Environmental regulation: choice of instruments under imperfect compliance

Compliance is an important issue in environmental regulation. In this paper, we discuss some of the key elements of the problem and analyze a situation where emissions are not random and firms are risk-neutral. We study the firm's decision on emissions and compliance when the environmental regulation is based on standards and the enforcement agency audits the firm with a certain probability. We then compare total emissions when environmental regulation is based on different instruments: standards, taxes, and tradable permits. We show that when compliance is an issue, environmental taxes are superior to the other instruments. We also analyze the (static) efficiency of the solution.

Payments for environmental services in watersheds: insights from a comparative study of three cases in Central America

We have compared three cases of payments for water-related environmental services (PES) in Central America, in terms of socioeconomic background, opportunity costs of forest conservation and stakeholders’ perceptions on the conditions of water resources and other issues. We found that, in general, the foregone benefits from land uses alternative to forest cover are larger than the amount paid, which apparently contradicts the economic foundation of PES schemes. A number of possible explanations are explored. The results also suggest that trade-offs between different environmental and social goals are likely to emerge in PES schemes, posing some doubts on their ability to be multipurpose instruments for environmental improvement and rural development. We also found that PES schemes may work as a conflictresolution instrument, facilitating downstream -upstream problem solving, though at the same time they might introduce changes in social perceptions of property rights.

Global Warming And Extreme Events: Rethinking The Timing And Intensity Of Environmental Policy

The possibility of low-probability extreme events has reignited the debate over the optimal intensity and timing of climate policy. In this paper we therefore contribute to the literature by assessing the implications of low-probability extreme events on environmental policy in a continuous-time real options model with “tail risk”. In a nutshell, our results indicate the importance of tail risk and call for foresighted pre-emptive climate policies.

Factors Affecting Audit Quality in the 2007 UK Regulatory Environment: Perceptions of Chief Financial Officers, Audit Committee Chairs and Audit Engagement Partners

In line with global changes, the UK regulatory regime for audit and corporate governance has changed significantly since the Enron scandal, with an increased role for audit committees and independent inspection of audit firms. UK listed company chief financial officers (CFOs), audit committee chairs (ACCs) and audit partners (APs) were surveyed in 2007 to obtain views on the impact of 36 economic and regulatory factors on audit quality. 498 usable responses were received, representing a response rate of 36%. All groups rated various audit committee interactions with auditors among the factors most enhancing audit quality. Exploratory factor analysis reduces the 36 factors to nine uncorrelated dimensions. In order of extraction, these are: economic risk; audit committee activities; risk of regulatory action; audit firm ethics; economic independence of auditor; audit partner rotation; risk of client loss; audit firm size; and, lastly, International Standards on Auditing (ISAs) and audit inspection. In addition to the activities of the audit committee, risk factors for the auditor (both economic and certain regulatory risks) are believed to most enhance audit quality. However, ISAs and the audit inspection regime, aspects of the ‘standards-surveillance compliance’ regulatory system, are viewed as less effective. Respondents commented that aspects of the changed regime are largely process and compliance driven, with high costs for limited benefits, supporting psychological bias regulation theory that claims there is overconfidence that a useful regulatory intervention exists.

Influence of age, risk factors, and cardiovascular and renal disease on arterial stiffness: clinical applications.

Age is the main clinical determinant of large artery stiffness. Central arteries stiffen progressively with age, whereas peripheral muscular arteries change little with age. A number of clinical studies have analyzed the effects of age on aortic stiffness. Increase of central artery stiffness with age is responsible for earlier wave reflections and changes in pressure wave contours. The stiffening of aorta and other central arteries is a potential risk factor for increased cardiovascular morbidity and mortality. Arterial stiffening with aging is accompanied by an elevation in systolic blood pressure (BP) and pulse pressure (PP). Although arterial stiffening with age is a common situation, it has now been confirmed that older subjects with increased arterial stiffness and elevated PP have higher cardiovascular morbidity and mortality. Increase in aortic stiffness with age occurs gradually and continuously, similarly for men and women. Cross-sectional studies have shown that aortic and carotid stiffness (evaluated by the pulse wave velocity) increase with age by approximately 10% to 15% during a period of 10 years. Women always have 5% to 10% lower stiffness than men of the same age. Although large artery stiffness increases with age independently of the presence of cardiovascular risk factors or other associated conditions, the extent of this increase may depend on several environmental or genetic factors. Hypertension may increase arterial stiffness, especially in older subjects. Among other cardiovascular risk factors, diabetes type 1 and 2 accelerates arterial stiffness, whereas the role of dyslipidemia and tobacco smoking is unclear. Arterial stiffness is also present in several cardiovascular and renal diseases. Patients with heart failure, end stage renal disease, and those with atherosclerotic lesions often develop central artery stiffness. Decreased carotid distensibility, increased arterial thickness, and presence of calcifications and plaques often coexist in the same subject. However, relationships between these three alterations of the arterial wall remain to be explored.

Advanced mapping of environmental data: Geostatistics, Machine Learning and Bayesian Maximum Entropy

This book combines geostatistics and global mapping systems to present an up-to-the-minute study of environmental data. Featuring numerous case studies, the reference covers model dependent (geostatistics) and data driven (machine learning algorithms) analysis techniques such as risk mapping, conditional stochastic simulations, descriptions of spatial uncertainty and variability, artificial neural networks (ANN) for spatial data, Bayesian maximum entropy (BME), and more.

Genetic variants in novel pathways influence blood pressure and cardiovascular disease risk.

Blood pressure is a heritable trait influenced by several biological pathways and responsive to environmental stimuli. Over one billion people worldwide have hypertension (≥140 mm Hg systolic blood pressure or  ≥90 mm Hg diastolic blood pressure). Even small increments in blood pressure are associated with an increased risk of cardiovascular events. This genome-wide association study of systolic and diastolic blood pressure, which used a multi-stage design in 200,000 individuals of European descent, identified sixteen novel loci: six of these loci contain genes previously known or suspected to regulate blood pressure (GUCY1A3-GUCY1B3, NPR3-C5orf23, ADM, FURIN-FES, GOSR2, GNAS-EDN3); the other ten provide new clues to blood pressure physiology. A genetic risk score based on 29 genome-wide significant variants was associated with hypertension, left ventricular wall thickness, stroke and coronary artery disease, but not kidney disease or kidney function. We also observed associations with blood pressure in East Asian, South Asian and African ancestry individuals. Our findings provide new insights into the genetics and biology of blood pressure, and suggest potential novel therapeutic pathways for cardiovascular disease prevention.

NanoImpactNet - Stakeholders' knowledge needs for research on the health and environmental impact of nanomaterials

NanoImpactNet (NIN) is a multidisciplinary European Commission funded network on the environmental, health and safety (EHS) impact of nanomaterials. The 24 founding scientific institutes are leading European research groups active in the fields of nanosafety, nanorisk assessment and nanotoxicology. This 4−year project is the new focal point for information exchange within the research community. Contact with other stakeholders is vital and their needs are being surveyed. NIN is communicating with 100s of stakeholders: businesses; internet platforms; industry associations; regulators; policy makers; national ministries; international agencies; standard−setting bodies and NGOs concerned by labour rights, EHS or animal welfare. To improve this communication, internet research, a questionnaire distributed via partners and targeted phone calls were used to identify stakeholders' interests and needs. Knowledge gaps and the necessity for further data mentioned by representatives of all stakeholder groups in the targeted phone calls concerned: potential toxic and safety hazards of nanomaterials throughout their lifecycles; fate and persistence of nanoparticles in humans, animals and the environment; risks associated to nanoparticle exposure; participation in the preparation of nomenclature, standards, methodologies, protocols and benchmarks; development of best practice guidelines; voluntary schemes on responsibility; databases of materials, research topics and themes. Findings show that stakeholders and NIN researchers share very similar knowledge needs, and that open communication and free movement of knowledge will benefit both researchers and industry. Consequently NIN will encourage stakeholders to be active members. These survey findings will be used to improve NIN's communication tools to further build on interdisciplinary relationships towards a healthy future with nanotechnology.

Report of the National Taskforce on Obesity: Obesity - the policy challenges: Executive Summary

The prevalence of overweight and obesity has increased with alarming speed over the past twenty years. It has recently been described by the World Health Organisation as a ‘global epidemic’. In the year 2000 more than 300 million people worldwide were obese and it is now projected that by 2025 up to half the population of the United States will be obese if current trends are maintained. The disease is now a major public health problem throughout Europe. In Ireland at the present time 39% of adults are overweight and 18% are obese. Of these, slightly more men than women are obese and there is a higher incidence of the disease in lower socio-economic groups. Most worrying of all is the fact that childhood obesity has reached epidemic proportions in Europe, with body weight now the most prevalent childhood disease. While currently there are no agreed criteria or standards for assessing Irish children for obesity some studies are indicating that the numbers of children who are significantly overweight have trebled over the past decade. Extrapolation from authoritative UK data suggests that these numbers could now amount to more than 300,000 overweight and obese children on the island of Ireland and they are probably rising at a rate of over 10,000 per year. A balance of food intake and physical activity is necessary for a healthy weight. The foods we individually consume and our participation in physical activity are the result of a complex supply and production system. The growing research evidence that energy dense foods promote obesity is impressive and convincing. These are the foods that are high in fat, sugar and starch. Of these potentially the most significant promoter of weight gain is fat and foods from the top shelf of the food pyramid including spreads (butter and margarine), cakes and biscuits, and confectionery, when combined are the greatest contributors to fat intake in the Irish diet. In company with their adult counterparts Irish children are also consuming large amounts of energy dense foods outside the home. A recent survey revealed that slightly over half of these children ate sweets at least once a day and roughly a third of them had fizzy drinks and crisps with the same regularity. Sugar sweetened carbonated drinks are thought to contribute to obesity and for this reason the World Health Organisation has expressed serious concerns at the high and increasing consumption of these drinks by children. Physical activity is an important determinant of body weight. Over recent decades there has been a marked decline in demanding physical work and this has been accompanied by more sedentary lifestyles generally and reduced leisure-time activity. These observable changes, which are supported by data from most European countries and the United States, suggest that physical inactivity has made a significant impact on the increase in overweight and obesity being seen today. It is now widely accepted that adults shoud be involved in 45-60 minutes, and children should be involved in at least 60 minutes per day of moderate physical activity in order to prevent excess weight gain. Being overweight today not only signals increased risk of medical problems but also exposes people to serious psychosocial problems due mainly to widespread prejudice against fat people. Prejudice against obese people seems to border on the socially acceptable in Ireland. It crops up consistently in surveys covering groups such as employers, teachers, medical and healthcare personnel, and the media. It occurs among adolescents and children, even very young children. Because obesity is associated with premature death, excessive morbidity and serious psychosocial problems the damage it causes to the welfare of citizens is extremely serious and for this reason government intervention is necessary and warranted. In economic terms, a figure of approximately â,¬30million has been estimated for in-patient costs alone in 2003 for a number of Irish hospitals. This year about 2,000 premature deaths in Ireland will be attributed to obesity and the numbers are growing relentlessly. Diseases which proportionally more obese people suffer from than the general population include hypertension, type 2 diabetes, angina, heart attack and osteoarthritis. There are indirect costs also such as days lost to the workplace due to illness arising from obesity and output foregone as a result of premature death. Using the accepted EU environmental cost benefit method, these deaths alone may be costing the state as much as â,¬4bn per year. The social determinants of physical activity include factors such as socio-economic status, education level, gender, family and peer group influences as well as individual perceptions of the benefits of physical activity. The environmental determinants include geographic location, time of year, and proximity of facilities such as open spaces, parks and safe recreational areas generally. The environmental factors have not yet been as well studied as the social ones and this research gap needs to be addressed. Clearly there is a public health imperative to ensure that relevant environmental policies maximise opportunities for active transport, recreational physical activity and total physical activity. It is clear that concerted policy initiatives must be put in place if the predominantly negative findings of research regarding the determinants of food consumption and physical activity are to be accepted, and they must surely be accepted by government if the rapid increase in the incidence of obesity with all its negative consequences for citizens is to be reversed. So far actions surrounding nutrition policies have concentrated mostly on actions that are within the remit of the Department of Health and Children such as implementing the dietary guidelines. These are important but government must now look at the totality of policies that influence the type and supply of food that its citizens eat and the range and quality of opportunities that are available to citizens to engage in physical activity. This implies a fundamental examination of existing agricultural, industrial, economic and other policies and a determination to change them if they do not enable people to eat healthily and partake in physical activity. The current crisis in obesity prevalence requires a population health approach for adults and children in addition to effective weight-reduction management for individuals who are severely overweight. This entails addressing the obesogenic environment where people live, creating conditions over time which lead to healthier eating and more active living, and protecting people from the widespread availability of unhealthy food and beverage options in addition to sedentary activities that take up all of their leisure time. People of course have a fundamental right to choose to eat what they want and to be as active as they wish. That is not the issue. What the National Taskforce on Obesity has had to take account of is that many forces are actively impeding change for those well aware of the potential health and well-being consequences to themselves of overweight and obesity. The Taskforce’s social change strategy is to give people meaningful choice. Choice, or the capacity to change (because the strategy is all about change), is facilitated through the development of personal skills and preferences, through supportive and participative environments at work, at school and in the local community, and through a dedicated and clearly communicated public health strategy. High-level cabinet support will be necessary to implement the Taskforce’s recommendations. The approach to implementation must be characterised by joined-up thinking, real practical engagement by the public and private sectors, the avoidance of duplication of effort or crosspurpose approaches, and the harnessing of existing strategies and agencies. The range of government departments with roles to play is considerable. The Taskforce outlines the different contributions that each relevant department can make in driving its strategy forward. It also emphasises its requirement that all phases of the national strategy for healthy eating and physical activity are closely monitored, analysed and evaluated. The vision of the Taskforce is expressed as: An Irish society that enables people through health promotion, prevention and care to achieve and maintain healthy eating and active living throughout their lifespan. Its high-level goals are expressed as follows: Its recommendations, over eighty in all, relate to actions across six broad sectors: high-level government; education; social and community; health; food, commodities, production and supply; and the physical environment. In developing its recommendations the Taskforce has taken account of the complex, multisectoral and multi-faceted determinants of diet and physical activity. This strategy poses challenges for government, within individual departments, inter-departmentally and in developing partnerships with the commercial sector. Equally it challenges the commercial sector to work in partnership with government. The framework required for such initiative has at its core the rights and benefits of the individual. Health promotion is fundamentally about empowerment, whether at the individual, the community or the policy level.

Obesity - the policy challenges: The report of the National Taskforce on Obesity

Click here to download PDF The prevalence of overweight and obesity has increased with alarming speed over the past twenty years. It has recently been described by the World Health Organisation as a ‘global epidemic’. In the year 2000 more than 300 million people worldwide were obese and it is now projected that by 2025 up to half the population of the United States will be obese if current trends are maintained. The disease is now a major public health problem throughout Europe. In Ireland at the present time 39% of adults are overweight and 18% are obese. Of these, slightly more men than women are obese and there is a higher incidence of the disease in lower socio-economic groups. Most worrying of all is the fact that childhood obesity has reached epidemic proportions in Europe, with body weight now the most prevalent childhood disease. While currently there are no agreed criteria or standards for assessing Irish children for obesity some studies are indicating that the numbers of children who are significantly overweight have trebled over the past decade. Extrapolation from authoritative UK data suggests that these numbers could now amount to more than 300,000 overweight and obese children on the island of Ireland and they are probably rising at a rate of over 10,000 per year. A balance of food intake and physical activity is necessary for a healthy weight. The foods we individually consume and our participation in physical activity are the result of a complex supply and production system. The growing research evidence that energy dense foods promote obesity is impressive and convincing. These are the foods that are high in fat, sugar and starch. Of these potentially the most significant promoter of weight gain is fat and foods from the top shelf of the food pyramid including spreads (butter and margarine), cakes and biscuits, and confectionery, when combined are the greatest contributors to fat intake in the Irish diet. In company with their adult counterparts Irish children are also consuming large amounts of energy dense foods outside the home. A recent survey revealed that slightly over half of these children ate sweets at least once a day and roughly a third of them had fizzy drinks and crisps with the same regularity. Sugar sweetened carbonated drinks are thought to contribute to obesity and for this reason the World Health Organisation has expressed serious concerns at the high and increasing consumption of these drinks by children. Physical activity is an important determinant of body weight. Over recent decades there has been a marked decline in demanding physical work and this has been accompanied by more sedentary lifestyles generally and reduced leisure-time activity. These observable changes, which are supported by data from most European countries and the United States, suggest that physical inactivity has made a significant impact on the increase in overweight and obesity being seen today. It is now widely accepted that adults shoud be involved in 45-60 minutes, and children should be involved in at least 60 minutes per day of moderate physical activity in order to prevent excess weight gain. Being overweight today not only signals increased risk of medical problems but also exposes people to serious psychosocial problems due mainly to widespread prejudice against fat people. Prejudice against obese people seems to border on the socially acceptable in Ireland. It crops up consistently in surveys covering groups such as employers, teachers, medical and healthcare personnel, and the media. It occurs among adolescents and children, even very young children. Because obesity is associated with premature death, excessive morbidity and serious psychosocial problems the damage it causes to the welfare of citizens is extremely serious and for this reason government intervention is necessary and warranted. In economic terms, a figure of approximately â,¬30million has been estimated for in-patient costs alone in 2003 for a number of Irish hospitals. This year about 2,000 premature deaths in Ireland will be attributed to obesity and the numbers are growing relentlessly. Diseases which proportionally more obese people suffer from than the general population include hypertension, type 2 diabetes, angina, heart attack and osteoarthritis. There are indirect costs also such as days lost to the workplace due to illness arising from obesity and output foregone as a result of premature death. Using the accepted EU environmental cost benefit method, these deaths alone may be costing the state as much as â,¬4bn per year. The social determinants of physical activity include factors such as socio-economic status, education level, gender, family and peer group influences as well as individual perceptions of the benefits of physical activity. The environmental determinants include geographic location, time of year, and proximity of facilities such as open spaces, parks and safe recreational areas generally. The environmental factors have not yet been as well studied as the social ones and this research gap needs to be addressed. Clearly there is a public health imperative to ensure that relevant environmental policies maximise opportunities for active transport, recreational physical activity and total physical activity. It is clear that concerted policy initiatives must be put in place if the predominantly negative findings of research regarding the determinants of food consumption and physical activity are to be accepted, and they must surely be accepted by government if the rapid increase in the incidence of obesity with all its negative consequences for citizens is to be reversed. So far actions surrounding nutrition policies have concentrated mostly on actions that are within the remit of the Department of Health and Children such as implementing the dietary guidelines. These are important but government must now look at the totality of policies that influence the type and supply of food that its citizens eat and the range and quality of opportunities that are available to citizens to engage in physical activity. This implies a fundamental examination of existing agricultural, industrial, economic and other policies and a determination to change them if they do not enable people to eat healthily and partake in physical activity. The current crisis in obesity prevalence requires a population health approach for adults and children in addition to effective weight-reduction management for individuals who are severely overweight. This entails addressing the obesogenic environment where people live, creating conditions over time which lead to healthier eating and more active living, and protecting people from the widespread availability of unhealthy food and beverage options in addition to sedentary activities that take up all of their leisure time. People of course have a fundamental right to choose to eat what they want and to be as active as they wish. That is not the issue. What the National Taskforce on Obesity has had to take account of is that many forces are actively impeding change for those well aware of the potential health and well-being consequences to themselves of overweight and obesity. The Taskforce’s social change strategy is to give people meaningful choice. Choice, or the capacity to change (because the strategy is all about change), is facilitated through the development of personal skills and preferences, through supportive and participative environments at work, at school and in the local community, and through a dedicated and clearly communicated public health strategy. High-level cabinet support will be necessary to implement the Taskforce’s recommendations. The approach to implementation must be characterised by joined-up thinking, real practical engagement by the public and private sectors, the avoidance of duplication of effort or crosspurpose approaches, and the harnessing of existing strategies and agencies. The range of government departments with roles to play is considerable. The Taskforce outlines the different contributions that each relevant department can make in driving its strategy forward. It also emphasises its requirement that all phases of the national strategy for healthy eating and physical activity are closely monitored, analysed and evaluated. The vision of the Taskforce is expressed as: An Irish society that enables people through health promotion, prevention and care to achieve and maintain healthy eating and active living throughout their lifespan. Its high-level goals are expressed as follows: Its recommendations, over eighty in all, relate to actions across six broad sectors: high-level government; education; social and community; health; food, commodities, production and supply; and the physical environment. In developing its recommendations the Taskforce has taken account of the complex, multisectoral and multi-faceted determinants of diet and physical activity. This strategy poses challenges for government, within individual departments, inter-departmentally and in developing partnerships with the commercial sector. Equally it challenges the commercial sector to work in partnership with government. The framework required for such initiative has at its core the rights and benefits of the individual. Health promotion is fundamentally about empowerment, whether at the individual, the community or the policy level.

Machine learning algorithms for spatial data. Case studies: Environmental pollution, natural hazards, renewable resources

This paper presents general problems and approaches for the spatial data analysis using machine learning algorithms. Machine learning is a very powerful approach to adaptive data analysis, modelling and visualisation. The key feature of the machine learning algorithms is that they learn from empirical data and can be used in cases when the modelled environmental phenomena are hidden, nonlinear, noisy and highly variable in space and in time. Most of the machines learning algorithms are universal and adaptive modelling tools developed to solve basic problems of learning from data: classification/pattern recognition, regression/mapping and probability density modelling. In the present report some of the widely used machine learning algorithms, namely artificial neural networks (ANN) of different architectures and Support Vector Machines (SVM), are adapted to the problems of the analysis and modelling of geo-spatial data. Machine learning algorithms have an important advantage over traditional models of spatial statistics when problems are considered in a high dimensional geo-feature spaces, when the dimension of space exceeds 5. Such features are usually generated, for example, from digital elevation models, remote sensing images, etc. An important extension of models concerns considering of real space constrains like geomorphology, networks, and other natural structures. Recent developments in semi-supervised learning can improve modelling of environmental phenomena taking into account on geo-manifolds. An important part of the study deals with the analysis of relevant variables and models' inputs. This problem is approached by using different feature selection/feature extraction nonlinear tools. To demonstrate the application of machine learning algorithms several interesting case studies are considered: digital soil mapping using SVM, automatic mapping of soil and water system pollution using ANN; natural hazards risk analysis (avalanches, landslides), assessments of renewable resources (wind fields) with SVM and ANN models, etc. The dimensionality of spaces considered varies from 2 to more than 30. Figures 1, 2, 3 demonstrate some results of the studies and their outputs. Finally, the results of environmental mapping are discussed and compared with traditional models of geostatistics.

Involvement of environmental mercury and lead in the etiology of neurodegenerative diseases.

The incidence of neurodegenerative disease like Parkinson's disease and Alzheimer's disease (AD) increases dramatically with age; only a small percentage is directly related to familial forms. The etiology of the most abundant, sporadic forms is complex and multifactorial, involving both genetic and environmental factors. Several environmental pollutants have been associated with neurodegenerative disorders. The present article focuses on results obtained in experimental neurotoxicology studies that indicate a potential pathogenic role of lead and mercury in the development of neurodegenerative diseases. Both heavy metals have been shown to interfere with a multitude of intracellular targets, thereby contributing to several pathogenic processes typical of neurodegenerative disorders, including mitochondrial dysfunction, oxidative stress, deregulation of protein turnover, and brain inflammation. Exposure to heavy metals early in development can precondition the brain for developing a neurodegenerative disease later in life. Alternatively, heavy metals can exert their adverse effects through acute neurotoxicity or through slow accumulation during prolonged periods of life. The pro-oxidant effects of heavy metals can exacerbate the age-related increase in oxidative stress that is related to the decline of the antioxidant defense systems. Brain inflammatory reactions also generate oxidative stress. Chronic inflammation can contribute to the formation of the senile plaques that are typical for AD. In accord with this view, nonsteroidal anti-inflammatory drugs and antioxidants suppress early pathogenic processes leading to Alzheimer's disease, thus decreasing the risk of developing the disease. The effects of lead and mercury were also tested in aggregating brain-cell cultures of fetal rat telencephalon, a three-dimensional brain-cell culture system. The continuous application for 10 to 50 days of non-cytotoxic concentrations of heavy metals resulted in their accumulation in brain cells and the occurrence of delayed toxic effects. When applied at non-toxic concentrations, methylmercury, the most common environmental form of mercury, becomes neurotoxic under pro-oxidant conditions. Furthermore, lead and mercury induce glial cell reactivity, a hallmark of brain inflammation. Both mercury and lead increase the expression of the amyloid precursor protein; mercury also stimulates the formation of insoluble beta-amyloid, which plays a crucial role in the pathogenesis of AD and causes oxidative stress and neurotoxicity in vitro. Taken together, a considerable body of evidence suggests that the heavy metals lead and mercury contribute to the etiology of neurodegenerative diseases and emphasizes the importance of taking preventive measures in this regard.

Distribution and Schistosoma mansoni infection of Biomphalaria glabrata in different habitats in a rural area in the Jequitinhonha Valley, Minas Gerais, Brazil: environmental and epidemiological aspects

This paper examines the distribution and infection of Biomphalaria glabrata with Schistosoma mansoni in all aquatic snail habitats in a rural area in the state of Minas Gerais, Brazil, in relation to physico/biotic and behavioral factors. Snail and environmental surveys were carried out semi-annually between July 2001 and November 2002 at 106 sites. Collected snails were examined in the laboratory for infection. B. glabrata densities were highest in overflow ponds, irrigation ponds, springs, canals and wells, and lowest in fishponds and water tanks. Snail densities were higher during the hot, rainy season except for streams and canals and were statistically associated with the presence of fish, pollution, and vegetation density. Tilapia fish and an unidentified Diptera larva were found to be predators of B. glabrata but ducks were not. Twenty-four of the 25 infected snails were collected in 2001(1.4% infection rate) and only one in 2002, after mass chemotherapy. The occurrence of B. glabrata in all 11 snail habitats both at and away from water contact sites studied indicates widespread risk of human infection in the study area. In spite of the strong association between B. glabrata and tilapia in fishponds we do not recommend its use in schistosomiasis control for ecological reasons and its relative inefficiency in streams and dams.