Metals, toxic effects

Respiratory Effects. Although the SMR for respiratory diseases was 1.31 among workers at a thorium refinery (Polednak et al. 1983), the increase may have been attributable in part to smoking Exposure level estimates for inhalation intakes ranged from 0.003-0.192 nCi/m (0.001-0.007 Bq/m ) for a period of 1 -33 years. Because the workers were exposed to other toxic compounds (uranium dust) as well as other radioactive metals, toxic effects cannot necessarily be attributed to thorium. Therefore, no quantitative information from the study is reported in Table 2-1 or Figure 2-1. 

Metal Toxic Effects person) Source of Exposure Absorption... 

Solders. Modem dental solders are made from mostly corrosion-resistant, nontoxic metals. Minimal quantities of tin and other elements are often added, some of which could produce toxic effects in the unalloyed state. Each solder is used for specific appHcations (180—188) typical compositions and properties of solders used in dentistry are presented in Table 11. Most of the ingredients of solders are resistant to corrosion, and alloying them with other ingredients renders the alloy safe for use in appHances placed in the oral environment. Silver solders corrode, but are used only for temporary appHances. Available products do not contain cadmium, although cadmium was an ingredient of some silver solders up to ca 1980. 

Heavy metals on or in vegetation and water have been and continue to be toxic to animals and fish. Arsenic and lead from smelters, molybdenum from steel plants, and mercury from chlorine-caustic plants are major offenders. Poisoning of aquatic life by mercury is relatively new, whereas the toxic effects of the other metals have been largely eliminated by proper control of industrial emissions. Gaseous (and particulate) fluorides have caused injury and damage to a wide variety of animals—domestic and wild—as well as to fish. Accidental effects resulting from insecticides and nerve gas have been reported. 

Coyer, R.A. (1996). Toxic effects of metals. In Casarett and DoulTs Toxicology The Baste Science of Poisons (C. D. Klaassen, Ed.), pp. 691-736. McGiaw -Hill, New York,... 

Among the physical factors, current velocity has a special significance for benthic biofilms because it can modulate the diffusion of metals through the biofilm and their effects [18, 40]. pH and organic complexation are particularly significant for metal bioavailability [42]. Therefore, metal toxicity will also depend on the influence that environmental variability has on its bioavailability. 

Overall the results reported in this review indicate that water scarcity might increase metal exposure (due to low dilution), metal uptake (due to higher retention under low flow), and metal toxicity and/or accumulation (depending on the dose and time of exposure), but also might cause opposite effects depending on the source of pollution. In addition, water scarcity will influence nutrient loads and will also modulate the fate and effects of metals. Thus, future studies addressing the role of environmental stress on the effects of toxicants at community scale are key to predict the impact of toxicants in the aquatic ecosystems. 

Other papers in the Symposium deal with the antioxidant and hypolipidemic effects of IP6, its chelating effects in heavy metal toxicity, inhibition of renal stones and other beneficial effects such as inhibition of platelet aggregation, inhibition of inflammatory responses (Shamsuddin, 1998). The lipid lowering effect and anti-neoplastic effect of 1P6 were extensively reviewed (Jariwalla, 1999). Hence, 1P6 is a valuable component of rice bran in preventing disease and maintaining health. 1P6 is present at 1.8-2% in rice bran. 

All metals, regardless of whether they are essential or nonessential, can exhibit toxic effects at high concentrations.14-16 Excess concentrations of essential metals can lead to nonspecific binding, which can affect the enzyme structure and function. Because controlling metal concentrations is vital for maintaining homeostatic conditions within bacterial cells, evolution has bestowed upon organisms a number of ways to regulate concentrations of essential metals and to resist the toxicity of nonessential metals.17-20... 

Many studies have reported the effects of metals on general soil microbiological processes. Metals including cadmium, chromium, copper, lead, mercury, nickel, and zinc have been reported to inhibit many of the microbial processes listed above. Metal toxicity in the environment ultimately decreases litter decomposition, which can be measured by the rate of mass loss. Both copper (0.5 mg Cu g4 soil) and zinc (1.0 mg Zn g 1 soil) were shown to decrease the rate of decomposition of unpolluted Scots pine needle litter near a brass mill in Sweden.61 Duarte et al.63 also determined that copper and zinc toxicity reduced leaf decomposition rates and fungal reproduction. Other metals, such as cadmium, nickel, and lead, have also been reported to decrease litter decomposition.77... 

Metal toxicity is also affected by physiochemical factors, such as pH and the concentration of divalent cations. Adding divalent cations, such as zinc, has been reported to mitigate toxicity produced by other metals. For example, the addition of 60 pM zinc reduced toxicity in Pseudomonas putida caused by 3 mM cadmium.148 Zinc had no effect on cells grown in the absence of cadmium. Little is understood surrounding the mechanism of protection however, cadmium uptake was observed to be dependent on zinc concentration.149 Zinc was found to be a competitive inhibitor of cadmium uptake. 

Ivanov, A.I., Fomchenkov, V.M., Khasanova, L.A., and Gavriushkin, A.V., Toxic effect of hydroxylated ions of heavy metals on the cytoplasmic membrane of bacterial cells, Mikrobiologiia, 66 (5), 588-594,1997. 

Sandrin, T. and Hoffman, D., Bioremediation of organic and metal co-contaminated environments Effects of metal toxicity, speciation, and bioavailability on biodegradation, in Environmental Bioremediation Technologies, Singh, S.N. and Tripathi, R.D., Eds, Springer, Berlin, Germany, 2007, pp. 1-34. 

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