Toxicology chemical interactions

In order to understand toxicological chemistry, it is necessary to have some understanding of the environmental context in which toxicological chemical phenomena occur. This in turn requires an understanding of the broader picture of environmental science and environmental chemistry, which are addressed in this chapter. Also needed is an understanding of how environmental chemicals interact with organisms and their ecosystems, as addressed by the topic of ecotoxicology, covered in Chapter 5. 

Biochemical toxicology deals with processes that occur at the cellular and molecular levels when toxic chemicals interact with living organisms. Defining these interactions is fundamental to our understanding of toxic effects, both acute and chronic, and is essential for the development of new therapies, for the determination of toxic... 

Figure 1 Exposure pathways and receptors in a typical terrestrial food web. (Reprinted with permission from Lanno R (ed.) (2003) Contaminated soils. In Soil-Chemical Interactions to Ecosystem Management, 400pp. Pensacola, FL Society of Environmental Toxicology and Chemistry SETAC, Pensacola, FL, USA.)...

Quinone exists in the atmosphere in the gas phase. The dominant atmospheric loss process for quinone is expected to be by reaction with the hydroxyl (OH) radical (reaction with ozone is expected to be slow because of the >C(0) substituent groups). The estimated half-life and lifetime of quinone in the atmosphere due to reaction with the OH radical are 3 and 4 h, respectively. Bolton JL, Trush MA, Penning TM, Dryhurst G, and Monks TJ (2000) Role of quinones in toxicology. Chemical Research in Toxicology 13 135-160. Monks TJ and Jones DC (2002) The metabolism and toxicity of quinones, quinoimines, quinone methides, and quinone-thioethers. Current Drug Metabolism 3 425 38. O Brien PJ (1991) Molecular mechanisms of quinone cytotoxicity. Chemico-Biological Interactions 80 1-14. 

A Weight-of-Evidence (WOE) Method To provide further guidance on the evaluation of chemical interactions and their impact on risk values calculated from data not reflective of the mixture, a weight-of-evidence (WOE) method was developed [25,26], The assessment of WOE for interactions enables assessors to judge if the interactions influence the overall toxicity of the mixture and if the anticipated joint toxicity will be greater than or less than expected based on the principle of additivity. The WOE method yields a composite representation of all the evidence on toxicologic interactions from human studies to animal bioassay data relevance of route, duration, and sequence and the significance of interactions. The method consists of a classification... 

Because of the relative dearth of toxicological testing data, hazard identification for environmental pollutants becomes a challenging task. Until such data become available, computational approaches and tools are being routinely used. The US EPA s MIXTOX database [14,32,33] is a collection of bibliographic summaries of chemical interaction studies, most of which are studies of binary mixtures. Veteran mixtures risk assessors may be familiar with the... 

This book deals with the potential health consequences of pesticides, food additives, and drugs. All of these are chemicals. The sciences of toxicology, nutrition, and pharmacology revolve around the study of how such chemicals interact with our bodies. As will be demonstrated, the only factor which often puts a specific chemical under the umbrella of one of these disciplines is the source and dose of the chemical or the intent of its action. The science is the same in all three. This is often forgotten ... 

Aquatic sites contaminated with military-related materials are likely to contain mixtures of a variety of energetic compounds and their transformation products, as well as other classes of chemicals. Although individual compounds may be present below effects concentrations at contaminated sites, simultaneous exposure to a mixture of these compounds and their transformation products may result in adverse toxicological effects. However, the ecological risks associated with contaminants are often considered on an individual chemical basis without consideration of chemical interactions affecting bioaccumulation and toxicity. Interacting chemicals result... 

The keys of toxicology are based on all the above-mentioned domains that try to focus on understanding how the toxic chemicals interacts with environment, and what should we do in order to protect harmful effects. For... 

Sastry, B. V. R. (1991). Placental toxicology Tobacco smoke, abused drugs, multiple chemical interactions and placental function. Repnod. Fertil. Dev. 3, 355-372. 

Calabrese, E. J. (1995). Toxicological consequences of multiple chemical interactions A primer. Toxicology 105, 121-135,... 

Dr. Soaring Bear has been collecting herbal data, with a focus on toxicology, since the early 1970s. He earned a B.S. in biochemistry with honors and a Ph.D. in pharmacology from the University of Arizona. His doctoral research on structure-activity relationships and chemical interactions provides him with a unique perspective on bioactivity of herbs. He created herbmed.org and edited over ten thousand quick summaries and links into Medline. His work at the National Library of Medicine in the Medical Subject Headings (MeSH) section included significant revisions of the herbal, alternative medicine, and chemistry sections of MeSH, which improves the quality of millions of searches done every day on the pubmed.gov database. 

Gaido, K.W., Barlow, K.D. and Leonard, L. Use of a yeast-based oestrogen receptor assay to assess chemical interactions with the oestrogen receptor, SOT 1996 Annual Meeting, Abstract 731 cited in Fundamental and Applied Toxicology, Supplement, The Toxicologist, 30(1), Part 2, March 1996. 

Restania P., Restellia A.R., Gallia C.L. Formaldehyde and hexamethylenetetramine as food additives Chemical interactions and toxicology. Food Additives and Contaminants, 9 597-605 (1992). 

FIGURE 7.4 Structures of selected industrial chemicals that have been shown to cause cancer. Many carcinogenic chemicals interact with DNA, causing mutations that are necessary but not sufficient for cancer to develop. (Reprinted with permission from Ernest Hodgson and Patricia Levi, Textbook of Modem Toxicology [New York Elsevier, 1987], 146.)... 

The interpretation of the studies on toxicological risk from PAH exposure is complicated by several factors. The toxicity of PAH mixtures can not be accurately predicted based on chemical analysis, due to chemical interactions or to the presence of imidentified chemicals. In addition, it is practically impossible for epidemiology to disentangle the risk posed by each individual PAH. Indeed PAHs occur invariably as mixtures, whose composition depends mainly on the raw material and the combustion circumstances, and they are often adsorbed to particles in the environment. As a consequence epidemiologic data are inadequate to evaluate the possible interaction between PAHs and particles in the induction of cancer in humans. Finally, exposure to PAHs is ubiquitous and the risk associated with complex mixtures remains a challenge to predict. 

Although toxicology testing is often performed with only a single material or a material in a relatively inert solvent, in most practical situations there is simultaneous exposure to multiple chemicals and thus a potential for complex biological interactions. The following descriptive terms are useful in classifying such effects. 

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