Ionizing toxicity

For dissociating ionizable toxicants, the overall Koc (of the nondissociated plus the ionized fraction) can again (see Section 2.4.1.4.1 on the single-compartment organic equilibrium model) be calculated by Koc = Koc nondissociatedx (0.9 x nondissociated fraction + 0.1) (USEPA 2000b), where the nondissociated fraction is calculated from the pH in the water and the pXa of the toxicant. If the toxicity of the freely dissolved toxicant is estimated by comparison with experimental toxicity data, the pH shift in toxicity also has to be taken into account. 

Alkalosis Alkalosis shifts the equilibrium between NH4 and NH3 to the non-ionized, toxic NHs- Only this form is able to pass the blood-brain barrier and the membrane of the cerebral cells. (37) (s. fig. 15.2)... 

The nitroaromatic compounds such as the nitrofurans are known to be activated by a bacterial nitroreductase system in susceptible microorganisms. Intermediate, highly reactive species such as free radicals produced during the reduction process are likely responsible for damage to DNA strands that lead to bacterial and protozoal cell death. Thus a reduced nitroaryl anion radical could be oxidized by 02 to produce superoxide anions (Eq. 7.3). Under the influence of superoxide dismutase (SOD) (Chapter 4) hydrogen peroxide can be produced (Eq. 7.4), which, in turn, interacts with additional superoxide anion radical, producing ionizing toxic hydroxyl radicals (Eq. 7.5). 

When inhaled, ingested, or adsorbed through the skin, thorium isotopes are potentially harmful because of ionizing radiation and chemical toxicity. 

Gas ionization may cause dissociation of gas stream constituents and result in creation of toxic byproducts... 

Fumigation with ethylene oxide does indeed lead to a considerable reduction in the germ count (and at the same time destruction of insects), but the process, because of the formation of toxic reaction products (ethylene chlorhydrin, ethylene glycol) has been banned throughout the European Community since 01.01.1990 Ionizing irradiation a declaration of the treatment is obligatory, but such drugs find little acceptance by the public who expect nature s products as such. 

Systems for monitoring Working environments Toxic contaminants Temperature Noise Lighting Vibration Ionizing radiation Occupational health... 

Toxic Effects on the Blood-Forming Tissues Reduced formation of erythrocytes and other elements of blood is an indication of damage to the bone marrow. Chemical compounds toxic to the bone marrow may cause pancytopenia, in which the levels of all elements of blood are reduced. Ionizing radiation, benzene, lindane, chlordane, arsenic, chloramphenicol, trinitrotoluene, gold salts, and phenylbutazone all induce pancytopenia. If the damage to the bone marrow is so severe that the production of blood elements is totally inhibited, the disease state is termed aplastic anemia. In the occupational environment, high concentrations of benzene can cause aplastic anemia. 

The chemistry, and hence hazards, of hot, or radioactive, elements parallels that of their cold isotopes. However, the radiation poses additional toxicity hazards. A qualitative classification of selected isotopes in terms of their toxicity is given in Table 10.2. The biological effects of ionizing radiation stem mainly from damage to individual cells following ionization of the water content. Oxidizing species, e.g. hydrogen peroxide. 

Ferritin, an iron-binding protein, prevents ionized iron (Fe ) from reaching toxic levels within cells. Elemental iron stimulates ferritin synthesis by causing the release of a cytoplasmic protein that binds to a specific region in the 5 nontranslated region of ferritin mRNA. Disruption of this protein-mRNA interaction activates ferritin mRNA and results in its translation. This mechanism provides for rapid control of the synthesis of a protein that sequesters Fe +, a potentially toxic molecule. 

The structure-selective, electron-capture detector (ECD) is the second aost widely used ionization detector [115-118]. It owes Buch of its popularity to its unsurpassed sensitivity to a wide range of toxic and biologically active coapounds. Consequently, it is widely used in trace analysis for the detemination of pesticides, herbicides and industrial chemicals in the... 

One can see by the complexity of these types of manufacturing procedures that much care and attention to detail must be maintained by the manufacturer. This sterile manufacturing procedure must then be validated to prove that no more than 3 containers in a lot of 3000 containers (0.1%) are nonsterile. Ultimately, it is the manufacturer s responsibility to ensure the safety and efficacy of the manufacturing process and the absence of any adverse effect on the product, such as the possible formation of substances toxic to the eye, an ever-present possibility with gas sterilization or when using ionizing radiation. For ophthalmic products sterilized by terminal sterilization (sterilization in the final sealed container, e.g., steam under pressure), the sterilization cycle must be validated to ensure sterility at a probability of 106 or greater. 

Ionization. Many organic chemicals contain functional groups that dissociate to yield charged species. The toxicity and chemical reactivity of the uncharged (neutral) molecule and its charged ions can be very different. Differences in reactivity of ionic species can be accommodated in fate models when rate constants are expressed in terms of the individual species. 

Ionization is the process of separation or dissociation of a molecule into particles of opposite electrical charge (ions). The presence and extent of ionization has a large effect on the chemical behavior of a substance. An acid or base that is extensively ionized may have markedly different solubility, sorption, toxicity, and biological characteristics than the corresponding neutral compound. Inorganic and organic acids, bases, and salts may be ionized under environmental conditions. A weak acid HA will ionize to some extent in water according to the reaction ... 

Table 3 gives an overview of the environmental impact categories that are taken into account in the environmental impact assessment according to the baseline method that is recommended in the Dutch LCA Handbook [1], The characterization for toxicity is based on factors derived by the Usetox model [12], The impact categories depletion of water and ionizing radiation are not taken into account because reliable characterization factors are not available. 

Bacterial cell walls contain different types of negatively charged (proton-active) functional groups, such as carboxyl, hydroxyl and phosphoryl that can adsorb metal cations, and retain them by mineral nucleation. Reversed titration studies on live, inactive Shewanella putrefaciens indicate that the pH-buffering properties of these bacteria arise from the equilibrium ionization of three discrete populations of carboxyl (pKa = 5.16 0.04), phosphoryl (oKa = 7.22 0.15), and amine (/ Ka = 10.04 0.67) groups (Haas et al. 2001). These functional groups control the sorption and binding of toxic metals on bacterial cell surfaces. 

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