Human Risks from the Combustion of SRM-Derived Tallow in Ireland

Abstract

The identification of meat and bone meal (MBM) as a significant factor in the spread of bovine spongiform encephalopathy (BSE) has resulted in the introduction of restrictions on the use and movement of MBM and tallow. This has led to a requirement for alternative uses for these products. This paper reports on a risk assessment performed on the use of tallow as a fuel oil extender in diesel engines. With up to 4000 tonnes of tallow being produced each year in Ireland, combustion with energy recovery represents a viable, cost-efficient utilization route. A stochastic (Latin Hypercube sampling) simulation model was developed to assess the infectivity risk to humans associated with potential airborne exposure to the combustion products when using tallow as a combustion fuel in diesel engines. The model simulates the potential infectivity pathways that tallow follows, including its production from animals with potentially subclinical BSE and processing the tallow with segregation and heat treatments. The model uses probability distributions for the most important input parameters. The assessment takes into account a number of epidemiological parameters that include tissue infectivity, species barrier, disease incidence, and heat inactivation. Two scenarios, reflecting the infectivity risk in different animal tissues defined by the European Commissions Scientific Steering Committee (SSC), were performed. It is seen from the model results that the risk of a human contracting variant Creutzfeldt-Jakob Disease (vCJD) from potential airborne exposure to BSE, resulting from the combustion of tallow, is extremely small even when model uncertainty is taken into account (mean individual risk values ranging from to 10-7.23 per year/person). The risks are a number of Cummins et al.orders of magnitude less than the sporadic annual incidence level of CreutzfeldtJakob Disease (CJD) in Europe (approximately ) .

Transmissible Spongiform Encephalopathy Risk Assessment: The UK experience

“…A more natural choice would be to assign a triangular distribution ranging from 1 to 10,000 with a peak at 10 (as used in Cummins et al . ( 80 ) ). Similarly, for uncertainty in the infectivity of CNS tissue, no grounds are provided for the choice of a log‐normal in preference to (say) a log‐logistic dose‐response model curve.…”

“…Alarmingly, this implies there is a probability of zero that the cattle-to-human species barrier factor might take any other value (for example, 15, or 101, etc). A more natural choice would be to assign a triangular distribution ranging from 1 to 10,000 with a peak at 10 (as used in Cummins et al (80) ). Similarly, for uncertainty in the infectivity of CNS tissue, no grounds are provided for the choice of a log-normal in preference to (say) a log-logistic dose-response model curve.…”

An evaluation of United Kingdom environmental bovine spongiform encephalopathy risk assessment

“…This could be modified further into a 2‐step uniform distribution consisting of weighted‐probability distributions, most obviously as 10 / 10,000 and 9,900 / 10,000 for the respective intervals of 1 to 10 and 10 to 10,000, to reflect a lesser perceived likelihood of lying below 10 and a higher overall probability of lying between 10 and 10,000. Another alternative is to assign a triangular distribution ranging from 1 to 10,000 with a peak at 10 (as used in Cummins et al 2002). A justification was not provided in the DNV risk assessments regarding the selection of a log‐normal distribution to characterize the uncertainty of the infectivity of CNS tissue.…”

Exposure Assessment of TSEs from the Landspreading of Meat and Bone Meal

“…50%) led to its previous inclusion in animal diets throughout the world. Many elements relating to BSE and associated risks have been previously reviewed (Cummins et al ., 2001, 2002a, 2002b). Control measures introduced by the European Commission to combat BSE in the European Union (EU) include the addition of a requirement for a severe hyperbaric treatment (133°Celsius at 3 bar pressure for 20 minutes) in the rendering process and the destruction of specified risk material (SRM).…”