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Thirty workers were hospitalised after clinical and laboratory screening of 65 women and 35 men from electrical lamp factory. The mercury concentration in air of the working places varied from normal value (0.01 mg/m3) to 0.04-0.05 mg/m3. Target neurological anamnesis, internal and neurological examination, EEG, renal function tests and several laboratory parameters of large extent were carried out. The analysis of results establishes the signs of micromercurialism in 20% of the examinees. The authors determine the peculiar clinical (neurasthenic syndrome, periodontal diseases ) and biochemical (blood Hg level and urinary mercury) parameters of this early, functional stage of the chronic Hg poisoning.

Examination are carried out on 64 school children Ist class from school "104", town of Sofia where computer training on mathematics and mother tongue is introduced in the frames of pedagogic experiment. The studies are performed parallelly at traditional and computer lessons, realized in two variants (with one and two school hours daily). In order to establish the functional status of the visual analyzer during computer training the following methods are used: studying the distance of the nearest point for clear vision (punctum proximum), stability of clear vision, threshold of the electric eye sensitivity, critical frequency of fusing of the light flickerings. A full preliminary ophthalmological examination is made by "Vision test", as well as chronometric control of each student to establish the real time of work with computers. Taken into consideration are also the data for illumination of the working places in the computer studies and class rooms where the traditional school hours are held. The analysis of the data received shows that the computer training (1 and 2 computer lessons daily) with schoolchildren, Ist class, has no unfavourable effect on the functional status of the visual analyzer in the limits of study hours up to 25 minutes.

A study is carried out on 64 first grade school children for establishing the effect of computer training on the functional status of principally engaged systems with the purpose to determine the optimum duration of work with video terminal during the school day. The examinations are performed before and after computer lessons in mathematics and Bulgarian language in days with one and two lessons, and with the same subjects taught in the traditional way (control group). Traced are the changes in the accommodation, the eye rheobase, critical frequency of fusing the light flickers, resistance, volume and accuracy of the visual perception, static tremor and excretion of sodium and potassium in the saliva. The data point out to relatively higher pressure at work on video terminal in comparison with the traditional education. This imposes restriction in the duration of the lesson up to 20 minutes. The inclusion of second inconsistent computer lessons in the educational programme has no unfavourable effect on the functional status of the organism.

Examinations were performed on the nervous system (directed anamnesis, neurological and vegetative status) of workers from enterprises for economic melioration and erosion control. The following was established: presence of vegetative vascular disturbances in the upper extremities, radicular syndromes, neurosis-like [correction of neurosimilar] syndrome, with higher frequency at the exposure of vibrations in comparison to nonexposed workers; in conditions of vibrations and noise above the norms work persons, with organic disturbances of the nervous system, which certifies for the nonobservance of the medical contraindications and for necessity of special control on these workers.

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.