PubMed Health⌕ Search

Biomedical subjects

V Riihimäki

Publications and source records attributed to V Riihimäki.

17 recordsLinked to original sources
PubMed1992

Assessment of exposure to carbon disulfide in viscose production workers from urinary 2-thiothiazolidine-4-carboxylic acid determinations.

The follow-up of environmental carbon disulfide (CS2) exposure and urinary excretion of 2-thiothiazolidine-4-carboxylic acid (TTCA) among 20 operatives over a 4-day working week in two viscose producing factories confirmed earlier observations that TTCA is a sensitive and reliable indicator of exposure to CS2. Exposure to as low as 0.5-1.0 ppm (1.6-3.2 mg/m3) of CS2 (8-hour time-weighted average [TWA]) was associated with detectable amounts of TTCA in end-of-shift urine. Moreover, the excretion of TTCA, relative to estimated CS2 uptake, appeared surprisingly constant in the studied work force. Approximately 3% (range 2-6.5%) of absorbed CS2 was detected in urine as TTCA. The proportional TTCA excretion did not show dose dependency in the estimated CS2 dose range which varied by about 20-fold. TTCA elimination exhibited both a fast (T 1/2 6 hour) and a slow (T 1/2 68 hour) phase. The slow elimination is compatible with a high lipid solubility and reversible protein binding of CS2. Consequently, urinary excretion of TTCA, relative to CS2 exposure, increased by about a third during the workweek. Urinary TTCA concentration of 4.5 mmol/mol creatinine in a postshift sample corresponded to a TWA exposure to 10 ppm CS2 towards the end of the working week.

Adult↗
PubMed1992

In vivo measurements of lead in bone at four anatomical sites: long term occupational and consequent endogenous exposure.

Measurements of bone lead concentrations in the tibia, wrist, sternum, and calcaneus were performed in vivo by x ray fluorescence on active and retired lead workers from two acid battery factories, office personnel in the two factories under study, and control subjects. Altogether 171 persons were included. Lead concentrations in the tibia and ulna (representative of cortical bone) appeared to behave similarly with respect to time but the ulnar measurement was much less precise. In an analogous fashion, lead in the calcaneus and sternum (representative of trabecular bone) behaved in the same way, but sternal measurement was less precise. Groups occupationally exposed to lead were well separated from the office workers and the controls on the basis of calculated skeletal lead burdens, whereas the differences in blood lead concentrations were not as great, suggesting that the use of concentrations of lead in blood might seriously underestimate lead body burden. The exposures encountered in the study were modest, however. The mean blood lead value among active lead workers was 1.45 mumol l-1 and the mean tibial lead concentration 21.1 micrograms (g bone mineral)-1. The kinetics of lead in the tibia appeared to be noticeably different from that in the calcaneus. Tibial lead concentration increased consistently both as a function of intensity of exposure and of duration of exposure. Calcaneal lead concentration, by contrast, was strongly dependent on the intensity rather than duration of exposure. This indicated that the biological half life of lead in calcaneus was less than the seven to eight year periods into which the duration of exposure was split. Findings for retired workers clearly showed that endogenous exposure to lead arising from skeletal burdens accumulated over a working lifetime can easily produce the dominant contribution to systemic lead concentrations once occupational exposure has ceased.

Adult↗
PubMed1992

Pesticide-related incidents treated in Finnish hospitals--a review of cases registered over a 5-year period.

Pesticide-related incidents are uncommon in Finland. They comprised 0.11% of all hospitalizations due to poisoning in 1987-88. A search of the nationwide Hospital Discharge Register revealed 78 pesticide-related incidents in a 5-year period. Some 30 different agents were involved, the most frequent being organophosphate and MCPA. Only 36 cases (46%) were judged to be unequivocal or probable pesticide poisonings; 26 (33%) were probably other illnesses because of no or minimal exposure and of the children admitted for follow-up, nine (12%) had potentially marked exposure, but no poisoning developed owing to vigorous early treatment which limited absorption, and seven (9%) cases remained undetermined. According to our analysis, the management of patients with (suspected) pesticide poisoning at hospitals could be further improved if the following procedures were emphasised: decontamination of the skin when appropriate, systematic early estimation of the likely dose involved, analytical verification of pesticide absorption whenever feasible, and consistent collaboration with a toxicological advisory service.

Adolescent↗
PubMed1992

Biological monitoring of occupational exposure to low levels of benzene.

To obtain reference values for the biological monitoring of benzene, the kinetics of benzene were studied in volunteers. Benzene in blood and expired air could easily be followed until the next morning after a 4-h exposure to a benzene concentration of 10 cm3.m-3. Even after exposure to 1.7 cm3.m-3 the benzene levels in the morning blood and expired air samples differed from those in unexposed subjects. One hour after exposure to 10 and 1.7 cm3.m-3 the mean levels of benzene were 238 and 25 nmol.l-1 in blood and 13.2 and 2.5 mumol.m-3 in exhaled air, respectively. It was concluded that, at high benzene levels (approximately 10 cm3.m-3), samples collected 16 h after exposure reflect the body burden of benzene, while at low exposure (< 1 cm3.m-3) samples collected 1 h after exposure may be used to estimate the exposure over the preceding few hours. Exposure to benzene from smoking is a potential confounder in estimating occupational exposure to low levels of benzene.

Adult↗
PubMed1991

Distribution and effects on cytochrome P450 system of two hexachlorobiphenyl isomers in the rat.

Tissue distribution and effects induced by 2,2',4,4',5,5'-hexachlorobiphenyl (245-HCB) on cytocrome P450 isozymes were compared with those of 2,2',3,3',6,6'-hexacholorobiphenyl (236-HCB). Male Wistar rats were given a single intragastric dose (23 mg/kg body wt) of either isomer, and killed after 72 h. At termination the tissue concentrations of 245-HCB were considerably higher than those of 236-HCB, suggesting a more effective metabolism of the latter. The binding affinity of 236-HCB to cytochrome P450 was higher and the magnitude of binding greater than of 245-HCB. 245-HCB-treatment elevated the hepatic concentration of cytochrome P450 and also the activities of 7-pentoxyresorufin O-depentylase (50-fold), aniline p-hydroxylase (2-fold) and 7-ethoxycoumarin O-deethylase (2-fold), a response typical of phenobarbital-type inducers. In the Western immunoblot of liver microsomes from 245-HCB treated rats, an increased amount of P450IIB 1/2 was detected by a monoclonal antibody 2-66-3, which specifically detects phenobarbital inducible isoenzymes. The minimum molecular mass of the P450 isozyme induced was 52 kDa. After 236-HCB administration, a weak inducing effect was observed.

Animals↗
PubMed1991

Metabolic interaction and disposition of methyl ethyl ketone and m-xylene in rats at single and repeated inhalation exposures.

1. Rats were exposed to m-xylene (300 ppm) and methyl ethyl ketone (MEK, 600 ppm) vapour, separately and in combination. 2. Repeated exposures to m-xylene enhanced liver drug-metabolizing capacity, whereas MEK showed no effects. After mixed exposure the cytochrome P-450-dependent monooxygenase activities were additively or synergistically induced. 3. In the presence of MEK the overall metabolism of xylene was strongly inhibited both after single and repeated exposures, an effect accompanied by elevation of xylene concentration in blood (18-29%) and fat (25-32%). 4. The 24-h excretion of the urine metabolites of m-xylene was decreased by 22-24% in mixed exposures: the excretion of methylhippuric acid was decreased (29%), but that of 2,4-dimethylphenol increased (9-35%). 5. After repeated inhalation exposures the excretion of xylene metabolites in urine was consistently higher, whereas the concentrations of xylene in fat (but not the concentration of MEK) were lower than after a single treatment, conceivably due to accelerated metabolic clearance of xylene. 6. Thioether excretion in urine was enhanced in xylene-treated rats (7-13-fold), but was not influenced by the induced changes in the metabolism of xylene. Xylene inhalation caused liver GSH to decrease slightly (10%), as did inhalation of MEK, but the latter did not enhance the excretion of thioethers. 7. MEK is a potent inhibitor of the side-chain oxidation of m-xylene producing methylhippuric acid, but not of its ring oxidation to 2,4-dimethylphenol, and exhibits a synergistic inducing effect on liver enzymes responsible for the oxidation of m-xylene. The increased ring oxidation of m-xylene was not associated with increased production of reactive metabolites indicated by GSH-depletion or thioether formation.

Administration, Inhalation↗
PubMed1979

Distribution of m-xylene to subcutaneous adipose tissue in short-term experimental human exposure.

When volunteers were exposed in three different patterns of exposure to approximately 3.7--8.2 mumol/l (90--200 ppm, constant or time-weighted average concentration) of m-xylene for five consecutive days plus one day after the weekend, approximately 3.7--8.0% of the total body uptake was estimated to be distributed to the adipose tissue on the basis of m-xylene determinations made from subcutaneous fat. Distribution seemed to be affected by the exposure pattern; a proportionately greater distribution to subcutaneous fat occurred when the volunteers performed physical exercise part of the time, particularly when the peak xylene concentrations in the air coincided with the exercise. The median elimination half-time of m-xylene from subcutaneous fat was 58 h (range 25--128 h). A positive correlation was found between the individual elimination half-times of m-xylene in subcutaneous fat and the relative fat mass of the individuals in two exposure groups, but not in one.

Adipose Tissue↗
PubMed1978

Evaluation of occupational exposure to xylene by blood, exhaled air and urine analysis.

Occupational xylene exposure in the breathing zone of 15 painters was measured during three consecutive workdays. The applicability of the use of different biological samples was tested by the monitoring of xylene concentrations in blood and exhaled air, and urinary methylhippuric acid excretion as well. The best relation to the time-weighted average of xylene exposure was obtained for urinary methylhippuric acid concentration at the end of the workday; an amount of 665 mg/g of creatinine corresponded to 50 ppm of xylene. The amount of methylhippuric acid in a morning sample at the end of the work week, on the other hand, correlated to the mean exposure of the three preceding days. Xylene concentrations in exhaled air and blood sampled after the workday correlated poorly to the exposure of the preceding day. The urinary elimination of methylhippuric acid after the finished work week showed two distinct phases of excretion, with different biological half-times (1.9-5.3 h for the first 10 h after exposure and 16.5-48.4 h for the next two days).

Adult↗
PubMed1978

Percutaneous absorption of solvent vapors in man.

It is known from industrial experience and experimental studies that percutaneous absorption of concentrated liquid solvents may be considerable and even hazardous if large enough areas of skin are exposed for long periods of time. Percutaneous penetration of xylene, styrene, toluene, 1,1,1-trichloroethane and tetrachloroethylene vapors at ambient air concentrations of 600 ppm for 3.5 h was studied in a dynamic exposure chamber with a restricted number of human volunteers. Although the small number of exposed persons precluded conclusive quantitation of absorption and valid intercompound comparisons, aromatic solvents and tetrachloroethylene appear to penetrate skin much more readily than 1,1,1-trichloroethane. Skin penetrating properties of solvents seem, under the circumstances, to be associated primarily with lipid solubility. It was approximated that percutaneous exposure (total body surface) to 600 ppm of xylene vapor for 3.5 h corresponded to an equally long inhalation exposure of less than 10 ppm. Similar percutaneous exposure to 1,1,1,-trichloroethane corresponded to an inhalation exposure of only 0.6 ppm. Disease-affected skin may display altered permeability characteristics, and one volunteer with atopic dermatitis exhibited a more than three times larger absorption of xylene vapor when compared to subjects with normal skin. It may be concluded that in the work environment percutaneous absorption of solvent vapors from the surrounding air through undamaged skin is likely to be insignificant.

Adult↗
PubMedDate not supplied

Electroencephalographic findings during experimental human exposure to m-xylene.

Aromatic hydrocarbon solvents, used widely in industry, cause central nervous system symptoms in exposed workers. Acute effects of m-xylene were studied in nine voluntary subjects exposed experimentally to stable or varying concentrations of m-xylene at rest or while exercising. Each subject participated in four exposure and two control sessions in a single-blind fashion. The time-weighted average (TWA) m-xylene concentration was always 200 parts per million (ppm) (8.2 mumol/l) during the 4-h exposure period, complying to a TWA of 4.1 mumol/l.8 h, which is equivalent to the hygienic limit allowed in work situations. The short-term peak concentrations were 400 ppm or less. Electroencephalography was recorded at the beginning of exposure, during exposure, and after exposure was stopped. Eighteen 60-s EEG samples for each subject on each experimental day were analyzed automatically. Exercise increased theta percentage and delta power and percentage; these changes were more prominent in the control session without exposure. Exposure increased the dominant alpha frequency and alpha percentage during the early phase of exposure and also counteracted the effects of exercise. The effects of short-term m-xylene exposure on EEG were minor, and no deleterious effects were noted. Perhaps alpha activation is indicative of stimulating and excitatory effects induced by m-xylene exposure, which has been noted heretofore in the absorption phase of alcohol intake.

Adult↗