The application of quantitative risk assessment to microbial food safety

Quantitative risk assessment (QRA) is rapidly accumulating recognition as the most practical method for assessing the risks associated with microbial contamination of foodstuffs. These risk analyses are most commonly developed in commercial computer spreadsheet applications, combined with Monte Carlo simulation add-ins that enable probability distributions to be inserted into a spreadsheet. If a suitable model structure can be defined and all of the variables within that model reasonably quantified, a QRA will demonstrate the sensitivity of the severity of the risk to each stage in the risk-assessment model. It can therefore provide guidance for the selection of appropriate risk-reduction measures and a quantitative assessment of the benefits and costs of these proposed measures. However, very few reports explaining QRA models have been submitted for publication in this area. There is, therefore, little guidance available to those who intend to embark on a full microbial QRA. This paper looks at a number of modeling techniques that can help produce more realistic and accurate Monte Carlo simulation models. The use and limitations of several distributions important to microbial risk assessment are explained. Some simple techniques specific to Monte Carlo simulation modelling of microbial risks using spreadsheets are also offered which will help the analyst more realistically reflect the uncertain nature of the scenarios being modeled. simulation, food safety.     

Topics in microbial risk assessment: dynamic flow tree process

Microbial risk assessment is emerging as a new discipline in risk assessment. A systematic approach to microbial risk assessment is presented that employs data analysis for developing parsimonious models and accounts formally for the variability and uncertainty of model inputs using analysis of variance and Monte Carlo simulation. The purpose of the paper is to raise and examine issues in conducting microbial risk assessments. The enteric pathogen Escherichia coli O157:H7 was selected as an example for this study due to its significance to public health. The framework for our work is consistent with the risk assessment components described by the National Research Council in 1983 (hazard identification; exposure assessment; dose-response assessment; and risk characterization). Exposure assessment focuses on hamburgers, cooked a range of temperatures from rare to well done, the latter typical for fast food restaurants. Features of the model include predictive microbiology components that account for random stochastic growth and death of organisms in hamburger. For dose-response modeling, Shigella data from human feeding studies were used as a surrogate for E. coli O157:H7. Risks were calculated using a threshold model and an alternative nonthreshold model. The 95% probability intervals for risk of illness for product cooked to a given internal temperature spanned five orders of magnitude for these models. The existence of even a small threshold has a dramatic impact on the estimated risk.     

Food poisoning. Causes, remedies, and prevention

Food producers and consumers must continue to take precautions against foodborne diseases, and early diagnosis and appropriate treatment of these illnesses are essential. Food products and water can become contaminated with microorganisms and toxins that make people ill, and the very young, the elderly, and immunocompromised individuals are especially susceptible. Education of healthcare providers, food handlers, and the public is critical in reducing the incidence and spread of foodborne illness. Changes in eating habits and lifestyle and increased availability of both domestic and imported foods have made food hazards a more complex public health issue. Although most foodborne illnesses can be avoided by safe food handling procedures (see box on page 134), risk reduction is very important at every step from source to table. A concerted effort is needed to ensure continuing safety of the food supply in the United States while also assuring access to a wide variety of healthful foods. Time will tell whether consumers will accept irradiation of meats. If accepted, irradiation could rank in importance with pasteurization of milk and chlorination of water as a public health measure.     

Method of Up-Slope Mitigation Priority for Alishan Mountain Road in Taiwan

Rainfall-induced up-slope failure has been a major issue for the mountain road mitigation. To determine the mitigation priority of the roadside slopes, a model to evaluate the stability of the up-slopes is proposed in this paper. This model is developed using Bayesian classification theorem, historical rainfall and landslide data, and an artificial intelligence skill—Gaussian process. The parameters needed for this model include the up-slope features, catchment area, lithology, vegetation coverage, and rainfall data. Among these parameters, rainfall is considered to be the triggering factor of landslide in this study. In addition, each slope has also demonstrated a unique failure probability relationship with the 72-h accumulated rainfalls. Such a relationship is adopted to define a threshold rainfall factor which is used as an index to estimate the likelihood of landslide occurrence under a rainfall event. Using the threshold rainfall factor of each slope, a priority list is proposed for the mitigation of roadside up-slopes along the Alishan mountain road in Taiwan.     

Dietitians employed by health care facilities preferred a HACCP system over irradiation or chemical rinses for reducing risk of foodborne disease

OBJECTIVE: To survey dietitians in health care facilities about the acceptability of alternative meat and poultry processing methods designed to reduce the risk of foodborne disease and their willingness to pay for these processes. SUBJECTS: A geographically representative sample of 600 members of The American Dietetic Association who work in health care facilities. The response rate was 250 completed questionnaires from 592 eligible subjects (42%). DESIGN: A mail survey was used to gather information on the acceptability of a Hazard Analysis and Critical Control Point (HACCP) system, chemical rinses, and irradiation for increasing the safety of food. Discrete choice contingent valuation was used to determine the acceptability at current prices and at 5, 10, and 25 cents per pound above current prices. STATISTICAL ANALYSES: Logistic regression was used to estimate mean willingness to pay (the maximum amount respondents are willing to pay) for each process. A simultaneous equations regression model was used to estimate the effects of other variables on acceptability. RESULTS: Respondents expressed a high level of concern for food safety in health care facilities. The estimated mean willingness to pay was highest for a HACCP system and lowest for chemical rinses. CONCLUSIONS/APPLICATIONS: The successful adoption of alternative methods to increase food safety depends on their acceptance by foodservice professionals. The professionals sampled were most accepting of a HACCP system, somewhat less accepting of irradiation, and least accepting of new chemical rinses. Poultry and beef processors and government agencies concerned with food safety may want to take into account the attitudes of foodservice professionals.     

Risk-Based Prioritization of Terrorist Threat Mitigation Measures on Bridges

This paper describes a risk-based methodology developed to facilitate prioritization of terrorist threat mitigation strategies on individual bridges. Numerous risk-based methods have been used for prioritization among a group of bridges or other assets. However, this methodology is unique in that it is specifically designed to focus on a single bridge and the risk associated with each of its many individual structural components. “Risk,” as discussed herein, describes the relative potential for a terrorist attack against a specific component and the associated consequence from the attack. It is based on such factors as the component’s importance to overall structural stability, its location and thus accessibility to terrorists, and its resistance to the specific threat. The component-specific risk factors and their modifying attributes are described. The result of the methodology is a rank-ordered list of components most at risk to an attack, allowing prioritization and optimization of the mitigation design for the bridge. Once mitigation schemes are identified, the methodology can then be utilized to recalculate mitigated risk, allowing for a direct indication of cost/benefit of the mitigation design. The methodology and comparison criteria are described and a simple application example is given to demonstrate the usefulness of the methodology.     

The regulation of progesterone and hCG production from placental cells by interleukin-1beta

Recent outbreaks of foodborne illness and studies by expert groups have established the need for fundamental change in the United States meat and poultry inspection programme to reduce the risk of foodborne illness. The Food Safety and Inspection Service (FSIS) of the United States Department of Agriculture (USDA) has embarked on a broad effort to bring about such change, with particular emphasis on the reduction of pathogenic micro-organisms in raw meat and poultry products. The publication on 25 July 1996 of the Final Rule on pathogen reduction and hazard analysis and critical control point (HACCP) systems was a major milestone in the FSIS strategy for change. The Final Rule provides a framework for change and clarifies the respective roles of industry and government in ensuring the safety of meat and poultry products. With the implementation of this Final Rule underway, the FSIS has been exploring ways in which slaughter inspection carried out under an HACCP-based system can be changed so that food safety risks are addressed more adequately and the allocation of inspection resources is improved further. In addition, the FSIS is broadening the focus of food safety activities to extend beyond slaughter and processing plants by working with industry, academia and other government agencies. Such co-operation should lead to the development of measures to improve food safety before animals reach the slaughter plant and after products leave the inspected establishment for distribution to the retail level. For the future, the FSIS believes that quantitative risk assessments will be at the core of food safety activities. Risk assessments provide the most effective means of identifying how specific pathogens and other hazards may be encountered throughout the farm-to-table chain and of measuring the potential impact of various interventions. In addition, these assessments will be used in the development and evaluation of HACCP systems. The FSIS is currently conducting a quantitative risk assessment for eggs, and several surveys and studies are being performed to supply data needed to conduct other risk assessments. The FSIS has established a food safety research agenda which will fill data gaps.     

Prevention of Listeria monocytogenes contamination on dairy farms and in the cheese industry

Listeria monocytogenes remains a pathogen bacteria the prevention of which, in food products, stays delicate. A complete organization, from the farmer's production to the industry and the consumer is necessary to eliminate Listeria in a type of food product. Listeria monocytogenes is susceptible of contaminate raw milk. The silage may be a major source of the occurrence of Listeria monocytogenes in raw milk. In this case, the contamination sources in a dairy farm and the good hygienic practices must be well-defined. In dairy industry, the contamination must be managed by the application of a systematic and methodically system like H.A.C.C.P. (Hazard Analysis Critical Control Points). It is useful for the study of Listeria monocytogenes contamination and involve the hazard analysis of each industry plant. In fact, the raw products, food products, manufacturing process, environmental conditions, process equipment, materials and staff organizational are specific and characteristic.     

Modeling epidemiologic studies of occupational cohorts for the quantitative assessment of carcinogenic hazards

Epidemiologic studies of occupational cohorts have played a major role in the quantitative assessment of risks associated with several carcinogenic hazards and are likely to play an increasingly important role in this area. Relatively little attention has been given in either the epidemiologic or the risk assessment literature to the development of appropriate methods for modeling epidemiologic data for quantitative risk assessment (QRA). The purpose of this paper is to review currently available methods for modeling epidemiologic data for risk assessment. The focus of this paper is on methods for use with retrospective cohort mortality studies of occupational groups for estimating cancer risk, since these are the data most commonly used when epidemiologic information is used for QRA. Both empirical (e.g., Poisson regression and Cox proportionate hazards model) and biologic (e.g., two-stage models) models are considered. Analyses of a study of lung cancer among workers exposed to cadmium are used to illustrate these modeling methods. Based on this example it is demonstrated that the selection of a particular model may have a large influence on the resulting estimates of risk.     

Use of predictive microbiology in meat hygiene regulatory activity

New Zealand is a supplier of refrigerated raw meat to world markets. To maintain this supply, from regulatory and commercial perspectives, production standards need to deliver products that are both hygienically adequate and commercially viable. A dynamic Temperature Function Integration (TFI) model, as a form of predictive microbiology, was used jointly by regulators and processors to develop justifiable criteria for the management of refrigeration during the production of hot and warm-boned meat, the post-slaughter handling of ovine carcasses and the handling of offals. Current processes operating according to accepted standards for Good Manufacturing Practice (GMP) were quantified in terms of TFI. The hygienic adequacy of new processes were similarly determined using the TFI model and compared to relevant GMP standards. From a regulatory perspective, the dynamic TFI model has provided a rapid and cost effective method of quantifying a temperature dependent process in terms of the potential for microbial proliferation. It has also produced a method for determining parameters for new or intended processes by comparing the potential for microbial proliferation with previously validated outputs, and has complemented traditional quantitative microbiology to provide a rapid, cost effective method of verifying that a process is performing according to design parameters. However, it could not be used to validate standards for processing in the absence of existing standards for GMP, or in the absence of microbial standards previously established using the principles of risk assessment.     

Foodborne illness in the elderly

The elderly (> or = 65 years of age) are more susceptible to morbidity and mortality from foodborne-induced gastroenteritis than younger individuals. Several factors contribute to the increased susceptibility to foodborne infections as well as other infections in elderly populations. These include an age-associated decrease in humoral and cellular immunity, age-related changes in the gastrointestinal tract (decreased production of gastric acid and decreased intestinal motility), malnutrition, lack of exercise, entry into nursing homes, and excessive use of antibiotics. Data from foodborne outbreaks associated with nursing homes indicate that the elderly are more likely to die from foodborne Campylobacter, Clostridium perfringens, Escherichia coli O157:H7, Salmonella, and Staphylococcus aureus infections than the general population. Infections by Salmonella species are the most common cause of illness and death in nursing homes with Salmonella enteritidis as the major cause of both morbidity and mortality. While it is impossible to turn back the clock, practicing a healthy life-style with regular exercise, maintaining a balanced diet, receiving regular health care, paying attention to personal hygiene, and monitoring food preparation and handling should lead to a reduced incidence of foodborne and other infections in the elderly.     

The large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase is fragmented into 37-kDa and 16-kDa polypeptides by active oxygen in the lysates of chloroplasts from primary leaves of wheat

Foodborne illness of microbial origin is the most serious food safety problem in the United States. The Centers for Disease Control and Prevention reports that 79% of outbreaks between 1987 and 1992 were bacterial; improper holding temperature and poor personal hygiene of food handlers contributed most to disease incidence. Some microbes have demonstrated resistance to standard methods of preparation and storage of foods. Nonetheless, food safety and public health officials attribute a rise in incidence of foodborne illness to changes in demographics and consumer lifestyles that affect the way food is prepared and stored. Food editors report that fewer than 50% of consumers are concerned about food safety. An American Meat Institute (1996) study details lifestyle changes affecting food behavior, including an increasing number of women in the workforce, limited commitment to food preparation, and a greater number of single heads of households. Consumers appear to be more interested in convenience and saving time than in proper food handling and preparation.     

Automatic Calibration of the U.S. EPA SWMM Model for a Large Urban Catchment

The Storm Water Management Model was adapted and calibrated to the Ballona Creek Watershed, a large urban catchment in Southern California. A geographic information system (GIS) was used to process the input data and generate the spatial distribution of precipitation. An optimization procedure using the complex method was incorporated to estimate runoff parameters, and ten storms were used for calibration and validation. The calibrated model predicted the observed outputs with reasonable accuracy. A sensitivity analysis showed the impact of the model parameters, and results were most sensitive to imperviousness and impervious depression storage and least sensitive to Manning roughness for surface flow. Optimized imperviousness was greater than imperviousness predicted from land-use information. The results demonstrate that this methodology of integrating GIS and stormwater model with a constrained optimization technique can be applied to large watersheds.     

Epiduroscopy with access via the sacral canal. Some constructional equipment requirements from the anatomic and biomechanical viewpoint

Food safety is a complex matter that depends on a number of interrelated environmental, cultural, and socioeconomic factors. The purpose of epidemiology and surveillance is to define these factors, how they interact, and their relative importance in foodborne infections. The tools epidemiologists use to study foodborne disease include surveillance of specific infections in humans, monitoring of contamination with specific pathogens in foods and animals, intensive outbreak investigations, collecting reports of outbreaks at the regional or national level, and studies of sporadic infections. With sufficiently elaborate systems of surveillance and investigation, it is possible to provide quantitative risk data for foodborne diseases that will permit the wisest allocation of food safety resources.     

Prospects of glutamate antagonists in the therapy of Parkinson''s disease

BACKGROUND AND AIMS OF THE STUDY: Several different biological, bioprosthetic and mechanical devices are available for heart valve replacement. We present a quantitative methodology to estimate the (event-free) life-expectancy and lifetime risk of valve-related events for individual patients after implantation of any one of these valve types. METHODS: We modelled the age-dependent prognosis of a patient after aortic valve replacement with a discrete-time Markov model and Monte-Carlo simulation to estimate (event-free) life-expectancy and life-time risk of valve-related events, respectively. Quantitative estimates to parameterize these models used hypothetical devices and presumed data were based on a limited review of published literature. RESULTS: This decision-analytical approach allowed an estimation of the overall and event-free life-expectancy as well as the lifetime risk of valve-related events after implantation of different types of prosthetic heart valve in the aortic position. In the current, hypothetical model, one valve type excelled for all age groups in terms of life expectancy and life-time risk of valve-related events. The choice of the second-best alternative varied according to patient age and comorbidity. Sensitivity analyses showed results to be especially dependent on the durability of the replacement valve and surgical risk. CONCLUSIONS: This methodological approach is very flexible, and its quantitative results may guide decision making, if increasing quantitative information on heart valve prosthesis performance becomes available in future. Markov models and Monte Carlo simulation may be used to obtain a better understanding of the effect that different types of prosthetic heart valves have on patient prognosis, while quantitative results may help cardiologists and cardiac surgeons to choose a specific valve type for an individual patient.     

A multivariate logistic model (MLM) for analyzing binary family data

We consider modeling the familial correlation between 2 related individuals using a multiple logistic regressive model. It is shown that there is a discrepancy in the marginal probability of the second individual. We investigate the conditions under which this discrepancy can be minimized and show how it can have a direct effect on handling missing values and ascertainment. We derive a functional relationship between the parameters in the model that eliminates this discrepancy, hence solving the problems that can arise in the handling of missing values and ascertainment. Because this methodology fails when there are more than 2 related individuals, we present a new model based on a multivariate logistic distribution. Residual familial correlations can be directly related to the parameters of this model. The likelihood for family data under this model is independent of the order in which the family members enter the calculation. The marginal probabilities can be easily computed.     

Economic costs and trade impacts of microbial foodborne illness

This article presents the economic costs of foodborne diseases for selected countries, the approaches used to calculate these costs, and a discussion on the interaction between microbial food safety issues and international trade in food. The human illness costs due to foodborne pathogens are estimated most completely in the United States of America, where, each year, 7 foodborne pathogens (Campylobacter jejuni, Clostridium perfringens, Escherichia coli O157:H7. Listeria monocytogenes, Salmonella, Staphylococcus aureus, and Toxoplasma gondii) cause an estimated 3.3-12.3 million cases of foodborne illness and up to 3900 deaths. These 7 pathogens are found in animal products and cost the United States an estimated $6.5-$34.9 billion (1995 US$) annually. The presence of foodborne pathogens in a country's food supply not only affects the health of the local population, but also represents a potential for spread to pathogens to visitors to the country and to consumers in countries which import food products. With more complete data on foodborne illnesses, deaths, costs and international trade rejections in each country, indicators could be developed by which changes in food safety can be monitored.     

Buying and Selling Prices of Investments: Configural Weight Model of Interactions Predicts Violations of Joint Independence

Judges evaluated buying and selling prices of hypothetical investments, based on the previous price of each investment and estimates of the investment's future value given by advisors of varied expertise. Effect of a source's estimate varied in proportion to the source's expertise, and it varied inversely with the number and expertise of other sources. There was also a configural effect in which the effect of a source's estimate was affected by the rank order of that source's estimate, in relation to other estimates of the same investment. These interactions were fit with a configural weight averaging model in which buyers and sellers place different weights on estimates of different ranks. This model implies that one can design a new experiment in which there will be different violations of joint independence in different viewpoints. Experiment 2 confirmed patterns of violations of joint independence predicted from the model fit in Experiment 1. Experiment 2 also showed that preference reversals between viewpoints can be predicted by the model of Experiment 1. Configural weighting provides a better account of buying and selling prices than either of two models of loss aversion or the theory of anchoring and insufficient adjustment. Copyright 1998 Academic Press.     

Risk perceptions: Assessment and relationship to influenza vaccination.

Objective: Accurate measurement of beliefs about risk probability is essential to determine what role these beliefs have in health behavior. This study investigated the ability of several types of risk perception measures and of other constructs from health behavior theories to predict influenza vaccination. Design: Prospective study in which students, faculty, and staff at 3 universities (N = 428) were interviewed in the fall, before influenza vaccine was available, and again early in the next calendar year. Main Outcome Measure: Self-reported influenza vaccination. Results: Two interview questions that asked about feeling at risk and feeling vulnerable predicted subsequent behavior better (r = .44, p = .001) than 2 questions that asked for agreement or disagreement with statements about risk probability (r = .25, p = .001) or 4 questions that asked respondents to estimate the magnitude of the risk probability (r = .30, p = .001). Of the 4 perceived risk magnitude scales, a 7-point verbal scale was the best predictor of behavior. Anticipated regret was the strongest predictor of vaccination (r = .45, p = .001) of all constructs studied, including risk perceptions, worry, and perceived vaccine effectiveness. Conclusion: Risk perceptions predicted subsequent vaccination. However, perceived risk phrased in terms of feelings rather than as a purely cognitive probability judgment predicted better. Because neither feeling at risk nor anticipated regret is represented in the most commonly used theories of health behavior, the data suggest that these theories are missing important constructs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)