Prevention of Occupational Poisonings

This includes the following:

· Administrative-legislative measures (the list of harmful industries - medical contra-indications, privileges, age restrictions, etc.);

· Hygienic measures – a preventive and current sanitary control;

· Medical-preventive measures - preliminary and current medical examinations, investigation and treatment of occupational poisonings; medical-preventive nutrition in harmful industries;

· Technological measures - change of chemical technologies in industry, ventilation, hermetic sealing, automation, sewage disposal plants, etc.;

· Individual measures - overalls, gas masks, respirators, dietetic therapy.

 

 

Table 42

Remote and Specific Effects of Industrial Poisons and Pollutants of

the Environment

Remote effects	Specific effects
Oncogenous (cancerogenic)	Gonadotropic
Mutagenic	Allergenic
Teratogenic	Embryotropic
Decrease of life expectancy	Immunodepressive
Acceleration of organism ageing

Oncogenous (Cancerogenic) Effect

Chemical cancerogen is:

· substance or its admixture which can cause in man or animal the formation of tumors that are not encountered without its action (true cancerogens - the initiators);

· substance which can cause acceleration of formation or earlier occurrence of usual tumors (promoters – pre-cancerogens).

Classification of Cancerogens

(By International Agency of Cancerogenic Investigation)

v Cancerogenic for the man (there are 23 substances - arsenic, asbestos, chrome, beryllium, nickel, carbon black, petroleum, benzene, etc.— their cancerogenic effect on people is proved by the epidemiological data);

v Probably cancerogenic for the man:

Ø Probable cancerogens causing tumours in 80-100% of experimental animals during 4-6 month; they include 14 substances, such as benzpyrene, chlorine – organic combinations, etc.

Ø Possible cancerogens causing tumors in 20-30% of experimental animals during life; there are 47 substances, e.g. cadmium, nitrosocombinations, some pesticides.

v Not categorized by cancerogenic ability (data about cencerogenic activity are discordant) - 64 substances are included, for example, lead and its salts;

v Probably not cancerogenic for man – this group includes all other substances for which no data about cancerogenic effect have been obtained up to now.

Mutagenicity of Chemical Substances

Nowadays more than 600 substances are found out which have a mutagenic effect on the man or laboratory animals.

Classification of Chemical Mutagens

They are subdivided into:

· Natural - inorganic and organic substances encountered in the nature (mycotoxins, nitrogen oxide, nitrites, etc.);

· Anthropogenic - medicines, pesticides, food additives, etc.

· Investigation of mutagenic action of substancesis carried out in the following way:

· In experiments on cell systems - microbes, plants, hexapods, cells of the man and animal in experiments in vitro, in vivo;

· Cytogenetic monitoring of the population and people working in contact with mutagenic factors

· Biological indication of mutagens in biosphere (ecumene)

To prove mutagenicity of chemical substances for man 4 systems are used:

· Dotted mutations in microorganisms with a metabolic activation

· Dominant lethal mutations for mice

· Chromosome changes in bone marrow of mammalia

· Chromosome disturbances in human leucocytes

Embryotropic Action

Types of fetation disorders under the influence of chemical substances include the following:

· Embryotoxic action - destruction of fetus, decrease of mass and dimensions of embryo, disturbance of normal differentiation of tissues;

· Teratogenic action - anomalies and defects of a new-born development.

Now there is a new science in toxicology – chemical teratology studying teratogenicity of chemical substances for the man and animals, in biosphere.

The list of chemical teratogens includes more than 600 materials, such as hydrargyrum and its compunds, dioxines, pesticides, benzol, benzine, etc.

The evaluation of embryotoxicity is carried out in experiments on laboratory animals.

Parameters of Embryotoxic Action

· Common embryonal mortality

· Pre-implantation and post-implantation mortality

· Number of newborn laboratory animals

· Average mass and dimensions of embryos

Parameters of Teratogenic Action

· External and internal anomalies of development

· State of places of ossification

· Subdivision of newborn laboratory animals by sex.—

 

Lim sp. and Z sp. = Lim integr / Lim sp.

 

If Z sp. > 1, the material has a selective embryotropic action and this is taken into account at establishment of MPC.

Other Remote Effects of Chemical Substances

· Neuropsychic disorders at effect of phosphorus-organic combinations.

· Disturbance of hemopoiesis (anemia), cardiac dysfunctions (acceleration of infarctions, development of atherosclerosis) occur at effect of chlorine-organic combinations.

Toxicologic and Hygienic Characteristics of Basic Industrial Poisons

Irritating Substances (Chemical Substances of Primary Irritating Action)

To such poisons ammonia, oxides of nitrogen, sulfur, vapours of chloric, hydrochloric, nitric acid, CO2, CO, chlorine and its compounds refer.

These substances are widely used in industry and can frequently affect the working people.

The common features of their effect are: irritation of respiratory tract and eye mucous membranes. The effect depends on solubility in water; hence they are divided into highly soluble, e.g. chlorine, sulfurous gas, ammonia which are basically retained in the upper parts of the respiratory tract and cause chemical irritation or burns here, and less soluble, e.g. oxides of nitrogen which reach deep parts and can cause pulmonary edema.

Effect of chlorine. Chlorine is a yellow gas with a specific smell, 2.5 times heavier than air. Getting on mucous membranes, chlorine dissolves with the formation of hydrochloric acid and atomic oxygen producing an irritating effect on the lung tissue causing inflammation and sometimes addition of secondary infection.

Chlorine poisonings are more often of an acute form and have two stages:

· initial - irritation of the upper respiratory tract and mucous membranes;

· lung hypostasis – respiratory failure, increase of temperature, leucocytosis.

At chronic poisoning bronchitis, emphysema, pneumosclerosis, dermatitis and eczema on the skin occur.

Effect of ammonia.Its effect issimilar to that of poisoning with chlorine; there are severe damages at its entry into eyes and on skin.

Effect of nitrogen oxides and vapours of nitric acid.It is more often results in acute poisoning of 3 stages:

· initial - irritations,

· latent period – any symptoms are absent,

· increasing lung hypostasis.

In blood there may be the formation of methemoglobin resulting in hypoxia, disorders of CNS and vegetative NS.

Effect of CO2. It affects the respiratory center, causes hypoxia.

Effect of CO (carbonic oxide). CO is agas without color and smell formed at incomplete combustion of fuel in insufficiently ventilated premises. In blood it forms carboxyhemoglobin having scarlet color. Affinity of Hb to CO is 300 times higher than to O2. It causes scarlet spots on skin. It cannot transport oxygen in blood that leads to occurrence of hemic hypoxia. The direct effect of CO on tissue breathing in the CNS and internal organs is blockade of cytochrome oxidase.

Stages of acute poisoning are:

· initial - headache, disorders of the CNS;

· euphoria - aggravation of CNS damage;

· coma - loss of consciousness, suppression of reflexes, paralysis of the respiratory center.

In the remote period after poisoning with CO loss of memory, disorder of consciousness, affection of the CNS, etc., occur.

Poisonings by  Heavy Metals

To this group such metals as lead, tetraethyl lead, mercury, etc., belong.

Poisonings by lead. More than 100 occupations have contact with lead or its compounds. Poisonings are chronic, more often through inhalation. Pathogenesis - blockade of carbothiolic enzymes (containing SH-groups) and others. Mutagenic, gonado- and hepatotropic effect is produced. (See attachement 2 – pictures an the end of textbook)

The main symptoms of lead poisoningare the following:

· Lead border – a grey border at the edge of tooth gum due to sulphurous lead (lead is excreted with saliva and lead sulphide is formed in the mouth).

· Lead colour – a pale colouring of skin - angiospasm and increased content of porphyrin in blood.

Characteristic changes of lead poisoning in blood are:

· Reticulocytosis –increase of reticulocytes (over 15 per 10 thousand) in blood (irritation of hemopoietic organs).

· Basophilic erythrocytes in blood - irritation of hemopoietic organs.

Characteristic changes of lead poisoning in urine are:

· Porphyrinuria - more than 50-60 µg/l.

· The increased content of lead in urine - more than 0.04 mg/l.

Besides in symptomatology the following is marked:

· Affection of the nervous system - at the beginning the asthenic syndrome, then lead encephalopathy and polyneuritis.

· Changes in blood: at the beginning reticulocytosis and basophilic granularity of erythrocytes, then - anemia and decrease of Hb.

· Involvement of the gastrointestinal tract - dyspepsia, in severe cases – lead colic accompanied by severe pains in the stomach which are not controlled by spasmolytics.

· Liver injury - toxic hepatitis with disturbance of all its functions, bilirubinemia.

Poisonings by  Tetraethyl Lead (TEL)

Organic compounds of heavy metals are more toxic than elementary metals. TEL is used as an additive to gasoline to decrease detonation. Poisonings with TEL occur through inhalation and are very severe (TEL presents the 1 class of danger). They cause disturbances of the CNS - headache, asthenyc syndrome, euphoria, disorders of sleep, memory, suppression of CNS. Suppression of the vegetative NS results in vegetative triad: hypotonia, bradycardia (rare cardiac contractions), hypothermia. In severe cases there may be mental disorders and organic lesions of CNS.In years after poisoning the remote effects occur, such as astenization, emotional imbalance, decrease of intelligence.

Poisonings by  Mercury

More often they occur through inhalation (mercury vapours).Rather often asymptomatic course (the content in urine is 0.05 mg/l and over) and chronic poisonings by mercury are possible.

Symptoms of poisonings. First of all there is effect on the CNS. In Europe in the past there was a saying “as fool as a hat maker” because in the past at making hats mercury was widely used. It is marked by

· mercurial “border“on gingivas of black colour;

· mercurial neuroticism;

· mercurial erethism (psychological disorders in emotional sphere - whining, anxiety);

· mercurial encephalopathy;

· mercurial gingivitis (inflammation of the tongue), and stomatitis, gastritis, colitis;

· disturbances of the cardiac system (changes of electrocardiogram), kidneys (nephroses);

· in blood - lymphocytosis, monocytosis, leukopenia, anemia;

· content of hydrargyrum in urine is over 0.01-0.02 mg/l.

The organic compounds of mercury are more toxic, e.g. Minamata disease (poisoning with methyl mercury).