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Biomedical subjects

F Valić

Publications and source records attributed to F Valić.

16 recordsLinked to original sources
PubMed1992

Interconvertibility of asbestos fibre count concentrations recorded by three most frequent methods.

Simultaneous airborne chrysotile asbestos fibre samples were collected with three types of instruments, namely, the konimeter, the thermal precipitator and the membrane filter, in four asbestos plants (textile manufacturing, asbestos cement production, mining, milling). Linear regression analyses were performed of the membrane filter on the konimeter and thermal precipitator count concentrations, respectively. Sampling was performed at 24-35 locations in each of the processes studied. In order to linearize the relationships and to stabilize the sample variances the data were transformed using the transformation ln(x+1) for both the predictor and the response variables. Eight linear regression equations were developed. The slope coefficients of regressions differed significantly (P < 0.05 or < 0.01) between all the asbestos processes except for the differences of coefficients in mining and milling (P > 0.05). It is concluded that no single conversion factor can be used to reliably convert the konimeter or thermal precipitator to membrane filter asbestos fibre concentrations; a separate conversion factor must be derived for each technological process. In this case the confidence limits of estimates are acceptable for practical occupational hygiene purposes.

Air Pollutants, Occupational↗
PubMed1991

Relationship between cumulative occupational exposure to asbestos fibres and respiratory symptoms.

A survey of chronic respiratory symptoms was undertaken in 1127 asbestos workers engaged in asbestos mining, asbestos cement production, production of friction materials or in the manufacture of asbestos textile. A control group of 593 persons was also surveyed. The exposure of asbestos workers was analysed by evaluating separately the cumulative exposure to total airborne particles and to airborne asbestos fibres. The prevalences of all the respiratory symptoms (chronic cough, chronic phlegm, chronic bronchitis, dyspnoea grade 3+) were significantly higher in asbestos workers compared to controls in both nonsmokers and smokers (p less than 0.01). The prevalences of all the respiratory parameters in asbestos workers increased with both the length of employment and cumulative exposure to total airborne particles. Prevalences of chronic cough, chronic phlegm and chronic bronchitis did not show an increase with cumulative exposure to airborne asbestos fibres expressed as fibres/cc years. It is concluded that the development of chronic cough, chronic phlegm and chronic bronchitis in asbestos workers is likely to be an unspecific effect of the exposure to the difficulty soluble airborne particles rather than a specific effect of the exposure to airborne asbestos fibres.

Adolescent↗
PubMed1990

[Is it necessary to remove fibrous insulation material from buildings?].

Because of potential negative health effects of exposure to airborne fibres, removal of fibrous insulating materials from buildings, particularly asbestos, has become a frequent, in many cases unjustified, undertaking. The results are presented of the determination of airborne mineral respirable and non-respirable fibres, fragments and total airborne dust in a public building before the substitution of the insulating material, shortly after, and about two months later. There were no differences (P greater than 0.05) between the mean concentrations of respirable fibres (diameter less than or equal to 3 microns, length greater than or equal to 5 microns, aspect ratio greater than or equal to 3:1) measured before (0.0038 and 0.0031 f/cm3, resp.) and about two months after (0.0038 and 0.0028 f/cm3, resp.) the substitution, suggesting that the substitution was unnecessary. However, the concentrations measured two and eight days after the substitution were significantly elevated (P less than 0.05; P less than 0.01, resp.), indicating that the unnecessary disturbance of the insulating material caused an increase of exposure levels of the employees. It is concluded that the removal or substitution of fibrous insulating materials, solely on the basis of their presence in the buildings, is unjustified. The decision should be based on elevated concentrations of airborne fibres objectively quantified. Unnecessary substitution brings about an increase, not a decrease, of the concentrations through a shorter or longer period of time.

Air Pollutants↗
PubMed1990

Ventilatory lung function changes in family members of asbestos workers.

A group of 114 adult family members of asbestos workers were examined for the prevalence of chronic nonspecific respiratory symptoms and ventilatory function changes. There was no difference in the prevalence of any respiratory symptom between the examinees and the matching members of the general population in the study areas. No difference was found between the measured and predicted values of FVC or FEV, or FEF50 in either smoking or nonsmoking men (P greater than 0.05). In contrast, all the measured values in women were significantly lower (P less than 0.0001) than their normal predicted values. Airborne chrysotile weight concentrations in five houses of asbestos workers were found significantly higher than those in four houses without inhabitants occupationally exposed to asbestos.

Asbestos↗
PubMed1979

Respiratory function in coffee workers.

Respiratory function was studied in three groups of workers employed in processing coffee. The prevalence of almost all chronic respiratory symptoms was significantly higher in coffee processors than in control workers. In each group during the Monday work shift there was a significant mean acute decrease in the maximum expiratory flow rate at 50% vital capacity (VC), ranging from 4.0% to 8.7%, and at 25% VC, ranging from 6.0% to 18.5%. Acute reductions in FEV1.0 were considerably lower, ranging from 1.3% to 2.8%. On Thursdays the acute ventilatory function changes were somewhat lower than on Mondays. Acute decreases in flow rates at low lung volumes suggest that the bronchoconstrictor effect of the dust acts mostly on smaller airways. Administration of Intal (disodium cromoglycate) before the shift considerably diminished acute reductions in flow rates. A comparison of Monday pre-shift values of ventilatory capacity in coffee workers with those in controls indicates that exposure to dust in green or roasted coffee processing may lead to persistent loss of pulmonary function.

Adult↗
PubMed1977

Effects of fluorocarbon propellants on respiratory flow and ECG.

Ten subjects were exposed to the propellants freon 11, freon 12, freon 114, to two mixtures of freon 11 and 12 and to a mixture of freon 12 and 114. The length of exposure was 15, 45 or 60 seconds. Maximum expiratory flow-volume (MEF) curves and ECG were recorded before, and intermittently up to 1 hour after, exposure. Breathing level concentrations of propellants during exposure were determined by gas chromatography. All freons induced biphasic reduction of ventilatory capacity on inhalation. The first fall occurred within a few minutes of exposure while the second was delayed 13-30 minutes after exposure. The effects of mixtures were greater than those of individual freons. The relative fall in MEF 75% was more pronounced than that in MEF 50%. No clear-cut pathological changes in ECG were found. Nevertheless, most subjects developed variations in heart rate exceeding those noted before exposure. In a few cases inversion of the T wave, and in one case atrioventricular block, were observed.

Adult↗
PubMed1976

Respiratory response to tobacco dust exposure.

Results of a study of the respiratory responses of 318 nonsmoking female workers to long-term tobacco dust exposure are reported. The mean total tobacco dust concentrations ranged from 0.9 to 27.5 mg per m3; the respirable fraction, from 0.3 to 3.6 mg per m3. The mean length of exposure to tobacco dust was 14.9 years; 24 per cent of the workers had been exposed to tobacco dust for 20 years or more. Comparatively low prevalences of chronic respiratory symptoms were found, and only the prevalences of chest tightness and wheezing were significantly higher among workers exposed to tobacco dust than those of the control group (P less than 0.01). Calculating the expected 1-sec forced expiratory volume and forced vital capacity values by means of multiple linear regression equations, developed on the basis of data obtained in the 210 control subjects, revealed no significant differences between the measured and expected ventilatory capacity values among any of the groups of the workers observed. In contrast to negative findings with regard to chronic respiratory effects, significant acute decreases in ventilatory capacity during the work shift were recorded. No dose-response relationship was found between the level of exposure and the acute decreases in ventilatory capacity.

Adolescent↗
PubMed1975

Lung function in textile workers.

Acute changes in ventilatory function during a workshift with exposure to hemp, flax, and cotton dust were measured on Mondays in a group of 61 textile workers, all working on carding machines. In addition, single-breath diffusing capacity (DLCOSB) was measured before dust exposure on Monday in 30 of the 61 workers. Large acute reductions during dust exposure were recorded in maximum expiratory flow rate at 50% VC (MEF50%), ranging from 38 to 22%. Acute reductions of FEV1-0 were considerably smaller, ranging from 17 to 9%. There was a statistically significant increase in residual volume (RV) with very small and insignificant changes in total lung capacity (TLC). Although preshift FEV1-0 and FVC were decreased, DLCOSB was within normal limits. Plethysmographic measurements in six healthy volunteers exposed to hemp-dust extract confirmed the results obtained in textile workers, that is, that TLC does not change significantly during dust-induced airway constriction and that maximum expiratory flow rate at 50% VC (MEF50%) is a more sensitive test than FEV1-0 in detecting acute ventilatory changes caused by the dust extract.

Adult↗
PubMed1975

Change in the respiratory response to coarse cotton dust over a ten-year period.

Changes in respiratory function during a 10-year period were studied in a group of 34 men and 19 women exposed to coarse cotton dust. The prevalence of byssinosis increased significantly in the 10-year period both in men and women; in addition, there was an increase in the prevalence of all other chronic respiratory symptoms in 1973 compared to 1963. There was a significant decrease in forced expiratory volume in 1 sec and forced vital capacity over the Monday shift both in 1963 and 1973. In subjects who were without byssinosis in 1963 but who had developed it by 1973, there was a considerable decrease in forced expiratory volume in 1 sec in 1973. The mean annual decline of forced expiratory volume in 1 sec (70 ml) during the 10-year period in the men was much greater than expected on the basis of the prediction equation for normal males, and it was most pronounced in those with byssinosis at the time of both surveys (111 ml).

Adult↗
PubMedDate not supplied

[Chlorofluorocarbons--a new environmental health problem].

A review of health problems caused by the use of chlorofluorocarbons--chemical substances of widespread and varied applications is presented. There is a recent evidence that fully halogenated chlorofluorocarbons are air pollutants inducing hazardous health effects. Direct effects of chlorofluorocarbons on respiratory and cardiac functions are described among which some with lethal outcome. Recent data are given and models described forecasting indirect effects of chlorofluorocarbons induced by their ozone depleting reactions in the stratosphere which bring about a higher exposure of the population to UV-B radiation. As a consequence of which, an increase of the incidence of nonmelanoma and melanoma skin cancers, immunosuppression, and eye disorders is predicted. The latest international activities aimed at urgent prevention of these effects are described.

Air Pollutants↗