[The assessment of the occupational risk to workers in electric steel production]. / Otsenka na professionalniia risk na rabotnitsite ot elektrostomanodobiva.

These studies, centering on occupational environmental factors, biologic monitoring, and toxicodynamic investigations, involved a total of 105 workers distributed into eight job groups, who were 45 years, of age on the average and had from 5 to 10 years of special occupational experience at "Electrosteel" Works. Evidence was obtained for presence of unfavorable microclimate conditions, elevated equivalent levels of noise, excess of general and local vibrations, exposure to manganese aerosols, carbon monoxide, and nitrogen oxides; some of the subjects and deviations in hepatic status and connective tissue. Job groups found to be at risk were those of steel founders, crane workers, and pourers.

[The assessment of arsenic exposure in copper smelting]. / Otsenka na ekspozitsiiata na arsen v medodobivnoto proizvodstvo.

The arsenic exposure in the main departments and occupational groups of the copper smelter in Pirdop has been estimated in the present study. The contents of arsenic is measured in the air and in biological samples--urine and nails. At most of the workplaces the time-weighted average (TWA) concentrations do not exceed the threshold limit value (0.05 mg/m3). The maximum TWA level is about three times higher. The intake of arsenic is significantly increased in almost all observed occupational groups. However, the excretion of only 8% of the workers is higher than the maximum background level (100 micrograms/l). The estimated degree of exposure corresponds to a low health risk. Some of the most heavily exposed occupational groups may be expected to reach higher levels of intake and health risk.

[The toxic hygiene problems of workers in the Dinamik automobile tire plant in Sofia]. / Toksikokhigienni problemi pri raboteshtite v zavod za avtomobilni gumi "Dinamik"--Sofiia.

Toxic hygienic investigations were carried out involving a representative group of 131 workers (50 females and 81 males) distributed into three main workshops--preparatory, confection, and vulcanization--at "Dynamic" automobile tire plant in Sofia. The majority of male and female workers were in the age range beyond 40 years, having a general occupational experience in excess of 10 years and specialized occupational experience from 10 to 20 years or more. The chemical hazard was among the leading ones in the occupational environment, differing in nature according to the technologies used. Included were various chemical substances and compounds: synthetic rubbers, fillers (soot, chalk, kaolin); softeners (mazut, paraffin, etc.); accelerants (mercaptothiazoles--captax and altax); dithiocarbamates (thiuram); vulcacides (diphenylguanidine); antiwear agents (antioxidants and antiozonators-isopropyl-phenyl-paraphenylene diamine, naphthyl-beta-naphthylamine); antiaccelerants (phthalic anhydride, ets.); organic solvents and others. The indicated chemical substances and compounds, though often found at concentrations below the mean-shift MACs, do produce health impacts by virtue of prolonged and combined exposures. Use was made of the questionnaire method. Also, hematologic, clinical laboratory, and toxic chemical testing was performed. Findings pointed to changes in hemopoiesis, deviations in hepatic functional state, while sulfate and glucuronide values confirmed the workers' high exposures.

[The cytogenetic effects (the frequency of micronuclei) in lymphocyte cultures from the peripheral blood of workers in automobile tire manufacture]. / Tsitogenetichni (chestota na mikronukleusi) v limfotsitni kulturi ot periferna kruv na rabotnitsite ot proizvodstvoto na avtomobilni gumi.

At the Preparatory Workshop of the Plant for Automobile Tires (PAT), Sofia, complex investigations were undertaken to reveal possible genotoxic exposure. The studies included chemical analyses for levels of identifiable human carcinogens in the occupational ambient air (benz(a)pyrene, mineral oils, 2-naphthylamine); special techniques--questionnaire investigations and cytogenetic analysis by cytokinesis-block micronucleus method in peripheral lymphocyte cultures from 23 workers in occupational groups at risk; and urinalysis for contents of mercapturic acids. An out-of-house control group of 13 nonexposed subjects was concurrently investigated. For contents of benz(a)pyrene and mineral oils exceeding 2.5 to 3.5 times the respective occupational environment MACs, evidence from cytogenetic analysis showed substantial, 4-fold, increase in indexes of genotoxic impairment (frequency of micronucleated-binucleated lymphocytes, number of micronuclei per 1000 binucleated lymphocytes) in the workers investigated. These results are an indicator of genotoxic exposure and point to an increased potential risk of cancer development in the group of workers studied.

[Determining the occupational risk of skin diseases at the chemical plant "G. Genov" in Ruse]. / Opredeliane na profesionalniia risk ot zaboliavaniia na kozhata v niakoi proizvodstva na SKhK "G. Genov"--Ruse.

A study is performed on workers from some productions of a Chemical Plant--H-acid, phthalic anhydride, ferrum-oxidate dyes and lacquers, in view of estimating the occupational risk of skin diseases. It is established that the highest occupational risk of skin diseases to which workers are exposed is in the production "H-acid"--25.8%, followed by "Phthalic anhydride"--13.2% and "Ferrum-oxidate dyes"--13%. The epicutaneous test shows positivation of the samples with phthalic-anhydride in 20% of the examined. In those engaged in the production of ferrum-oxidate dyes positive tests are observed in 23.2% of the examined; the highest relative part is taken by the potassium--56.2% and the sodium-bichromate--37.5%. The study of immunoglobulin A, M and G in workers from the lacqueur shop proved the irritating effect of the noxae, and established statistical significant higher values of immunoglobulin "A". The study of some functional investigations--pH and alkaline resistance of the skin give no significant deviations, save single cases. The authors consider the necessity of technological improvement of the production processes in the production "H-acid" where the workers are exposed to the highest occupational risk of skin diseases.

[Epidemiological studies of the effect of organophosphate pesticides on health]. / Epidemiologichno izsledvane v'rkhu zdravnite effekti na fosfororganichnite pestitsidi.

The subject of study are agricultural workers applying organophosphorus and other pesticides in an area with intensive agriculture and a control group from the same area having no professional contact with pesticides. The studies include: personal and professional anamnesis, a battery of neurobehavioral tests, electroneuromyography, evoked potentials, neurological status, internal status, hematological tests, liver enzymes, variability of the heart rhythm. The level of the exposure is assessed by: measuring the concentration of PhO compounds in the air of the work environment and deposit on the skin. The biological monitoring is carried out by measuring the level of the cholinesterase activity in serum and erythrocytes, neuropathy target esterase in lymphocytes and alkylphosphates in urine. The tests are performed before and after the active season of spraying. The results from the studies show that at continuous exposure to low concentrations of organophosphorus compounds, applicated in agriculture, no significant health disorders occur. Specific deviations are observed after the season of spraying in the neuro-behavioural tests as increasing the number of incorrectly put dots in the Aiming test, the time of reaction and evoked potentials. The interpretation of the results is impeded because of the large number of interfering factors and considerable quantity of alcohol.

[The occupational risk in the manufacture of mineral pigments and iron oxide dyes]. / Profesionalen risk pri proizvodstvo na mineralni pigmenti i zhelezno-oksidni boi.

The mineral pigments and ferric oxide dyes are used on a large scale in the paint and varnish industry, in building, chemical industry, polygraphy etc. For their production as basic raw materials are used lead, chromium and iron compounds. The concentrations of the toxic and accummulating lead and chromium in the air of the work environment surpass MAC and create most frequently "especially unfavourable" conditions of work. In all industrial processes the leading unfavourable factor is the chemical combined with unfavourable physical factors and overstress on the locomotor system. Changes were established in the organism of examined workers as result from the chronic effect of the factors of the work environment of the peripheral blood, digestive, nervous system and the skin. In view of reducing the risk of exposure to the toxic chemical factor it is imposed to take measures for sanitation of the work environment.

[Experimental assessment of the risk for offspring in lead exposure]. / Eksperimentalno otseniavane na riska za pokoleniiata pri ekspozitsiia na olovo.

Multigenerational studies were carried out on albino rats obtained from parent progeny - female-intact and male-perorally exposed to lead acetate, in the drinking water - 0.2 mg/kg (group I) and 20 mg/kg (group II); the data were compared with a control group. Changes were found in each progeny as follows : in PI - reduced erythrocyte count, increased reticulocytes (group II); enhanced ATP activity in brain homogenates (group II), as will as increased disulphide groups in homogenates from brain, liver and testis (group II), highly reduced indices of fertility - 50% and of gestation - 62% (group II), in 100% level of the same indices in the control animals respectively. In P2 - reticulocytosis, reduced CytO in homogenates of liver, reduced activity of ATP and SucDH, enhanced activity of LDH and G6PDH in brain homogenates (group I), reduced fertility index - 67% versus 100% of the controls. In P3 - increased erythrocyte count (group II), changes in the electrophoretic protein profile of serum (group II); reduction of ChEA (groups I and II) and CytO (group II) in liver, reduced ChEA in brain (group II). The results obtained suggest an eventual high real and potential risk for the human generation, when the males are exposed to considerable concentrations (doses) of lead under working conditions.

Prenatal toxicity of xylene.

Prenatal inhalation toxicity of xylene (industrial mixture of isomers) was studied in experiments of white Wistar rats exposed daily (6 hours a day, 5 days in a week) to concentrations of 10, 50 (MAC for xylene in the air of work environment in Bulgaria) and 500 mg.m-3 throughout the period of gestation from the first to the 21st day. Both routine teratological indices and biochemical and physiological methods of observation were used to evaluate the integrity of the individual organs - liver, brain, lungs and myocardium of the generation in the postnatal period of development. In concentrations of 50 and 500 mg.m-3, xylene exhibits pronounced embryotoxic and teratogenic effects. Postimplantation embryonal mortality increases, the process of physical development of the fetus is delayed, the incidence of induced anomalies of internal organs (hydrocephalus, microphthalmia, intracerebral haematomas, haemorrhages in the liver) is enhanced, the processes of ossification of the sternum and the skull are impaired. In concentrations of 50 and 500 mg.m-3, xylene causes disturbances in postnatal development of F1 generation. The concentration of 50 mg.m-3 is the threshold of the embryotropic effect of the solvent. Measures for the protection of women at work are proposed to reduce industrial hazard of developing antenatal pathology in the newborn of workwomen in xylene works.

[Early behavioral and neurofunctional deviations following prenatal carbon disulfide exposure]. / Ranni povedencheski i nevrofunktsionalni otkloneniia sled prenatalna serovuglerodna espozitsiia.

The effect of prenatal carbon disulphide exposure with a concentration 10 and 0.33 mg/m3 is studied (MAC for a working zone and atmospheric air resp.) upon the behavioural and neurofunctional development of the generation. A neurotoxicological screening was employed for the assessment of the early postnatal development. It was established that carbon disulphide with a MAC level of the working zone, disturbed the postnatal development without inducing congenital malformations, inducing buit sensory, neurofunctional and behavioural deviations. The results stress upon the high sensitivity of the central nervous system of the growing fetus to carbon disulphide and confirm the expedience of the utilization of neurobehavioural testing as a sensitive method for detecting of sequelae of the effect of prenatal stress with low intensity.

[Effect of the intermittent and continuous action of dimethylformamide on adaptation processes]. / Vliianie na intermitentnoto i monotonno deistvie na dimetilformamida vurkhu protsesite na adaptatsiia.

Two series of experiments were carried out with 960 mg/kg and 3840 mg/kg DMF, applied dermally to albino rats every second, third day and daily as well. The treatment scheme quarantees equitoxic quantities of DMF with a dynamic observation by the 4th, 8th, 14th and 28th day from the beginning of the exposure and after 14 days of rehabilitation. The complex investigation with integral and specific clinical-laboratory tests revealed a cumulation of the toxic effect with progressing changes in the liver function, better manifested with the intermittent regimes. The dose of 3840 mg/kg induced distinct deviations in the lipid metabolism and serum enzymes. In contact with 960 mg/kg DMF, a phase-state was established during the first terms of observation with the development of adaptation under a monotonous effect and absence of restoration -- mainly in case of intermittent effect. Dermal toxicity of DMF should be given consideration in the assessment of the risk from exposure during production of polyacryl fibres.

[Assessment of the potential risk for progeny in work with endodan (experimental studies)]. / Otsenka na potentsialniia risk za pokolenieto pri rabota s endodan (eksperimentalni prouchvaniia).

An experimental assessment was made on endodan (ETM) effect, dithiocarbamate preparation, on the reproductive function of the parent generation albino rats, perorally intoxicated (by a sound) with doses 1/10 and 1/100 LD50, daily in the course of 6 months (LD50 = 380 mg/kg). The postnatal development of the three successive generations (F1, F2, F3) was studied. For that purpose, a complex of integral toxicological methods was used: weight, neurobehavioural activity, nortality (by 1st, 5th, 21st day), with the calculation of the indices of survival and lactation, and fertility with calculation of the indices of fertility and gestation and biochemical and clinical laboratory methods for the assessment of the functional state of liver, brain and testes. The embryotoxic and teratogenic activity of endodan was assessed with a single (175 and 70 mg/kg, administered on the 9th, 11th and 13th day) and repeated (daily 70 and 35 mg/kg) peroral administration in the course of gestation. The routine teratological methods were used: number of yellow bodies, number of implantation with resorption autolysis and living fetuses, structural anomalies; assessment of the state of the internal organs (Wilson) and the skeletal system (Dowson). A test for dominant lethality was used for the evaluation of the mutagenic effect, under the conditions of subacute experiment. As a result a light gonadotropic effect was found (single deviations in the early postnatal development of the progeny, light teratogenic and mutagenic activity). The authors drew conclusions concerning the relatively higher perspectives of that dithiocarbamate preparation for the practice as regards the potential risk of the population. Consideration given to its higher dermal toxicity and cumulation effect, confirmed with the previous investigations and the total toxicological characteristic of dithiocarbamate, they stressed upon the necessity of the strictest observation of the hygienic standards and rules of safe work.

[Effect of dimethylformamide on the health status of workers]. / Vliianie na dimetilformamida vurkhu zdravoslovnoto sustoianie na rabotnitsi.

Results are reported of the clinical examination and some laboratory tests performed in a group of workers, employed in the production of polyacrylnitryl fibers "Bulana" at the oil- processing and chemical works in Burgas, who have been exposed for 3 to 5 years to dimethylformamide (DMF). DMF concentrations in the air of the work environment were within the threshold ones, or exceeded them from 3 to 6 times. The most common constitutional symptoms were: fatigue, weakness, numbness of the extremities, eye and throat irritation. The results of physical examination were comparatively scanty. In spite of careful search, liver function and hemopoiesis were normal, neither were significant arterial pressure variations observed. These data will be used as baseline for comparison in a furture study of the technological staff, working in contact with DMF.

[Comparative study of the changes in the EEG and cholinesterase activity in experimental Dipterex poisoning]. / Sravnitelno izsledvane na promenite v EEG i kholinesteraznata aktivnost pri eksperimentalna intoksikatsiia s diptereks.

A systematic study is conducted on cats, poisoned with the organophosphorus insecticide Dipterex. The changes in spontaneous and induced cortical activity along with those in serum and erythrocyte cholinesterase after intraperitoneal and intramuscular injection of Dipterex are investigated. Against the background of lowered cholinesterase activity, recorded in all the experiments , the changes in EEG appear to be discrete and inconstant. Uron single treatment with Dipterex, desynchronization prevails in the spontaneous EEG, whereas in the responses induced by light stimulants an increase of delayed negative potentiale prevails. Upon repeated Dipterex introduction, theta-like waves appear, associated with activation of paroxysmal manifestations existing in advance. Finally, the correlation between changes in cholinesterase activity and EEG is discussed.