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Exposure Scenarios (exposure + scenario)
Selected AbstractsMethodology for the evaluation of cumulative episodic exposure to chemical stressors in aquatic risk assessment,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2000Michael G. Morton Abstract An ecological risk assessment method was developed to evaluate the magnitude, duration, and episodic nature of chemical stressors on aquatic communities. The percent of an ecosystem's species at risk from a designated chemical exposure scenario is generated. In effects assessment, probabilistic extrapolation methods are used to generate estimated safe concentrations (ESCs) for an ecosystem using laboratory toxicity test results. Fate and transport modeling is employed to generate temporal stressor concentration profiles. In risk characterization, area under the curve integration is performed on predicted exposure concentration profiles to calculate a cumulative exposure concentration (CEC) for the exposure event. A correction is made to account for the allowable exposure duration to the stressor ESC. Finally, the CEC is applied to the extrapolation model (curve) of the stressor to predict percent species at risk to the episodic exposure. The method may be used for either prospective or retrospective risk assessments. The results of a retrospective risk assessment performed on the Leadenwah Creek, South Carolina, USA, estuarine community are presented as a case study. The creek experienced periodic episodes of pesticide-contaminated agricultural runoff from 1986 through 1989. Although limited biological data were available for method validation, the risk estimates compared well with the Leadenwah Creek in situ bioassay results. [source] Carbon black and lung cancer,testing a novel exposure metric by multi-model inferenceAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 11 2009Peter Morfeld PhD Abstract Background In a recent analysis of a UK cohort Sorahan and Harrington [2007: Am J Ind Med 50: 555,564] assessed the most recent 15 years of exposure ("lugging") to support their hypothesis that carbon black acts as a late stage lung carcinogen. We tested this metric in a German cohort of 1,528 carbon black workers. Methods We used a multi-model Cox regression approach (720 models) to explore the impact of duration and cumulative exposure to carbon black "lugged" by 0, 5, 10, 15, and 20 years. This approach covered four sub-cohorts, including an inception cohort, different exposure scenarios and varying combinations of confounders. Results Seven hundred nineteen models returned negative coefficients. Only one model estimated a small positive, but clearly non-significant coefficient (P,=,0.8). Conclusions Despite extensive searching, no exposure scenario suggested an adverse effect of "lugged" carbon black exposure on lung cancer mortality. Our analysis does not support the hypothesis of carbon black being a late stage carcinogen. Am. J. Ind. Med. 52:890,899, 2009. © 2009 Wiley-Liss, Inc. [source] Formaldehyde-releasers: relationship to formaldehyde contact allergy.CONTACT DERMATITIS, Issue 2 2009Contact allergy to formaldehyde, inventory of formaldehyde-releasers This is one of series of review articles on formaldehyde and formaldehyde-releasers (others: formaldehyde in cosmetics, in clothes and in metalworking fluids and miscellaneous). Thirty-five chemicals were identified as being formaldehyde-releasers. Although a further seven are listed in the literature as formaldehyde-releasers, data are inadequate to consider them as such beyond doubt. Several (nomenclature) mistakes and outdated information are discussed. Formaldehyde and formaldehyde allergy are reviewed: applications, exposure scenarios, legislation, patch testing problems, frequency of sensitization, relevance of positive patch test reactions, clinical pattern of allergic contact dermatitis from formaldehyde, prognosis, threshold for elicitation of allergic contact dermatitis, analytical tests to determine formaldehyde in products and frequency of exposure to formaldehyde and releasers. The frequency of contact allergy to formaldehyde is consistently higher in the USA (8,9%) than in Europe (2,3%). Patch testing with formaldehyde is problematic; the currently used 1% solution may result in both false-positive and false-negative (up to 40%) reactions. Determining the relevance of patch test reactions is often challenging. What concentration of formaldehyde is safe for sensitive patients remains unknown. Levels of 200,300 p.p.m. free formaldehyde in cosmetic products have been shown to induce dermatitis from short-term use on normal skin. [source] Carcinogenicity of acetaldehyde in alcoholic beverages: risk assessment outside ethanol metabolismADDICTION, Issue 4 2009Dirk W. Lachenmeier ABSTRACT Aims In addition to being produced in ethanol metabolism, acetaldehyde occurs naturally in alcoholic beverages. Limited epidemiological evidence points to acetaldehyde as an independent risk factor for cancer during alcohol consumption, in addition to the effects of ethanol. This study aims to estimate human exposure to acetaldehyde from alcoholic beverages and provide a quantitative risk assessment. Methods The human dietary intake of acetaldehyde via alcoholic beverages was estimated based on World Health Organization (WHO) consumption data and literature on the acetaldehyde contents of different beverage groups (beer, wine, spirits and unrecorded alcohol). The risk assessment was conducted using the European Food Safety Authority's margin of exposure (MOE) approach with benchmark doses obtained from dose,response modelling of animal experiments. Life-time cancer risk was calculated using the T25 dose descriptor. Results The average exposure to acetaldehyde from alcoholic beverages was estimated at 0.112 mg/kg body weight/day. The MOE was calculated to be 498, and the life-time cancer risk at 7.6 in 10 000. Higher risk may exist for people exposed to high acetaldehyde contaminations, as we have found in certain unrecorded alcohol beverages in Guatemala and Russia, for which we have demonstrated possible exposure scenarios, with risks in the range of 1 in 1000. Conclusions The life-time cancer risks for acetaldehyde from alcoholic beverages greatly exceed the usual limits for cancer risks from the environment set between 1 : 10 000 and 1 : 1 000 000. Alcohol consumption has thus been identified as a direct source of acetaldehyde exposure, which in conjunction with other sources (food flavourings, tobacco) results in a magnitude of risk requiring intervention. An initial public health measure could be to reduce the acetaldehyde content in alcoholic beverages as low as technologically possible, and to restrict its use as a food flavour additive. [source] Mixture toxicity and gene inductions: Can we predict the outcome?ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2008Freddy Dardenne Abstract As a consequence of the nature of most real-life exposure scenarios, the last decade of ecotoxicological research has seen increasing interest in the assessment of mixture ecotoxicology. Often, mixtures are considered to follow one of two models, concentration addition (CA) or response addition (RA), both of which have been described in the literature. Nevertheless, mixtures that deviate from either or both models exist; they typically exhibit phenomena like synergism, ratio or concentration dependency, or inhibition. Moreover, both CA and RA have been challenged and evaluated mainly for acute responses at relatively high levels of biological organization (e.g., whole-organism mortality), and applicability to genetic responses has not received much attention. Genetic responses are considered to be the primary reaction in case of toxicant exposure and carry valuable mechanistic information. Effects at the gene-expression level are at the heart of the mode of action by toxicants and mixtures. The ability to predict mixture responses at this primary response level is an important asset in predicting and understanding mixture effects at different levels of biological organization. The present study evaluated the applicability of mixture models to stress gene inductions in Escherichia coli employing model toxicants with known modes of action in binary combinations. The results showed that even if the maximum of the dose,response curve is not known, making a classical ECx (concentration causing x% effect) approach impossible, mixture models can predict responses to the binary mixtures based on the single-toxicant response curves. In most cases, the mode of action of the toxicants does not determine the optimal choice of model (i.e., CA, RA, or a deviation thereof). [source] Bioaccessibility studies of ferro-chromium alloy particles for a simulated inhalation scenario: A comparative study with the pure metals and stainless steelINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 3 2010Klara Midander Abstract The European product safety legislation, REACH, requires that companies that manufacture, import, or use chemicals demonstrate safe use and high level of protection of their products placed on the market from a human health and environmental perspective. This process involves detailed assessment of potential hazards for various toxicity endpoints induced by the use of chemicals with a minimum use of animal testing. Such an assessment requires thorough understanding of relevant exposure scenarios including material characteristics and intrinsic properties and how, for instance, physical and chemical properties change from the manufacturing phase, throughout use, to final disposal. Temporary or permanent adverse health effects induced by particles depend either on their shape or physical characteristics, and/or on chemical interactions with the particle surface upon human exposure. Potential adverse effects caused by the exposure of metal particles through the gastrointestinal system, the pulmonary system, or the skin, and their subsequent potential for particle dissolution and metal release in contact with biological media, show significant gaps of knowledge. In vitro bioaccessibility testing at conditions of relevance for different exposure scenarios, combined with the generation of a detailed understanding of intrinsic material properties and surface characteristics, are in this context a useful approach to address aspects of relevance for accurate risk and hazard assessment of chemicals, including metals and alloys and to avoid the use of in vivo testing. Alloys are essential engineering materials in all kinds of applications in society, but their potential adverse effects on human health and the environment are very seldom assessed. Alloys are treated in REACH as mixtures of their constituent elements, an approach highly inappropriate because intrinsic properties of alloys generally are totally different compared with their pure metal components. A large research effort was therefore conducted to generate quantitative bioaccessibility data for particles of ferro-chromium alloys compared with particles of the pure metals and stainless steel exposed at in vitro conditions in synthetic biological media of relevance for particle inhalation and ingestion. All results are presented combining bioaccessibility data with aspects of particle characteristics, surface composition, and barrier properties of surface oxides. Iron and chromium were the main elements released from ferro-chromium alloys upon exposure in synthetic biological media. Both elements revealed time-dependent release processes. One week exposures resulted in very small released particle fractions being less than 0.3% of the particle mass at acidic conditions and less than 0.001% in near pH-neutral media. The extent of Fe released from ferro-chromium alloy particles was significantly lower compared with particles of pure Fe, whereas Cr was released to a very low and similar extent as from particles of pure Cr and stainless steel. Low release rates are a result of a surface oxide with passive properties predominantly composed of chromium(III)-rich oxides and silica and, to a lesser extent, of iron(II,III)oxides. Neither the relative bulk alloy composition nor the surface composition can be used to predict or assess the extent of metals released in different synthetic biological media. Ferro-chromium alloys cannot be assessed from the behavior of their pure metal constituents. Integr Environ Assess Manag 2010;6:441,455. © 2009 SETAC [source] Refined avian risk assessment for aldicarb in the United StatesINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 1 2010Dwayne RJ Moore Abstract Aldicarb was recently reviewed by the US Environmental Protection Agency (USEPA) for re-registration eligibility. In this paper, we describe a refined avian risk assessment for aldicarb that was conducted to build upon the screening-level methods used by USEPA. The goal of the refined ERA was to characterize and understand better the risks posed by aldicarb to birds in areas where the pesticide is applied. Aldicarb is a systemic insecticide sold in granular form under the trade name Temik®. It is applied directly to soil and is used to control mites, nematodes, and aphids on a variety of crops (e.g., cotton, potatoes, peanuts). Consumption of grit is necessary for proper digestion in many bird species, particularly for granivores and insectivores. Thus, aldicarb granules may be mistaken for grit by birds. The Granular Pesticide Avian Risk Assessment Model (GranPARAM) is described in a companion paper and was used to estimate the probability and magnitude of effects to flocks of birds that frequent aldicarb-treated fields. One hundred thirty-five exposure scenarios were modeled that together include a range of bird species, crops, application methods and rates, and regions in the United States. The results indicated that, even for the most sensitive bird species, the risks associated with the agricultural use of granular aldicarb are negligible to low. There are several reasons for the limited risk: 1) the Temik formulation includes a gypsum core and a graphite coating and is black in color, all of which have been shown to be unattractive to birds, and 2) the pesticide is applied subsurface and rapidly dissolves following contact with water. The fact that no bird kill incidents involving appropriate label uses of aldicarb have been conclusively documented in the United States over its 38 years of use supports the results of this refined risk assessment. Integr Environ Assess Manag 2010; 6:83,101. © 2009 SETAC [source] Hypothesis: exposure to endocrine-disrupting chemicals may interfere with timing of pubertyINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 2 2010A. Mouritsen Summary A recent decline in onset of puberty , especially among girls , has been observed, first in the US in the mid-1990s and now also in Europe. The development of breast tissue in girls occurs at a much younger age and the incidence of precocious puberty (PP) is increasing. Genetic factors and increasing prevalence of adiposity may contribute, but environmental factors are also likely to be involved. In particular, the widespread presence of endocrine-disrupting chemicals (EDCs) is suspected to contribute to the trend of earlier pubertal onset. The factors regulating the physiological onset of normal puberty are poorly understood. This hampers investigation of the possible role of environmental influences. There are many types of EDCs. One chemical may have more than one mode of action and the effects may depend on dose and duration of the exposure, as well as the developmental stage of the exposed individual. There may also be a wide range of genetic susceptibility to EDCs. Human exposure scenarios are complex and our knowledge about effects of mixtures of EDCs is limited. Importantly, the consequences of an exposure may not be apparent at the actual time of exposure, but may manifest later in life. Most known EDCs have oestrogenic and/or anti-androgenic actions and only few have androgenic or anti-oestrogenic effects. Thus, it appears plausible that they interfere with normal onset of puberty. The age at menarche has only declined by a few months whereas the age at breast development has declined by 1 year; thus, the time span from initiation of breast development to menarche has increased. This may indicate an oestrogen-like effect without concomitant central activation of the hypothalamic,pituitary axis. The effects may differ between boys and girls, as there are sex differences in age at onset of puberty, hormonal profiles and prevalence of precocius puberty. [source] Evaluation of physiologically based pharmacokinetic models for use in risk assessment,JOURNAL OF APPLIED TOXICOLOGY, Issue 3 2007Weihsueh A. Chiu Abstract Physiologically based pharmacokinetic (PBPK) models are sophisticated dosimetry models that offer great flexibility in modeling exposure scenarios for which there are limited data. This is particularly of relevance to assessing human exposure to environmental toxicants, which often requires a number of extrapolations across species, route, or dose levels. The continued development of PBPK models ensures that regulatory agencies will increasingly experience the need to evaluate available models for their application in risk assessment. To date, there are few published criteria or well-defined standards for evaluating these models. Herein, important considerations for evaluating such models are described. The evaluation of PBPK models intended for risk assessment applications should include a consideration of: model purpose, model structure, mathematical representation, parameter estimation, computer implementation, predictive capacity and statistical analyses. Model purpose and structure require qualitative checks on the biological plausibility of a model. Mathematical representation, parameter estimation, computer implementation involve an assessment of the coding of the model, as well as the selection and justification of the physical, physicochemical and biochemical parameters chosen to represent a biological organism. Finally, the predictive capacity and sensitivity, variability and uncertainty of the model are analysed so that the applicability of a model for risk assessment can be determined. Published in 2007 by John Wiley & Sons, Ltd. [source] Carbon black and lung cancer,testing a novel exposure metric by multi-model inferenceAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 11 2009Peter Morfeld PhD Abstract Background In a recent analysis of a UK cohort Sorahan and Harrington [2007: Am J Ind Med 50: 555,564] assessed the most recent 15 years of exposure ("lugging") to support their hypothesis that carbon black acts as a late stage lung carcinogen. We tested this metric in a German cohort of 1,528 carbon black workers. Methods We used a multi-model Cox regression approach (720 models) to explore the impact of duration and cumulative exposure to carbon black "lugged" by 0, 5, 10, 15, and 20 years. This approach covered four sub-cohorts, including an inception cohort, different exposure scenarios and varying combinations of confounders. Results Seven hundred nineteen models returned negative coefficients. Only one model estimated a small positive, but clearly non-significant coefficient (P,=,0.8). Conclusions Despite extensive searching, no exposure scenario suggested an adverse effect of "lugged" carbon black exposure on lung cancer mortality. Our analysis does not support the hypothesis of carbon black being a late stage carcinogen. Am. J. Ind. Med. 52:890,899, 2009. © 2009 Wiley-Liss, Inc. [source] Estimating exposures in the asphalt industry for an international epidemiological cohort study of cancer riskAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 1 2003Igor Burstyn Abstract Background An exposure matrix (EM) for known and suspected carcinogens was required for a multicenter international cohort study of cancer risk and bitumen among asphalt workers. Methods Production characteristics in companies enrolled in the study were ascertained through use of a company questionnaire (CQ). Exposures to coal tar, bitumen fume, organic vapor, polycyclic aromatic hydrocarbons, diesel fume, silica, and asbestos were assessed semi-quantitatively using information from CQs, expert judgment, and statistical models. Exposures of road paving workers to bitumen fume, organic vapor, and benzo(a)pyrene were estimated quantitatively by applying regression models, based on monitoring data, to exposure scenarios identified by the CQs. Results Exposures estimates were derived for 217 companies enrolled in the cohort, plus the Swedish asphalt paving industry in general. Most companies were engaged in road paving and asphalt mixing, but some also participated in general construction and roofing. Coal tar use was most common in Denmark and The Netherlands, but the practice is now obsolete. Quantitative estimates of exposure to bitumen fume, organic vapor, and benzo(a)pyrene for pavers, and semi-quantitative estimates of exposure to these agents among all subjects were strongly correlated. Semi-quantitative estimates of exposure to bitumen fume and coal tar exposures were only moderately correlated. EM assessed non-monotonic historical decrease in exposures to all agents assessed except silica and diesel exhaust. Conclusions We produced a data-driven EM using methodology that can be adapted for other multicenter studies. Am. J. Ind. Med. 43:3,17, 2003. © 2003 Wiley-Liss, Inc. [source] Estimation of whole-body SAR from electromagnetic fields using personal exposure metersBIOELECTROMAGNETICS, Issue 4 2010Wout Joseph Abstract In this article, personal electromagnetic field measurements are converted into whole-body specific absorption rates for exposure of the general public. Whole-body SAR values calculated from personal exposure meter data are compared for different human spheroid phantoms: the highest SAR values (at 950,MHz) are obtained for the 1-year-old child (99th percentile of 17.9,µW/kg for electric field strength of 0.36,V/m), followed by the 5-year-old child, 10-year-old child, average woman, and average man. For the 1-year-old child, whole-body SAR values due to 9 different radiofrequency sources (FM, DAB, TETRA, TV, GSM900 DL, GSM1800 DL, DECT, UMTS DL, WiFi) are determined for 15 different scenarios. An SAR matrix for 15 different exposure scenarios and 9 sources is provided with the personal field exposure matrix. Highest 95th percentiles of the whole-body SAR are equal to 7.9,µW/kg (0.36,V/m, GSM900 DL), 5.8,µW/kg (0.26,V/m, DAB/TV), and 7.1,µW/kg (0.41,V/m, DECT) for the 1-year-old child, with a maximal total whole-body SAR of 11.5,µW/kg (0.48,V/m) due to all 9 sources. All values are below the basic restriction of 0.08,W/kg for the general public. 95th percentiles of whole-body SAR per V/m are equal to 60.1, 87.9, and 42.7,µW/kg for GSM900, DAB/TV, and DECT sources, respectively. Functions of the SAR versus measured electric fields are provided for the different phantoms and frequencies, enabling epidemiological and dosimetric studies to make an analysis in combination with both electric field and actual whole-body SAR. Bioelectromagnetics 31:286,295, 2010. © 2009 Wiley-Liss, Inc. [source] GSM base stations: Short-term effects on well-being,BIOELECTROMAGNETICS, Issue 1 2009Christoph Augner Abstract The purpose of this study was to examine the effects of short-term GSM (Global System for Mobile Communications) cellular phone base station RF-EMF (radiofrequency electromagnetic fields) exposure on psychological symptoms (good mood, alertness, calmness) as measured by a standardized well-being questionnaire. Fifty-seven participants were selected and randomly assigned to one of three different exposure scenarios. Each of those scenarios subjected participants to five 50-min exposure sessions, with only the first four relevant for the study of psychological symptoms. Three exposure levels were created by shielding devices in a field laboratory, which could be installed or removed during the breaks between sessions such that double-blinded conditions prevailed. The overall median power flux densities were 5.2 µW/m2 during "low," 153.6 µW/m2 during "medium," and 2126.8 µW/m2 during "high" exposure sessions. For scenario HM and MH, the first and third sessions were "low" exposure. The second session was "high" and the fourth was "medium" in scenario HM; and vice versa for scenario MH. Scenario LL had four successive "low" exposure sessions constituting the reference condition. Participants in scenarios HM and MH (high and medium exposure) were significantly calmer during those sessions than participants in scenario LL (low exposure throughout) (P,=,0.042). However, no significant differences between exposure scenarios in the "good mood" or "alertness" factors were obtained. We conclude that short-term exposure to GSM base station signals may have an impact on well-being by reducing psychological arousal. Bioelectromagnetics 30:73,80, 2009. © 2008 Wiley-Liss, Inc. [source] | |||||||||||||