Manganese toxicity concentrations

Manganese occurs in the liver of the animal body. Even though the amount ol manganese present in mammalian tissues is very small, its concentration seems to be accurately controlled by elaborate mechanisms These mechanisms function primarily by promoting the excretion of excesses of the element from the body rather than by regulating the amounts ol manganese the body absorbs. The mechanisms are located in the liver and on the mucosa of the gut. In cases of manganese toxicity, it is assumed that these mechanisms become saturated. 

Manganese toxicity in plants may be expected when soils Mn levels exceed lOOOmgkg- DW (WHO 1981). In leaves, this concentration is mostly sufficient to induce symptoms of toxicity. As with manganese deficiency, the ability of plants to tolerate an excess of manganese varies greatly... 

Health and Environment. Manganese in trace amounts is an essential element for both plants and animals and is among the trace elements least toxic to mammals including humans. Exposure to abnormally high concentrations of manganese, particulady in the form of dust and fumes, is, however, known to have resulted in adverse effects to humans (36,37) (see Mineral nutrients). 

Human and animal studies indicate that inorganic manganese compounds have a very low acute toxicity by any route of exposure. The toxicity values for a given Mn compound are shown in Table 20 to depend on the species of test animal as well as the route of exposure. Manganese concentrations as high as 2000 ppm were found to be tolerated by test animals over a six-month period without any ill effects (208). 

The mobility of arsenic compounds in soils is affected by sorp-tion/desorption on/from soil components or co-precipitation with metal ions. The importance of oxides (mainly Fe-oxides) in controlling the mobility and concentration of arsenic in natural environments has been studied for a long time (Livesey and Huang 1981 Frankenberger 2002 and references there in Smedley and Kinniburgh 2002). Because the elements which correlate best with arsenic in soils and sediments are iron, aluminum and manganese, the use of Fe salts (as well as Al and Mn salts) is a common practice in water treatment for the removal of arsenic. The coprecipitation of arsenic with ferric or aluminum hydroxide has been a practical and effective technique to remove this toxic element from polluted waters... 

Statham [448] has optimised a procedure based on chelation with ammonium dithiocarbamate and diethylammonium diethyldithiocarbamate for the preconcentration and separation of dissolved manganese from seawater prior to determination by graphite furnace atomic absorption spectrometry. Freon TF was chosen as solvent because it appears to be much less toxic than other commonly used chlorinated solvents, it is virtually odourless, has a very low solubility in seawater, gives a rapid and complete phase separation, and is readily purified. The concentrations of analyte in the back-extracts are determined by graphite furnace atomic absorption spectrometry. This procedure concentrates the trace metals in the seawater by a factor of 67.3. 

Falandysz, J., W. Kotecka, and K. Kannan. 1994. Mercury, lead, cadmium, manganese, copper, iron and zinc concentrations in poultry, rabbit and sheep from the northern part of Poland. Sci. Total Environ. 141 51-57. Fernandez, T.V. and N.V. Jones. 1990. Studies on the toxicity of zinc and copper applied singly and jointly to Nereis diversicolor at different salinities and temperatures. Trop. Ecol. 31 47-55. 

Manganese Mining, industrial wastes Toxic to plants in high concentrations None established... 

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