Document ZnLO6qezy4J798bEgLMyN2n2L

ard, and severe injuries and deaths have oc curred from ignition of powdered magnesium m the clothing of workers who have done hand grinding on magnesium alloys Also, fires and dust explosions have occurred in ex haust systems carrying powdered magnesium from grinding operations Exhaust systems should go as directly as possible to a dust separator which will remove the magnesium powder and trap it under water without permitting it to get into the main exhaust system The wet powder from these dust collectors and tuming-chips that are wet with coolant should be removed from the plant as soon as they are taken from the collecting equipment Workers in magnesium-grinding operations should be provided with and required to wear flame-resistant clothing Massive pieces of magnesium in the form of castings or machined work are not a severe fire hazard because they are hard to ignite When once ignited, however, the metal in the massive forms will bum vigorously Malathion (O.O-dimethyl dithiophosphate of diethyl mercaptosuccmate) is one of the organic phosphate insecticides Like the others of its class, its principal toxic action on warm-blooded animals is its inhibition of acetylcholinesterase It seems to be one of the least toxic of this type of insecticide In halation of 5 ppm (56 mg/cu m) by dogs and guinea pigs produced no effects except tears and a slight decrease m the plasma cho linesterase activity Maleic anhydride is an irritant to the skin and mucous membranes, especially in the presence of moisture Maleic anhydride does not usually cause an immediate burning sensa tion upon contact with the skin, especially if the skin is dry If not removed by washing, it will cause reddening and, occasionally, blistering, if the exposure is prolonged and severe Maleic anhydride dust and vapors are exceedingly irritating and severe acute expo sures are not voluntarily tolerated Upon in halation of dust or vapors, coughing and sneezing, together with burning and irritation of the throat may occur The eyes are par ticularly sensitive to the dust and vapors Maleic anhydride is not a serious industrial hazard provided workers are adequately in structed and effectively supervised in the proper handling of the chemical Employees should be instructed to report any signs of irritation or burning of skm, eyes, or mucous membranes Because maleic anhydride is a combustible solid having a flash point of 215 F, care must be exercised in handling and storage to keep it away from flame or spades Dust and the vapors from the molten product are also flam mable Manganese is found in a wide variety of minerals The dioxide is its most common in organic compound and is used as a chemical intermediate, enamel additive, and drier The probability of contracting manganese poisoning is low, but the effects are severe-- total disablement may result from a few months' exposure to high concentrations This effect, however, is more likely to occur after prolonged and repeated exposures above 30 mg/cu m The main hazard is usually from the inhala tion of manganese dioxide, which may pro duce neurological lesions The symptoms are many and are similar to Parkinson's syndrome Symptoms include weakness, instability, dif ficulty in walking, immobility of facial ex pression, monotonous and intermittent speech, spasmodic laughter, and other grotesque signs Exposures to finely divided dusts of man ganese dioxide may produce pneumonitis Mercury and its compounds are not nearly so widely used as are lead compounds and consequently mercury poisoning is not so well known nor so often seen as is lead poisoning Mercury metal is a liquid at room tempera ture with a vapor pressure high enough to produce poisoning if a considerable area of the metal surface is exposed to air If mer cury gets into the cracks of a wood or hie floor or into the pores of a concrete floor, the contamination may become so great as to necessitate leplacement or sealing of the floor before the plant or laboratory can be safely used again Although it cannot be removed, mercury can be sealed into such floors by covering them completely with an asphalt mastic, preferably after the vapor pressure of the mercury has been reduced by flooding 1153