Recent developments in the application of risk analysis to waste technologies.

The European waste sector is undergoing a period of unprecedented change driven by business consolidation, new legislation and heightened public and government scrutiny. One feature is the transition of the sector towards a process industry with increased pre-treatment of wastes prior to the disposal of residues and the co-location of technologies at single sites, often also for resource recovery and residuals management. Waste technologies such as in-vessel composting, the thermal treatment of clinical waste, the stabilisation of hazardous wastes, biomass gasification, sludge combustion and the use of wastes as fuel, present operators and regulators with new challenges as to their safe and environmentally responsible operation. A second feature of recent change is an increased regulatory emphasis on public and ecosystem health and the need for assessments of risk to and from waste installations. Public confidence in waste management, secured in part through enforcement of the planning and permitting regimes and sound operational performance, is central to establishing the infrastructure of new waste technologies. Well-informed risk management plays a critical role. We discuss recent developments in risk analysis within the sector and the future needs of risk analysis that are required to respond to the new waste and resource management agenda.

Assessment and management of risks arising from exposure to cadmium in fertilisers. I.

A risk assessment protocol has been developed for use by individual EU Member States with appropriate selection of input data, to assess the risks to humans and the environment arising from exposure to cadmium in fertilisers. The protocol comprises of three modules: (1) the accumulation module, in which the net accumulation of cadmium in soil and soil solution, resulting from the application of fertiliser, is computed over time. The accumulation module allows for a range of inputs from different sources (atmospheric deposition, sludge addition, manure and fertiliser application) as well as for average and extreme rates of fertiliser application. A critical parameter is the solid/liquid partition coefficient, which in turn is a function of soil properties such as pH and is highly variable depending on the algorithm selected as being representative of national conditions. (2) The exposure module, in which the uptake of cadmium from soil into plants and the subsequent intake of cadmium by humans is computed, using exposure parameters characterising both average and extreme exposure scenarios. The protocol focuses on food types known to be sensitive to cadmium uptake (grain, cereals, potatoes, root vegetables and leafy vegetables). Environmental exposure is also characterised. (3) The risk characterisation module, in which Member States may estimate the incidence and severity of the adverse effects likely to occur due to actual or predicted exposure to cadmium. This is undertaken by modelling the Predicted Environmental Concentrations (PECs) in humans and the environment using the accumulation and exposure modules, and then comparing these values against the relevant Predicted No Effect Concentrations (PNECs). A range of environmental PNEC values are reported in the literature; the European Commission recommends that normally the lowest No Observed Adverse Effect Level (NOAEL) should be used in the risk characterisation. For humans, the current WHO Provisional Tolerable Weekly Intake (PTWI) is equivalent to a daily intake of 70 microg Cd day(-1). Particular risk groups can be characterised, namely of: children; smokers; women with low iron stores; consumers of food items with high cadmium content; and extreme consumers of staple food items. At present, with the data available, it is not possible to characterise risk groups in detail, either at EU level or at Member State level. However, most Member States appear to have an average intake of cadmium which is lower than the WHO's PTWI.

Assessment and management of risks arising from exposure to cadmium in fertilisers--II.

A preliminary, illustrative human health risk assessment of exposure to cadmium in phosphate fertilisers was performed using typical UK data and a protocol previously developed for application by individual Member States in the European Union. The risk assessment indicated that the for the most pessimistic population exposures characterised by both extreme (97th percentile) cereal and potato consumption and high susceptibility to cadmium uptake, the estimated dose was under the WHO Provisional Tolerable Weekly Intake (PTWI) for fertiliser cadmium concentrations ranging from 15 to 100 mg Cd/kg P2O5 applied over 100 years. However, the low margin of safety for high risk groups and the uncertainties inherent in the overall risk assessment suggested that a prudent risk management strategy would involve maintenance of low levels of cadmium in fertilisers and/or conditions that permitted low accumulation of cadmium in soils. On this basis, two main risk reduction measures were developed and assessed: (a) imposition of limits on cadmium concentration in fertilisers; and (b) imposition of charges on levels of cadmium in phosphate fertilisers. An assessment of the economic impact of these risk reduction measures indicated that, at all price elasticities, the most significant impact in terms of changes in demand and changes in consumer expenditure on phosphate fertilisers will be seen with cadmium charges where no thresholds are defined. The impact on the consumer (i.e. farmer) will be an increase in spending of approximately US $4000 per year, which is considered significant, accompanied by a decrease in demand above 20%. If a threshold is set at 60 mg Cd/kg P2O5, the impact is significantly reduced, but stays relatively high compared to the other options. The analysis also indicates that the use of low-cadmium rock is the low cost option. At a likely rock price increase of approximately 5% and assuming a likely price elasticity of -0.2, the yearly costs to farmers will be approximately US $82 which is considered a minimal impact. In the worst case scenario (elasticity of -0.6 and a 10% increase in rock prices), the increase in spending by farmers will be of 3.9% or US $221 which is also considered to represent a minimal impact. At similar price elasticities, the use of decadmation technologies is predicted to be more costly than the use of low-cadmium rock but this option can still be considered as having a minimal impact on the consumer (increase in expenditure of 1.9-13.3% or US $106-748).

Trends in risk assessment and risk management.

Environmental risk assessment has matured into a powerful analytical tool, which is finding ever-wider applications in the arena of policy making and regulation. However, the principal focus of its development to date has been on the technical challenges of characterising and modelling the environmental behaviour and biological action of chemicals, whereas issues concerning its broader socio-political context have been generally neglected. Problem definition, risk analysis and decision making have, therefore, tended to be dominated by experts and by expert opinion. Fresh insights from the social sciences advocate a pluralistic, inclusive approach, with experts participating alongside other stakeholders in a consensual decision making process. Adoption of this paradigm has far reaching consequences for the form and conduct of risk assessment and risk management.

Immunochemical analysis for dioxins--progress and prospects.

Recent developments in antibody design and sample preparation have considerably enhanced the use of enzyme immunoassay (EIA) as an alternative to the conventional techniques based on gas chromatography and mass spectroscopy for the analysis of the trace organic pollutants polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in source and environmental samples. The EIA-specific sample preparation technique for solid matrices using a compatible extracting solvent coupled with an assay using a more sensitive antibody permits screening of source and environmental samples to be undertaken with minimal sample preparation. EIA has been validated on an increasing range of environmental and source samples as a cost effective I-TEQ screening tool, exploiting the commonly recognised general strengths of immunoassays such as speed, simplicity, low cost and parallel processing of many samples, greatly reducing the number of samples requiring conventional GCMS analysis. Further research and developmental work is required in the areas of sample extraction and extract cleanup to ensure compatibility with the immunoassay from the outset, and to standardise as far as is possible an assay format relevant to the application of interest, covering sample preparation, sample cleanup, quality control, assay procedure and data analysis.

Validation of a methodology for modelling PCDD and PCDF intake via the foodchain.

The US EPA foodchain exposure methodology has been assessed, linking background concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in the atmosphere with eventual intake of these chemicals by humans via the foodchain. The methodology is assessed against background environmental concentrations of PCDD/Fs and the background daily adult intake of PCDD/Fs in the UK diet comprising meats, vegetables, dairy produce, fish and miscellaneous food groups. The environmental fate and transport of PCDD/Fs is estimated for each of the seventeen, 2,3,7,8-positional PCDD/F isomers individually from the atmospheric burden in the atmosphere and into the environmental medium or food product of interest. The model predicts PCDD/F deposition rate and soil concentration to within +/-50% of the measured I-TEQ values. For grass, the model underpredicts PCDD/F concentrations but the lack of a reliable and coherent data set precludes further investigation as to the likely causes. The model performs well on food products, with the exception of potatoes (under-predicts by a factor of 20) and 'other' vegetables (underpredicts by a factor of 3). The total modelled PCDD/F intake via the diet is 61 pg I-TEQ day-1 as opposed to the measured intakes of 69 pg I-TEQ day-1 (excluding plant foods) and 81 pg day-1 (including data for plant foods measured in a previous survey, and not representative of contemporary exposures). The major contributor to total PCDD/F intake is via milk and milk products, accounting for about 40% of the daily dietary intake. 'Hidden' fats and oils account for 35% of the PCDD/F intake, followed by the ingestion meat and meat products (12%). As a group, vegetables do not appear to contribute significantly to the total adult background intake of PCDD/Fs via the diet.