are under consideration as potential contaminated land (GE March 06).

The debate centred around the way a local authority might assess whether the amount of a substance in the ground could lead to an unacceptable intake in humans.

Circular 2/05 from the Department for Environment, Food and Rural Affairs (Defra) confirms that soil guideline values (SGVs), as currently derived, do not represent a concentration of contaminant which might pose an unacceptable intake.

It is up to local authorities to decide how much more than the SGV is unacceptable. Clearly, they are not in a position to make such judgements without central guidance. This is where the SGV Task Force comes in.

Over the last few months it has been working to consider how 'unacceptable' might be defined.

What is unacceptable to one person might be acceptable to another in terms of risk of exposure to chemicals in the ground - so much depends on the benefits which come alongside the exposure.

Ultimately, it is a subjective decision, and one which must balance both sides of the equation.

Setting intervention values at levels where risk is minimal ignores the different set of health impacts that comes with the application of Part IIA to housing developments - very real mental distress, often leading to physical illness.

The task force appeared to be moving towards a conclusion on how best to deal with the issue in December, but paused while government departments and agencies considered both the toxicological issues and the public policy position.

These deliberations took place in January and February, but the timetable for taking things forward is unclear.

Defra, as the leading government department on environmental protection, says it wishes to base any new policy decisions on sound evidence - and this may be the main stumbling block to progress.

The simple fact is that there is no sound evidence about the absolute effects of contaminants in the soil on human health. If Defra is seeking evidence from toxicologists, it needs only to look at the number and size of uncertainty factors applied to the 'No observed adverse effect level' to generate 'Tolerable daily intakes' to realise we have little evidence about the effects of a range of substances.

At the moment, SGVs are set at an acceptable level of intake. This is not the unacceptable level that defies contaminated land under Part IIA.

If determinations proceed on sites which marginally exceed an SGV, they will very likely be open to challenge when a remediation notice is served.

The recent Sevenoaks Circular Facilities court case highlights the diffiulties of taking Part IIA to court. The potential appropriate person (the polluter who caused or knowingly permitted the pollution to occur) appealed the service of a remediation notice in the magistrates court and a subsequent appeal against the first decision resulted ultimately in the withdrawal of the remediation notice, and the cessation of the appeal process. The local authority incurred substantial legal costs.

So where does that leave local authorities in dealing with potential Part IIA sites where there is genuine concern about harm to health?

Voluntary action by potential appropriate persons provides a backdrop of co-operation and positive progress.

Local authorities may feel that Part IIA gives them the control to ensure sufficient remedial work is carried out, but in practice, Part IIA limits what can be required to just dealing with the identified pollutant linkages.

Voluntary action as an alternative to determination opens up the way for additional work to be carried out, and with the threat of Part IIA still up its sleeve, a local authority may be able to propose and agree further works which deal with residual non-proven linkages at the same time as the main works.

A way forward has been identifi ed, and it is time for both public and private sectors to move on from the current state of confusion and paralysis.

Part IIA should be about dealing with the serious risks to health and the environment from land contamination. It was never intended to address marginal sites.

The new Part IIA radiological regime has already grasped this nettle and has set assessment criteria at two levels - the higher being that appropriate for intervention under Part IIA.

While this may not provide a direct parallel for the chemical side of Part IIA, it shows that in a relatively short time, and where there is a will to make decisions, practical ways to implement this legislation can be found.

Phil Crowcroft is a partner of Environmental Resources Management UK and a member of the Environmental Industries Commission's contaminated land sector working group. The EIC is an association for companies in the environmental technology and services sector.

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