Organ-based toxicity

Maximum acceptable toxicant concentration values (MATC) for toxaphene and aquatic organisms, based on exposure for the entire or most of the life cycle... 

Niimi, A.J. and G.P. Kissoon. 1994. Evaluation of the critical body burden concept based on inorganic and organic mercury toxicity to rainbow trout (Oncorhynchus mykiss). Arch. Environ. Contam. Toxicol. 26 169-178. 

In aquatic environments, Spear (1981) spotlights three research needs (1) development of analytical procedures for measurement of individual dissolved zinc species, notably the aquo ion and zinc chloride, and for nondissolved species that occur in natural waters (2) separation of natural from anthropogenic influences of sediment-water interactions on flux rates, with emphasis on anoxic conditions, the role of microorganisms, and the stability of organozinc complexes and (3) establishment of toxicity thresholds for aquatic organisms based on bioaccumulation and survival to determine the critical dose and the critical dose rate, with emphasis on aquatic communities inhabiting locales where zinc is deposited in sediments. These research needs are still valid. 

Table 27.3 Maximum Acceptable Toxicant Concentration Values (MATC) for Toxaphene and Aquatic Organisms, Based on Exposure for the Entire or Most of the Life Cycle (Concentrations are in micrograms of toxaphene per liter [ppb].)... 

There are two possibilities for the organic base. One is pyridine, which is the base in the traditional Karl Fischer recipe. The structure of pyridine is similar to that of benzene. The difference is that one of the carbons in the benzene ring is replaced by a nitrogen. Pyridine is toxic, has a disagreeable odor, and does not give the optimum pH for the determination. More recently, imidazole has been used for the base. The structures of pyridine and imidazole are shown in Figure 14.13. 

Vanwezel, A.P. and Opperhuizen, A. (1995) Narcosis due to environmental pollutants in aquatic organisms - residue-based toxicity, mechanisms, and membrane burdens. Crit. Rev. Toxicol.,... 

CAS [110-86-1] used as a solvent and an intermediate in organic synthesis colorless liquid characteristic disagreeable odor boils at 115°C freezes at -41.5°C density 0.98 g/ml miscible with water and most organic solvents weak base toxic and flammable. 

The biomagnification LOE involves determining concentrations of contaminants such as DDT, PCBs, dioxins, TBT, and methyl mercury in benthic invertebrates or fish. This LOE only applies to those few organic contaminants that actually biomagnify. Concentrations are compared to reference areas or literature-based toxicity reference values (TRVs) and assessed via food chain bioaccumulation models (Grapentine et ah, 2002). 

OPs have been in use for several decades as important chemicals for the control of crop pests. With their chemical and biochemical reactions, OPs have been well established as extremely poisonous chemicals. This classification is due to the inhibition of the marker enzyme ChE, which is produced in the liver. Blood enzymes provide an estimate of tissue enzyme activity. After acute exposure to OPs or a nerve agent, the erythrocyte enzyme activity most closely reflects the activity of the tissue enzyme. Once the OPs inhibit the tissue enzyme, it cannot hydrolyze ACh, and the accumulation stimulates the affected organ. Based on the manner of exposure (dose and duration) to different OPs, a series of toxicity signs and symptoms set in the organism, leading to death. These are important aspects to be closely monitored among pest control operators and occupational workers exposed to OPs. 

Organization guidelines for drinking water quality (World Health Organization, 1984) include limit values for the organic and toxic substances (see Table 11.6), based on acceptable daily intakes (ADI). These can be adopted direcdy for ground-water protection purposes, but in view of the possible accumulation of certain toxic elements in plants (e.g. cadmium and selenium), the intake of toxic materials... 

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