[The validation of the maximum permissible concentration of pyromellitic dianhydride in the atmosphere]

The maximum allowable concentration (MAC) of pyromellitic acid dianhydride (PMAD) in the ambient air was substabtiated by physiological, hematological, and physiological methods. The inhalation of this substance by animals reduced their body weight, erythrocytic osmotic resistance, enhanced animals' sensitization. The mean daily MAC of PMAD was found to be 0.01 mg/m3. PMAD was considered to be Hazard Class 2.

Ketone potentiation of intrahepatic cholestasis: effect of two aliphatic isomers

Occupational exposure to methyl isobutyl ketone (MiBK) or methyl n-butyl ketone (MnBK) normally occurs by inhalation. The present study reports that exposure to both ketones can potentiate cholestasis experimentally induced by taurolithocholic acid (TLC, 30 mumol/kg) or by a combination of manganese (Mn, 4.5 mg/kg) and bilirubin (BR, 25 mg/kg). Male Sprague-Dawley rats were exposed for 3 d, 4 h/d, to MiBK or MnBK vapors using 0.5, 1, 1.5, or 2 times the minimal effective concentration (MEC). The estimated MiBK or MnBK MEC for potentiating TLC- or Mn-BR-induced cholestasis were 400 and 150 ppm, respectively. Eighteen hours after ketone exposure, rats were injected i.v. with TLC or Mn-BR. Bile flow was measured from 15 to 150 min after the cholestatic regimen. Rats exposed to MiBK or MnBK exhibited an enhanced diminution in bile flow compared to controls that was dose-dependent with the inhaled ketone dose. The dose-effect characteristics of the potentiation phenomenon were established. Results indicate that MiBK or MnBK inhalation potentiated both TLC and Mn-BR cholestasis in a dose-related fashion. Quantitative differences, however, exist between both ketones with respect to their ability to potentiate both models. Comparison between the two isomers was established, and MnBK was found to be more potent than MiBK.

[The maximum permissible concentrations, the approximate safe exposure levels and diagnostic tests for poisoning by inhibitors of metal corrosion]

Submitted in the paper are data on maximum permissible concentrations and tentative threshold limit values for those inhibitors of atmospheric metal corrosion and inhibitors of corrosion under acid conditions that have come into widespread use. Experimental animal studies together with observations over those occupationally exposed to the inhibitors permitted recommending tests of early diagnosis of intoxication such as measurement of blood and urine content of inhibitors, accumulation of methemoglobin in blood for methemoglobin-producers, alterations in peripheral blood, changes in biochemical reactions (activities of transferases, alkaline phosphatase, lactatdehydrogenase in blood serum), parameters characterizing the functional status of cardiovascular system.

[The characteristics of the biological action and regulation of submicroscopic aerosols in the industrial environment]

Biologic action was studied of the silicon nitride powder with varying disperse composition. When producing and using the silicon nitride powder on an enlarged scale one must remember of its higher toxicity and fibrogenicity. There is a need of employing some method of determination of the submicroscopic aerosol disperse composition under industrial conditions.

Synthetic vitreous fibers--inhalation studies

Synthetic vitreous fibers (SVFs), often referred to as "man-made vitreous fibers," are a class of materials that have their major uses for insulation against heat and sound. The original fibers are produced by melting various types of rock, clay, etc. and then blowing or extruding them into fibers of particular properties. During production and use small fractions of airborne fibers can be generated. Because of this a series of state-of-the-art inhalation studies was initiated to study the possible health hazards presented by the four major types of vitreous materials [two types of insulation glass wool, rock wool, slag wool, and four types of refractory ceramic fibers (RCF)] found in the workplace or to which the general public may be exposed. Rats and hamsters (30 mg/m3 kaolin-based RCF only) were exposed by nose-only inhalation to 3, 16, or 30 mg/m3 for 6 hr/day, 5 days/week, for 18 (hamsters) or 24 (rats) months and were held for lifetime observation (until approximately 20% survival) to study the chronic toxicity and potential carcinogenic activity of these classes of SVFs. Chrysotile or crocidolite asbestos served as positive controls. All of the fibers stimulated an inflammatory response characterized by an increase in the number of pulmonary macrophages at the level of the terminal bronchioles and proximal alveoli. RCF produced interstitial fibrosis in the walls of the proximal alveoli as early as 3 months and rock wool by 12 months. The only fiber which showed carcinogenic activity was RCF which produced a dose-related increase in both primary lung neoplasms (rats only) and mesotheliomas (rats and hamsters).

Concentrations of urinary metabolites in workers exposed to monochlorobenzene and variation in the concentration during a workshift

Urinary concentrations of metabolites of monochlorobenzene were examined in 10 male workers exposed to the compound while synthesising intermediate products for dyes. Their individual exposure concentrations were monitored for the whole workshift and samples of urine were collected at the start and end of the workshift, during it, and during the noon recess. The concentrations of four metabolites, 4-chlorocatechol and o-, m-, and p-chlorophenol, in the urine samples were measured. The investigation was performed on Monday and Tuesday in one week and on Tuesday and Wednesday in another week. The concentrations of 4-chlorocatechol in urine collected during the last four hours and at the end of the workshift were proportional to the eight hour time weighted average exposure to monochlorobenzene. The concentration in urine collected during the noon recess showed a linear correlation with the four hour time weighted average in the morning. Similarly, linear relations were obtained for urinary p-chlorophenol. The ratio (as monochlorobenzene) of p-chlorophenol to 4-chlorocatechol concentrations at the start of the workshift was 0.39 and at the end of the workshift was 0.22. The ratios of the urinary concentrations 15 hours after exposure to those at the end of exposure were 0.24 for 4-chlorocatechol and 0.44 for p-chlorophenol. The present study also showed that variations in exposure at the workplace were reflected by changes in concentrations of urinary metabolites during the workshift.

[Experimental data for evaluation of biological effect during exposure to chemical and biological factors]

Joint effects of lysin, eprin and formaldehyde in acute and subacute experiments were investigated. As shown, this effect can be evaluated as a partial summing with coefficient 1.84.

Sensitization of dairy farmers to bovine antigens and effects of exposure on specific IgG and IgE titers

Sensitization of dairy farmers to bovine-derived allergens and factors influencing this process were studied during the indoor cattle-feeding season. Eighteen typical family farms in eastern Finland were included in the study. Samples of airborne particulate material from stationary sites and the breathing zones of farmers were analyzed for bovine epithelial antigen (BEA) by the immunochemical enzyme-linked immunosorbent assay (ELISA) inhibition test. The levels of specific IgG and IgE antibodies against BEA and bovine urinary antigen (BUA) were measured from serum samples collected from farmers three times during the study. An association was found between anti-BUA IgG titers and BEA concentrations in the breathing zone. No major changes were observed between the antibody levels of sera collected at different times. In the samples from subjects with allergic rhinitis, however, a slight tendency toward descending anti-BUA IgE titers was found.