Lead oxide, toxicity

Sulfur Polymer Cement. SPC has been proven effective in reducing leach rates of reactive heavy metals to the extent that some wastes can be managed solely as low level waste (LLW). When SPC is combined with mercury and lead oxides (both toxic metals), it interacts chemically to form mercury sulfide, HgS, and lead sulfide, PbS, both of which are insoluble in water. A dried sulfur residue from petroleum refining that contained 600-ppm vanadium (a carcinogen) was chemically modified using dicyclopentadiene and oligomer of cyclopentadiene and used to make SC (58). This material was examined by the California Department of Health Services (Cal EPA) and the leachable level of vanadium had been reduced to 8.3 ppm, well below the soluble threshold limit concentration of 24 ppm (59). 

The common acid acceptors, red lead oxide and barium carbonate, are both toxic when inhaled or ingested. They are, and should be, used in industry as dispersions in EPDM and ECO. SuppHers of red lead oxide include Polymeries, Inc., Rhein Chemie Corp., and Akrochem Co., Akron, Ohio. Barium carbonate in an ECO binder is available from Rhein Chemie Corp. and Synthetic Products Co. 

Emissions from other nonferrous metal facilities are primarily metal fumes or metal oxides of extremely small diameter. Zinc oxide fumes vary from 0.03 to 0.3 jiim and are toxic. Lead and lead oxide fumes are extremely toxic and have been extensively studied. Arsenic, cadmium, bismuth, and other trace metals can be emitted from many metallurgical processes. 

Beyer, W.N. and A. Anderson. 1985. Toxicity to woodlice of zinc and lead oxides added to soil litter. Ambio 14 173-174. 

Lead oxide is highly toxic as a dust. Use with adequate ventilation, and keep away from food and food products Refs 1) Gmelin, Syst Nr. 47, Teil C, Lfg 1 (1969), 122ff la) EngDesHdbk, Properties of Materials Used In Pyrotechnic Compositions , AM CP 706-187 (Oct 1963), 166-68 2)... 

Lead Inorganic lead oxides and salts Gastrointestinal, respiratory Soft tissues redistributed to skeleton (> 90% of adult body burden) CNS deficits peripheral neuropathy anemia nephropathy hypertension reproductive toxicity Inhibits enzymes interferes with essential cations alters membrane structure Renal (major) feces and breast milk (minor)... 

Esterase activity is important in both the detoxication of organophosphates and the toxicity caused by them. Thus brain acetylcholinesterase is inhibited by organophosphates such as paraoxon and malaoxon, their oxidized metabolites (see above). This leads to toxic effects. Malathion, a widely used insecticide, is metabolized mostly by carboxylesterase in mammals, and this is a route of detoxication. However, an isomer, isomalathion, formed from malathion when solutions are inappropriately stored, is a potent inhibitor of the carboxylesterase. The consequence is that such contaminated malathion becomes highly toxic to humans because detoxication is inhibited and oxidation becomes important. This led to the poisoning of 2800 workers in Pakistan and the death of 5 (see chap. 5 for metabolism and chap. 7 for more details). 

Metabolism of foreign compounds is not necessarily detoxication. This has already been indicated in examples and will become more apparent later in this book. This may involve activation by a phase 1 or phase 2 pathway or transport to a particular site followed by metabolism. Phase 1 reactions, particularly oxidation, can be responsible for the production of reactive intermediates such as epoxides, quinones, hydroxy la mines, and free radicals, which lead to toxicity. However, phase 2 reactions can also result in toxicity in some cases. 

Similarly, amino phenols can be oxidized to semiquinones and quinoneimines. This can be carried out by oxyhemoglobin (Hb-FeII-02). However, the reactive products, semiquinones and quinoneimines can oxidize the hemoglobin to ferrihemoglobin (Hb-Felll), which leads to toxicity as it cannot carry oxygen. 

Lead and lead oxides Car batteries Lead and its compounds are toxic and particularly affect the nervous system... 

SCHEME 11.19 The nitrogen atom is a site for oxidation, potentially leading to toxic by-products. 

As the induction of hepatic microsomal oxidative activity by a lipid-soluble drug (e.g. phenobarbitone) or xenobiotic could decrease the duration of action of therapeutic agents that are mainly eliminated by microsomal oxidation, the effect of induction would be considered a form of biochemical antagonism. Drug-induced inhibition of microsomal oxidative activity, without adjustment of dosage of a concomitantly administered therapeutic agent that undergoes extensive hepatic metabolism, could lead to toxicity. Cimetidine, ketoconazole and chloramphenicol inhibit hepatic microsomal enzyme activity. 

Bivalent lead oxide, litharge (PbO), is among the oldest PVC stabilizers and its properties include its basicity, its complexing properties and its extremely fine particle size, which facilitates incorporation. The improvements in lead stabilizers over the years can be viewed as improvements on the basic characteristics of litharge, with the yellow colour, of course, being one of the apparent disadvantages, but the greatest deterrent to the use of lead stabilizers is their acute and cumulative toxicity. 

---