Rat liver foci study on coexposure with 50 Hz magnetic fields and known carcinogens

A study was performed to investigate possible interactions by magnetic fields (MF) with the processes of initiation and promotion of chemically induced preneoplastic lesions in rat liver. Male Sprague-Dawley rats were subjected to a 70% partial hepatectomy followed after 24 h by i.p. injection of diethylnitrosamine (DENA) as a tumour initiator. Starting one week after the DENA-treatment phenobarbital (PB) was given to promote growth of enzymatically altered foci of liver cells. MF was applied immediately after the partial hepatectomy and continued until sacrifice after 12 weeks of PB exposure. Homogenous horizontal AC magnetic fields with a frequency of 50 Hz and flux densities of 0.5 mu T or 0.5 mT were used. The rats coexposed with MF and DENA plus PB did not gain weight as much as the rats exposed to the chemical agents only. The MF-exposure also resulted in a slight reduction in size and numbers of the focal lesions. The results suggest an interaction of MF with the processes of chemical carcinogenesis either as a result of stress or depending on effects on the proliferation of preneoplastic cells.

Single-dose L-dopa response in early Parkinson's disease: measurements with optoelectronic recording technique

Twenty-five patients with suspected Parkinson's disease were submitted to optoelectronic movement analysis with the Posturo-Locomotor-Manual (PLM) test before and 60 min after a single dose of L-Dopa. They were then examined clinically for diagnosis. Two patients were excluded due to L-Dopa intolerance. Seventeen of the remaining patients were classified as having Parkinson's disease. The movement time (MT) in the PLM test was increased for all these patients, and they improved their performance after L-Dopa. The degree of improvement was roughly proportional to the pretreatment augmentation of MT in comparison to healthy subjects of the same age. The PLM phase analysis showed a specific disability profile for each individual. Six patients were given diagnoses other than PD. Some improvement was found in one patient with suspected olivopontocerebellar atrophy and one patient with multiple brain injury. Two patients with progressive supranuclear palsy, one with suspected striatonigral degeneration, and one with functional disturbance deteriorated after L-Dopa. In conclusion, truly objective and fully reproducible evaluation of the motor performance before and after a single L-Dopa dose is easily accomplished with computer-assisted modern optoelectronic recording equipment. The technique is a valuable tool for the quantitative measurement of treatment effects and contributes to the differential diagnosis.

Occupational implications of the chlorofluorocarbon ban in Sweden

Limitations on the use of full halogenated chlorofluorocarbons (CFCs) may create occupational environmental problems. These are currently largely unknown, because the toxicology of most CFC substitutes is unknown. Therefore, toxicity testing of CFC substitutes is necessary, and this can best be done before their use commences. Destruction of CFC and materials containing CFC could generate new chemical compounds, especially during incineration. In addition, problems with higher noise and vibration levels may occur when CFC substitutes are employed, and we should keep in mind that occupational environment problems could also develop when new routines are introduced for transporting, storing, and handling new materials.

New Swedish occupational standards for some organic solvents

In 1987, the Swedish government requested a unique investigation of the consequences of a 50% reduction of permissible exposure levels (PEL) for organic solvents. As a result, 29 solvents were investigated and for 25 of them a reduction--if not to 50%--was suggested. For 13 of the solvents, there existed scientific arguments for a reduction of the PEL. For 12 solvents, no specific biomedical information was available. Presumed interactions between solvents may have influenced the decisions, but technological/economic feasibility criteria may also have been used by the regulators. This suggests that the use of technological/economic feasibility criteria can give lower PELs than health criteria. This is within the intentions of the Swedish Work Environment Act.

CSF and urine biogenic amine metabolites in Rett syndrome

The metabolites of dopamine (homovanillic acid-HVA), noradrenaline (4-hydroxy-3-methoxy-phenylglycol-HMPG), and serotonin (5-hydroxyindoleacetic acid-5-HIAA) were measured in cerebrospinal fluid (CSF) from 38 patients and urine from 36 patients with typical Rett syndrome (RS) and compared with controls of similar age. CSF metabolite concentrations were the same in the patients and controls. Urinary metabolites expressed per mol creatinine were significantly higher in older RS patients. This difference is partly explained by lower urinary creatinine levels in older RS patients, due to their known reduction in muscle mass. Alterations in CSF or urine biogenic amine metabolite concentrations do not appear to represent the primary abnormality in RS, and their measurement cannot be regarded as a reliable means of diagnosis.

Assessment and management of occupational risks in the Nordic (Scandinavian) countries

Occupational health standards in the Scandinavian countries are of national concern and may thus vary from country to country. There is an internordic collaboration in the scientific criteria work, but there are also national formal procedures for standard setting. There is a greater tendency to accept eye, nose, or throat irritations as indices of harm than the American Conference of Governmental Industrial Hygienists (ACGIH) does. For organic solvents, neurotoxicity has been focused on for many years, although the differences between values in the ACGIH list and in the Nordic countries have diminished. Occupational standard setting in the Nordic countries is much influenced by technological feasibility and socioeconomic criteria. Sweden has a formalized procedure for the underlying scientific and transscientific assessments.

Haemodynamic, anti-anginal and anti-ischaemic effects of sublingual nitroglycerin: dose-response, duration and time of onset of action

To establish the time of onset of action and magnitude of response to the quickest disintegrating sublingual nitroglycerin tablet available in Scandinavia (Nitromex), nine patients with stable exercise-induced angina were studied whilst performing bicycle exercise tests. In the first session, placebo, 0.25, 0.50 and 0.75 mg sublingual nitroglycerin (Nitromex) was given in a double-blind cross-over fashion on different days. In the second session (1 h after Session 1), nitroglycerin 0.5 mg (Nitromex), placebo and 0.5 mg of a different brand of nitroglycerin were compared for the time of onset of attenuation of ST-segment depression when administered during exercise. In Session 1, there was a dose-dependent fall in systolic blood pressure and a concordant rise in heart rate whilst sitting at rest prior to exercise. Exercise time and ST-segment depression were dose-dependently prolonged, significantly by the two higher doses, (mean 20 and 26%, respectively) which did not differ from one another. In Session 2, nitroglycerin (Nitromex) caused ST-segment reversal after a mean of 123 s after administration, which was shorter than after ordinary nitroglycerin (mean 157 s) and placebo (two tests, 186 and 192 s). It is suggested that when nitroglycerin is administered during exercise, chest pain and ischaemic ECG-changes are largely improved through coronary vasodilatation and reduced afterload rather than through increased venous pooling and reduction in preload.

Effects of exposure to vehicle exhaust on health

Exposure to combustion engine exhaust and its effect on crews of roll-on roll-off ships and car ferries and on bus garage staff were studied. The peak concentrations recorded for some of the substances studied were as follows: total particulates (diesel only) 1.0 mg/m3, benzene (diesel) 0.3 mg/m3, formaldehyde (gasoline and diesel) 0.8 mg/m3, and nitrogen dioxide (diesel) 1.2 mg/m3. The highest observed concentration of benzo(a)pyrene was 30 ng/m3 from gasoline and diesel exhaust. In an experimental study volunteers were exposed to diesel exhaust diluted with air to achieve a nitrogen dioxide concentration of 3.8 mg/m3. Pulmonary function was affected during a workday of occupational exposure to engine emissions, but it normalized after a few days with no exposure. The impairment of pulmonary function was judged to have no appreciable, adverse, short-term impact on individual work capacity. In the experimental exposure study, no effect on pulmonary function was observed. Analyses of urinary mutagenicity and thioether excretion showed no sign of exposure to genotoxic compounds among the occupationally exposed workers or among the subjects in the experimental study.

Three industrial solvents investigated for tumor promoting activity in the rat liver

Dioxane, perchloroethylene, and trichloroethylene were investigated as rat liver altered foci promoters in an initiation/promotion protocol. Animals were initiated with diethylnitrosamine, 30 mg/kg, injected i.p. 24 h after 2/3 partial hepatectomy. The chemical under study was administered by gavage once a day, 5 times a week for 7 weeks. Ten days after the last administration the animals were killed. Liver sections were stained for gamma-glutamyl-transpeptidase (GGT) and the number and total volume of GGT-positive foci was studied. Dioxane (1000 mg/kg) significantly increased the number and total volume of foci while a marginal effect was noted for the high dose of trichloroethylene (1100 mg/kg). A high dose of perchloroethylene (1100 mg/kg) had no effect.

Mortality and incidence of cancer among Swedish rubber workers, 1952-1981

The mortality and incidence of cancer was studied among 8,734 workers from two Swedish rubber manufacturing companies. Mortality was investigated from 1952 to 1981 and cancer incidence from 1959 to 1980. The expected numbers of deaths were calculated from national statistics. No significant risk excesses were detected when the cohort was analyzed without consideration of employment time or latency period. However, the mortality from coronary heart disease and the incidence of lung cancer were increased when the study period was limited to greater than or equal 40 years since first employment. The standardized mortality ratio for coronary heart disease correlated positively with employment duration. The mortality from asthma, bronchitis, and emphysema was nonsignificantly increased. The incidence of bladder cancer was increased among individuals with heavy and long-term exposure in the weighing and mixing departments. Twenty-five percent of the individuals in the cohort were not Swedish citizens at the time of employment, and an analysis of the mortality and cancer incidence in this group showed a markedly increased lung cancer incidence for certain immigrant groups, probably mainly due to ethnic factors. The results indicate that ethnic factors must be considered in the analysis of occupational groups when a high proportion of the workers are immigrants.

Venous blood levels of inhaled trichloroethylene in female rats and changes induced by interacting agents

The concentration from inhalation of trichloroethylene (TCE) in venous blood from female rats was studied. Exposure consisted of 200, 400 and 500 ppm for 6 hrs, or 50 and 100 ppm for 2 hrs. In each experiment, 1 rat was exposed at a constant concentration of TCE. Blood samples were obtained from an indwelling jugular cannula throughout the experiment. Combination effects with chloral hydrate (0.2 g/kg), ethanol (0.8 ml/kg), isopropanol (0.8 ml/kg), pyrazole (0.2 g/kg), tetraethylthiuram disulfide (TETD; 0.2 g/kg) or tetrachloroethylene (TTCE; 1 g/kg) given orally were observed. The experimental data on the uptake of TCE in blood were fitted, by use of nonlinear regression analysis, to a simple toxicokinetic model. TETD caused the greatest increase in the steady state concentration of TCE (3.7 X), compared to TCE alone at 200 ppm. Isopropanol, pyrazole and TTCE also produced pronounced effects, but chloral hydrate treatment resulted in no significant change. At 50 and 100 ppm TCE exposure for 2 hrs, a significant increase (almost 3 X) in the steady state concentration of TCE from both ethanol and isopropanol was observed.

Benzene: standards, occurrence, and exposure

The national occupational standard values for benzene are 10 ppm for Australia, 10 ppm for Denmark, 10 ppm for Finland, 10 ppm for Japan, 10 ppm for The Netherlands, 10 ppm for the United States, and 5 ppm for Sweden; in the Federal Republic of Germany the technical guideline value is 8 ppm. Crude mineral oil contains benzene as a natural constituent of approximately 0.1%. Gasoline in Sweden may contain 4-5% benzene by volume. The 8-hour time-weighted average (TWA) exposure levels of Swedish petroleum refinery workers vary between 0.1 to 1 mg benzene/m3 in air. The exposures of benzene in various other occupations were measured and described. Other environmental exposures to benzene may have their origin in pyrolysis, such as tobacco smoking and burning of substances such as polyvinylchloride.

Induction of single-strand breaks in DNA of mice after inhalation of vinyl chloride

Female mice were exposed to 500 ppm vinyl chloride (VC) for 6 h/day 5 days/week for 1-8 weeks. Groups of mice were killed at different times during this period. DNA damage, expressed as single-strand breaks (SSB), was studied in liver, kidneys, lungs, spleen and brain. The level of SSB increased in liver, kidneys, spleen and lungs with time of exposure and reached a plateau for kidneys and lungs after 80 and 120 h of exposure. In spleen there was only a slight increase in the SSB, and in brain no detectable increase was found.

Mortality and cancer rates among workers in the Swedish PVC processing industry

Personnel lists from four PVC-processing industries were collected on production of employees with at least three months of employment at the beginning of 1945 and the last day of employment December 31, 1974. Of 2073 persons, 103 could not be followed up, because they had moved abroad. The remaining persons comprise the cohort of 1970 individuals who were analyzed and compared with the national population with respect to mortality from various diseases and cancer morbidity. The death risk from myocardial infarction is elevated in the cohort. This elevation is most clearly apparent in the subcohort which had at least two years of exposure time and where the analysis was directed at circumstances chronologically close to the time of exposure. The myocardial infarction risk related to vinyl chloride exposure is discussed in relation to earlier studies on the vascular effects of vinyl chloride. An indication of an elevated risk of morbidity and mortality from tumors in the digestive organs is also present. However, this is not statistically confirmed. A few future follow-ups of the present study are necessary in order to clarify any possible elevated risk of tumors in the PVC-processing industry.

Skin pathology following epicutaneous exposure to seven organic solvents

1,1,1,-Trichloroethane, benzene, trichloroethylene, tetrachloroethylene, dibromoethane, 1,2-dichloroethane, and 1,1,2,2-tetrachloroethane were applied to the skin of guinea-pigs for histopathological studies. Biopsies taken at different times of exposure showed the presence of karyopyknosis for all solvents tested; 1,1,1-trichloroethane, benzene, trichloroethylene, and tetrachloroethylene showed karyolysis; 1,1,1-trichloroethane, benzene, trichloroethylene, tetrachloroethylene, and dichloroethane induced spongiosis. All solvents, except 1,1,2,2-tetrachloroethane, produced junctional separation. Pseudoeosinophilic infiltration occurred for all solvents, except for 1,2-dichloroethane. The results are discussed in terms of occupational hazards and in relation to parallel studies on blood uptake and systemic toxicity at epicutaneous administration.

The effect of long term treatment with disulfiram on content of cytochrome P-450 and on benzo(a)pyrene monooxygenase activity in microsomes isolated from the rat small intestinal mucosa

Disulfiram (DS) was administered perorally once a day to rats for 30 days to investigate the effects on cytochrome P-450 content and benzo(a)pyrene (BP) monooxygenase activity in microsomes isolated from the small intestinal mucosa. 50 mg or 100 mg DS/kg body weight caused a dose-related increase in BP monooxygenase activity, whereas the content of cytochrome P-450 was increased at the higher dose only. Similar absorption characteristics of cytochrome P-450 and turnover rates for BP on the basis o f cytochrome P-450 was observed among the different microsomal preparations. The addition of DS or diethyldithiocarbamate (DDTC) to incubates of intestinal microsomes inhibited BP monooxygenase activity. Microsomes isolated from DS-treated rats were however less sensitive to in vitro inhibition by DS.

Toxicological aspects of chemical hazards in the rubber industry

Only three recognized strong carcinogens are used in the Swedish rubber industry: mineral oil, ethylene thiourea, and trichloroethylene. Besides, many curing agents, accelerators, antioxidants/antiozonants, and retarders may possess mutagenic and/or carcinogenic activity and may thus contribute to the total cancer risk in the rubber industry. Irritating compounds as well as modifiers of biotransformation further contribute to the complex exposure panorama of the rubber industry. Cancer risks in the work environment of the rubber industry can probably be more effectively reduced by general sanitary measures aimed at reduction of total exposure than by specific regulation of only a few established carcinogenic chemicals.

Worker involvement in risk assessment

When performing an epidemiologic study, the central trade unions should be informed. On the local (company and plant) level, the safety committee, trade unions, and shop stewards are contacted to discuss the aim and design of the study, as well as the participation of workers' and employers' representatives in collecting relevant data. When publishing the results of the epidemiologic study, as well as the results of an experimental study, open communication with the population at risk is preferable. When evaluating the risk and assessing a code of practice or an occupational standard for a carcinogen, the participation of trade union representatives is important. Scientists do not have a monopoly on decisions about future risks and actions against risks, nor can they decide better than the risk population what degree of risk should be accepted.

Acute and subchronic kidney injuries in mice induced by diphenylamine (DPA)

Adult and female mice were fed with diphenylamine by oral gavage. Mice of both sexes showed up with kidney injuries involving tubuli and some glomeruli. RE-cells in livers of both sexes were activated with content of yellowish-brown pigment.

Variations in the blood concentration of 1,1,2-trichloroethane by percutaneous absorption and other routes of administration in the guinea pig

The blood concentration of 1,1,2-trichloroethane was studied after epicutaneous application, by an intracutaneous, subcutaneous or intraperitoneal injection. An equation with three exponential terms was necessary for a satisfactory description of the experimental data in the case of intraperitoneal injection. Subcutaneous and intracutaneous injections seem to give essentially the same king of blood concentration curves as for intraperitoneal injection. In the case of percutaneous absorption an equation with three exponential terms and a constant was necessary to account for the experimental data. The complex toxicokinetics of 1,1,2-trichloroethane by percutaneous absorption was assumed to be associated with progressive skin damage observed in previously reported experiments, a damage apparently involving a change in barrier function.

Morphological lesions in guinea pigs during skin exposure to 1,1,2-trichloroethane

Guinea pigs were exposed to 1,1,2-trichloroethane applied directly on the skin of the back for periods between 15 minutes and twelve hours under anaesthesia. Morphological changes could be observed in the epidermis after 15 minutes and continued to progress during continuing exposure. The changes consisted of pyknotic nuclei, perinuclear oedema of basal and suprabasilar cells as well as a focal separation of the epidermis from the corium with vesicle formations. The liver tissue showed reduction of glycogen content as well as hydropic changes in the centrilobular areas six hours after the start of exposure. The liver changes were less marked 12 hours after exposure and absent in nonanaesthetized animals. No morphological changes were observed in the kidney or the brain.

Occupational health standards. An international comparison

The background for establishing standards for toxic agents is reviewed, and the standards of 14 different countries, including Sweden, are compared with special reference to criteria and organizational aspects. The differences among countries in the numerical limit values for toxic substances are largely due to differences in definitions, biomedical criteria, technical feasibility and sociopolitical judgements.

A study on the distribution of methylchloroform and n-octane in the mouse during and after inhalation

The distribution of methylchloroform and n-octane, respectively, in the blood, liver, kidney, and brain of mice was studied at different inspired air concentrations and after different exposure times. The air concentration varied between 10 and 10,000 ppm; and the exposure time, between 0.5 and 24 h. The resulting solvent concentrations in kidney and brain were about the same, but the liver concentrations were usually somewhat higher for both solvents. There was a linear dependence between inspired air concentration and tissue concentrations at fixed exposure times. A correlation between blood and organ concentrations was observed in animals exposed at different inhalation air concentrations but not in animals exposed only at one fixed concentration. The ratios between the concentrations of the solvents in the organs and blood were higher for n-octane than for methylchloroform. The ratios increased as the exposure concentration increased for all organs studied in the case of n-octane but only for the liver in the case of methylchloroform. When the exposure dose, i.e., inspired air concentration X time, was generated in different ways, a high concentration during a short exposure resulted in a ten times higher organ concentration than a low concentration during a long exposure. The liver, kidney, and brain concentrations generally did not differ more than twice between methylchloroform and n-octane after exposure of the same concentration and duration. The blood concentration, however, was much less in n-octane exposed animals than in methylchloroform exposed ones. A pharmacokinetic model with both uptake and elimination of the first order fitted the empirical data better for methylchloroform than a model with zero order uptake and first order elimination. Postexposure concentrations of methylchloroform were linear in a semilog graph. A one-compartment pharmacokinetic model was in accordance with the experimental data for methylchloroform. For n-octane, however, at least a two-compartment model must be assumed.

Lens lesions in the elk

During the period 1973–1976, eyes from 17 elks (Alces a. alces L) were examined, bilateral cataract being found in nine elks, and a cataract found in an additional elk, from which only one eye was submitted for examination. Macro-scopically, the lenses were more or less deformed and reduced in size, being milky white or brownish grey and shrunk, their surface uneven and granular. Microscopically, there was a marked fluid accumulation between the lens fibers and apparently also a swelling of the lens fibers. Proliferation and swelling of epithelial cells were observed as well. Etiological factors are discussed.

The pathology of vinyl chloride exposed mice

Outbred albino laboratory mice were exposed to 50 p.p.m. and 500 p.p.m. vinyl chloride by inhalation 6 hrs./day, 5 days/week during 52 and 26 weeks, respectively. Pathologic examination showed the presence of histologically benign alveologenic lung adenomas, haem-angiosarcomas in fat tissue as well as a few benign and malignant tumours at various sites. Only one liver haemangiosarcoma was noted. All animals exposed to 500 p.p.m. developed tumours; 71 % of the animals given 50 p.p.m. were tumour bearing. The frequency of all tumours, number of tumour foci and size of foci in both groups suggest a dose-dependent carcinogenic effect of vinyl chloride. Haemocoelia due to blood vessel rupture was a common cause of death. Telangiectasis of the liver was also observed in a few animals. The role of fat tissue as well as blood vessel involvement in the pathology of vinyl chloride is discussed.