Considerations in deriving quantitative cancer criteria for inorganic arsenic exposure via inhalation

The inhalation unit risk (IUR) that currently exists in the United States Environmental Protection Agency's (US EPA's) Integrated Risk Information System was developed in 1984 based on studies examining the relationship between respiratory cancer and arsenic exposure in copper smelters from two US locations: the copper smelter in Anaconda, Montana, and the American Smelting And Refining COmpany (ASARCO) smelter in Tacoma, Washington. Since US EPA last conducted its assessment, additional data have become available from epidemiology and mechanistic studies. In addition, the California Air Resources Board, Texas Commission of Environmental Quality, and Dutch Expert Committee on Occupational Safety have all conducted new risk assessments. All three analyses, which calculated IURs based on respiratory/lung cancer mortality, generated IURs that are lower (i.e., less restrictive) than the current US EPA value of 4.3 × 10^− 3 (μg/m³)^− 1. The IURs developed by these agencies, which vary more than 20-fold, are based on somewhat different studies and use different methodologies to address uncertainties in the underlying datasets. Despite these differences, all were developed based on a cumulative exposure metric assuming a low-dose linear dose–response relationship. In this paper, we contrast and compare the analyses conducted by these agencies and critically evaluate strengths and limitations inherent in the data and methodologies used to develop quantitative risk estimates. In addition, we consider how these data could be best used to assess risk at much lower levels of arsenic in air, such as those experienced by the general public. Given that the mode of action for arsenic supports a threshold effect, and epidemiological evidence suggests that the arsenic concentration in air is a reliable predictor of lung/respiratory cancer risk, we developed a quantitative cancer risk analysis using a nonlinear threshold model. Applying a nonlinear model to occupational data, we established points of departure based on both cumulative exposure (μg/m³-years) to arsenic and arsenic concentration (μg/m³) via inhalation. Using these values, one can assess the lifetime risk of respiratory cancer mortality associated with ambient air concentrations of arsenic for the general US population.     

Assessing the risk of an excess fluoride intake among Swedish children in households with private wells — Expanding static single-source methods to a probabilistic multi-exposure-pathway approach

It is often assumed that water consumption is the major route of exposure for fluoride and analysis of water fluoride content is the most common approach for ensuring that the daily intake is not too high. In the present study, the risk of excess intake was characterized for children in households with private wells in Kalmar County, Sweden, where the natural geology shows local enrichments in fluorine. By comparing water concentrations with the WHO drinking water guideline (1.5 mg/L), it was found that 24% of the ca. 4800 sampled wells had a concentration above this limit, hence providing a figure for the number of children in the households concerned assessed to be at risk using this straightforward approach. The risk of an excess intake could, alternatively, also be characterized based on a tolerable daily intake (in this case the US EPA RfD of 0.06 mg/kg-day). The exposure to be evaluated was calculated using a probabilistic approach, where the variability in all exposure factors was considered, again for the same study population. The proportion of children assessed to be at risk after exposure from drinking water now increased to 48%, and when the probabilistic model was adjusted to also include other possible exposure pathways; beverages and food, ingestion of toothpaste, oral soil intake and dust inhalation, the number increased to 77%. Firstly, these results show how the risk characterization is affected by the basis of comparison. In this example, both of the reference values used are widely acknowledged. Secondly, it illustrates how much of the total exposure may be overlooked when only focusing on one exposure pathway, and thirdly, it shows the importance of considering the variability in all relevant pathways.     

Conceptual Framework of Tourism Carrying Capacity for a Tourism City： Experiences from National Parks in the United States

There is no universally-accepted definition of tourism carrying capacity(TCC).Numerical TCC focuses on use level and is considered as"a magic number"of the saturation point for tourism.There are several reasons why numerical tourism capacity is inadequate.Alternatively,tourism capacity can be defined in terms of limits of acceptable change,which shifts the focus from"how much use is too much"to"how much change is acceptable".This article proposes an improved conceptual framework for evaluating carrying capacity for the tourism city based on approaches used in US national parks,which consider the impact of human use on a city's economic,environmental/resource,and socio-cultural conditions.Based on the basic data of indicator values and relevant standards,the framework monitors the current indicators and predicts future indicator values; it can also be used to assess and predict TCC.     

Uncertainty in biokinetic parameters on bioremediation: health risks and economic implications

Human health risk assessment is one of the rapidly evolving tools used in the management of contaminated aquifers. Health risk assessments have been traditionally based on the point estimate approach. Due to the uncertainty and variability inherent in subsurface properties and exposed human population characteristics, probabilistic risk assessment is becoming widely accepted. This study is focused on understanding the uncertainty in biokinetic parameters in describing biodegradation under natural and enhanced remediation conditions. The uncertain parameters considered in this work are key biokinetic parameters and the uncertainty is assessed using the predicted receptor maximum concentration, maximum of 30-year average concentration, time to reach maximum concentration, maximum mass of decay, and the time for maximum decay. The results of this analysis were extended to health risk assessment and risk-based economic analysis. The paper discusses the approach and methodology adopted in this study and the implication of uncertainty of key parameters on decision-relevant information.     

Carbon monoxide intrusion into sustained-use vehicles

In its evaluation of federal ambient air quality criteria for carbon monoxide (CO), the U.S. Environmental Protection Agency is seeking to identify the mechanisms of CO exposure and the populations at risk. The suitability of existing fixed-site monitoring networks to characterize population exposure is also being studied. This paper describes field measurements in two major metropolitan areas of CO exposure in the passenger sections of 1164 buses, taxis, and police cars. The objectives of the program were to identify high-CO vehicles and to elucidate the mechanisms for high passenger exposures. Vehicle fleets were initially screened with passive dosimeters and pump-driven personal samplers. Selected vehicles were then instrumented with portable electrochemical-cell continuous analyzers coupled to recorders. Principal CO sources and intrusion pathways were pinpointed by use of an inert tracer gas (SF₆) detection system. Intrusion tests were made at idle and with the vehicles in motion. Fixed-station monitoring values were found to underpredict, in a nonuniform manner, out-of-vehicle CO exposures determined by the field measurements. In 58% of the 120 personal sampler readings for rides greater than eight hours, the EPA eight-hour ambient air quality standard for carbon monoxide (9 ppm) was exceeded.     

Study sensitivity: Evaluating the ability to detect effects in systematic reviews of chemical exposures

A critical step in systematic reviews of potential health hazards is the structured evaluation of the strengths and weaknesses of the included studies; risk of bias is a term often used to represent this process, specifically with respect to the evaluation of systematic errors that can lead to inaccurate (biased) results (i.e. focusing on internal validity). Systematic review methods developed in the clinical medicine arena have been adapted for use in evaluating environmental health hazards; this expansion raises questions about the scope of risk of bias tools and the extent to which they capture the elements that can affect the interpretation of results from environmental and occupational epidemiology studies and in vivo animal toxicology studies, (the studies typically available for assessment of risk of chemicals). One such element, described here as “sensitivity”, is a measure of the ability of a study to detect a true effect or hazard. This concept is similar to the concept of the sensitivity of an assay; an insensitive study may fail to show a difference that truly exists, leading to a false conclusion of no effect. Factors relating to study sensitivity should be evaluated in a systematic manner with the same rigor as the evaluation of other elements within a risk of bias framework. We discuss the importance of this component for the interpretation of individual studies, examine approaches proposed or in use to address it, and describe how it relates to other evaluation components. The evaluation domains contained within a risk of bias tool can include, or can be modified to include, some features relating to study sensitivity; the explicit inclusion of these sensitivity criteria with the same rigor and at the same stage of study evaluation as other bias-related criteria can improve the evaluation process. In some cases, these and other features may be better addressed through a separate sensitivity domain. The combined evaluation of risk of bias and sensitivity can be used to identify the most informative studies, to evaluate the confidence of the findings from individual studies and to identify those study elements that may help to explain heterogeneity across the body of literature.     

A normative model of balanced nature management

The risk of erroneous regulation in multilevel normative environmental chains, at the federal, regional, and lower levels, down to the corporate one, has been studied. This risk has been demonstrated to increase unacceptably rapidly in the framework of the existing system of “unconditional acceptance” of normative standards. To mend the situation, it is necessary to use the “conditional acceptance” model by regarding post hoc decisions made at higher levels as a priori ones at the next (lower) levels. A strategy of environmentally and economically balanced corporate regulation of nature management through minimization of the losses resulting from both excessive caution and breaching the existing regulations has been proposed. This system, combined with the European approach to nature conservation, requires that the “riskless” regulation should be abandoned and is expected to improve the parameters of nature management quality by three to four orders of magnitude.     

Towards a coherent conceptual framework for emergency preparedness/response and rehabilitation – the application of the new ICRP recommendations given in ICRP 103

In the past, most emphasis in planning for and response to an emergency situation has been placed on selected protective measures in the early phase of an emergency to keep the doses received below levels where severe deterministic health effects can be excluded and/or where the risk of stochastic effects in the population is considered “acceptable”. Less emphasis has been placed on the development of comprehensive protection strategies which include considerations of the consequences of all exposure pathways and all phases, e.g. long-term rehabilitation. In its new publication 103, ICRP proposed a coherent conceptual framework for protection in all types of exposure situations including “emergency exposure situations” and “existing exposure situations”. In the context of developing protection strategies for these exposure situations, the Commission recommends that national authorities set reference levels between, typically, 20 mSv and 100 mSv annual effective dose (emergency exposure situation) and 1 mSv and 20 mSv (existing exposure situation). In order to optimise protection strategies, it is necessary to identify the dominant exposure pathways, the timescales over which the dose will be received, and the effectiveness of available protection options. The characteristics of the development and implementation of such protection strategies is described.     

全氟辛烷磺酰基化合物水生生态风险和人体健康风险评价

全氟辛烷磺酰基化合物（Perfluorooctanesulfonate,PFOS ）广泛用于工农业生产,PFOS可通过不同的迁移路径迁移到大气、水和土壤等环境介质中。研究表明,PFOS是一种新的持久性有机物污染物,具有毒性,可通过食物链富集。2006年PFOS被欧盟议会和部长理事会列为限制销售和使用物质。本文引用中国沿海、亚洲海域和美国部分水域的PFOS暴露浓度数据,采用商值法对PFOS的水生生态环境风险进行了评价,建立了5 种因素水平的数学模型,并应用此数学模型对PFOS的人体健康风险进行了评价。结果表明我国部分地区和亚洲沿海PFOS的水生生态风险低于美国水域,亚洲沿海、我国部分地区以及美国部分城市水体中PFOS个人风险大小依次是我国部分地区<亚洲沿海<美国部分城市。     

Heredity and risk of disease

Mathematical modeling of competing risks often uses a single risk function for all individuals within a population. In this paper we use several specific examples to argue that such representations remain approximations until account is taken of the existence of genetic variability within and between populations, and the impact of this upon liability to disease. The extent of human genetic variability is also indicated.     

A review of the existing methodology in competing-risk theory

The theory of competing risks is concerned with assessing a specific risk in the complicating presence of other risks. This paper reviews existing methods for dealing with the problem. Much of the existing methodology (both parametric and nonparametric) involves the assumption of independent risks. This situation receives most of the attention in this paper, although a brief discussion summarizing attempts to deal with the complicated problem of dependent risks is given. Adaptations of methods used to incorporate concomitant information in survival analyses are discussed. Brief reference is made to the most relevant graphical methods that have been proposed. The review tends to be verbal in nature, leaving the interested reader to check out mathematical details in the references.     

Modelling microbial health risk of wastewater reuse: A systems perspective

There is a widespread need for the use of quantitative microbial risk assessment (QMRA) to determine reclaimed water quality for specific uses, however neither faecal indicator levels nor pathogen concentrations alone are adequate for assessing exposure health risk. The aim of this study was to build a conceptual model representing factors contributing to the microbiological health risks of reusing water treated in maturation ponds. This paper describes the development of an unparameterised model that provides a visual representation of theoretical constructs and variables of interest. Information was collected from the peer-reviewed literature and through consultation with experts from regulatory authorities and academic disciplines. In this paper we explore how, considering microbial risk as a modular system, following the QMRA framework enables incorporation of the many factors influencing human exposure and dose response, to better characterise likely human health impacts. By using and expanding upon the QMRA framework we deliver new insights into this important field of environmental exposures. We present a conceptual model of health risk of microbial exposure which can be used for maturation ponds and, more importantly, as a generic tool to assess health risk in diverse wastewater reuse scenarios.     

Probabilistic risk assessment's use of trees and distributions to reflect uncertainty and variability and to overcome the limitations of default assumptions

Probabilistic risk assessment is an emerging approach to exposure assessment and quantitative cancer and non-cancer risk characterizations. The approach is easily extended to other types of risks and outcomes. A tree, like a decision tree or probability tree, encourages the evaluation of not only the default assumptions but also alternatives to those defaults, and reflects the uncertainty in the current state of knowledge. Trees are used in both the characterization of the dose received by individuals in a potential exposure situation and the characterization of the dose-response relationship for a specified response of concern. Probability distributions are used to reflect the variability in exposure, dose, and dose-response relationships among individuals and over time within individuals. Distributions incorporating variabilities, uncertainties, subjective probabilities, and expert judgments are used to characterize the probabilities of observing an individual in a population with a specified dose from exposure, with a specified probability of a certain adverse health effect for a designated dose, and with a specified probability of a certain adverse health effect (i.e., a specified risk). Some suggestions are given on how a risk manager can incorporate a distributional risk characterization into decision making. Some discussion is included concerning sensitivity analyses and path analyses. The major finding is methodology to explicitly incorporate variability, uncertainty, and alternatives to defaults into exposure, dose-response, and risk characterizations.     

Evaluating the effect of flood damage-reducing measures: a case study of the unembanked area of Rotterdam,the Netherlands

Empirical evidence of increasing flood damages and the prospect of climatic change has initiated discussions in the flood management community on how to effectively manage flood risks. In the Netherlands, the framework of multi-layer safety (MLS) has been introduced to support this risk-based approach. The MLS framework consists of three layers: (i) prevention, (ii) spatial planning and (iii) evacuation. This paper presents a methodology to evaluate measures in the second layer, such as wet proofing, dry proofing or elevating buildings. The methodology uses detailed land-use data for the area around the city of Rotterdam (up to building level) that has recently become available. The vulnerability of these detailed land-use classes to flooding is assessed using the stage–damage curves from different international models. The methodology is demonstrated using a case study in the unembanked area of Rotterdam in the Netherlands, as measures from the second layer may be particularly effective there. The results show that the flood risk in the region is considerable: EUR 36 million p.a. A large part (almost 60 %) of this risk results from industrial land use, emphasising the need to give this category more attention in flood risk assessments. It was found that building level measures could substantially reduce flood risks in the region because of the relatively low inundation levels of buildings. Risk to residential buildings would be reduced by 40 % if all buildings would be wet-proofed, by 89 % if all buildings would be dry-proofed and elevating buildings over 100 cm would render the risk almost zero. While climate change could double the risk in 2100, such building level measures could easily nullify this effect. Despite the high potential of such measures, actual implementation is still limited. This is partly caused by the lack of knowledge regarding these measures by most Dutch companies and the legal impossibility for municipalities to enforce most of these measures as they would go beyond the building codes established at the national level.     

A review of regulatory decisions for environmental protection: part I - challenges in the implementation of national soil policies

Since many soil studies have already revealed the possible risks to human health and the environment arising from contaminated soils it is therefore crucial to preserve soil quality under current and future conditions. In the last three decades a number of countries already introduced national policies and practices for the management of contaminated sites, and in 2002, an EU Thematic Strategy for Soil Protection was proposed by the European Commission. In this paper we review and analyse several national contaminated land policy regimes already in place in order to assess common elements and to identify specific needs in the development of national soil policies. We propose a framework that combines the D-P-S-I-R structure of policy evaluation with the Source-Pathway-Receptor approach to health risk assessment to support the development of effective country specific regulatory decisions for managing contaminated land in countries where these are yet to be implemented. The framework proposed allows decision makers to effectively use available information and to identify existing data gaps. As a result it is apparent that while there are technical aspects of site characterisation, risk assessment and remediation processes that could be commonly implemented at an EU level there are certain trans-scientific aspects that require political choices and need to be customized by EU Member States.     

A holistic approach to achieving energy efficiency for interoperable machining systems

In the twenty-first century, the continuous demand in energy resource has put sustainability on the agenda of many businesses. This is particularly true for the manufacturing industry, where a large amount of energy is consumed to sustain daily operations. This paper studies energy-efficient computer numerical control machining systems. To achieve overall energy efficiency in machining systems, several activities are involved as in the proposed research framework of a global energy-efficient machining system (GEMS). These activities are described as modules, i.e. energy monitoring, energy analysis and optimisation, energy-based optimal control and energy-enriched database. In a GEMS, one critical issue is data interoperability. Seamless data sharing enables collaboration for improving energy efficiency. Using the EXPRESS language, energy data models are proposed for each module in the GEMS, and integrated with the existing STEP-NC (STandard for Exchange of Produce-compliant Numerical Control) standards. Two case studies are presented to demonstrate how the proposed data models may be used. One study updates an existing production file to include general energy information for auditing or reviewing purposes; the other study maintains machine tool energy profiles in a database. Many other energy-efficient activities, e.g. online energy optimisation, can be realised with the proposed data models. The present study proved that interoperable energy information can enhance the energy-efficient performance of a machining system.     

Regional multi-compartment ecological risk assessment: Establishing cadmium pollution risk in the northern Bohai Rim,China

Ecological risk assessment (ERA) has been widely applied in characterizing the risk of chemicals to organisms and ecosystems. The paucity of toxicity data on local biota living in the different compartments of an ecosystem and the absence of a suitable methodology for multi-compartment spatial risk assessment at the regional scale has held back this field. The major objective of this study was to develop a methodology to quantify and distinguish the spatial distribution of risk to ecosystems at a regional scale. A framework for regional multi-compartment probabilistic ecological risk assessment (RMPERA) was constructed and corroborated using a bioassay of a local species. The risks from cadmium (Cd) pollution in river water, river sediment, coastal water, coastal surface sediment and soil in northern Bohai Rim were examined. The results indicated that the local organisms in soil, river, coastal water, and coastal sediment were affected by Cd. The greatest impacts from Cd were identified in the Tianjin and Huludao areas. The overall multi-compartment risk was 31.4% in the region. The methodology provides a new approach for regional multi-compartment ecological risk assessment.     

A critical review of frameworks used for evaluating reliability and relevance of (eco)toxicity data: Perspectives for an integrated eco-human decision-making framework

Considerable efforts have been invested so far to evaluate and rank the quality and relevance of (eco)toxicity data for their use in regulatory risk assessment to assess chemical hazards. Many frameworks have been developed to improve robustness and transparency in the evaluation of reliability and relevance of individual tests, but these frameworks typically focus on either environmental risk assessment (ERA) or human health risk assessment (HHRA), and there is little cross talk between them. There is a need to develop a common approach that would support a more consistent, transparent and robust evaluation and weighting of the evidence across ERA and HHRA. This paper explores the applicability of existing Data Quality Assessment (DQA) frameworks for integrating environmental toxicity hazard data into human health assessments and vice versa. We performed a comparative analysis of the strengths and weaknesses of eleven frameworks for evaluating reliability and/or relevance of toxicity and ecotoxicity hazard data. We found that a frequent shortcoming is the lack of a clear separation between reliability and relevance criteria. A further gaps and needs analysis revealed that none of the reviewed frameworks satisfy the needs of a common eco-human DQA system. Based on our analysis, some key characteristics, perspectives and recommendations are identified and discussed for building a common DQA system as part of a future integrated eco-human decision-making framework. This work lays the basis for developing a common DQA system to support the further development and promotion of Integrated Risk Assessment.     

The internal exposure of Taiwanese to phthalate--an evidence of intensive use of plastic materials

Phthalates are widely used in industry and consumer products. Di-(2-ethylhexyl) phthalate (DEHP) and di-n-butylphthalate (DBP) show the greatest potency of reproductive toxicants among phthalates. The purposes of this study are to examine the migration level of phthalate from PVC films by simulating food handling and to reveal the body burden of phthalate for Taiwanese. In order to estimate a worst-case of phthalate migration, food was covered with polyvinyl chloride (PVC) films and then microwave heated. Results show that DEHP level in food increased significantly after heating for 3 min. Under the heating condition, the calculated intake of phthalate and the percentage of the tolerable daily intake (TDI, based on body weight of 60 kg) from eating one 400-g meal were 1705.6 microg and 92.2% for DEHP. Determination of urinary metabolites from 60 subjects reveals more than 90% of samples were detectable for mono-methyl phthalate (MMP), mono-butyl phthalate (MBP) and mono-ethylhexyl phthalate (MEHP). Notably, the median value of estimated daily intake of DEHP had reached 91.6% of TDI established by the European Union Scientific Committee for Toxicity, Ecotoxicity and the Environment (CSTEE) (1998). Thirty-seven percent of the study population exceeded the TDI and 85% exceeded the reference dose (RfD) of the US EPA. We conclude that the body burden of DEHP for Taiwanese reflects the intensives use of plastic materials in the region. The regulation of PVC for food preparation is necessary.