Chemical substances toxic properties

While the vesicant agents, in addition to vesication, exert divers complex physiological effects, their physical, chemical, and toxic properties are such that they form a well-defined group with many characteris-(ics in common, and for this reason they were grouped by the Germun> iind< r the general name of Yellow Cross substances. 

Professor Martel s book addresses specifically some of the more technical eispects of the risk assessment process, mainly in the areas of hazard identification, and of the consequence/effect analysis elements, of the overall analysis whilst where appropriate setting these aspects in the wider context. The book brings together a substantial corpus of information, drawn from a number of sources, about the toxic, flammable and explosive properties and effect (ie harm) characteristics of a wide range of chemical substances likely to be found in industry eind in the laboratory, and also addresses a spectrum of dangerous reactions of, or between, such substances which may be encountered. This approach follows the classical methodology and procedures of hazard identification, analysing material properties eind... 

Partition processes determine how a substance is distributed among the liquid, solid, and gas phases and determine the chemical form or species of a substance. Partitioning usually does not affect the toxic properties of the substance. Partitioning can, however, affect the mobility of the waste, its compatibility with the injection zone, or other factors that influence fate in the deep-well environment. The major partition processes are as follows ... 

Adsorption is a physicochemical process whereby ionic and nonionic solutes become concentrated from solution at solid-liquid interfaces.3132 Adsorption and desorption are caused by interactions between and among molecules in solution and those in the structure of solid surfaces. Adsorption is a major mechanism affecting the mobility of heavy metals and toxic organic substances and is thus a major consideration when assessing transport. Because adsorption is usually fully or partly reversible (desorption), only rarely can it be considered a detoxification process for fate-assessment purposes. Although adsorption does not directly affect the toxicity of a substance, the substance may be rendered nontoxic by concurrent transformation processes such as hydrolysis and biodegradation. Many chemical and physical properties of both aqueous and solid phases affect adsorption, and the physical chemistry of the process itself is complex. For example, adsorption of one ion may result in desorption of another ion (known as ion exchange). 

Ingestion Toxicity Data are available for the acute (single-dose) ingestion/oral toxicity of many toxic materials (National Institute for Occupational Safety and Health, Registry of Toxic Effects of Chemical Substances, 1983 Lewis, Sax s Dangerous Properties of Industrial Materials, 9th ed., 1996). However, very few data are available for prolonged ingestion or periodic doses of toxic materials. It is likely that metabolic processes would operate to increase the total burden required for toxic effects for such chronic exposures, except for some materials (such as mercury and lead) which apparently can accumulate in the body. 

For the analysts, laboratories wishing to dispose of materials containing dilute concentrations of these constituents should contact the Department of Environmental Health and Safety for advice regarding the proper disposition of the materials. In addition, the list of such materials is not included here, as it is subject to periodic updates. Furthermore, the list is not meant to be complete and may not include substances that have the hazardous characteristics as defined above. Omission of a chemical from this list does not mean that it is without toxic properties or any other hazard. 

In snmmary, many of the specific chemicals in petroleum are hazardous because of their chemical reactivity, fire hazard, toxicity, and other properties. In fact, a simple definition of a hazardons chemical (or hazardous waste) is that it is a chemical substance (or chemical waste) that has been inadvertently released, discarded, abandoned, neglected, or designated as a waste material and has the potential to be detrimental to the environment. Alternatively, a hazardons chemical may be a chemical that may interact with other (chemical) snbstances to give a prodnct that is hazardous to the environment. Whatever the case, methods of analysis mnst be available to determine the nnrture of the released chemical (waste) and from the data predict the potential hazard to the environment. 

Air, water, soil, and food are all unavoidable components of the human environment. Each of those elements influences the quality of human life, and each of them may be contaminated. Food is not only the elementary source of nutrients, but may also contain natural chemical substances with toxic properties, e.g., cyanogenic glycosides (many plants), solanine (green parts of potatoes, sprouted potatoes, and potatoes stored in light), industrial pollutants (heavy metals), biogenic amines (fish), or mycotoxins (moldy foodstuffs). 

It is time to inquire about the methods used to identify the toxic properties of chemicals. So far a few key principles have been introduced and some information on specific substances has been discussed, but little has been said about how these principles and information have been learned. Without some appreciation of the basic methods of toxicology, and what can and cannot be accomplished with them, it will not be possible to gain a solid understanding of the strengths and, more importantly, the limitations in our knowledge of chemical risk. 

The substances we have described in this book turn out to be, for the most part, minor threats to our health. There are, however, perhaps thousands of these threats, and so a regulatory system has evolved to reduce the risks of individual substances to very low levels. There is considerable work yet to be done, to learn the toxic properties of many poorly tested chemicals, and to assess their health risks, but once this is done, regulatory officials have available strong weapons (which they do not always choose to deploy) to reduce exposures when necessary. The burden for exposure reduction falls not on exposed individuals (as in the case of lifestyle factors), but rather upon those who have caused the exposures to occur. 

There are different approaches to estimating the toxicity of various PHs. One method is to examine the known individual compounds in each PH fraction, based on the data collected for a limited number of compounds and assuming the known materials are representative of the entire mixture. A second method is to divide the mixture into several fractions that contain substances with similar chemical and physical properties, which therefore are considered to have comparable toxicity. A third approach is to consider the entire mixture. The actual content of each mixture depends mainly on the origin of the PH and the distillate fractions. 

Ideally, a full data set should be available for the hazard assessment of a chemical substance, including animal tests to evaluate the toxicokinetics and the following toxicological properties acute toxicity, irritation, sensitization, toxicity following repeated exposure to the substance, mutagenicity and genotoxicify, carcinogenicity, and effects on fertility and fetal development. 

The aim of the hazard assessment of a chemical substance under evaluation is to assess whether exposure to the chemical might result in adverse health effects in humans, based on a critical evaluation of the available data on the inherent toxicological properties of the substance as well as the toxicological mode(s) of action/mechanisms of toxicity. 

Chromium hexacarbonyl is highly toxic by all routes of exposure. The symptoms include headache, dizziness, nausea and vomiting. The LD5o(oral) in mice is 150 mg/kg (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nd ed. NewYork John Wiley Sons). It explodes upon heating at 210°C. 

This handbook is an encyclopedic treatment of chemical elements and their most important compounds intended for professionals and students in many areas of chemistry throughout the manufacturing, academic, and consulting communities. Chemicals are presented in alphabetical order in a descriptive format highlighting pertinent information on physical, chemical, and thermodynamic properties of chemicals, methods of preparation, industrial applications, chemical analyses, and toxic and hazardous properties. Synonyms, CAS Registry Numbers, brief history of discovery and natural occurrence are provided for many entries. The objective is to provide readers a single source for instant information about important aspects each substance. In this sense it should serve as a combination handbook and encyclopedia. 

Hazard (Toxic) The set of inherent properties of a chemical substance or mixture which makes it capable of causing adverse effects in man or the environment when a particular degree of exposure occurs. 

Residual solvents are organic volatile chemicals that remain in active substances, excipients, and other pharmaceutical products after processing. In spite of their toxic properties, solvents play an important role in the production of pharmaceuticals, during the synthesis, separation, or purification, and their use cannot be avoided. Solvents in this category do not include those used as excipients. 

---