Dermal exposure assessment in occupational medicine.
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The importance of dermal exposure has increased during the last few years, mainly because of the reduction of respiratory exposure to toxicants. Pesticides, aromatic amines and polycyclic aromatic hydrocarbons are considered to be the chemicals at highest dermal risk. In the occupational exposure limit lists of the American Conference of Governmental Industrial Hygienists (ACGIH) and of many countries, compounds that can be absorbed through the skin are identified by a skin notation. However, a generally accepted criterion for assigning skin notation does not exist. The recent attempts to develop health-based dermal occupational exposure limits (DOELs) have not been accepted, thus in practice their use has remained limited. To predict the systemic risk associated with dermal exposure and to enable agencies to set safety standards, penetration data are needed. Moreover, there is a need for a practical risk assessment model, particularly for small and medium-sized enterprises. (+info)
Gene expression assay for hazard assessment of chemicals.
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Recent progress in our knowledge of gene expression systems provides evidence that many industrial chemicals affect the transcriptional machineries directly or indirectly, and gene expression is now recognized as one of the main targets of many chemicals. In view of the increasing number of man-made chemicals, it is therefore necessary to establish a reliable gene expression assay with rapidity and high sensitivity. Among various gene expression assays, the so-called reporter assay is now accepted as a suitable tool to assess hazardous effects of chemicals on gene expression. This article focuses on the principle and applications of the reporter assay in research on endocrine disrupters. (+info)
Time extrapolation and interspecies extrapolation for locally acting substances in case of limited toxicological data.
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In the case of substances with a limited toxicological data base there is often (i) a lack of qualified human toxicological data; and (ii) a paucity of studies with adequate exposure duration. Hence, several extrapolations have to be performed to arrive at appropriate risk assessments or derive occupational exposure limits. The present paper deals with the possibilities for extrapolating the change in effect concentrations over time (time extrapolation, e.g. from subacute to chronic exposure) and for interspecies extrapolation (from animal to human) in connection with locally acting substances (respiratory toxicants). To justify the time extrapolation factors, 46 technical reports produced by the US National Toxicology Program (NTP) involving studies with subacute, subchronic and chronic exposure duration were evaluated. On the basis of geometric mean values, decreases in effect concentrations by factors of 3.2 (subacute --> subchronic), 2.7 (subchronic --> chronic) and 6.6 (subacute --> chronic) were found. Differentiation according to animal species (mouse, rat), sex or substance properties did not result in any relevant changes of the mean value. NTP studies with less than lifetime exposure periods (subacute, subchronic) in many cases showed different locations of respiratory effects compared with chronic studies, and thus offered limited possibilities for qualitative prediction of long-term respiratory effects (occurrence of effects in certain regions of the respiratory tract). With regard to interspecies extrapolation, gaseous and particulate substances were evaluated separately. With some modifications (e.g. consideration of the clearance of particles of low solubility), the 1994 US Environmental Protection Agency (EPA) model for deriving reference concentrations for humans on the basis of experimental data in animals is proposed for inhalable particulate substances. In the case of gaseous substances, the assumptions of the EPA model do not seem to consider sufficiently the local inhomogeneity in substance distribution and anatomical and histological differences between the upper respiratory tracts of rodents and humans. Considerable uncertainty would attach to a default factor for interspecies extrapolation for gaseous substances. (+info)
A Dirichlet Tessellation-based sampling scheme for measuring whole-body exposure.
(60/726)
Dermal sampling can be conducted using small pads or patches attached to various areas of the skin or clothing, or by using a whole-body coverall. Both techniques are recognized standardized methods for collecting chemicals. Patch sampling is simple to perform and inexpensive to analyse compared with an entire overall, but may require some user intervention. Extrapolation from a small sampled area to the total body area can lead to inaccurate estimates of total body exposure because of a lack of uniformity of deposition. Whole-body overall analysis eliminates the problems associated with using patches and gives a more accurate estimate of total body exposure. Therefore, if it were possible to measure the whole-body overall accurately and quickly, we would have a better assessment of dermal exposure. In this study we develop a working protocol using a standardized approach, to measure the contamination over an entire overall. The protocol takes into account size differences and establishes a reproducible pattern of sampling in order to map the distribution of contamination over each overall. The working protocol has been applied to 10 overalls collected from companies using copper-based biocides. A portable X-ray fluorescence spectrometer (PXRF) was used to measure the copper in the biocide. The exposure estimate from the PXRF results uses an averaging scheme based on the Dirichlet tessellation of the sampling locations. This allows unbiased estimates to be obtained from a complex sampling scheme that allocates more measurements to areas of high exposure. The Dirichlet tessellation method has been compared to the patch sampling method and the conventional total digestion of the entire overall method. Using the whole-suit digestion method as the benchmark, exposures ranged from 92.0 to 5848.5 mg. Mean absolute percentage errors (from the benchmark acid digestion of the whole suit) varied from approximately 20% for the Dirichlet-based PXRF method to 60% for the patch methods. The patch methods underestimated the true dermal exposure (-28 to -82% for acid digestion of the patches). Analysis of this data indicates that the Dirichlet PXRF method gives a more accurate estimate of whole-body contamination than the patch method. Furthermore, the 104 measurements give a much greater spatial resolution to the exposure data than analysis of the whole overall or patches by inductively coupled plasma-atomic emission mass spectrometry (ICP-AES). This detailed knowledge of the pattern of deposition on the body is of potential importance in chemical risk assessments. (+info)
Hazardous materials: revision to standards for infectious substances. Final rule.
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RSPA is revising transportation requirements for infectious substances, including regulated medical waste, to: adopt defining criteria and packaging requirements consistent with international standards; revise the current broad exceptions for diagnostic specimens and biological products; and authorize bulk packaging options for regulated medical waste consistent with requirements in international standards and DOT exemptions. These revisions will assure an acceptable level of safety for the transportation of infectious substances, and facilitate domestic and international transportation. (+info)
Assessing exposure to air toxics relative to asthma.
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Asthma is a respiratory disease whose prevalence has been increasing since the mid 1970s and that affects more than 14.6 million residents of the United States. Environmental triggers of asthma include air pollutants that are respiratory irritants. Air toxics emitted into the ambient air are listed in the 1990 Clean Air Act Amendments as hazardous air pollutants (HAPs) if they can adversely affect human health, including the respiratory tract. HAPs include particulate and gaseous-phase pollutants, individual organic compounds and metals, and mixtures. Associations between asthma exacerbation and both particles and indoor volatile organic compounds (VOCs), often referred to as indoor air quality, have been reported. Studies conducted in the United States, Canada, and Europe over the past two decades have shown that most people living in the developed countries spend the majority of their time indoors and that the air concentrations of many air toxics or HAPs are higher indoors than in the ambient air in urban, suburban, and rural settings. Elevated indoor air concentrations result from emissions of air toxics from consumer products, household furnishings, and personal activities. The Relationship of Indoor, Outdoor and Personal Air (RIOPA) study was designed to oversample homes in close proximity to ambient sources, excluding residences where smokers lived, to determine the contribution of ambient emissions to air toxics exposure. The ratios of indoor to outdoor air concentrations of some VOCs in homes measured during RIOPA were much greater than one, and for most other VOCs that had indoor-to-outdoor ratios close to unity in the majority of homes, elevated ratios were found in the paired samples with the highest concentration. Thus, although ambient emissions contribute to exposure of some air toxics indoors as well as outdoors, this was not true for all of the air toxics and especially for the higher end of exposures to most volatile organic air toxics examined. It is therefore critical, when evaluating potential effects of air toxics on asthma or other adverse health end points, to determine where the exposure occurs and the source contributions for each air toxic and target population separately and not to rely solely on ambient air concentration measurements. (+info)
Structure of genes for Hsp30 from the white-rot fungus Coriolus versicolor and the increase of their expression by heat shock and exposure to a hazardous chemical.
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We isolated and analysed two genomic DNAs that encode the heat-shock protein Hsp30 from Coriolus versicolor. The amino acid sequences substitute only three amino acid substitutions. The promoter regions contain the consensus heat-shock element, a xenobiotic-response element, a stress-response element, and a metal-response element. The levels of mRNAs for Hsp30 increased markedly after exposure of C. versicolor to pentachlorophenol and levels were higher than those after heat shock. (+info)
Workers' understanding of chemical risks: electroplating case study.
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BACKGROUND: There is limited research concerning how small companies in particular, respond to health and safety messages. AIMS: To understand individuals' knowledge and beliefs about chemical risks and to compare these with those of experts. METHODS: The use of chromic acid in particular, and also other chemicals associated with chrome plating were studied. All chromium plating firms were based in the West Midlands. The methodology involved initial face to face interviews (n = 21) with chromium platers, structured questionnaires (n = 84) to test the prevalence of beliefs identified in the interviews, an expert questionnaire, and a workshop to discuss findings. The responses of platers were compared with those of occupational health and safety experts. RESULTS: Although chromium platers appeared to understand the short term adverse effects of the chemicals to which they are exposed, their understanding of long term, or chronic effects appeared to be incomplete. They had good knowledge of acute effects based primarily on experience. Platers were aware of the hazardous nature of the chemicals with which they work, but did not draw distinction between the terms "hazards" and "risks". They had difficulties articulating the effects of the chemicals and how exposure might occur; although it is inappropriate to equate this with lack of knowledge. A significant minority of platers displayed deficiencies in understanding key technical terms used in Safety Data Sheets. CONCLUSIONS: This study provides a method which can be used to gain some understanding of workers' knowledge and beliefs about risks that they are exposed to in the workplace. The study also identifies gaps between the platers' knowledge and beliefs and those of experts. New risk information needs to be designed which addresses the information needs of platers using language that they understand. (+info)