Enviros study and its limitations

A report was produced for DEFRA, which conducted a review of such studies [Enviros Consulting et al, 2004]. The report describes the health impacts of various waste management options. It includes useful data on pollutant emissions from waste incinerators, and an assessment of the health impacts from air pollutants. It is recommended that you read the report if you want to know more about this topic.

The conclusions of the DEFRA report may have a significant influence on the policy decisions made by waste management authorities. Therefore, given the importance of this document, it is useful to acknowledge its worth and to also point out its limited scope. Waste management authorities should not make decisions based entirely on the contents of this report. They should recognise that some critical aspects have not been investigated in the DEFRA report.

The report recognised the difficulties associated with epidemiological studies and noted that it was not ideal for producing a clear conclusion. Consequently, the report also investigated the potential impact from incinerators by modelling scenarios based on standard emission rates, average population densities, and average meteorological data. The results for these scenarios indicated there would be negligible impact on human health. The authors’ overall conclusion was based on: the review of health studies; their modelling of air pollution; and the assumption that future emissions should comply with the more stringent regulations of the Waste Incineration Directive. They concluded that the impact on health would be negligible.

However, in the last appendix of that report the comments by the Royal Society following a review of the draft report clearly stated that the report should note the uncertainties and should be cautious in quantifying effects and drawing conclusions.

In particular, the Royal Society stated that:

  • In view of the large uncertainties associated with some of the data examined, particularly in the epidemiological studies, it would have been more appropriate to adopt a cautious approach, rather than use inadequate data in a quantitative framework. The latter may give a misleading impression of the robustness of the results.
  • Caveats associated with the uncertainties in the results are not presented adequately, particularly in the quantification of the health effects, which could mislead the reader.
  • The report’s relevance to waste management decision-making by Local Authorities is limited, as several important issues are not addressed. These include the effect of local environmental and health sensitivity to pollutants and the impact on emissions of specific waste management activities operating under non-standard conditions.
  • Bias in the availability of good quality information means the report concentrates mainly on the effects of air pollution. Consideration of the potential effects of exposure to pollutants through other pathways is not consistent throughout the report and therefore prevents adequate comparison of the options.”

The Royal Society finally said of the revised report that it “is satisfied that a significant number of its concerns have been addressed”. However, it is the opinion of the author of this paper that the above points are some of those that were not fully addressed in the final version of the report.

The issue of the impact of non-standard emissions is further emphasised by the statement of the Chief Scientific Advisor, to DEFRA, in the foreword to the report:

“The review has concluded that the effects on health from emissions from incineration, largely to air, are likely to be small in relation to other known risks to health. I have confidence in this conclusion, particularly bearing in mind the fact that the current generation of municipal solid waste incinerators have to comply with much more stringent emission standards than those which formed the basis for the majority of studies of health effects in the literature. This does not mean that we can afford to be complacent; rigorous enforcement will be crucial to ensure that the new emission standards are not exceeded, and that non-standard operating conditions, as noted by the Royal Society, do not lead to levels of emission which would give rise to concern.”

This is an important point in the debate about whether incinerators are safe or not. The technology exists to substantially reduce emissions, but continuously low emissions can only be achieved if the technology is reliable, well maintained, and operated effectively by well trained staff at all times. It also requires a continuous waste stream that has a suitable calorific value, and low levels of problem substances that promote pollutant emissions.

In terms of the precautionary principle, there are potential risks still outstanding. A critical failure of the combustion control or emissions abatement technology could lead to unusually high emission rates. Similarly, incorrect operation of the plant or an accident could result in unusually high emission rates. Further, it is accepted that during the commissioning of a new incinerator plant that emissions will be unusually high over this period.

Rigorous monitoring and enforcement is indeed required to ensure that breaches of emission limits are prevented. Enforcement may not be working as rigorously as it needs to be to guarantee protection of health and the environment. Recently, the Eastcroft incinerator at Nottingham breached dioxin limits. The spot measurement showed that emissions during the sampling period were 9 times higher than the emissions limit. Critically, given that dioxins are usually only measured every six months, the question arises were emissions 9 times higher over the entire six months? This could lead to the assumption that over the year dioxin emissions were 5 times higher than the emissions limit. Of course, actual emissions between measurements over the six month period could have been lower, or higher.

Based the the work of Dr Adam Bostock

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