Assessment of intracranial translucency (IT) in the detection of spina bifida at the 11-13-week scan.

OBJECTIVE: Prenatal diagnosis of open spina bifida is carried out by ultrasound examination in the second trimester of pregnancy. The diagnosis is suspected by the presence of a 'lemon-shaped' head and a 'banana-shaped' cerebellum, thought to be consequences of caudal displacement of the hindbrain. The aim of the study was to determine whether in fetuses with spina bifida this displacement of the brain is evident from the first trimester of pregnancy. METHODS: In women undergoing routine ultrasound examination at 11-13 weeks' gestation as part of screening for chromosomal abnormalities, a mid-sagittal view of the fetal face was obtained to measure nuchal translucency thickness and assess the nasal bone. In this view the fourth ventricle, which presents as an intracranial translucency (IT) between the brain stem and choroid plexus, is easily visible. We measured the anteroposterior diameter of the fourth ventricle in 200 normal fetuses and in four fetuses with spina bifida. RESULTS: In the normal fetuses the fourth ventricle was always visible and the median anteroposterior diameter increased from 1.5 mm at a crown-rump length (CRL) of 45 mm to 2.5 mm at a CRL of 84 mm. In the four fetuses with spina bifida the ventricle was compressed by the caudally displaced hindbrain and no IT could be seen. CONCLUSION: The mid-sagittal view of the face as routinely used in screening for chromosomal defects can also be used for early detection of open spina bifida.

[Dust exposure and cancer risk associated with amphibolite mining and processing]. / Narazenie na pyl oraz ryzyko nowotworowe zwiazane z wydobyciem i przerobem amfibolitu.

Mining and processing of amphibolite is associated with workers' exposure to dust containing asbestos minerals (actinolite, tremolite) and with the presence of respirable fibers, i.e. small particles above 5 microns long and below 3 microns in diameter (with length-to-diameter ratio higher than 3:1). Results of epidemiological and laboratory studies show that such dust may be responsible for the development of cancer in dust-exposed people. This work reports the measurement results of concentrations of total dust, respirable fibers and mineral composition of samples collected in plant mining and processing amphibolite rock. Based on the results, cumulated exposure was calculated for the 10-, 20- and 30-year exposure periods. The cumulated exposure was classified into two categories: 0.1-1.0 f/cm3 years and 1.0-10 f/cm3. x years. It has been found that mining and processing of amphibolite is associated with increased risk of death from mesothelioma--11.2 x 10(-5) (crushers--10 years of exposure) to 240.0 x 10(-5) (miners--30 years of exposure). The risk of excessive mortality from lung cancer was not high (below 1. x 10(-4)) for all workplaces and periods of exposure.

[Chrysotile asbestos: biological effects, the work environment highest allowable concentration and neoplasm risk]. / Azbest chryzotylowy--dzialanie biologiczne, najwyzsze dopuszczalne stezenia w srodowisku pracy I ryzyko nowotworowe.

The authors present the most essential data on physical and chemical properties of chrysotile, sources of its emission, the extent of occupational exposure, and biological effect, used in setting MAC values for chrysotile-containing dusts. Exploitable asbestos deposits do not exist in Poland, but admixtures of asbestos minerals have been found in some deposits of mineral raw materials located in the area of Lower Silesia (melafir, gabbro, dolomite. ore, nickel, magnesite, serpentinite). In the 1970s, about 100,000 tonnes of asbestos, containing 90% of chrysotile, were used annually in Poland. This figure decreased to 30,000 tonnes in 1991. In 1985 the use of crocidolite asbestos was stopped, and in 1999, the use of asbestos-containing products was banned by the virtue of the legal act. At present, the Minister of Economy in agreement with the Minister of Environmental Protection sets regularly the list of asbestos-containing products permitted for the production or in the customs area. Nowadays, the range of dust concentrations in plants which use asbestos products amounts to 0.1-0.6 mg/m3 for total dust and 0.002-0.07 f/cm3 for respirable mineral fibres; and during exploitation of rock raw material deposits 0.7-280 mg/m3, and 0.01-3.3 f/cm3, respectively. During the years 1976-96, 1520 cases of asbestos-related occupational diseases were diagnosed. This figure included 1314 cases of asbestosis, 154 cases of lung cancer and 52 cases of pleura mesothelioma. MAC values for chrysotile and chrysotile-containing dusts are: 0.2 f/cm3 and 1 mg/m3.

[Influence of the degree of carbohydrate metabolism imbalance in gestational diabetes on pregnancy and newborns condition]. / Wplyw stopnia nasilenia zaburzen metabolizmu weglowodanów w momencie rozpoznania cukrzycy ciazowej na przebieg ciazy i stan noworodków.

UNLABELLED: The aim of our study was the evaluation of the correlation between carbohydrate metabolism imbalance at the moment of gestational diabetes mellitus (GDM) diagnosis and regulation of glycemia during pregnancy, pregnancy complications, time and mode of delivery and conditions of the newborns. MATERIAL: 231 women with GDM delivered in our hospital between 1993-1996 were investigated. This population was divided into 6 groups, according to glycemia levels. METHOD: The term of diagnosis of the GDM, medical treatment (diet or diet and insulin), the degree of metabolic regulation archived, mode and time of delivery, as well as state of newborns were analysed. RESULTS: In groups I and VI we noticed the greatest percentage of patients treated with insulin (68%, 67%), versus 26% in group II and 17% in group III. In group VI in all cases treated with insulin we begun this therapy shortly after marking GDM. Glycemia in 24 hrs period after GDM diagnosis in group I were 122.7 +/- 28.6 mg/dl, in group VI 112.0 +/- 23.6 mg/dl, while we noticed 90.3 +/- 15.6 mg/dl in group II and 87.7 +/- 15.9 mg/dl in group III. Blood glucose level < 100 mg/dl in first determination of 24 hrs profiles we noticed in 5% in group I, 2% in group VI while 20% in group II and 51% in group III. Average levels of glycemia in last 24 hrs profiles before delivery in group I were 93.0 +/- 15.8 mg/dl, in group VI 96.2 +/- 21.1 mg/dl while 87.8 +/- 13.5 mg/dl in group II and 86.8 +/- 14.1 mg/dl in group III. Blood glucose level < 100 mg/dl of daily profile before the end of pregnancy was discovered in 8% in group I, 47% in group III. The greatest amount of complications (pregnancy induced hypertension and imminent premature delivery) was diagnosed in group VI-75% and in group III-55%. Surgical delivery took place in group I in 50%, in group V in 46%, in group VI in 67% while 17% in group II, 35% in group III and 30% in group IV. Macrosomy of newborns (> 4000 g) was diagnosed in group I in 36% in group V in 23% and in group VI in 42% while 9%, 6% and 15% in groups, II, III and IV respectively. The condition of newborns in the 1st minute of life was determined as good (8-10 points in Apgar scale) in significant percentage, in 87%, 75%, 70% in groups II, III, IV while only 59%, 62%, 58% in groups I, V, VI respectively. CONCLUSION: Serious intensification of carbohydrates metabolism disorders at the moment of diagnosing GDM, such as fasting glycemia > 140 mg/dl and the result after 2 hours > 200 mg/dl in 75 g OGTT more often requires insulin treating connect with numerous difficulties both in pregnancy monitoring and also has inadventageous influence on obstetrics outcomes-increasing percentage of surgery deliveries and macrosomies, that change the condition of newborns for worse.

[Silicon carbide, occupational exposure, proposed MAC values]. / Weglik krzemu, narazenie zawodowe, propozycje NDS.

Occupational exposure to dust silicon carbide production and exploitation of its products was evaluated. Individual dosimetry was used to measure concentrations of total and respirable dusts; concentration of respirable mineral fibres was measured by means of light microscopy; the distribution of fiber length was analysed by employing a laser FM-7400; morphology of dust molecules was analysed in light and electron microscopes; x-ray diffraction and infrared spectrometry was used to identify dust mineral composition. Concentrations of total dust at workposts involved in silicon carbide production ranged between 5.0 and 14.0 mg/m3 (mean = 10.3 mg/m3); concentration of respirable fraction between 0.1 and 1.9 mg/m3 (mean = 1.1 mg/m3); and concentration of respirable mineral fibres between 0.42 and 1.04 f/cm3 (mean = 0.64 f/cm3). In the plants where SiC products were used the mean concentrations of total dust and respirable mineral fibres were about two times lower, and the concentrations of respirable fraction about five times lower. In the workpost air the presence of carborundum, mullite and cristobalite was revealed. A proposed MAC value for SiC dust (nonfibrous) containing less than 2% of free crystalline silica accounts for 10 mg/m3 for total dust.

[Refractory ceramic fibers, kinds, health effects after exposure, TLVs]. / Ogniotrwale wlókna ceramiczne, rodzaje, skutki zdrowotne ekspozycji, NDS.

Ceramic fibres are amorphous or crystalline synthetic mineral fibres which are characterised by refractory properties (i.c. stability in temperature above 1000 degrees C). In general, ceramic fibres are produced from aluminium oxide, silicon oxide and other metal oxides and less frequently from non-oxide materials such as silicon carbide, silicon nitride and boron nitride. In Poland, the production of ceramic fibres was begun in the Refractory Materials Plant, Skawina, during mid-eighties. The production capacity accounts for about 600 tons annually. It is estimated that approximately 3000 persons are exposed to the effect of ceramic fibres in Poland. During the production of ceramic fibres, concentrations of respiral fibres in the air at work places range from 0.07 to 0.27 f/cm3; during the manufacture of ceramic fibre products from 0.23 to 0.71 f/cm3 and during the application of ceramic fibre products from 0.07 to 1.67 f/cm3. As published data depict, fibres longer than 5 microns are most common in the work environment, and the proportion of fibres with diameters below 1 micron accounts for 40-50%. Bearing in mind the present situation in Poland, namely combined exposure to asbestos (during removal of worn out heat-insulating materials) and ceramic fibres (during installation of new insulation), as well as in view of own investigations and literature data which evidence a strong carcinogenic effect of certain fibres, the following MAC values have been adopted: Dusts of refractory ceramic fibres: total dust-2 mg/m3; respirable fibres-1 f/cm3 (L > 5 microns; D < 3 microns; L: D < 3:1) Dusts of reflactory ceramic fibres mixed with asbestos: total dust-1 mg/m3; respirable fibres-1 f/m3. Dusts of refractory ceramic fibres mixed with other man-made mineral fibres (MMMF): total dust-2 mg/m3; respirable fibres-1 f/m3. According to the IARC, ceramic fibres have been included into group 2B-suspected human carcinogen.

[Exposure to dust mixtures containing free crystalline silica and mineral fibers]. / Ocena narazenia na pyly stanowiace mieszanine wolnej krystalicznej drzemionki I wlókien mineralnych.

Exposure to dust mixture containing at the same time respirable mineral fibres and free crystalline silica may occur in Poland in mines and in the Lower Silesia plants processing mineral raw materials as well as in all plants which use asbestos products and MMMF. Workposts where thermal insulation is exchange with possible phase transformations during operations under conditions of high temperature, expose particularly complex problems. In the work environment of this kind, dust concentration of free crystalline silica becomes important but not sufficient criterion for evaluating working conditions and it may be misleading. A range of studies indispensable for the proper evaluation of exposure to dust, covering together with measurement of dust and SiO2 concentrations, determination of the mineral composition of dust, was developed. It was also found that the acceptable level of risk for neoplastic disease, namely 10(-3) can be attained in the work environment only if the concentration ranges from 0.05 to 0.1 f/cm3, that is equal to 20% of MAC value which is now binding in Poland. Cancer risk (lung cancer and mesothelioma jointly) during a 20-year exposure to concentrations equal to present MAC values should be estimated as about 10(-2) what indicates that risk is too high and it is necessary to diminish MAC values for asbestos dust.

[Amorphous silica. Types, health effects of exposure, NDS]. / Krzemionki bezpostaciowe. Rodzaje, skutki zdrowotne ekspozycji, NDS.

Maximum allowable concentration (MAC) values for amorphous silica dust have not been identified in the Polish legal regulations up-to-date. In this work the authors review values of allowable (recommended) amorphous silica dust concentrations in other countries. Data on other types of amorphous silica (natural and synthetic) used in industry as well as data on health effects of exposure to these types of dust are presented. The work encompasses 42 entries in the references and one Table which includes the following proposed MAC values: Non-calcinate diatomaceous earth (diatomite) and synthetic silica: Total dust--10 mg/m3 Respirable dust--2 mg/m3 Calcinate diatomaceous earth (diatomite) and fused silica (vitreous silica): Total dust--2 mg/m3 Respirable dust--1 mg/m3.

[Exposure to mineral fibers in selected ceramics plants]. / Narazenie na wlókna mineralne w wybranych zakladach ceramicznych.

The aim of the work was to check, in the selected ceramic plants, whether the replacement of asbestos heat-insulating material by mixed material or fibrous material free from asbestos decreased the risk of exposure to mineral fibre dust among workers engaged in the overhaul of furnace trucks and ceramic furnaces. In the 6 selected plants which used various heat-insulating materials, dust concentration was measured (personal dosimetry), composition of mineral dust, collected from air at overhaul posts, was identified (RTG and IR methods), and morphology of dust particles was examined (optic microscopy and TEM). The highest concentration of respirable mineral fibres was found during the overhaul of a truck with asbestos insulation; respirable fibre concentration reached the value of 5 f/cm3, and total dust concentration-the value of about 80 mg/m3. Insulating plates made of asbestos paper-board proved to be the major source of the mineral fibre emission; mean weighted dust concentration in the plants under study ranged from 2.0 to 2.7 f/cm3. The replacement of asbestos plates by plates made of other heat-insulating materials have lowered respirable mineral fibre dust concentration by ten times. In dust samples collected from the air at the overhaul workposts, the presence of chrysotile, forsterite, quartz and cristobalite (asbestos heat-insulating materials) as well as cristobalite and mullite (non-asbestos heat-insulating materials) was found.

[Respirable mineral fibers in atmospheric air of Wroclaw]. / Respirabilne wlókna mineralne w powietrzu atmosferycznym Wroclawia.

Serpentine asbestos from the Naslawice mine, which contains mineral impurities of the serpentinite group--chrysotile and antigortie, has been used to built school sports grounds as well as roads and playgrounds within residential areas. The study was aimed to measure concentrations of respirable mineral fibres in the atmospheric air at the time children were playing on one of the playgrounds as well as at four other sites of Wroclaw. Air samples were collected using individual dosimeters and distributions of length and concentration of fibres were measured by means of a laser fiber monitor FM7400. X-ray diffraction and infrared spectrometry were used to determine the mineral composition of raw material collected from the playground. Morphology of particles of dust from the atmospheric air was analysed by means of electronic microscopy. It was found that the concentration of mineral fibres in the air in question depended on the number of children playing, namely when 7 children were playing the concentration value was equal to 165 fibres/litre and 549 fibres/litre with the number of 20 children. The concentration of fibres in a flat in the vicinity of the playground covered with serpentinite was about 11 times higher than at a street crossing with heavy traffic of motor vehicles. Antigorite and chrysotile were found in samples of raw material used to cover the playground. Numerous particles of fibrous structure were observed in the electronic microscopy image of air dust samples collected from the playground.

[Effect of water sprinkling on total dust and mineral fiber concentration during serpentine asbestos processing]. / Wplyw zraszania wodnego na stezenia pylu calkowitego i stezenia wlókien mineralynch przy przerobie serpentynitu.

By means of personal air sampler and Fibre Monitor FM-7400 concentrations of total dust and respirable mineral fibre were measured at work-posts, after sprinkling places with the highest emission of dust, in the plant where serpentine asbestos, used as road stone, was processed. It was found that due to sprinkling mean concentrations of total dust during a shift decreased by 1.5 (at inspection post) to 13.5 times at the post where crushing and sorting machines were served (before sprinkling -29.7 mg/m3 and after 2.2 mg/m3). It was found, at the same time, that sprinkling no decreased the concentration of mineral fibres.

Experimental carcinogenicity and mutagenicity of non-asbestos natural fibres--preliminary report.

The aim of this investigation was to quantify the carcinogenic and mutagenic activity of antigorite occurring in the form of admixtures in different mineral raw materials (serpentinite, magnesite, dolomite and nickel ore). The carcinogenicity of dusts was evaluated after intraperitoneal injections of 5 mg (mice) or 20 mg (rats) of dust suspended in saline. A pathomorphological examination was performed in all the dead animals. For two raw materials--serpentinite and nickel ore--their mutagenic potency was investigated (SCE test was used in this study). Results obtained in the experiments on animals (rats and mice) showed that the biological aggressiveness of the mineral raw materials tested was associated with the content of antigorite fibres. Particularly the frequency of mesothelioma (5-85%) was related to the number of antigorite fibres longer than 5 microns. Both of the investigated raw materials (serpentinite and nickel ore) were mutagenic in the SCE test.

[Various ecological problems related to mining and processing of serpentine. Evaluation of non-occupational exposure of the population of Naslawice to fibrous mineral dust]. / Niektóre problemy ekologiczne towarzyszace wydobyciu i przetwarzaniu serpentynitu. Ocena narazenia pozazawodowego na mineralny pyl wlóknisty ludnosci zamieszkalej w Naslawicach.

Non-occupational exposure of the population living in the vicinity of the serpentine mining and processing mill in Naslawice was assessed. The evaluation was based on the phase analysis and determination of respirable mineral fibres content in the samples of dust fall and soil in the fields nearby the mine, as well as on the in-door and out-door measurements of airborne fibres concentration. All soil samples contained antigorite--a mineral the structure of which is close to that of chrysotile asbestos add exhibiting high biological aggressiveness. The respirable mineral fibres content in the dust fall-out and in the soil ranged from 98,000 to 480,000 per 1 mg and from 48,000 to 122,000 per 1 mg, respectively, whereas the airborne concentrations were from 2 to 1540 fibres/l (outdoor) and from 4 to 7 fibres/l (indoor). The fall of dust in the years 1989-1990, recorded at all measuring points, exceeded 200,000 kg/km2 yearly (admissible value). The airborne concentrations of respirable mineral fibres were also higher than the admissible value (1 fibre/l of the air). The results obtained indicate that the exposure of the population in Naslawice to mineral fibrous dusts has significantly exceeded to maximum admissible concentrations established for non-occupational exposure.

[Asbestos substitutes and their biological effects. 2. Synthetic amphiboles--their physico-chemical characteristics]. / Zamienniki azbestu i ich dzialanie biologiczne. 2. Amfibole syntetyczne--charakterystyka fizyczno-chemiczna.

Metal content in the chemical structure of asbestos and man-made mineral fibres can affect their carcinogenic properties. As the chemical composition (metal content) of man-made silicate substitutes for asbestos can be varied almost at will in the process of their manufacture, the search for potentially least carcinogenic silicates appears to be of utmost importance. This paper presents diffractometric characteristics, dimensional analysis and morphology data for 4 synthetic amphibole fibres with chemical compositions differing from that of natural crocidolite amphibole. Those included the following synthetic amphiboles: Na2Mg6Ge8O22(OH)2; Na2Ni6Si8O22(OH)2; Na2Mg6Si8O22(OH)2; Na2Co6Si8O22(OH)2. The studied amphiboles differed in fibre length and diameter. The magnesium amphibole contained the longest (6.03 microns) fibres, and the nickel amphibole contained the shortest (2.7 microns) fibres, resembling those of crocidolite. The highest content (54.7%) of respirable fibres was found in the magnesium amphibole, and the lowest (15.9%) in the natural crocidolite. The authors suggest that the detected differences in the physical and chemical characteristics of the synthetic amphiboles may affect their biological properties.

[Asbestos substitutes and their biological effects. 3. Carcinogenic effects of synthetic amphiboles in animal experiments]. / Zamienniki azbestu i ich dzialanie biologiczne. 3. Dzialanie kancerogenne amfiboli syntetycznych oceniane w doswiadczeniu na zwierzetach.

This work presents the results of the test performed on rats to evaluate the carcinogenic effect of 4 synthetic amphiboles compared to that of the natural amphibole--crocidolite. The dose of the magnesium amphibole (Na2Mg6Si8(OH)2) administered to the animals contained 240 x 10(6) respirable fibres; the corresponding value for the nickel amphibole (Na2Ni6Si8O22(OH)2) was 339 x 10(6), for the cobalt amphibole (Na2Co6Si8O22(OH)2)--1000 x 16(6) for the geranium amphibole (Na2Mg6Ge8(OH)2)--250 x 10(6), and of the natural crocidolite amphibole (Na2Fe2Fe3Si8O22(OH)2) x 380 x 10(6) respirable fibres. The control animals (rats) received physiological NaCl solution. The number of peritoneal mesotheliomas following single intraperitoneal administration of 20 mg of the dust was adapted to be the measure of the carcinogenic activity of the dust. 3 synthetic (magnesium, cobalt and nickel) amphiboles and crocidolite caused development of malignant peritoneal mesothelioma in 11.1% to 71% rats. The results show that there is a relationship between the chemical composition of the synthetic amphiboles and their carcinogenic effect. Out of 4 investigated synthetic amphiboles, the magnesium amphibole, which contained magnesium and silicon, displayed most severe carcinogenic effect. The synthetic amphiboles containing either silicon and cobalt or silicon and nickel displayed 8.3 and 6.2 times weaker ability to induce peritoneal mesothelioma.

[Asbestos substitutes and their biological action. I. Types, use, exposure and MPEL]. / Zamienniki azbestu i ich dzialanie biologiczne. 1. Rodzaje, zastosowanie, narazenie i skutki biologiczne, NDS.

Referring to literature, the authors present problems of exposure to asbestos, its production and MACs in Poland. In our country artificial mineral fibres are produced in seven plants employing about 2000 workers. These plants produce basalt wool, sag wool and glass fibres used in industrial and building insulating materials and in cement and mortar additives and as a free insulating material. Mean concentrations of total dust at the work-posts measured in 1986-1989 ranged between 1.06 mg/m3 and 3.10 mg/m3. Concentrations of respirable fibres ranged from 0.041 fibre/cm3 to 0.173 fibre/cm3. In Poland, the MAC for mineral fibres for total dust amounts to 4 mg/m3 and for respirable mineral fibres to 2 fibres/cm3.

[Evaluation of long-term occupational exposure to dust and its effect on health during production of ceramic tiles]. / Ocena narazenia zawodowego i skutków zdrowotnych przewleklej ekspozycji na pyl wystepujacy przy produkcji plytek ceramicznych.

A medical examination has been carried out of 500 workers (290 men and 210 women) of a ceramic plates plant. Also, the measurements of dust concentrations were made at some standard work places . In the materials used for manufacturing the plates crystalline phases and the content of free crystalline silica were determined using the X-ray diffraction method. In the animal experiments the fibrogenic activity of all materials used in the plant was examined and compared to the fibrogenic activity of standard quartz. As a result of the medical examination 64 cases of pneumoconiosis were diagnosed (13% of the subjects). The incidence rate of pneumoconiosis was similar for men and women. The radiological changes characteristic of pneumoconiosis took approximately 24 years of the workers tenure to develop. Type q changes were most frequent (69%), types p and r were observed in 14% of workers (mostly women). In 31% of workers tuberous changes of size B were observed. In 43.8% of the subjects restrictive disorders of ventilation were found. In 30% of workers chronic bronchitis was diagnosed. Dust concentrations at 11 work places were measured using the individual dosimetry method. Total dust concentrations ranged from 0.6 mg/m3 at the electricians posts to 60.1 mg/m3 at the workposts where the furnace truck restorers worked. Dust concentrations exceeded the MACs at 7 workposts. The respirable fraction concentrations ranged from 0.1 mg/m3 to 8.4 mg/m3. During the replacement of asbestos ropes and asbestos board used for insulating the furnace trucks mineral fibres (0.1-0.5 fibre/cm3) were found in the air. The following crystalline phases were determined in the materials: kaolinite, illite, quartz, orthoclase and microline.(ABSTRACT TRUNCATED AT 250 WORDS)

[Evaluation of occupational exposure of workers engaged in mining of rock raw materials in the Sleza massif]. / Ocena narazenia zawodowego pracowników zatrudnionych przy wydobyciu surowców skalnych na obszarze masywu Slezy.

In two serpentinite mines and in a factory producing asphalt pavements using serpentinite, exposure to dusts and polycyclic aromatic hydrocarbons (WWA-fraction soluble in benzene) was assessed. In rock samples taken in the serpentinite mine and in dust samples from work posts crystalline phases were determined (using X-ray radiography and spectrometry in infrared). Also, morphology of dust particles was performed using electron microscopy. Both in the rock samples and in dust fibrous antigorite, a mineral of strong cancerogenic properties, was found. Total dust concentrations varied between 1.05 and 280 mg/m3, concentration of respirable mineral fibres from 0.01 to 3.56 fibre/cm3, and concentration of aromatic hydrocarbons varied between 266.7 and 850 micrograms/m3. The study will be continued concerning evaluation of biological effect of serpentinite in animal experiments and assessment of extraoccupational exposure of people living in the neighbourhood of serpentinite mines and plants processing this mineral.

The fibrogenic activity and neurotoxicity of heat-treated chrysotile.

Thermal degradation of heated chrysotile results in dehydration and changes in its crystalline structure. The impact of heat treatment at 150-1200 degrees C on the biological activity of chrysotile was tested in rats. Heating the chrysotile produced an increase in its biological aggressiveness measured in terms of animal survival rate and fibrogenic activity after intratracheal administration of the dust. The highest death rate (100% of the animals) was noted after administration of chrysotile heated at 600 degrees C. Moreover, increased fibrogenic activity of chrysotile heated at 150 degrees C up to 800 degrees C was found. The biological effect of chrysotile heated at 1200 degrees C did not differ from the effect exerted by unheated chrysotile. After intraperitoneal administration of the dust, the most violent reaction could be observed when chrysotile dust was heated at 600 degrees C, which resulted in symptoms of nervous system impairment (of the hind legs, no reaction to nociceptive stimuli, drop of internal body temperature) and death of the test animals. In male rats, the period between dust administration and the manifestation of symptoms and death was found to be longer than in females.

Biological activity of synthetic amphibole asbestos.

The carcinogenic and fibrogenic activity of four samples of synthetic amphibole asbestos with different chemical structure was examined in white rats. Pleural mesotheliomas were found: in 11 out of 27 rats (37.8%) treated with magnesium asbestos; in 4 out of 24 animals (6.7%) for nickel asbestos; 13 out of 22 (59.1%) for cobalt asbestos; and in the experiment with asbestos where germanium was substituted for silicon pleural mesotheliomas were observed in 2 out of 55 rats (3.6%). No tumours of this kind were found in the control group. As revealed by the study results, all the examined samples of synthetic amphibole asbestos exhibited carcinogenic potentials. Correlation between the carcinogenic and fibrogenic activity could also be observed. The replacement of silicon with germanium produced considerable decrease in the carcinogenic and fibrogenic potentials of asbestos.