Document yrOoZDpNYVQ5rMeb61y0BB9wD

Elements of Industrial Toxicology usually transitory and do not have any per manent ill effects Asphyxiation may be brought about by the reduction of the partial pressure of oxygen m the inspired air Carbon monoxide is an example of a chemcial asphyxiant Its action is to combine with the hemoglobin to form carboxyhemoglobin which cannot be utilized in carrying oxygen to its tissues As mentioned previously, the liver, kid neys, bones and other organs of the body may become affected by exposure to harmful materials Organic phosphates inhibit the enzyme, cholinesterase which is present in red blood cells In addition to consideration of exposure to a single material, combined toxic effects due to the simultaneous action of different mate rials may occur For example, a synergistic effect, greater than that from the same con centration of inhaled gas alone, will be pro duced by exposure to a mixture of sulfur dioxide and sodium chloride crystals So dium chloride crystals inhaled alone are rela tively inert Antagonistic, or potentiation effects are produced by inhaling fumes of iron, and gas eous nitrogen oxides, the reduction of effect m this case is explained on the basis of a firmly combined laver of nitrogen oxides on the iron oxide particles In the absence of other information it may be assumed that the effects of exposure to chemical agents should be considered as additive When purely local effects on differ ent organs of the body are produced by the various components of the mixture, it may be assumed that the chief effects upon exposure would be independent Harmful chemical agents may attack living organisms in two different ways --locally and systemically Caustic alkalis and strong acids are capable of producing severe damage and local tissue destruction Many of the mate rials exert a milder local action which usually consists of skin irritation or dermatitis, which is of a transitory nature Systemic poisons are carried by the blood stream to the tissues or organs where they exert their effects Studies of cellular metabolism have estab lished important mechanisms on the action of toxic agents involving interference with enzyme systems Ultimately, all toxic agents produce either directly or indirectly an altera tion in cellular metabolism, leading to changes in permeability, irritability, alteration of nor mal function, or some other physiological change Intensity of action The seventy of action of the toxic agent is a function of the concentration of the substance m the damaged organ This depends upon the rates of absorption, detoxification, and excretion Absorption is pnmanly dependent upon the solubility of the harmful matenal Detoxification is a result of the body's attempt to eliminate the toxic substance or to form a non-toxic product Excretion refers to the elimination of a toxic agent and its toxicmetabolites from the body Apparently, then the intensity of action of a harmful material is dependent upon the na ture of the material, the type and rate of ex posure, and the fate of matenal in the body A single large dose of a toxic substance may be expected to produce a greater response than the same total dose administered over a long penod of time, because a large dose may be able to produce its detnmental action be fore appreciable detoxification occurs The same amount given as a senes of small re peated doses can be handled by detoxifica tion and excretion mechanisms A toxic sub stance that is detoxified or excreted at a rate which is slower than the rate of intake of the substance is called a cumulative poison (Lead is an example of this type of poison ) As a mle, young people are more suscep tible to toxic substances than are their elders Either natural or acquired hypersensitivity may increase the response to toxic agents This abnormal sensitivity is called an idio syncrasy to the toxic agent Physiological tests are available to detect early stages of poisoning before clinical symp toms ordinarily appear Chest X rays often detect silicosis before it becomes disabling A reduction in the cholinesterase activity of the blood is a reliable indication of organic phosphate poisoning Periodic medical ex amination in conjunction with analysis of atmospheric contaminants may be necessary to completely define the worker's exposure in relationship to his environment Experimental toxicology Smyth (see "References") stated that four 1304