As a source of toxicity

Salinity affects microbial activity, in part, because it controls water availability. The higher the salinity, the more energy an organism must expend to maintain a favorable osmotic balance. Salts, of course, have effects on living organisms beyond water availability. For example, salts can be both a source of essential nutrients as well as a source of toxic heavy metals. Also, sulfate salts appear to be more favorable for life than chloride salts see the discussion in Sect. 5.1.2 (Aqueous Saline Environments). However, in this section on salinity, the focus will be on salinity as a control on water availability. 

Pedersen GA, Mortensen GK, Larsen EH. 1994. Beverages as a source of toxic trace element intake. Food Additives and Contaminants 11(3) 351-363. 

Concerns have often been expressed about coal utilization as a source of toxic and also of radioactive materials since coals contain uranium and thorium at concentration levels of one to four parts per million (ppm), with uranium at levels of 20 ppm rare and thorium as high as 20 ppm veiy rare (USGS, 1997). Coal combustion releases bothU and Th from the coal matrix. As a result, more than 99.5% of these elements ends up in the 10% of solid ash which is formed on the average, i.e., the concentrations of radioac-... 

Produced water may contain dispersed oil, dissolved oil, metals, ammonia, treating chemicals, and salts. Each of these constituents could act as a source of toxicity. Published research results indicate that organic compounds in produced water are significant factors in toxicity but not the source of toxicity in all cases. Common industry practice for water treating is to reduce the dispersed oil content of produced water effluent and as a result may not fully treat all sources of toxicity. 

Acetamide has been used experimentally as a source of nonprotein nitrogen for sheep and dairy cattie (13). It does not appear to be toxic in amounts of about 2—3% of ration. Buffering the diet with dibasic acids serves to allow higher levels of intake because the ammonia Hberated in the digestive process is then scavenged. 

Although the crystal structure of CODH or CODH/ACS has not yet been solved, a great deal of work has been done on these enzymes and plausible catalytic mechanisms have been proposed. Concerted action between the Ni ion and one of the Fe centers of a 4Fe-4S cluster are thought to elicit the formation of CO2 from CO. But perhaps the most extraordinary reaction is the one catalyzed by Cluster A the insertion of CO to a Ni-CHs complex. Through the two reactions catalyzed by CODH/ACS, the highly toxic, CO is not only removed, but is used as a source of carbon and electrons. 

Citrate is isomerized to isocitrate by the enzyme aconitase (aconitate hydratase) the reaction occurs in two steps dehydration to r-aconitate, some of which remains bound to the enzyme and rehydration to isocitrate. Although citrate is a symmetric molecule, aconitase reacts with citrate asymmetrically, so that the two carbon atoms that are lost in subsequent reactions of the cycle are not those that were added from acetyl-CoA. This asymmetric behavior is due to channeling— transfer of the product of citrate synthase directly onto the active site of aconitase without entering free solution. This provides integration of citric acid cycle activity and the provision of citrate in the cytosol as a source of acetyl-CoA for fatty acid synthesis. The poison fluo-roacetate is toxic because fluoroacetyl-CoA condenses with oxaloacetate to form fluorocitrate, which inhibits aconitase, causing citrate to accumulate. 

Gymnodinium catenatwn, first recognized as a cause of toxicity in an outbreak in Mazatlan (43,44), lacks a theca but otherwise bears some resemblance to the catenate Alexandrium species. It has now been recognized as a source of PSP in Spain (45), Portugal (46), Venezuela (A. La Barbera-Sanchez, personal communication), Tasmania (47), and Japan (48),... 

Oxidized species of nitrogen, chiefly nitrite and nitrate, occur in all soils and in the soil solution. Nitrite in the environment is of concern because of its toxicity. Its occurrence is usually limited because the oxidation of nitrite to nitrate is more rapid than the oxidation of ammonia to nitrite. Both nitrite and nitrate move readily in soil and nitrate is available to plants as a source of nitrogen and can move to plant roots with water. 

TOXIC COMPOUNDS IN SMOKED FOODS 13.5.1 Wood Smoke as a Source of Carcinogens... 

Potassium cyanide (KCN) is a white crystalline substance with a slight odor of bitter almonds. It is produced when hydrogen cyanide is absorbed in potassium hydroxide. It is used to extract gold and silver from their ores, in electroplating computer boards, and as an insecticide. Potassium cyanide is very toxic to the skin or when ingested or inhaled, and it is used as a source of cyanide (CN) gas in gas chambers. 

With increasing toxicity data of various kinds, more rehable predictions based on structure-toxicity relationships of toxic endpoints can be attempted [31-36]. Even the Internet can be used as a source for toxicity data, albeit with caution [37]. A number of predictive methods have been compared from a regulatory perspective [35]. Often traditional QSAR approaches using multiple Hnear regression are used [38]. Newer approaches include the use of neural networks in structure-toxicity relationships... 

As mentioned above we obtained most of the poison for our chemical and biological work from the Alaska butter clam. However our search for a dinoflagellate or any other poisonous organism in the water as a source of the poison in the clams was never definitely accomplished. In 1948, and in some years following, along with a survey for toxic butter clams in Southeastern Alaska by the staff at the Fishery Products Research Laboratory at Ketchikan, 1 collected plankton in areas where the clams were found to be toxic. Mouse assays of the plankton showed no toxicity. Microscopic examination of the water in these areas showed heavy growth of microscopic plankton but little or no evidence of... 

---