The Bhopal accident and methyl isocyanate toxicity

Reversibility and Low Commitment to Forward Catalysis in the Conjugation of Lipid Alkenals by Glutathione Transferase A4-4

High concentrations of electrophilic lipid alkenals formed during oxidative stress are implicated in cytotoxicity and disease. However, low concentrations of alkenals are required to induce antioxidative stress responses. An established clearance pathway for lipid alkenals includes conjugation to glutathione (GSH) via Michael addition, which is catalyzed mainly by glutathione transferase isoform A4 (GSTA4-4). Based on the ability of GSTs to catalyze hydrolysis or retro-Michael addition of GSH conjugates, and the antioxidant function of low concentrations of lipid alkenals, we hypothesize that GSTA4-4 contributes a homeostatic role in lipid metabolism. Enzymatic kinetic parameters for retro-Michael addition with trans-2-Nonenal (NE) reveal the chemical competence of GSTA4-4 in this putative role. The forward GSTA4-4-catalyzed Michael addition occurs with the rapid exchange of the C2 proton of NE in D₂O as observed by NMR. The isotope exchange was completely dependent on the presence of GSH. The overall commitment to catalysis, or the ratio of first order k_cat,f for 'forward' Michael addition to the first order k_cat,ex for H/D exchange is remarkably low, approximately 3:1. This behavior is consistent with the possibility that GSTA4-4 is a regulatory enzyme that contributes to steady-state levels of lipid alkenals, rather than a strict 'one way' detoxication enzyme.

Effects of carbamate pesticides intermediates on Escherichia coli membrane architecture: An in vitro and in silico approach

Methyl isocyanate (MIC), a low molecular weight synthetic aliphatic compound, having an isocyanate group (−NCO), has industrial application. In this study, the effects of methyl isocyanate and its mechanism on outer membrane protein of Escherichia coli were observed using experimental and computational methods. In vitro exposure of N-succinimidyl N-methylcarbamate (NSNM) a synthetic analogue of MIC on E. coli to a final concentration of 2 mM was found to affect the growth curve pattern and changes in cell morphology. Molecular docking studies of MIC and NSNM with E. coli outer membrane protein (OmpW, OmpX, OmpF OmpA), and periplasmic domain (PAL) were performed. The in-silico results revealed that outer membrane protein OmpF showed the highest negative binding energy, i.e. ΔG −4.11 kcal/mole and ΔG −3.19 kcal/mole by NSNM and MIC as compared to other proteins. Our study concludes that methyl isocyanate retains lethal toxicity which leads to cell death due to the membrane protein damage of E. coli membrane.

Recent Advances in Fabrication of Non-Isocyanate Polyurethane-Based Composite Materials

Polyurethanes (PUs) are a significant group of polymeric materials that, due to their outstanding mechanical, chemical, and physical properties, are used in a wide range of applications. Conventionally, PUs are obtained in polyaddition reactions between diisocyanates and polyols. Due to the toxicity of isocyanate raw materials and their synthesis method utilizing phosgene, new cleaner synthetic routes for polyurethanes without using isocyanates have attracted increasing attention in recent years. Among different attempts to replace the conventional process, polyaddition of cyclic carbonates (CCs) and polyfunctional amines seems to be the most promising way to obtain non-isocyanate polyurethanes (NIPUs) or, more precisely, polyhydroxyurethanes (PHUs), while primary and secondary –OH groups are being formed alongside urethane linkages. Such an approach eliminates hazardous chemical compounds from the synthesis and leads to the fabrication of polymeric materials with unique and tunable properties. The main advantages include better chemical, mechanical, and thermal resistance, and the process itself is invulnerable to moisture, which is an essential technological feature. NIPUs can be modified via copolymerization or used as matrices to fabricate polymer composites with different additives, similar to their conventional counterparts. Hence, non-isocyanate polyurethanes are a new class of environmentally friendly polymeric materials. Many papers on the matter above have been published, including both original research and extensive reviews. However, they do not provide collected information on NIPU composites fabrication and processing. Hence, this review describes the latest progress in non-isocyanate polyurethane synthesis, modification, and finally processing. While focusing primarily on the carbonate/amine route, methods of obtaining NIPU are described, and their properties are presented. Ways of incorporating various compounds into NIPU matrices are characterized by the role of PHU materials in copolymeric materials or as an additive. Finally, diverse processing methods of non-isocyanate polyurethanes are presented, including electrospinning or 3D printing.

The Gray-Box Based Modeling Approach Integrating Both Mechanism-Model and Data-Model: The Case of Atmospheric Contaminant Dispersion

With the profound understanding of the world, modeling and simulation has been used to solve the problems of complex systems. Generally, mechanism-models are often used to model the engineering systems following the Newton laws, and this kind of modeling approach is called white-box modeling; however, when the internal structure and characteristics of some systems are hard to understand, the black-box modeling based on statistic and data-modeling is often used. For most complex real systems, a single modeling approach can hardly describe the target system accurately. In this paper, we firstly discuss and compare the white-box and black-box modeling approaches. Then, to mitigate the limitations of these two modeling methods in mechanism-partially-observed systems, the gray-box based modeling approach integrating both a mechanism model and data model is proposed. In order to explain the idea of gray-box based modeling, the atmosphere dispersion modeling is studied in practical cases from two symmetric aspects. Specifically, the framework of data assimilation is used to illustrate the modeling from white-box to gray-box, while the Gauss features based Support Vector Regression (SVR) models are used to illustrate the modeling from black-box to gray-box. To verify the feasibility of the gray-box modeling method, we conducted both simulation experiments and real dataset symmetry experiments. The experiment results show the enhanced performance of the gray-box based modeling approach. In the end, we expect that this gray-box based modeling approach will be an alternative modeling approach for different existing systems.

TRPA1 and issues relating to animal model selection for extrapolating toxicity data to humans

The transient receptor potential ankyrin 1 (TRPA1) ion channel is a sensor for irritant chemicals, has ancient lineage, and is distributed across animal species including humans, where it features in many organs. Its activation by a diverse panel of electrophilic molecules (TRPA1 agonists) through electrostatic binding and/or covalent attachment to the protein causes the sensation of pain. This article reviews the species differences between TRPA1 channels and their responses, to assess the suitability of different animals to model the effects of TRPA1-activating electrophiles in humans, referring to common TRPA1 activators (exogenous and endogenous) and possible mechanisms of action relating to their toxicology. It concludes that close matching of in vitro and in vivo models will help optimise the identification of relevant biochemical and physiological responses to benchmark the efficacy of potential therapeutic drugs, including TRPA1 antagonists, to counter the toxic effects of those electrophiles capable of harming humans. The analysis of the species issue provided should aid the development of medical treatments to counter poisoning by such chemicals.

Exposure index of methyl isocyanate (MIC) gas disaster and a comprehensive spectrum of cytogenetic analysis after 30 years

Severity of clinical expression and high mortality could not facilitate establishing exposure index/association following MIC disaster in Bhopal. Mortality-based exposure stratification was critiqued by the International Medical Commission on Bhopal (IMCB). IMCB stratified exposure considering distance as surrogate at 2 km intervals after 10 years. The first follow-up cytogenetic screening of the pre-screened survivors after 30 years has demonstrated chromosome abnormalities (CA). Exposure stratification was attempted considering cytogenetic screening conducted during 1986-1988. Elevation of CA appeared proportional to exposure status and authenticated the initial mortality-based stratification. The one-on-one comparison of the previous and present cytogenetics has described the individual response to MIC exposure over 30 years. Chi-square test has been carried out for checking the cytogenetic changes at the individual level statistically, which revealed that differences of chromosomal aberrations collected immediately post-disaster and 30 years later are nonsignificant. The prominence of interindividual variation was noticed in general. The impact of overall exposure was higher in males. Constitutional abnormalities in 8.5% of the study population, including translocation, inversion, deletion, fragile sites, etc., necessitate screening of blood-linked members. The incidence of acrocentric association was prominent in the study population. Normal karyotype in children born to severely exposed parents with congenital anomalies indicates necessity of molecular karyotyping and/or screening of mutations. The study highlights follow-up of the health of the index cases at shorter (3-6 months) intervals. This comprehensive spectrum of cytogenetic report highlights immediate post-disaster chromosomal aberrations, the changes that occurred over 30 years in conjunction with other environmental factors at the individual level, constitutive genomic aberrations, polymorphic variations, and chromosomal patterns in congenitally malformed children of the survivors, which collectively indicate the possibility of acquisition/persistence of stable aberrations in MIC-exposed lymphocytes through interaction with environmental/biological confounders.

TRPs in Tox: Involvement of Transient Receptor Potential-Channels in Chemical-Induced Organ Toxicity-A Structured Review

Chemicals can exhibit significant toxic properties. While for most compounds, unspecific cell damaging processes are assumed, a plethora of chemicals exhibit characteristic odors, suggesting a more specific interaction with the human body. During the last few years, G-protein-coupled receptors and especially chemosensory ion channels of the transient receptor potential family (TRP channels) were identified as defined targets for several chemicals. In some cases, TRP channels were suggested as being causal for toxicity. Therefore, these channels have moved into the spotlight of toxicological research. In this review, we screened available literature in PubMed that deals with the role of chemical-sensing TRP channels in specific organ systems. TRPA1, TRPM and TRPV channels were identified as essential chemosensors in the nervous system, the upper and lower airways, colon, pancreas, bladder, skin, the cardiovascular system, and the eyes. Regarding TRP channel subtypes, A1, M8, and V1 were found most frequently associated with toxicity. They are followed by V4, while other TRP channels (C1, C4, M5) are only less abundantly expressed in this context. Moreover, TRPA1, M8, V1 are co-expressed in most organs. This review summarizes organ-specific toxicological roles of TRP channels.

Comparison of Machine Learning Models for Hazardous Gas Dispersion Prediction in Field Cases

Dispersion prediction plays a significant role in the management and emergency response to hazardous gas emissions and accidental leaks. Compared with conventional atmospheric dispersion models, machine leaning (ML) models have both high accuracy and efficiency in terms of prediction, especially in field cases. However, selection of model type and the inputs of the ML model are still essential problems. To address this issue, two ML models (i.e., the back propagation (BP) network and support vector regression (SVR) with different input selections (i.e., original monitoring parameters and integrated Gaussian parameters) are proposed in this paper. To compare the performances of presented ML models in field cases, these models are evaluated using the Prairie Grass and Indianapolis field data sets. The influence of the training set scale on the performances of ML models is analyzed as well. Results demonstrate that the integrated Gaussian parameters indeed improve the prediction accuracy in the Prairie Grass case. However, they do not make much difference in the Indianapolis case due to their inadaptability to the complex terrain conditions. In addition, it can be summarized that the SVR shows better generalization ability with relatively small training sets, but tends to under-fit the training data. In contrast, the BP network has a stronger fitting ability, but sometimes suffers from an over-fitting problem. As a result, the model and input selection presented in this paper will be of great help to environmental and public health protection in real applications.

Residual Isocyanates in Medical Devices and Products: A Qualitative and Quantitative Assessment

We conducted a pilot qualitative and quantitative assessment of residual isocyanates and their potential initial exposures in neonates, as little is known about their contact effect. After a neonatal intensive care unit (NICU) stockroom inventory, polyurethane (PU) and PU foam (PUF) devices and products were qualitatively evaluated for residual isocyanates using Surface SWYPE™. Those containing isocyanates were quantitatively tested for methylene diphenyl diisocyanate (MDI) species, using UPLC-UV-MS/MS method. Ten of 37 products and devices tested, indicated both free and bound residual surface isocyanates; PU/PUF pieces contained aromatic isocyanates; one product contained aliphatic isocyanates. Overall, quantified mean MDI concentrations were low (4,4'-MDI = 0.52 to 140.1 pg/mg) and (2,4'-MDI = 0.01 to 4.48 pg/mg). The 4,4'-MDI species had the highest measured concentration (280 pg/mg). Commonly used medical devices/products contain low, but measurable concentrations of residual isocyanates. Quantifying other isocyanate species and neonatal skin exposure to isocyanates from these devices and products requires further investigation.

The Bhopal Disaster of 1984

The 20th anniversary of the Bhopal calamity fell on December 3, 2004. The world's worst industrial disaster in Bhopal, India, happened because of inadequate maintenance by Union Carbide and poor monitoring by the Indian authorities. Malfunctioning safety measures, inappropriate location of the plant, and lack of information about the identity and toxicity of the gas worsened the effects of the accident on people and livestock. The Bhopal disaster has raised questions about the implications of the transfer of potentially hazardous technology to the developing countries. Even after 20 years, Bhopal has not recovered. In this article, we present what happened and why and what lessons can be learned at this terrible cost.

On the long-term effects of methyl isocyanate on cell-mediated immunity in Bhopal gas-exposed long-term survivors and their offspring

Methyl isocyanate (MIC) is a toxic industrial chemical that is documented as a potent respiratory toxicant. We investigated cell-mediated immunity (CMI) in the MIC-exposed long-term survivors and their offspring born after the Bhopal gas-leak tragedy in 1984. Several earlier reports show inconsistency in the assessment of immunological effects of MIC on the human population. In these studies, important factors including lifestyle attributes were overlooked. We incorporated these factors also in our study of the basic cell-mediated immune function in the Bhopal MIC-affected population. Twenty-seven years after exposure, we assessed the circulating T-lymphocyte frequency using E-Rosette assay. A total of 46 MIC-exposed healthy long-term survivors and their offspring were studied vis-a-vis parallel gender–age group-matched unexposed controls from Bhopal and various other regions of India. The influence of several lifestyle variabilities (smoking, alcohol intake, and tobacco chewing) on T-lymphocyte frequency was also taken into consideration. Our observations suggest that Erythrocyte-Rosette-forming cell (E-RFC) distribution frequency is largely insignificant in the MIC-affected population as compared to controls ( p > 0.05). In the MIC-affected tobacco chewers, there was a trend of suppression in CMI (relative decrease = 10.3%) as compared to nonchewers. Overall, our results show negligible long-term effect of MIC on CMI measured in terms of E-RFC frequency. These observations are not in agreement with earlier findings that immunosuppressive effects of MIC exposure persist in the T-cells of the affected population. However, atypical lymphocytes were frequently observed as E-RFC in the exposed females when compared to all other subgroups. Hematopoietic disorders (atypical lymphocytosis) in the MIC-affected population along with previous reports on the cytogenetic and humoral immune system linking cancer risk and chronic obstructive pulmonary disease (COPD) are important.

Mass spectrometric identification of isocyanate-induced modifications of keratins in human skin

In the current paper we show that exposure of human callus to isocyanates leads to covalent modifications within keratin proteins. Mass spectrometric analyses of pronase digests of keratin isolated from exposed callus show that both mono- and di-adducts (for di-isocyanates) are predominantly formed on the ε-amino group of lysine. In addition, numerous modified tryptic keratin fragments were identified, demonstrating rather random lysine modification. Interestingly, preliminary experiments demonstrate that in case of MDI a similar lysine di-adduct was formed with lung elastin. Our data support the hypothesis that skin sensitization through antigenic modifications of skin proteins by isocyanates could play a role in occupational isocyanate-induced asthma. It is further envisaged that the elucidated adducts will also have great potential for use as biomarkers to assess skin exposure to isocyanates. Advantageously, the various lysine adducts display the presence of a characteristic daughter fragment at m/z 173.1 [lysine-NCO](+), enabling generic and rapid screening for exposure to isocyanates.

Novel glutathione conjugates of phenyl isocyanate identified by ultra-performance liquid chromatography/electrospray ionization mass spectrometry and nuclear magnetic resonance

Phenyl isocyanate is a highly reactive compound that is used as a reagent in organic synthesis and in the production of polyurethanes. The potential for extensive occupational exposure to this compound makes it important to elucidate its reactivity towards different nucleophiles and potential targets in the body. In vitro reactions between glutathione and phenyl isocyanate were studied. Three adducts of glutathione with phenyl isocyanate were identified using ultra-performance liquid chromatography/electrospray ionization mass spectrometry and nuclear magnetic resonance (NMR). Mass spectrometric data for these adducts have not previously been reported. Nucleophilic attack on phenyl isocyanate occurred via either the cysteinyl thiol group or the glutamic acid α-amino group of glutathione. In addition, a double adduct was formed by the reaction of both these moieties. NMR analysis confirmed the proposed structure of the double adduct, which has not previously been described. These results suggest that phenyl isocyanate may react with free cysteines, the α-amino group and also with lysine residues whose side chain contains a primary amine.

Diagnosis and management of environmental thoracic emergencies

Physiologic sequelae from increasing ambient pressure in underwater activities, decreasing ambient pressure while at altitude, or the consequences of drowning present a unique set of challenges to emergency physicians. In addition, several environmental toxins cause significant respiratory morbidity, whether they be pulmonary irritants, simple asphyxiants, or systemic toxins. It is important for emergency physicians to understand the pathophysiology of these illnesses as well as to apply this knowledge to the clinical arena either in the prehospital setting or in the emergency department. Current treatment paradigms and controversies within these regimens are discussed.

New approaches to problem framing in environmental health: application to water

The relationship between human health and water in its many forms illustrates rather well, the greatest contemporary challenge for decision makers in environmental health - how to develop coherent and effective policy in a climate of significant and increasing complexity. In the study of water and health we recognise the types of complexity that emerge for scientists and epidemiologists in assessing and communicating environmental health risk but also the difficulty for policy makers in interpreting such advice and integrating it with a wider environmental/public health intelligence to shape an effective and proportionate response. Taking water as a point of reference, this paper discusses the sources of complexity for decision makers in environmental health and describes an approach in Scotland which is seeking to build a more sophisticated approach to environmental health policy for a new and uniquely challenging public health era.

Mitochondrial oxidative stress elicits chromosomal instability after exposure to isocyanates in human kidney epithelial cells

The role of oxidative stress is often attributed in environmental renal diseases. Isocyanates, a ubiquitous chemical group with diverse industrial applications, are known to undergo bio-transformation reactions upon accidental and occupational exposure. This study delineates the role of isocyanate-mediated mitochondrial oxidative stress in eliciting chromosomal instability in cultured human kidney epithelial cells. Cells treated with 0.005 microM concentration of methyl isocyanate displayed morphological transformation and stress-induced senescence. Along the time course, an increase in DCF fluorescence indicative of oxidative stress, depletion of superoxide dismutase (SOD) and glutathione reductase (GR) and consistent accumulation of 8-oxo-dG were noticed. Thus, endogenous oxidative stress resulted in aberrant expression of p53, p21, cyclin E and CDK2 proteins, suggestive of deregulated cell cycle, chromosomal aberrations, centromeric amplification, aneuploidy and genomic instability.

Analysis of cellular response to isocyanate using N-succinimidyl N-methylcarbamate exposure in cultured mammalian cells

Isocyanates (R--N==C==O), one of the highly reactive industrial intermediates, possess the capability to modulate the bio-molecules by forming toxic metabolites and adducts which may cause adverse health effects. Some of their toxic degradations have previously been unknown and overlooked; of which, molecular repercussions underlying their genetic hazards upon occupational/accidental exposures still remain as an intricate issue and are hitherto unknown. To assess the genotoxic potential of methyl isocyanate in cultured mammalian cells after in vitro exposure, we performed a study in three different normal cell lines MM55.K (mouse kidney epithelial), B/CMBA.Ov (mouse ovarian epithelial), and NIH/3T3 (primary mouse embryonic fibroblast). Cellular DNA damage response was studied for qualitative phosphorylation states of ATM, gammaH2AX proteins and quantitative state of p53 phosphorylation; DNA cell cycle analysis and measure of cellular apoptotic index before and after treatment were also investigated. Our results demonstrate that methyl isocyanate by negatively regulating the DNA damage response pathway, might promote cell cycle arrest, and apoptosis in cultured mammalian cells suggestive of causing genetic alterations. We anticipate that these data along with other studies reported in the literature would help to design better approaches in risk assessment of occupational and accidental exposure to isocyanates. We also predict that increasing knowledge on DNA damage-triggered signaling leading to cell death could provide new strategies for investigating the effects of DNA repair disorders and decreased repair capacity on the toxicity and carcinogenic properties of environmental toxins.

Transient receptor potential ankyrin 1 antagonists block the noxious effects of toxic industrial isocyanates and tear gases

The release of methyl isocyanate in Bhopal, India, caused the worst industrial accident in history. Exposures to industrial isocyanates induce lacrimation, pain, airway irritation, and edema. Similar responses are elicited by chemicals used as tear gases. Despite frequent exposures, the biological targets of isocyanates and tear gases in vivo have not been identified, precluding the development of effective countermeasures. We use Ca(2+) imaging and electrophysiology to show that the noxious effects of isocyanates and those of all major tear gas agents are caused by activation of Ca(2+) influx and membrane currents in mustard oil-sensitive sensory neurons. These responses are mediated by transient receptor potential ankyrin 1 (TRPA1), an ion channel serving as a detector for reactive chemicals. In mice, genetic ablation or pharmacological inhibition of TRPA1 dramatically reduces isocyanate- and tear gas-induced nocifensive behavior after both ocular and cutaneous exposures. We conclude that isocyanates and tear gas agents target the same neuronal receptor, TRPA1. Treatment with TRPA1 antagonists may prevent and alleviate chemical irritation of the eyes, skin, and airways and reduce the adverse health effects of exposures to a wide range of toxic noxious chemicals.

Revisiting rights and responsibility: the case of Bhopal

Purpose

This paper seeks to examine the activities and consequential effects of a transnational corporation in a developing country. Via an examination of the industrial accident in Bhopal and a discursive examination of the firm's strategies, the paper seeks to contest the firm's claims that it has been acting responsibly. The paper further suggests that the contexts and development of the relationships, and claims by Union Carbide and its supporters, and its place within the global economy, must be critically examined and subjected to a systemic analysis if corporate social responsibility is to have any significant resonance.

Design/methodology/approach

The paper seeks to integrate a wide range of epidemiological and social science literature relating to Bhopal. It seeks to examine Bhopal within the context of power discourse and the relationships engendered via its manifestations and practices. This discursive approach enables the researcher to disentangle various strands of practice within the context of the transnational firm and local communities

Findings

The paper finds that a more systemic approach to corporate governance and corporate social responsibility (CSR) is necessary, if developing countries and local communities are to be treated as critical in the development process and as stakeholders in the debate on CSR.

Originality/value

By its examination if this case, the paper emphasises the need for a more systemic approach to corporate governance and CSR.

Introduction--What critical care practitioners should know about terrorism agents

Terrorist attack by chemical, biologic, or radiologic agents is a prime concern of emergency planners, and would likely lead to casualties that require critical care. This article reviews the past military and terrorist uses of these agents and reviews the most likely agents to be used by terrorists against civilian populations.

Prehospital management of earthquake casualties buried under rubble

Earthquakes continue to exact a heavy toll on life, injury, and loss of property. Survival of casualties extricated from under the rubble depends upon early medical interventions by emergency teams on site. The objective of this paper is to review the pertinent literature and to analyze the information as a practical guideline for the medical management of casualties accidentally buried alive.

Differential inhibition of cellular glutathione reductase activity by isocyanates generated from the antitumor prodrugs Cloretazine™ and BCNU

The antitumor, DNA-alkylating agent 1,3-bis[2-chloroethyl]-2-nitrosourea (BCNU; Carmustine), which generates 2-chloroethyl isocyanate upon decomposition in situ, inhibits cellular glutathione reductase (GR; EC 1.8.1.7) activity by up to 90% at pharmacological doses. GR is susceptible to attack from exogenous electrophiles, particularly carbamoylation from alkyl isocyanates, rendering the enzyme unable to catalyze the reduction of oxidized glutathione. Evidence implicates inhibition of GR as a cause of the pulmonary toxicity often seen in high-dose BCNU-treated animals and human cancer patients. Herein we demonstrate that the prodrug Cloretazine (1,2-bis[methylsulfonyl]-1-[2-chloroethyl]-2-[(methylamino)carbonyl]hydrazine; VNP40101M), which yields methyl isocyanate and chloroethylating species upon activation, did not produce similar inhibition of cellular GR activity, despite BCNU and Cloretazine being equally potent inhibitors of purified human GR (IC(50) values of 55.5 microM and 54.6 microM, respectively). Human erythrocytes, following exposure to 50 microM BCNU for 1h at 37 degrees C, had an 84% decrease in GR activity, whereas 50 microM Cloretazine caused less than 1% inhibition under the same conditions. Similar results were found using L1210 murine leukemia cells. The disparity between these compounds remained when cells were lysed prior to drug exposure and were partially recapitulated using purified enzyme when 1mM reduced glutathione was included during the drug exposure. The superior antineoplastic potential of Cloretazine compared to BCNU in animal models could be attributed in part to the contribution of the methyl isocyanate, which is synergistic with the co-generated cytotoxic alkylating species, while at the same time unable to significantly inhibit cellular GR.

Critical care requirements after mass toxic agent release

There is an increasing risk of mass exposure of civil populations after release of toxic agents. These include military chemical warfare agents or industrial compounds, some of which have been used as a chemical. The traditional military divisions among chemical agents, toxins, and biologic agents may be viewed as a continuous spectrum of hazards. Each of these has four specific qualities (toxicity, latency, persistency, and transmissibility), which determine management of casualties and the toxic release. Toxic hazards may be released accidentally or deliberately, producing potentially large numbers of casualties. Previous incidents have shown that many of these require extended hospital care. This article reviews aspects of the nature of the toxic agents, the pathophysiology they produce, and therapeutic measures. The central and peripheral nervous systems and the respiratory systems are particularly vulnerable and may lead to fatal results unless early action is taken. Specific antidotes and life support care is required at all levels of prehospital and hospital management. Critical care management is required for severe cases, and this must combine continuing antidote, ventilatory and supportive therapy.

Risk assessment of peak exposure to genotoxic carcinogens: a pragmatic approach

Short-term exposures to relatively high concentrations or doses are a regular cause of concern. Since carcinogenicity is often of great personal and social relevance the question arises whether short-term exposure (1-10 days) to a carcinogenic substance may contribute to tumour development and, if so, whether this contribution to the cancer risk can be quantified. The present object was to explore the possibility of a pragmatic estimation of the cancer risk of peak exposure to a genotoxic carcinogen relative to the cancer risk of the same cumulative dose of this carcinogen distributed over lifetime. A report published by the Health Council of The Netherlands served as point of departure. Published data strongly suggests that short-term or single exposure can indeed give rise to tumour formation in animal experiments. The application of a dose-rate correction factor (DRCF), defined as a factor by which the tumour incidence caused by a specific dose of a chemical carcinogen at low-dose rates is multiplied to derive the tumour incidence at high-dose rates, appears to be a feasible approach. Theoretical models calculated maximum values for the DRCF of up to seven for a young child acutely exposed to an initiator or first-stage carcinogen. A maximum value of 8.3 was calculated from animal experiments. A decision tree is presented which allows the pragmatic assessment of the carcinogenic risk following short-term exposure to genotoxic carcinogens. It is recommended to validate this decision tree with model-substances.

Terrorism in Japan

Although the 1995 Tokyo subway sarin attack probably was the most widely reported terrorist event in Japan to date (5,500 injured, 12 dead), the country has suffered numerous other large terrorism-related events in recent decades, including bombings of the headquarters of Mitsubishi Heavy Industries in Tokyo in 1974 (207 injured, 8 dead), the Hokkaido Prefectural Government office building in Sapporo in 1976 (80 injured, 2 dead), and the Yosakoi-Soran Festival in Sapporo in 2000 (10 injured, none dead). Japan also has experienced two other mass-casualty terrorist events involving chemical releases, including the 1994 Matsumoto sarin attack (600 injured, 7 dead) and the 1998 Wakayama arsenic incident (67 injured, 4 dead). Until 1995, emergency management in Japan focused on planning and preparedness at the local level for the frequent disasters caused by natural events. Since that time, substantial progress has been made in advancing emergency planning and preparedness for terrorism-related events, including the designation of disaster centers in each prefecture, the implementation of several education and training programs for nuclear, biological, and chemical terrorism, and the establishment of a national Anti terrorism Office within the Ministry of Health, Labor, and Welfare.

Disaster medicine in the 21st century: future hazards, vulnerabilities, and risk

The prediction of future disasters drives the priorities, urgencies, and perceived adequacies of disaster management, public policy, and government funding. Disasters always arise from some fundamental dysequilibrium between hazards in the environment and the vulnerabilities of human communities. Understanding the major factors that will tend to produce hazards and vulnerabilities in the future plays a key role in disaster risk assessment. The factors tending to produce hazards in the 21st Century include population growth, environmental degradation, infectious agents (including biological warfare agents), hazardous materials (industrial chemicals, chemical warfare agents, nuclear materials, and hazardous waste), economic imbalance (usually within countries), and cultural tribalism. The factors tending to generate vulnerabilities to hazardous events include population growth, aging populations, poverty, maldistribution of populations to disaster-prone areas, urbanization, marginalization of populations to informal settlements within urban areas, and structural vulnerability. An increasing global interconnectedness also will bring hazards and vulnerabilities together in unique ways to produce familiar disasters in unfamiliar forms and unfamiliar disasters in forms not yet imagined. Despite concerns about novel disasters, many of the disasters common today also will be common tomorrow. The risk of any given disaster is modifiable through its manageability. Effective disaster management has the potential to counter many of the factors tending to produce future hazards and vulnerabilities. Hazard mitigation and vulnerability reduction based on a clear understanding of the complex causal chains that comprise disasters will be critical in the complex world of the 21st Century.

Risk factors for adverse health effects following hazardous materials incidents

To identify risk factors for persistent morbidity, we conducted a prospective study of individuals involved in hazardous materials incidents reported to the Washington Poison Center. Between December 1997 and October 1999, 202 subjects in 87 incidents were surveyed by telephone. Medical symptoms persisting for a minimum of 8 days after the incident were reported in 51 (25%) subjects, and 18 (9%) left work or school for more than 2 days because of the exposure. Medical intervention was reported in 46 (58%) of 79 subjects for whom medical records were available, and objective abnormalities were found in 57 (72%). Multiple logistic regression analysis indicated that subjects with dermal exposures, three or more alcoholic drinks per week, and previous use of psychiatric medications were more likely to report persistent symptoms. Divorced, widowed, or separated subjects, asthmatic subjects, and those having initial dermal symptoms were more likely to miss work or school for more than 2 days. Of patients evaluated at a health care facility, subjects with preexisting hypertension were more likely to receive medical treatment or have objective medical findings, whereas those with inhalation exposures and those decontaminated at the scene were less likely to be treated or have abnormalities. In our study, both incident and individual factors were predictive of adverse health effects, and these findings should be considered in planning the care of patients involved in hazardous materials incidents.

Simultaneous determination of two human urinary metabolites of N,N-dimethylformamide using gas chromatography-thermionic sensitive detection with mass spectrometric confirmation

Two human urinary metabolites of the industrial solvent N,N-dimethylformamide (DMF), N-hydroxymethyl-N-methylformamide (HMMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC), were assayed using a new analytical method (gas chromatography and thermionic sensitive detection). Clean-up of urine samples includes a liquid-liquid extraction step followed by a solid-phase extraction step to separate HMMF and AMCC from other urine components. During clean-up, AMCC is converted into ethyl-N-methylcarbamate (EMC), and during gas chromatography, HMMF is degraded in the injector to N-methylformamide (NMF). All the validation data necessary for a quantitative procedure are given. The method was applied to urine samples from workers exposed to DMF and from the general population. The results were confirmed by mass spectrometric determination. For this purpose a further liquid-liquid extraction step was introduced in the clean-up procedure. Background levels of AMCC in the general population were identified.

David R. Boyd lecture in trauma care and emergency medical systems: "The surgical complications of toxins."

Toxins have had major roles in our societies for thousands of years. Interactions between surgeons, both generalists and subspecialists, and those caring for poisoned patients have been extensive throughout history. The advancement of the science of toxicology, the development of regional poison control centers, the development of emergency medicine, and the development of the subspecialty of medical toxicology have led to more appropriate and creative interactions between medical toxicologists, emergency physicians, and surgeons. This article will review the diverse interfaces between the medical toxicologist and the surgeon.

The pre-hospital management of injury following mass toxic release; a comparison of military and civil approaches

Mass release of toxic substances may occur either accidentally or deliberately in both peace and war. Different approaches to the management of casualties from such an event have been developed by civil and military emergency medical teams, and reflect the different circumstances in which they operate. The nature and classification of toxic hazards is considered and the civil and military operational and medical responses compared. Both systems have different aspects that can contribute to early casualty management in a contaminated environment.

Formation, solvolysis, and transcarbamoylation reactions of bis(S-glutathionyl) adducts of 2,4- and 2,6-diisocyanatotoluene

During our ongoing studies of the reactions of toluene diisocyanate (2,4- and 2,6-diisocyanatotoluene, TDI) in vivo, it became apparent that reactive form(s) of these diisocyanates reach(es) the circulatory system after passage through the respiratory system. Based on recent work by others regarding the transcarbamoylation reactions of monoisocyanates, we hypothesized that the reactive form could be masked as an S-thiocarbamoylglutathione adduct of one or more of the isocyanato moieties. In this study, the glutathione adducts of 2,4- and 2,6-diisocyanatotoluene were synthesized under physiological conditions. Bis adducts were the major products when near-equimolar amounts of glutathione and the individual diisocyanato compounds were mixed at physiological pH, and were formed in high yield. Little to no mono adducts formed under these reaction conditions. The masses of the bis adducts were confirmed by electrospray mass spectrometry (MS), and 1H NMR analysis strongly suggested that the thiol of the cysteine residue of glutathione was the nucleophile in each case. The rates of solvolysis of the two bis adducts in aqueous buffer under conditions of physiological temperature and pH were determined, and electrospray MS analysis showed that the corresponding mono(glutathionyl)-TDIs were formed in these reactions. Incubation in vitro of each of the bis(glutathionyl)-TDI adducts with a 12 amino acid peptide (Thr-Cys-Val-Glu-Trp-Leu-Arg-Arg-Tyr-Leu-Lys-Asn) at pH 7.5 resulted in transfer of one mono(glutathionyl)-toluylisocyanato moiety to the peptide as detected by HPLC and on-line electrospray MS analyses. In both the solvolysis and transfer experiments, the 2,4-TDI-derived bis(glutathionyl) adduct reacted most quickly, while both the bis(glutathionyl)-2,6-TDI adduct and its transfer product with the peptide were more stable than their 2,4-TDI-derived counterparts. The results indicate high stoichiometry in formation and ready transfer to nucleophilic sites of protein, and suggest that the isocyanato moiety of both 2,4- and 2,6-TDI may be regenerated in vivo from their bis(glutathionyl) adducts. As a consequence, the thiol status of particular tissues may be a contributing factor to individual TDI toxicity susceptibility, and a mechanism by which toxicity at sites distant to the initial point of contact may be proposed.

[Amplified chemical disasters: a challenge for public health]

Chemical accidents involving explosions, large fires and leakages of hazardous substances occurring during transport, storage and industrial production of chemicals constitute a real challenge to health, environmental and industrial safety professionals. The aim of this article is to discuss the main questions that this kind of accident provokes, in terms of public health, particularly in developing countries such as Brazil. The paper defines and characterises these accidents and the various health risk they involve excluding the leakages of hazardous substances during "normal" production in industry--through the combination of quantitative and qualitative information drawn from the international literature on the subject. From some examples of chemical accidents such as occurred in Bhopal (India), Vila Socó (Brazil), São Paulo (México) and data of the World Health Organization (WHO), the authors seek to show that these events present a worsening, in terms of immediate deaths and injuries, in developing countries. The statistics of chemical accidents which occurred during the last ten years (1984 to 1993) in the State of Rio de Janeiro are used taken as a frame reference for the purpose of bringing to light the great number of occurrences made with no registration of basic information regarding assessment or surveillance. The complexity of causes and consequences, together with the structural problems of developing countries, present public health professionals and institutions, with some important tasks especially those of health risk assessment and the formulation of strategies to prevent and control future major chemical accidents.

Bhopal-A Case Study of International Disaster

This paper outlines what is known about the probable events leading up to the disaster in Bhopal, India, in 1984, wherein release of a gas cloud from an industrial plant killed over 3,800 people. It briefly reviews the toxicology of methyl isocyanate, a major component of the cloud; presents an overview of the acute and chronic health effects of the gas exposure from published human and animal studies; identifies some of the clinical dilemmas and medical management and epidemiologic issues being debated; provides an insight into national and transnational implications; and summarizes the lessons learned or not learned from this disaster of global significance.

The Bhopal accident and methyl isocyanate toxicity

The Bhopal accident, the world's worst industrial disaster, in which nearly 40 metric tons of methyl isocyanate (MIC) was released from the Union Carbide pesticide plant, occurred nearly 10 yr ago during the night of December 2 and 3, 1984. Over 3000 people residing in areas adjacent to the plant died of pulmonary edema within 3 d of the accident. Follow-up studies revealed pulmonary, ophthalmic, reproductive, immunologic, neurological, and hematologic toxicity among the survivors. Despite high reactivity, MIC can traverse cell membranes and reach distant organs, perhaps as a reversible conjugate with glutathione, which may explain some of the systemic effects of MIC. MIC can be degraded as a result of pyrolysis and interaction with water, but none of the breakdown products can duplicate the toxicity observed in Bhopal and in animal models. MIC may be the most toxic of all isocyanates because of its very high vapor pressure relative to other isocyanates and because of its ability to exert toxic effects on numerous organ systems.