March to May 2001 will be remembered by many, especially those living in Cumbria and Devon, for burning pyres and heavy smoke. With an almost sweet, sickly smell, this was distinctly different to the more familiar smokes emitted from bonfires and burning coal, and there were few who encountered it that did not know of its particular source. Peter Daley and Dr Richard Hill assess the health risks associated with the pyres

The outbreak of foot and mouth disease (FMD) that began in the UK in late February last year had, by October, caused infection on 2,030 premises, leading to the slaughter of approximately four million animals. Of this total, 44 per cent of the infected premises occurred in the county of Cumbria. From the outset of the outbreak, pyres were lit without consultation with local authorities or health authorities, despite many concerns being voiced. Many early pyres burned for over a week, stretching the tolerance of local communities, while the profession's collective voice appeared to be falling on deaf ears. In due course, the consultation process started and the Department of Health risk assessment document Effects on health of emissions from pyres used for disposal of animals, released on 24 April, recommended that EHOs and local public health doctors should be involved in any decisions made on the siting of pyres.1 Unfortunately, this advice came too late in Cumbria as the last pyre was lit on 18 April. There was a lack of available air monitoring data for pyres to help in making objective recommendations on the siting and composition of pyres and, in addition, there were concerns about the longer-term impacts of pyres on the foodchain. To address this situation, Westlakes Research Institute was commissioned to provide a scientific assessment for Cumbrian DCs, North Cumbria Health Authority and the CIEH about two key elements of the pollution caused by the use of pyres. These were: - to determine the health risks associated with the smoke and fumes being emitted from the pyres; and - to determine whether the atmospheric deposition of organic pollutants released from the pyres was likely to affect the future use of agricultural land. The monitoring of smoke from the pyre lit at Hazelsprings Farm in North Cumbria, the last pyre in the county, was conducted between 19 and 21 April, while the assessment of dioxin levels in agricultural land surrounding the pyre at Thwaites Farm, 10 miles away, was conducted between 25 and 26 June. Details of the location and materials burned on these pyres are given in table 1.

MONITORING AIR POLLUTANTS DOWNWIND
Air concentrations of respiratory irritants and carcinogens that are typically emitted from large combustion sources were monitored using mobile real-time sampling equipment. This equipment was positioned close to the nearest residences that were downwind of Hazelsprings Farm pyre. In addition, a high volume air sampler that can filter 300 litres of air per minute was used to collect samples for detailed chemical analysis of specific toxic chemicals. These chemicals were polycyclic aromatic hydrocarbons (PAHs) and dioxins (including furans). During the first three days following the ignition of the pyre, the wind direction was mainly from the north, resulting in the hamlet of Whelpo (approximately 4km from the pyre) being downwind of the pyre. On the fourth and fifth day, a change in wind direction resulted in several of the residences outlying the hamlet of Brocklebank being downwind of the pyre. These residences were within 1km of the pyre and, as would be expected, were subject to a much denser smoke plume than had been encountered at Whelpo. The monitoring equipment was moved to track the emissions. The results of the real-time air pollution monitoring for these two locations are presented using an air pollution index (table 2). The monitoring results showed that, overall, the air pollution levels were in the LOW band of the air pollution index. Hence, noticeable effects were unlikely, even on individuals that are known to be sensitive to air pollutants. However, the air quality for both SO2 and PM10 was found to worsen at the monitoring location closest to the pyre. For SO2, the air concentrations were close to the MODERATE classification. This meant that individuals sensitive to air pollutants might notice mild effects. The results of the laboratory analysis for dioxins and PAHs showed that higher air concentrations were measured at the locations downwind of the pyre, when compared with the background samples. However, the air concentrations of both dioxins and PAHs were comparable with urban background monitoring results from the Toxic Organic Micropollutants Network.2 This showed that while the pyres were likely to have emitted these pollutants, exposure downwind of the pyres would not have created a greater risk to health than if the local residents had spent an equivalent amount of time in a busy city.

MONITORING OF SOIL CONTAMINATION
The air pollution monitoring demonstrated that pyres can be a source of dioxins and PAHs. While air concentrations were not found to pose an appreciable risk to health, the potential exists for these pollutants to deposit from the atmosphere to agricultural land surrounding the pyre. As these pollutants can persist in the environment and accumulate in livestock, there was a potential risk to health following food consumption. Samples of soil, to a depth of 5cm, were collected using a 10cm diameter corer from nine sites surrounding the pyre at Thwaites Farm. An atmospheric dispersion modelling assessment was conducted to enable the targeting of eight of the soil samples at locations where the highest levels of contamination were likely to have occurred. The remaining soil sample was taken at a local background location within 2km of Thwaites Farm and was modelled to be relatively unaffected by emissions from the pyre. Grass samples were taken at both the "hot-spot" and background locations. A map showing the location of the monitoring sites, overlaid with the predictions of the atmospheric dispersion model is shown in figure 1. All of the soil and grass samples were analysed to determine dioxin concentrations using the international toxic equivalents (I-TEQ) system,3 rather than the World Health Organisation system (WHO-TEQ). Soil samples from the "hot spot" and background sites were also analysed for PAHs and dioxin-like poly chlorinated biphenyls (PCBs). All the following soil concentrations are presented as dry weight concentrations.

MONITORING RESULTS
Higher soil concentrations of PAHs and PCBs were recorded at the "hot spot" site than at the background site, indicating that the pyre was a source of these pollutants. The PAH soil concentrations were compared with the current mandatory guidance of 50 mg/kg-1 as an action level,4 while, due to the absence of UK guidance for PCBs, the Dutch action level of 1 mg/kg-1 was applied.5 The highest PAH measurement was 1.1 mg/kg-1 which was considerably below the UK mandatory guidance for contaminated land. The highest PCB reading of 0.009 mg/kg-1 was also considerably below the action levels from Dutch guidance and was actually lower than the quoted optimum level of 0.02 mg/kg-1. The dioxin concentrations in the soil at the background site was 0.86 ng {I-TEQ} kg-1 and only two of the sites that were close to the pyre had higher concentrations. The highest of these sites was the "hot spot" site predicted by the atmospheric modelling, which had a dioxin concentration of 2.1 ng {I-TEQ} kg-1, and a nearby site which had a dioxin concentration of 1.45 ng {I-TEQ} kg-1. As there are no current standards for dioxin levels in soil these dioxin concentrations were compared with rural measurements collected by Her Majesty's Inspectorate of Pollution (HMIP) in the 1995 survey, which ranged between 0.7 - 17 ng {WHO-TEQ} kg-1.6 It can be seen from this comparison that even the highest dioxin levels measured in the soil at Thwaites Farm were towards the lower end of the range of rural concentrations measured by HMIP. Very low levels of dioxins were found on the grass samples, with a higher reading from the background site (0.02 ng {I-TEQ} kg-1) than from the site at the "hot spot" location (0.01 ng {I-TEQ} kg-1). This was not surprising as dioxins have a half-life on grass of typically less than 14 days, as they react with sunlight and are lost through weathering caused by the actions of wind and rain. As the measurements were taken 12 weeks after the pyre was lit, it could theoretically be expected that less than 1.6 per cent of the total mass of dioxin that had initially deposited would still be on the grass by the time of sampling.

ASSESSMENT OF DIOXINS IN FOODSTUFFS
The EC Scientific Committee on Food currently recommends a tolerable weekly intake of dioxins of 14 pg {I-TEQ} kg{bodyweight}-1 week-1. A theoretical modelling assessment was conducted to determine whether the levels of soil contamination measured in the field could cause an exceedence of the EC tolerable weekly intake. This assessment investigated concentrations of dioxins in milk, beef and free-range eggs produced from the farm using a simple equilibrium transfer model.7 As only two sites showed dioxin concentrations above the local background values, a conservative assumption was made that livestock would be exposed to dioxin concentrations at these elevated levels. The model predicted that concentrations of dioxins in beef, milk and eggs produced on the farmland would be 14, 4 and 89 pg {I-TEQ} kg{fresh weight}-1 respectively. To check the accuracy of the model predictions, results were compared with the Food Standards Agency (FSA) monitoring of dioxin concentrations in eggs and milk collected from farms near to pyre sites.8 The FSA concentrations compare quite well with the model predictions, with monitored concentrations of dioxins in milk ranging between approximately 12 - 46 pg {WHO-TEQ} kg{fresh weight}-1 and concentrations in eggs ranging between approximately 66 - 1100 pg {WHO-TEQ} kg{fresh weight}-1. The dietary intake of dioxin was calculated by assuming that an individual (weighing 70 kg) obtained all their milk, beef and eggs from a farm close to a pyre. We also assumed that over a week a typical individual would eat 290g of beef and 160g of eggs and would drink 1.8 litres of milk. This data was derived from the results of a 1995 habit survey.9 The total dioxin intake calculated using these methods was 0.4 pg{I-TEQ} kg{bodyweight}-1 week-1; much lower than the EC tolerable weekly intake level and the FSA Committee on Toxicology's tolerable daily intake. It was therefore concluded that the levels of dioxins in the soil at this farm were unlikely to pose an appreciable risk to health.

NO SERIOUS RISK
The two sites investigated in this study showed that while the pyres were undeniably a source of both air and soil pollution, the levels which were monitored were not likely to pose a serious risk to health. However, as a note of caution, it cannot be assumed that the use of pyres in all circumstances would be without health risks and undoubtedly the pyres were a nuisance to local residents in many cases. Had the meteorology been more constant, or if a low lying inversion layer had formed, then the levels of air pollution measured in this study may have been much greater. In these cases the two pollutants which may have created the most significant problems would have been likely to be airborne SO2 and PM10. These pollution studies were only possible because of the joint funding arranged on a local level and the goodwill of Westlakes Research Institute. However, EHOs in foot and mouth-affected areas needed information from pollution studies like these at the start of the outbreak, not at the end. It is regrettable that adequate information on possible health risks from pyres was not available from national bodies much earlier. Indeed, this lack of information and co-operation caused significant delays to the air pollution monitoring reported herein. As a profession, we are uniquely aware of local issues which are often replicated throughout the country. If we are to serve our communities we need to ensure that we can communicate effectively among ourselves and have our voices heard at a national level as early as possible. It remains to be seen how much recognition will be given to the value of the expertise and local knowledge of EHOs in the Government's report on the outbreak.

ABOUT THE AUTHORS
Peter Daley is Environmental Health Unit Manager at Allerdale Borough Council and Dr Richard Hill is a Senior Scientist in the Air Pollution Group at Westlakes Research Institute, near Whitehaven in Cumbria.

REFERENCES 1 DoH (2001) "Foot and mouth: Effects on health of emissions from pyres used for disposal of animals". April 24 2001, Department of Health.
2 NETCEN (2001) Data obtained from the toxic organic micro pollutants section of the UK National Air Quality Information Archive (www.aeat.co.uk/netcen/airqual).
3 NATO/CCMS (1988) International toxicity equivalency factors (I-TEF) method of risk assessments for complex mixtures of dioxins and related compounds. North Atlantic Treaty Organization, Committee on the Challenges of Modern Society, Report No 176. Brussels, NATO.
4 ICRL (1983) 59/83 "Guidance on the assessment and redevelopment of contaminated land". Interdepartmental Committee on the Redevelopment of Contaminated Land. Department of the Environment.
5 VROM (1994) Intervention values and target values: Soil quality standards; Netherlands Ministry of Housing, Spatial Planning and Environment, Department of Soil Protection: The Hague, Netherlands.
6 HMIP (1995) "Determination of polyclorinated biphenyls, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in UK soils." HM's Inspectorate of Pollution.
7 Eduljee G H, and Gair A J, (1996) Validation of a methodology for modelling PCDD and PCDF intake via the foodchain. The Science of the Total Environment 187: 11-229.
8 FSA (2001) "Dioxins and dioxin-like polychlorinated biphenyls in foods from farms close to pyres." Third report (20 September 2001).
9 Byrom, J, Robinson, C, Simmonds, JR, Walters, B and Taylor, R R (1995) "Food consumption rates for use in generalised radiological dose assessments". Journal of Radiological Protection: 15, 335-341.

ACKNOWLEDGEMENTS
The dioxin, PAH, and PCB analysis carried out in this work was conducted by Scientific Analysis Laboratories, Manchester. Vicky Auld, Kate Charles, Henry Stewart and Ian Lowles from Westlakes Research Institute contributed to the technical work presented herein. This project was supported by Allerdale Borough Council, Carlisle City Council, Copeland Borough Council, Eden District Council, South Lakeland District Council, North Cumbria Health Authority and The Chartered Institute of Environmental Health.