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Ashes to. . . dioxins

technical & practice

A Newsnight report was wrong to portray the use of ash products as a major threat to public health

It is not very often these days that a news programme makes your jaw drop open in disbelief, but Newsnight's report on contaminated ash, broadcast on 3 July, was such a classic piece of paranoid over-reaction that it deserves a right to reply.

During the process of waste incineration, ash tends to divide into two groupings: bottom ash - the heavier, less contaminated ash - and fly ash - the lightweight particles that are contained in the gaseous products of combustion. Precipitator ash (another name for fly ash) is what has been electrostatically removed from the flue gases, so that the gases emerging from the flue are totally unpolluted by ash particulates. Precipitator ash is known to be relatively high in dioxins. Mixed ash is a mixture of precipitator and bottom ash.

The Newsnight report concerned the use of mixed ash in the construction industry, a practice that has been going on for a considerable time but which is no longer carried out, especially by those parties interviewed in the programme. Richard Watson, the Newsnight reporter, said that 'this story concerns chemicals that are among the most deadly known to mankind. They can cause cancer and birth defects in tiny amounts.'

However, Aaron Wildavsky's wellresearched book, But is it true? , suggests (page 124) that dioxin 'has serious health effects only at extremely high doses' - doses several orders of magnitude higher than those shown on Newsnight.

Currently, Newcastle City Council is being prosecuted by the Environment Agency for loose laying mixed ash in allotments in Byker - a case which is now going through the courts. The city council is charged with taking a mix containing a high proportion of fly ash to bottom ash and using it in an unregulated fashion.

Relatively high levels of dioxin were found in the paths, and the ash from the areas in question was swept up and removed to a licensed landfill site.

In Byker, one quarter of allotments had dioxin levels of about 40 nanograms per kilogram (ng/kg) and five allotments had levels at 100ng/kg.

But government advice is that 3050ng/kg is the level of dioxin deemed to occur normally in urban locations, so levels were not dramatically problematical. It is worth noting that the Environment Agency's action is being brought against Newcastle City Council because of its unauthorised dumping, rather than as a result of any actual harm caused. No one has been injured in Byker - the Agency just wants to ensure it makes the point that approvals must be sought, before loose laying, so that relatively high contamination of this nature does not occur again.

David York of Ballast Phoenix, who displayed a credible and professional attitude to the issues raised in the Newsnight report, seems to have been unjustly pilloried by the programme.

Ballast Phoenix was accused of using mixed ash (a practice that, at the time, was not deemed to be a problem), and of somehow hiding the addresses of the locations in which this mixed ash was used. (He offered on the programme to make all information available to the Environment Agency if statutorily requested to do so. ) York was engaged in discussions as early as the mid '90s about the benefits of recycling waste and, in 1996, joined the Ash Working group with the express intention of 'working with the EA's regulators to agree environmentally safe applications'. One of the 'sensible' recycling solutions was to make blocks, therefore bonding the ash with cementitious material and containing the aggregate. This was done in consultation with various academic bodies.

In committee sessions, chaired by the EA and comprising incinerator operators, chemists and engineers representing a broad range of specialist expertise, they drew up a 'safe policy'. This was further developed with research on leeching characteristics from bonded materials.

In August '98, the group started 18 months of negotiation. Although no formal documentation resulted, 'it was agreed that the mix for the ash component in bonded applications could be one part precipitator ash with 10 parts bottom ash. This was never a secret, ' says York. The draft policy in December 1999 confirmed that bound blocks constituted in this way could be manufactured without further reference to the EA, whereas unbound applications would need site-by-site EA approval.

Although the dioxin levels were tested once a year, after the Byker episode hit the headlines London Waste, the incinerator company mentioned in the Newsnight programme (and not involved at Byker) stopped putting precipitator ash in the mix. 'Dioxin levels are now significantly less than 3ng/kg, ' says York.

'Obviously, there may be residual risks if we consider the lifecycle of a building - including demolition - but this should be assessed within the standard risk assessment and should concern the COSHH recommendations for dust hazard: wet cutting and damping down, rather than any over-inflated concern about dioxins.'

Worries about dioxins being released by drilling into blockwork in a standard domestic situation, as portrayed by the Newsnight programme, are nonsensical.

Andy Watson, of environmental anti-landfill consultancy Public Interest Consultants, was the only 'scientific' opinion consulted. Interviewed on the programme, he said that given that one dioxin has been classified as a 'carcinogen' by the World Health Organisation (WHO) in 1977, 'it's very likely that the other dioxins will act in a similar way and be carcinogenic also'. This is not believable, scientifically rigorous nor particularly helpful. Dioxin is the name given to each of 75 compounds created by any but the most high-temperature burning process.

The WHO does indeed classify TCDD (2,3,7,8-tetrachlorodibenzop-dioxin) as 'a known carcinogen', but one is only left to assume that it was not found in the programme's research. Hans Muller writes (What Risk? , page 204) that TCDD is three orders of magnitude less toxic for humans than for guinea pigs. 'TCDD, ' he says, 'is a substance comparable in acute toxicity to nicotine, for example, but probably no more toxic than that, and therefore far less of an apocalyptic super-toxin than green pressure groups would have us believe.'

This compounds the view taken by Kenneth Smith that research on dioxin's effects on laboratory rats does not make a conclusive case for similar effects in humans: 'The usual assortment of high-dose rodent tests and man-animal extrapolations. . . have undermined regulatory 'science' in the past. To assume that humans are simply big rodents, similarly susceptible to alleged carcinogens, requires the same kind of leap of faith it takes to assume that there is no threshold below which a carcinogen becomes benign.'

Wildavsky cites a report into the infamous dioxin cloud over Serveso in Italy in 1976, which affected a population of 30,000, pointing out that claims of higher death rates as a result 'cannot be viewed as conclusive'. He even quotes the legal judgement in 1986 on the claims that dioxin contamination in the Vietnam War had caused illness and birth defects. 'All reliable studies of the effect of Agent Orange on members of the class so far published provide no support for plaintiffs claims of causation', summed up Judge Jack Weinstein (page 102).

The inconclusive ill-health consequences (although cases of chloracne have been verified) resulting from Serveso and Agent Orange were the result of doses many times higher than recorded by the EA in Byker. The prosecution - restarting at the beginning of August, having taken a brief recess - concerns Newcastle council's lack of notification of its actions, rather than its having caused any recorded illness or fatality. Watson's claim that the council 'stands accused of poisoning its own ratepayers' was somewhat wide of the mark.

Whatever the real facts of the matter, reports which do not make an even-handed assessment of the issues can only be said to be irresponsible.As a consequence of the Newsnight report, London mayor Ken Livingstone wrote to the capital's incinerator operators, asking for assurances that fly ash is not being used. Fair enough, maybe, but Livingstone says: 'We know that there is a potential risk from fly ash and there should be no question of it being reused in any way.'

York recognises that the dioxin scare is part of a bigger publicity campaign. 'Greenpeace is behind this really, ' he says. 'They have a major campaign against incinerators. They want composting rather than recycling, but composting is not going to be the answer. If it's green waste you want you have to put up with the downside.'

'They also want to reduce waste material production at source, and there is nothing wrong with that; in fact I'm totally in favour of minimising waste produce. We do not yet have a proper culture of responsible waste handling - we throw things in the bin and assume that it just disappears - but it has to go somewhere. But even though Greenpeace regularly quotes the environmental credentials of Holland or Germany, nobody realises that they actually incinerate much more than we do.'

York makes the case for incinerators: 'The landfill directives will not allow us, as a society, to carry on as we have been. Therefore, if by incineration we can dispose of waste quickly, generate energy and save fossil fuel, recover metals, and produce adequate aggregates rather than quarrying virgin countryside, then it is an eminently sensible and responsible thing to do.'

REFERENCES What Risk? Science, Politics and Public Health, editor Roger Bate, ButterworthHeinemann,1997 But is it True? A Citizen's Guide to Environmental Health and Safety Issues, Aaron Wildavsky, Harvard University Press, 1995 Kenneth Smith, 'Priorities', American Council on Science and Health, Volume 6 Number 4,1994 A new CIRIA training pack examines the risk assessment of contaminated land and explains the key elements of the necessary practices and procedures. It is intended to assist all practitioners to align their abilities at a common level so as to promote industry-wide consistency. To buy a copy, visit www. ciria. org. uk or contact CIRIA,6 Storey's Gate, Westminster, London, SW1P 3AU, tel 020 7222 8891.

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