BENZENE

From Big Medical Encyclopedia

BENZENE (C 6 H 6 ) — the simplest representative of aromatic hydrocarbons; valuable raw materials in production of dyes, medicines, etc. Colorless volatile liquid with a specific smell. Density is 0,879 g/cm 3  ; t°kip 80,1 °; stiffens in the cold in crystalline mass, edges melts at t ° 5,5 °. A solubility coefficient of vapors B. in water 3,73 at t ° 22 °; B. it is well dissolved in organic solvents, and also in fats and lipids. Under the influence of a number of reagents B. easily replaces hydrogen of benzene ring on halogen (halogenation), nitrogroup (nitration), sulfonate group (sulphonation). The corresponding derivatives are widely applied in chemical industry. So, nitrobenzene (C 6 H 5 NO 2 ) represents yellowish liquid with a smell of bitter almonds. For an organism it is toxic; is an initial product during the receiving aniline (see Nitrobenzol). Technical B. contains considerable impurity of thiophene, toluene, a xylol. The most important source of industrial receiving B. and other aromatic hydrocarbons is black coal. In large numbers of B. receive also by pyrolysis of petroleum distillates (kerosene, fuel oil) at t ° 500 — 600 ° (petroleum benzene). Crude B. is exposed to cleaning and rectification since it contains the higher homologues, unsaturated compounds, phenols, cresols, carbon sulfur, sulfur compounds, etc. Petroleum benzene — the colorless, transparent liquid containing about 60% of benzene, 15% of a xylol and 25% of gasoline (mix of naphthenic, paraffinic and unsaturated hydrocarbons).

B. finds broad application in the industry as good rubber solvent, pitches, various paints and alkaloids as a filler (or a thinner) at production of nitrovarnishes as an initial product for receiving various dyes, chemical - pharm. drugs, explosive substances and other products of chemical synthesis.

See also Hydrocarbons .

Professional harm

B. is industrial poison of polytropic action. Meets under production conditions at a floor the doctrine from black coal (the koksobenzolny plants), oil; is a part of some types of oil, motor fuel; in small amounts can contain in lighting gas, petroleum gas, etc. Under production conditions can cause acute and hron, poisoning with way of penetration into an organism through respiratory tracts or (more rare) through the unimpaired skin at hit on it. It is removed in not changed look through lungs, in the form of phenol, dihydroxy-benzene, pyrocatechin — with urine.

Action of high concentration of vapors B. affects hl. obr. on c. N of page (narcotic, partly convulsive action). At very high concentration there comes almost instant loss of consciousness and death from paralysis of a respiratory center within several minutes. Complexion at victims light pink or earthy and cyanotic. Mucous membranes of often cerise color.

Chronic poisoning arises at long influence of low concentrations of vapors B., proceeds with preferential defeat of blood and the hemopoietic system with development of a hypoaplasia. The hemopoietic function of marrow is broken, as a rule, in a certain sequence (a leukopoiesis, a thrombocytopoiesis, an erythrogenesis) though also deviations from the determined consistent pattern are possible. In a pathogeny of benzene cytopenias also formation of autoantibodies against various elements of blood plays a role. In addition to a hypoaplasia, long influence of B. can cause hyperplastic reaction up to development of true leukoses. The nervous system is involved in process both directly under the influence of B., and indirectly — in the presence of considerable defeat of system of blood. Long influence of B. causes disturbance of activity of digestive organs, a liver, cardiovascular system, a functional condition of coagulant system of blood and a vascular wall. Disorders of functions of bodies of incretion, disturbance of vitamin balance are observed. Nonspecific displays of this intoxication — frequent incidence of flu, quinsy, activation of tubercular process are noted.

Distinguish easy, moderately severe and heavy forms hron.

B. V poisonings mild cases the neurotic syndrome with dysfunction of the autonomic nervous system or astheno - a vegetative syndrome on a hyperreactive background prevails; symptoms of hypotonia are observed. The hemorrhagic syndrome is unsharply expressed. Disorder of secretory function of a stomach in the form of hypersecretion of a gastric juice on an empty stomach with low acidity and the digesting force is noted, is more rare with high content free salt to - you. In peripheral blood — lability of quantity of leukocytes: in the beginning leukocytosis, then leukopenia, sometimes tranzitorny; often a neutropenia with a relative lymphocytosis. The combination of a leukopenia to unsharp thrombocytopenia is possible. Sometimes the isolated easily expressed thrombocytopenia, a small reticulocytosis. In marrow activation of reparative processes takes place: hyperplasia of an erythroidal sprout, reticulocytosis, increase in young forms of a granulotsitarny row.

Chronic poisoning of moderate severity of B. is shown astheno - a vegetative syndrome with a hyperexcitability of the autonomic nervous system or vegetative hyporeactivity. The vegetative polyneuritis, a hemorrhagic syndrome (skin hemorrhages, nasal bleedings, menorrhagias), positive symptoms of a pinch and a cuff is quite often observed. The bleeding time is extended, thromboplastic activity is reduced, the fibrinolysis is strengthened, retraction of a blood clot is broken. Dystrophy of a myocardium, hypotonia is moderately expressed. Dysfunction of a stomach towards hyposecretion, the lowered gastric acidity, the low digesting force. The liver is moderately increased, its function is broken. The amount of gamma-globulins, sometimes beta globulins is unsharply increased. The adbumin-globulinovy coefficient is lowered. Changes of peripheral blood are most characteristic and continuous: leukopenia of various degree of manifestation, neutropenia, relative lymphocytosis, band shift. Moderate thrombocytopenia and anemia, reticulocytosis, acceleration of ROE. In marrow — various manifestations of an easy form of a hypoplastic state with strengthening of proliferative activity.

At a severe form of poisoning the phenomena of bleeding are considerably expressed, symptoms of a pinch and a cuff, can test of the II—III degree are sharply positive. Change of all phases of formation of thrombin and fibrin, and also stage of a fibrinolysis. Retraction of a blood clot is sharply broken. The expressed asthenic state or (we cut astheno - an organic syndrome (toxic encephalopathy). Vegetative polyneuritis. Dystrophy of a myocardium, hypotonia. Falloff of all indicators of gastric secretion. Toxic damage of a liver, hypergammaglobulinemia, reduction of albumine, sharp reduction of a proteinaceous indicator. In peripheral blood a deep pancytopenia, a reticulocytopenia, acceleration of ROE. Marrowy punctate is poor in cellular elements, the delay of maturing of cells of all three sprouts, signs of their degenerative changes, increase undifferentiated and plasmocytes is observed.

Basis of the diagnosis hron. to B.'s intoxication and one of the most reliable and its characteristic signs changes in cellular composition of peripheral blood are. The differential diagnosis is carried out with leykopenichesky conditions of various etiology, pernicious anemia, Verlgof's disease, a chlorosis. It must be kept in mind the diseases which are followed by a hypersplenism and some collagenic diseases at which in peripheral blood the cytopenia is defined. B.'s definition in blood for diagnosis of poisoning is disputable since it can be absent at patients and be found in almost healthy faces. Definition in urine of sulfates and phenols (products of transformations of B.) can be useful when B.'s concentration in air considerably exceeds admissible.

At the solution of questions of vrachebnotrudovy examination it must be kept in mind that any degree of manifestation hron. serves benzene intoxication as a contraindication to further contact with B. Establishment of group of disability, and also determination of terms of its preservation demands individual approach taking into account degree of manifestation of poisoning, character of a course of process, age of the patient, a profession, and also the accompanying general pathology.

For clinical picture of acute poisoning are characteristic: headache, dizziness, feeling of intoxication, nausea, vomiting, general weakness. The short-term loss of consciousness is possible.

In more hard cases — a long loss of consciousness, coma, clonic spasms, a collapse. Morphological changes at acute poisoning: a plethora of substance of a brain and its covers, internals and dot hemorrhages in them.

Treatment of acute poisoning symptomatic — an artificial respiration, oxygen therapy, - lobeline, cardiovascular means. Treatment of patients hron. B.'s intoxications the krovetvorniya is carried out differentially depending on extent of disturbance of this or that function, and also the nature of those frustration which arise at B. V influence mild cases use of haemo stimulators is inexpedient. Vitamins of group B are most effective. At more expressed poisoning — the complex therapy including haemo therapeutic and hemostatics, and also corticosteroid hormones.

Prevention of poisonings with benzene. Sealing of the equipment, ventilation. The number of B. which is a part of solvents shall not exceed 10%. B.'s replacement with less toxic solvents. So, in particular, in the USSR in production of cellulose lacquers, enamels and solvents of B. to them it is not applied.

It is impossible to allow to work with B. of pregnant women and the feeding women, teenagers up to 18 years. Medical examinations of workers with performing blood test are necessary preliminary and periodic (time in 6 months).

See also Poisonings , Poisons industrial

Benzene in the medicolegal relation

Objects court. - medical researches internals of corpses of people, sometimes clothes, and also air of production rooms serve. B.'s poisonings are possible at its hit in an organism through respiratory tracts, and sometimes and at intake. At a research of a corpse the sweetish and acid smell is noted. During the opening: punctulate hemorrhages in a brain and a meninx, in lungs, airways also went. - kish. path. In prolonged cases — necrobiotic changes with the subsequent septicopyemia and damage of marrow; the expressed plethora of internals, respiratory tracts, sharp hypostasis and a plethora of a brain.

B. and its metabolites (phenol, etc.) at court. - a chemical research are defined in a brain, a liver, blood and urine. B. take distillation and transfer to dinitrobenzene. Qualitative test of the last is carried out by means of acetone and caustic soda (blue-violet coloring appears). Quantitative definition is made colorimetric.

Bibliography: Harmful substances in the industry, under the editorship of N. V. Lazarev, p.1, page 90, L., 1971; Dragina E. A., Zorina L. A. both Gribova of I. A. Klinik and forecasts of changes of a nervous system at chronic intoxication benzene, the Gigabyte. work and the prof. having got sick., No. 5, page 18, 1971; Occupational diseases, under the editorship of A. A. Letavet, page 283, M., 1973; R and-shevsky A. M. and Zorina L. A. Occupational diseases of system of blood of a chemical etiology, page 65, M., 1968.

L. A. Zorina; S. Ya. Smusin (court.), M. K. Cheltsova (biochemical).

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