Neurotoxic effects in workers of the clinical thermometer manufacture plant

OBJECTIVES

Occupational exposure to mercury can induce adverse health effects, and the central nervous system is the major target of its toxic action. This problem especially arises in plants involved in the manufacture of mercury-containing products, where an appropriate protection against mercury exposure is not ensured. The aim of this study was to assess health effects of mercury, especially neurotoxic effects and oral disorders, in workers employed in a clinical thermometer manufacture plant and to determine mercury concentrations in the workplace ambient air.

MATERIALS AND METHODS

The study population comprised 143 workers, including 51 (35.7%) men and 92 (64.3%) women employed in the plant. Mean age in the whole group was 29 years (range, 18-55 years). It was divided into three groups: control, mercury absorption and mercury poisoning. A questionnaire-based interview was used to collect data on medical history, occupational exposure and employment. For clinical diagnosis, all subjects underwent physical, neurological and oral examinations. Mercury concentrations in the air were recorded by Hg monitoring instrument and mercury levels in collected urine samples were determined by cold vapor atomic absorption spectrophotometry.

RESULTS

Neurasthenic symptoms were found in 51.75% of the subjects, emotional changes in 27.27%, tremors in 11.19%, and inflammations in 21.68%. The case percentage of neurological symptoms in the control and mercury absorption groups did not show significant difference, but it was significantly higher in the mercury poisoning group.

CONCLUSIONS

The high occupational exposure to mercury, found in the plant and evidenced by urinary Hg concentration > or = 0.05 mg/l, can result in chronic quantitative neurotoxic effects and qualitative health changes. Therefore, constant monitoring of the work environment and checking of workers' health status should be ensured. In addition, appropriate steps should be taken to improve work conditions and promote health among the employees.

[Psychoemotional disorders in those working with epoxy compounds]

Psychoemotional status was studied in 125 female workers 21 to 50 years old having been exposed to epoxide resins and their compounds for 5 to 25 years. We undertook to carry out multifactor questionnaire survey together with pathopsychological testing, and determining levels of personal constitutional and reactive anxiety. Occupation-related neurotic disorders (neurasthenic-, obsessive and phobic-, and, to a lesser extent, hysterical type manifestations) were found out to develop during the stage of prenosologic forms against the background of high level of both constitutional and reactive anxiety. It is psychoconstitutional traits of workers being predisposing factors for the disorders in question that affect the epoxide-related origination and development of psychoemotional derangement. The following traits can be regarded as predisposing factors for derangement: excitability, bias towards anxiety, deestiming, demonstrable behaviour.

Alterations in heart rate and pupillary response in persons with organic solvent exposure

Cardiac and pupillary reactivity were examined in 25 persons with a history of exposure to organic solvents and 19 nonexposed controls during performance of a counting and a choice reaction task. The solvent-exposed group demonstrated an atypical pattern of responding across tasks. While control subjects showed a decline in heart rate across the two conditions (e.g., habituation), exposed persons had an increase in heart rate. Initial pupil diameter was similar for both groups, but only the control subjects exhibited habituation across the two tasks. In the exposed group, higher heart rate was not associated with higher levels of self-reported anxiety. Anticipatory cardiac deceleration preceding unpredictable events was significantly less in the exposed group, but there were no significant group differences on poststimulus acceleration. The results suggest that persons with solvent exposure have a deficiency in the allocation of attention (reduced anticipatory deceleration and decreased pupillary dilation). It is further suggested that difficulty in the allocation of attention produces an increase in tonic sympathetic levels when confronted with a cognitively challenging task. In this experiment, in which the choice reaction task was purposely presented last, and was apparently more challenging for exposed persons, a failure to exhibit autonomic habituation over the course of the session characterized the solvent-exposed group.

Neurasthenic fatigue, chemical sensitivity and GABAa receptor toxins

Following observation of fatigue syndromes in people who have been occupationally exposed to pesticides and insecticides which exert their toxicity through the GABAa receptor, we have formulated the hypothesis that fatigue syndromes in general may be secondary to altered sensitivity of the GABAa receptor. We discuss the possible involvement of organochlorine compounds which are widespread in the environment. Organophosphate compounds may have similar toxic effects through damaged cholinergic input to the dentate gyrus of the hippocampus where cholinergic and GABAergic transmission are closely linked.

[Health effects on workers exposed to low concentration carbon monoxide at high altitude]

Workers exposed to carbon monoxide (CO) at a concentration of 26.8mg/m3 at an altitude of 2,300 metres above sea level were compared with a control group of local inhabitants. There were significant differences in symptoms of headache, vertige fatigue and weakness memory impairment, insomnia, palpitation and neurobehavioral functions. CO concentration in respiratory air and HbCO in blood was higher but partial pressure of oxygen (PO2) and saturation of oxygen (SaO2) in blood was lower in the exposed group than the control group. Self-comparison of CO in respiratory air and HbCO in blood was higher after work than before work. Neurasthenia rate was significantly higher but PO2 and SaO2 significantly lower at high altitude than in the plain. The results indicated that under same CO concentrations the hazards to workers at high altitude were greater than to those working in the plain. The author recommends that at high altitude the CO permissible level should be appropriately lowered.

Dose-related subclinical neurobehavioral effects of chronic exposure to low levels of organic solvents

One hundred eight-seven workers (mean age +/- SD; 42 +/- 8.8 years) in two paint manufacturing plants were examined to determine if sustained low-level exposure to mixed organic solvents resulted in the painters' syndrome (a psycho-organic syndrome). The test battery consisted of a medical and occupational questionnaire, the Present State Examination, the Zung Depression Scale, the Scandinavian Questionnaire 16, a neuropsychological battery, and vibration thresholds. Solvent exposure, expressed as total hydrocarbon of combined selected solvents, was quantitated using 13-15 years of personal breathing zone samplings. Linear regression analysis controlling for several confounding variables demonstrated significant correlations between increasing exposure to mixed organic solvents and neurobehavioral performance for vibration threshold and several neuropsychological tests. Dose-related effects of chronic solvent exposure on neurobehavioral outcomes (all subclinical) were shown, but "typical" symptoms characteristic of the painter's syndrome were not found.

Neuropsychiatric effects of low exposure to styrene

Workers exposed to styrene concentrations of about 50 mg/m3 at a plant manufacturing reinforced polyester boats were examined for neuropsychiatric symptoms both in close connection with exposure and also seven months after exposure had ceased. Physical workload is important for the uptake of styrene and was about 50 W at this plant. On the first occasion, after one week with no exposure, the workers reported a high frequency of neuropsychiatric symptoms such as fatigue, irritation, and forgetfulness whereas seven months later the frequency of these symptoms was low. These observations indicate that exposure to styrene at about 50 mg/m3 may induce reversible neuraesthenic symptoms. Even the relatively low Swedish standard (110 mg/m3 = 25 ppm) may, therefore, need revising.

Do Vietnam veterans suffer from toxic neurasthenia?

This paper evaluates the claim that Vietnam veterans with psychiatric disorders are suffering from toxic neurasthenia--a neurasthenic syndrome caused by exposure to pesticides while serving in Vietnam.

Psychiatric and neurological symptoms in workers occupationally exposed to organic solvents--results of a differential epidemiological study

It is accepted knowledge today that repeated intoxication with organic solvents damages the central nervous system and causes persistent psycho-organic symptoms. That long-term but low-level occupational exposure--typical o painters and other blue-collar workers--can also induce such disorders has not generally been recognized. The present epidemiological study was undertaken to evaluate the possible neuropsychiatric effects of such exposure. 80 laquerers exposed to a mixture of industrial solvents (average hygienic effect 0.3) and 37 printers exposed almost only to toluene (average hygienic effect 1.0) were compared with a control group of 80 age-matched non-exposed subjects. In psychiatric interviews, the painters showed more mental symptoms. Fatigue, nervousness and lack of manual dexterity were most important and formed a typical neurasthenic syndrome. A general decrease in conduction velocity and action potential amplitude was also observed for the peripheral nerves. The printers showed a large decrease of the nerve action potential amplitude only for the sural nerve. No EEG abnormalities were found. Nor could any increase in mental symptoms be detected through psychiatric interviews compared to the controls. The results are interpreted as evidence for a CNS affection with consequent neuropsychiatric signs and symptoms after long-term occupational exposure to mixtures of industrial solvents below the current threshold limit values (TLV) but not after exposure to a single substance like toluene at about the TLV. The differential effects may be explained by synergistic amplification of the toxicity of solvent mixtures.

Effects on the regional cerebral blood flow of long-term exposure to organic solvents

Regional cerebral blood flow (rCBF, 133Xe inhalation method) was measured in 50 male paint-factory workers with a mean of 18 years of exposure to a mixture of organic solvents. A group of 50 workers in a sugar-refinery, matched for age and education, served as controls. The measurements were made during resting and during activation by mental tasks (4%; P less than 0.05) in the exposed group. Largest differences were seen in frontotemporal areas. The difference between the exposed group and and controls increased at higher dose levels. The largest rCBF-increases during mental activation were seen in the exposed group, especially in the highest exposed subjects. This finding might indicate mechanisms compensating for a somewhat defective brain function. Although the differences between the groups were generally small with considerable overlap, the results give some evidence of disturbances of brain blood flow and brain function likely related to the influence of organic solvents.

Neuropsychiatric symptoms in workers occupationally exposed to jet fuel--a combined epidemiological and casuistic study

Some aircraft personel and airline industry workers are exposed to jet fuel, a mixture of aliphatic hydrocarbons (petroleum 80%) and some organic solvents (petroleum 80%) and some organic solvents (aromatic hydrocarbons 20%). In order to evaluate the possible neuropsychiatric sequeale of such long-term occupational exposure, we examined 30 workers exposed at about 250 mg/m3 for 4-32 years at a jet motor factory. They were compared with two control groups (2 x 30) of matched non-exposed workers. The medical history was first assessed by standardized interviews and examination of medical records kept by the factory physician. The exposed subjects had, after their employment, much more often sought medical advice because of emotional dysfunctions, such as depression and anxiety, than had the control groups (P less than 0.005). When the prevalent mental symptoms, indicative of brain lesion, later were rated by psychiatrists, the exposed workers scored higher than did the controls (P less than 0.001). 14 subjects showing most symptoms were then selected for a thorough neuropsychiatric clinical investigation comprising psychosocial inquiries, psychological testing, personality assessment and neurological/neurophysiological examination. Seven were judged to suffer from mild organic brain syndrome (i.e. "organic neurasthenia") of which one subject was a severe case. The subjects had all undergone a slow but steady personality change over the years--starting from an ordinary strength without neurotic traits and moving towards an asthenic state with fatigue, anxiety and vegetative hyperreactivity. No other cause for this change could be identified as an alternative to the occupational exposure to jet fuel. It is concluded that personality changes and emotional dysfunctions are the foremost effects of such long-term exposure to petroleum products.

Neurasthenic symptoms in workers occupationally exposed to jet fuel

Long-term exposure to petroleum distillation products (e.g. jet fuel) has been suggested to cause chronic mental and neurological symptoms. In the present "cross-sectional epidemiological study" the extent of neuropsychiatric ill-health in 30 workers exposed to jet fuel was compared with that in 60 non-exposed matched controls. Standardized medical interviews showed a higher occurrence of neurasthenic symptoms in exposed subjects (P less than 0.001). The result was confirmed by examination of the medical records kept by the factory physician (P less than 0.01). The prevalence of psychiatric symptoms was assessed with a rating scale of 37 items (a modified CPRS). Again, the exposed workers scored higher than the controls (P less than 0.001), particularly regarding the neurasthenic symptoms, i.e. fatigue, anxiety, mood changes, memory difficulties, and various psychosomatic symptoms (P less than 0.01). The results could neither be explained by observer's bias, nor by a greater susceptibility for mental disorders in the exposed subjects. We therefore conclude that occupational exposure to jet fuel vapours around the present threshold limit values may induce a neurasthenic syndrome.

[Beta blockaders and general pathology]

The authors review the literature on the undesirable side effects of beta blockaders (excluding the cardiovascular system) and report the new therapeutic propects in psychiatry and in various metabolic disorders. The necessity of sufficient follow up made us choose propanolol as reference product without neglecting acebutolol, pindolol and oxprenolol.

Long-term exposure to jet fuel: an investigation on occupationally exposed workers with special reference to the nervous system

In the present study the results of a neurological and neurophysiological health examination of 29 aircraft factory workers chronically exposed to jet fuel vapors are presented. The exposed subjects were classified into a heavily exposed and a less heavily exposed group. The examination included a standardized clinical neurological examination, measurements of the conduction velocities in the peripheral nerves, and threshold determinations of vibratory sensations in the extremities. All 13 persons examined in the heavily exposed group and 7 of the 16 in the less heavily exposed group stated that they had repeatedly experienced acute effects (dizziness, respiratory tract symptoms, heart palpitations, a feeling of pressure on the chest, nausea, headache) of the jet fuel vapors in the inhaled air. A high rate of symptoms indicative of neurasthenia and psychasthenia and symptoms and signs indicative of polyneuropathy was observed both in the heavily exposed group and in the two groups combined in comparison with reference groups. Considering the presented facts concerning (a) the acute effects on repeated occasions, (b) the high rates of symptoms indicative of neurasthenia and psychasthenia and symptoms and signs indicative of polyneuropathy, and (c) the differences in the observations made between the two groups with varying degrees of exposure to jet fuel, the authors interpreted the results as indicative of a possible effect of long-term exposure to jet fuel on the nervous system.