[Concentration and fiber size of asbestos in lungs of residents living close to the serpentinite area]

Concentrations and fiber size distribution of asbestos in the lung tissue of 16 ( 8 males and 8 females) rural residents living close to the serpentinite area (neighboring group) were analyzed by low temperature ashing-analytical transmission electron microscopy, and were compared with those of 5 (5 males) rural and 53 (34 males and 19 females) urban residents living away from the serpentinite area (reference group). The results are as follows; 1. Pulmonary asbestos fibers were found in all rural residents. The types of asbestos fibers were chrysotile, amosite, crocidolite, actinolite, and tremolite. These findings were very similar to results for urban residents. 2. In males, the geometric mean concentration of actinolite-tremolite in the neighboring group (1.78 x 10(6) fibers/g dry lung) was significantly higher than those in the reference groups (rural: 0.32 x 10(6), urban: 0.31 x 10(6), p < 0.01). In females also, the geometric mean concentration of actinolite-tremolite in the neighboring group (0.59 x 10(6)) was significantly higher than that in the reference group (urban: 0.16 x 10(6), p < 0.05). There were no significant differences in the actinolite-tremolite concentrations between males and females in the neighboring group. 3. The serpentinite in this area have contained not only chrysotile but also both actinolite and tremolite. There was no significant relationship between actinolite-tremolite concentration and occupational history in the neighboring group. It is possible that actinolite and tremolite are liberated from the serpentinite to the atmosphere and inhaled by the residents near the serpentinite area which increases pulmonary actinolite-tremolite concentration. 4. The difference in the geometric mean concentration of chrysotile between the neighboring and the reference group was not statistically significant for both sexes, possibly due to the poor durability of chrysotile in the lung tissue. 5. There were no significant differences in the geometric mean of fiber length and diameter of actinolite-tremolite between the neighboring and the reference group.

Toluene induces behavioral activation without affecting striatal dopamine metabolism in the rat: behavioral and microdialysis studies

We examined the effects of toluene on the release of dopamine (DA) and its metabolites in rat striatum using microdialysis. Intraperitoneal injection of 800 mg/kg toluene significantly increased motor activity in rats, as did methamphetamine (MAP) (1 mg/kg). However, 800 mg/kg toluene did not affect the extracellular levels of DA, 3,4-dihydroxyphenylacetic acid, homovanillic acid, or 5-hydroxyindoleacetic acid. This is in contrast to MAP, which significantly increased extracellular DA and decreased the extracellular levels of its metabolites. These results suggest that toluene-induced behavioral augmentation may not be associated with alterations in DA or serotonin neurochemistry such as are associated with MAP-induced behavioral augmentation.

Metabolic acidosis and renal tubular injury due to pure toluene inhalation

A 22-y-old woman was hospitalized for muscle weakness of her lower extremities after she sniffed approximately 6 l of pure toluene during the month prior to admission. The examinations on serum and urine revealed mixed hyperchloremic and high anion gap metabolic acidosis accompanied by impaired urinary acidification. Histopathological changes of the kidney were patchy areas of tubular injury. Acidosis normalized on the fourth day of admission, but both proximal and distal tubular dysfunction persisted. These findings indicate that toluene is a tubular toxin and may contribute to the development of distal renal tubular acidosis.

Asbestos and nonasbestos fiber content in lung tissue of Japanese patients with malignant mesothelioma

BACKGROUND

Pulmonary fiber content of both asbestos and nonasbestos types were evaluated in Japanese patients with malignant pleural mesotheliomas.

METHODS

Pulmonary fiber content was analyzed in 16 patients and 16 case-matched control subjects by transmission electron microscopy with energy-dispersive X-ray analysis using a low-temperature ashing procedure.

RESULTS

The geometric mean content of total asbestos was significantly higher in the patients (22.0 x 10(6) fibers/g dry lung) than in the control subjects (2.24 x 10(6) fibers/g dry lung) (P < 0.01). When the asbestos content was analyzed by fiber type, the geometric means were also consistently and significantly higher among the patients compared with the control subjects (P < 0.01). Results were as follows: (1) amosite: patients 3.94 times 10(6) versus control subjects 0.23 x 10(6); (2) crocidolite: patients 3.56 times 10(6) versus control subjects 0.35 times 10(6); (3) total amphiboles: patients 16.0 times 10(6) versus control subjects 0.77 times 10(6); and (4) chrysotile: patients 3.76 times 10(6) versus control subjects 1.01 times 10(6). However, when individual total asbestos content was considered, 7 of the 16 patients (44%) had levels lower than the highest value noted among the control subjects. Pulmonary fiber content of patients and control subjects also revealed the presence of nonasbestos fibers. The geometric mean of nonasbestos fibers was significantly higher in the patients (87.3 x 10(6)) than in control subjects (33.8 x 10(6)) (P < 0.01). The major type of nonasbestos fibers in both groups was aluminum silicates. The mean of ratios of nonasbestos fiber contents to total asbestos contents in the patients and control subjects was 7.0 and 17.3, respectively.

CONCLUSIONS

The results were mainly in agreement with the findings of earlier investigations, but fiber content of both chrysotile and nonasbestos fiber as well as those of amphibole asbestos were significantly higher in the patients than in the control subjects.

[Medical examination of workers exposed to lead in the Philippines]

The medical examination of workers exposed to lead was conducted as part of the activity of the Occupational Safety and Health Center (OSHC) Project in the Philippines (JICA Project). The subjects of the medical examination were 21 male and 193 female workers of a semi-conductor plant (abbreviated A company), 59 male and 6 female workers of a refrigerator manufacture (B company); 199 male workers of a storage battery manufacturer (C company); and 107 male and 6 female workers of a lead smelter (D company). Among the examination items were questions regarding occupational history, subjective complaints and objective signs, determination of blood lead levels, urine delta aminolevulinic acid levels, and examination for anemia. The survey was conducted from June to September in 1990. The following results were obtained: 1) The mean age of the workers ranged from 21.8 to 33.8 years. Those of companies A and B were younger than those of companies C and D. The mean employment duration of males at C company was 10.7 yr, and the longest among the four companies. That in both sexes for A company was 1.8 yr and the shortest among the above mentioned companies. 2) The blood lead geometric mean levels of companies C and D showed the highest concentration. The level in males of C company was 64.5 micrograms/dl and that of D company was 80.8 micrograms/dl. The level in females of A company was 9.9 micrograms/dl and the lowest in concentration. The urine delta aminolevulinic acid geometric mean levels were less than 6.0 mg/l in the four companies. There was no company having hemoglobin mean values less than 14.0 g/dl in males or less than 12.0 g/dl in females. 3) The proportion of blood lead levels of 60 micrograms/dl or more was 67.3% in males of C company, and 89.7% in males and 16.7% in females of D company. The proportion of urine delta aminolevulinic acid levels of 6 mg/l or more was 1.0% in females of A company, 20.1% in males of C company, and 43.0% in males of D company. The proportion of hemoglobin values less than 14.0 g/dl in males or less than 12.0 g/dl in females was 4.7% in females of A company, 1.7% in males of B company, 3.5% in males of C company, and 12.1% in males of D company.(ABSTRACT TRUNCATED AT 400 WORDS)

[Inhaled nonasbestos fibers; pulmonary concentrations and fiber size in autopsied urban residents]

Nonasbestos fiber concentrations and fiber size distribution in autopsied lung tissues of 53 urban residents (34 males and 19 females) were analyzed by low temperature ashing-analytical transmission electron microscopy. The following findings were obtained. 1. Pulmonary nonasbestos fibers were found in all samples. Fiber consisting mainly of aluminum and silicon represented 80.0% of the total nonasbestos fibers observed. 2. The geometric mean concentration of nonasbestos fiber was significantly higher in males (47.6 x 10(6) fibers/g dry lung) than in females (18.2 x 10(6) fibers/g dry lung) (p < 0.05). This may be caused by differences in occupational exposure to nonasbestos fibers between males and females. 3. In females, the geometric mean concentration of nonasbestos fibers of smokers (34.6 x 10(6) fibers/g dry lung) was higher than that of nonsmokers (11.4 x 10(6) fibers/g dry lung), while, in males, the geometric mean concentration of nonasbestos fibers was lower in smokers (53.9 x 10(6) fibers/g dry lung) than in nonsmokers (89.1 x 10(6) fibers/g dry lung). These differences were not statistically significant. 4. The mean value for the ratio of nonasbestos fiber to asbestos concentration which ranged from 2.3 to 268 in males, and from 1.3 to 52.0 in females, was 30.1 and 20.2 respectively. 5. The mean length, diameter and aspect ratio for nonasbestos fibers were 1.01 microns, 0.103 microns and 11.3, respectively. Although nonasbestos fibers were almost equal in length to asbestos, the mean diameter of nonasbestos fibers was almost one-half of that of asbestos. Most of nonasbestos fibers (99.0%) were too small to be visible by light microscopy.

Urinary metabolite levels and symptoms in Filipino workers using organic solvents

To compare symptoms with urinary metabolite levels, 900 workers from 7 organic solvent-using industries were studied. Urinary metabolites were determined using a high performance liquid chromatograph. Urinary hippuric acid concentrations exceeding the reference value (2.5 g/g creatinine) were found in 78 (8.7%) workers. However, only 3 (0.3%) and 1 (0.1%) of the participants exceeded the reference value for mandelic (0.8 g/g creatinine) and total methylhippuric acid (1.5 g/g creatinine), respectively. The sum of the values of the ratio of measured urinary metabolite concentration to the corresponding ACGIH's biological exposure indices (BEI) [(HA/BEI of HA + MHA/BEI of MHA + MA/BEI of MA)] exceeded 1.0 in 166 (18.4%) workers. Majority of them were from the footwear manufacturing industry (63/129 or 49.2%). Questionnaire interviews were also administered to determine the prevalence of symptoms while at work (acute symptoms) or within the past 6 months (chronic symptoms). Urinary metabolite levels of individual and mixed solvents were compared with the symptoms of all workers. Analysis using Spearman's rank correlation showed in workers whose urinary hippuric acid exceeded 3.75 g/g creatine (1.5 x BEI), significant correlation between their hippuric acid levels and subjective complaints. Workers whose sum of the values of the ratio of measured urinary metabolite concentration to corresponding BEI exceeded 1.5 were selected and comparing this level with their symptoms, significant correlation was also noted in some complaints.

Modification of metabolism and neurotoxicity of hexane by co-exposure of toluene

The effects of co-exposure of hexane and toluene were investigated in field surveys and animal experiments. One field survey suggested that increase of hexane content in adhesives might have caused an outbreak of polyneuropathy in a vinyl sandal manufacture in Japan. The animal experiments proved that co-exposure of hexane and toluene decrease hexane neurotoxicity and urinary excretion of hexane metabolites in rats. The results also suggested that toluene might inhibit metabolism of hexane. Another recent field survey indicated that the ratio of urinary 2,5-hexanedione to hexane exposure in the workers co-exposed to hexane and toluene decreased in parallel with in more crease of toluene concentration. The results indicated that urinary excretion of 2,5-hexanedione could be depressed by co-exposure of toluene even in the workers exposed to relatively low concentrations. These above-mentioned results suggest that co-exposure of hexane and toluene could inhibit hexane metabolism and decrease hexane neurotoxicity in both experimental animals and workers. Although metabolism of hexane could be easily modified by toluene or other solvents and might not be a good indicator for hexane exposure in mixed exposure, urinary 2,5-hexanedione might be a good indicator for neurotoxicity of hexane even in mixed exposure.

Absence of blue-yellow color vision loss among workers exposed to toluene or tetrachloroethylene, mostly at levels below occupational exposure limits

Possible color vision loss was examined with Lanthony's new color test and Ishihara's color vision test in 261 solvent workers and 120 controls (48 men and 72 women). The solvent workers were exposed to either predominantly toluene [46 ppm as geometric mean (GM); 63 men and 111 women], tetrachloroethylene alone (13 ppm; 30 men and 34 women), or a mixture (14 men and 9 women) of tetrachloroethylene (12 ppm) and trichloroethylene (7 ppm). The only instances of color vision loss that were detected in either the exposed workers or the controls were six cases of red-green loss (all in men). These six cases of red-green loss showed an unbiased distribution between the exposed workers and the nonexposed controls.

[Asbestos concentration and fiber size in lungs of the urban residents]

Asbestos fiber concentrations and fiber size distribution in lung tissues of 53 urban residents (males: 34, female: 19) were analyzed by low temperature ashing-analytical transmission electronmicroscopy. The following findings were obtained. 1. Pulmonary asbestos fibers were found in 51 out of 53 patients. The types of asbestos fibers were chrysotile, amosite, crocidolite, actinolite and tremolite. 2. Thirty-six of 53 patients had no history of occupational asbestos exposure, and their geometric mean concentration of asbestos fibers was 1.67 x 10(6) fibers/g dry lung. Most of these asbestos fibers are probably attributable to general environmental contamination. Thirteen patients who had a history of occupational asbestos exposure showed a geometric mean of their pulmonary asbestos concentrations (5.82 x 10(6) fibers/g dry lung) which was significantly higher than that of patients without occupational asbestos exposure (p less than 0.01). 3. The geometric mean concentration of asbestos fiber in males (2.70 x 10(6)) was higher than in females (1.59 x 10(6)), probably due to a difference in the occupational asbestos exposure between males and females. 4. Regardless of the patient's sex, the geometric mean concentration of asbestos fibers in patients without a history of smoking (male: 4.91 x 10(6), female: 1.78 x 10(6)) was higher than that in patients with a smoking history (male: 2.76 x 10(6), female: 1.37 x 10(6)). The difference, however, was not statistically significant, and no correlation was seen between the concentration of asbestos fibers and smoking history. 5. Although most asbestos fiber utilized in Japan is chrysotile, the geometric mean concentration of chrysotile (0.87 x 10(6)) was almost identical to that of amphibole asbestos fiber (0.90 x 10(6)). 6. Of the asbestos fibers observed, 95% of chrysotile and 85% of amphibole asbestos were less than 5 microns in length and 93% of the total asbestos fibers were too small to be visible by light microscopy.

Determination of urinary 2,5-hexanedione concentration by an improved analytical method as an index of exposure to n-hexane

2,5-Hexanedione is a main metabolite of n-hexane and is considered as the cause of n-hexane polyneuropathy. Therefore, it is useful to measure 2,5-hexanedione for biological monitoring of exposure to n-hexane. The analytical methods existing for n-hexane metabolites, however, were controversial and not established enough. Hence, a simple and precise method for determination of urinary 2,5-hexanedione has been developed. Five ml of urine was acidified to pH 0.5 with concentrated hydrochloric acid and heated for 30 minutes at 90-100 degrees C. After cooling in water, sodium chloride and dichloromethane containing internal standard were added. The sample was shaken and centrifuged. 2,5-Hexanedione concentration in an aliquot of dichloromethane extract was quantified by gas chromatography using a widebore column (DB-1701). Urinary concentration of 2,5-hexanedione showed a good correlation with exposure to n-hexane (n = 50, r = 0.973, p less than 0.001). This method is simple and precise for analysis of urinary 2,5-hexanedione as an index of exposure to n-hexane.

Effects of subacute toluene exposure on neuronal and glial marker proteins in rat brain

The behavior of marker proteins of neurons (gamma-enolase) and glial cells (alpha-enolase, beta-S100 protein and creatine kinase-B) was investigated quantitatively by using enzyme immunoassay systems in toluene-exposed rat brains. Three groups of animals were exposed to toluene vapor at 300 ppm, 1000 ppm, and 3000 ppm, respectively, 8 h/day, 6 days/week, for 2 weeks. After subacute repeated solvent exposure, both neuron-specific gamma-enolase and glial marker proteins displayed an overall concentration-dependent increase tendency in separate brain regions. In cerebrum, only the 3000 ppm group showed a significant increase in alpha-enolase by 27% and creatine kinase-B (CK-B) by 26%. alpha-Enolase and gamma-enolase exhibited a pronounced elevation in cerebellum relative to other brain regions, while beta-S100 protein appeared to be the most markedly altered marker in brainstem. The development of gliosis, which is a frequent phenomenon following CNS damage, is presumed to be responsible for the elevation of glial marker content. Energy metabolism disruption in brain tissues may also bring about the compensatory oversynthesis of glycolytic enzymes such as gamma-enolase, alpha-enolase and CK-B. The dose-dependent alteration patterns following toluene exposure suggest the feasibility of using these brain specific markers to evaluate solvent-induced CNS effects.

Effects of MEK on kinetics of n-hexane metabolites in serum

The neurotoxicity of n-hexane is thought to be caused ultimately by 2,5-hexanedione (2,5-HD), one of the n-hexane metabolites. The potentiation of n-hexane neurotoxicity by co-exposure with MEK, therefore, is suspected to be related to kinetics of 2,5-HD in blood. To clarify the kinetics of n-hexane metabolites in the mixed exposure of n-hexane and MEK, rats were exposed to 2000 ppm n-hexane or a mixture of 2000 ppm n-hexane and 2000 ppm MEK, and the time courses of serum n-hexane metabolites were determined. 2,5-HD in serum increased until 2 h after the end of exposure, when serum 2,5-HD concentration reached a peak of 16.35 micrograms/ml in the n-hexane-alone group. In contrast, 2,5-HD in the mixed exposure group increased much more slowly during and after exposure than in the n-hexane-alone group. It reached a peak of 2.12 micrograms/ml at 8 h after the end of exposure. Serum MBK, a precursor of 2,5-HD in the co-exposure group, was about half in the n-hexane-alone group during exposure. However, MBK decreased more slowly in the co-exposure group than in the n-hexane-alone group after the end of the exposure. The results suggest that co-exposed MEK might inhibit oxidation of n-hexane and decrease clearance of n-hexane metabolites. Co-exposed MEK did not increase serum 2,5-HD, which was considered a main neurotoxic metabolite. Therefore the enhancement of neurotoxicity could not be attributed to increased serum 2,5-HD in the co-exposed group.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in urinary n-hexane metabolites by co-exposure to various concentrations of methyl ethyl ketone and fixed n-hexane levels

To make clear how the n-hexane metabolism is modified by co-exposure with MEK, rats were exposed to various concentrations of MEK mixed with a fixed concentration of n-hexane. Twenty-four male Wistar rats were divided into four equal groups. Each group was exposed for 8 h to 2000 ppm n-hexane, 2000 ppm n-hexane plus 200 ppm MEK, 2000 ppm n-hexane plus 630 ppm MEK and 2000 ppm n-hexane plus 2000 ppm MEK, respectively. Free metabolites and the sum of free and conjugated metabolites of n-hexane were analyzed by gas chromatography. The main metabolite was 2-hexanol during the exposure and 2,5-hexanedione (2,5-HD) after the exposure in any group. The main metabolites, 2-hexanol and 2,5 HD, decreased in inverse proportion to the co-exposed MEK concentrations. The results suggest that augmentation of n-hexane neurotoxicity by MEK co-exposure could not be explained only by 2,5-HD. In addition, 2,5-HD is recommended as an index for biological monitoring of n-hexane exposure. However, one should be careful to evaluate the exposed n-hexane concentration by urinary 2,5-HD, because n-hexane metabolism could be largely modified by co-exposure with MEK.

Effects of chronic n-hexane exposure on nervous system-specific and muscle-specific proteins

Two kinds of nervous system-specific and muscle-specific proteins, enolase and S-100 protein, were quantitatively determined in peripheral nerves and skeletal muscles of rats chronically exposed to a neurotoxic solvent - n-hexane. Three groups of animals were exposed to n-hexane vapor at three different solvent concentrations (500 ppm, 1200 ppm, 3000 ppm) for 12 h/day, 7 days/week for 16 weeks. The body weight gain and motor nerve conduction velocity (MCV) in exposure groups show progressively concentration-dependent decreases compared to control values. Histopathological examination also demonstrates the degeneration of peripheral nerves in 3000 ppm- and 1200 ppm-exposed rats. The significant decrease in the amount of S-100 protein in peripheral nerves was observed not only in the high level exposure groups (3000 ppm and 1200 ppm), but also in the lowest level group (500 ppm), although the MCV and morphological examination remained unchanged at this level. In addition, the muscle-specific S-100 protein in 3000 ppm exposed rats' soleus also displayed a significant reduction. In contrast to this, however, enolase isozymes were not significantly changed by either dosage level in both nervous tissue and skeletal muscle. The experiment suggests that beta- and alpha-S-100 proteins which are specifically localized in nervous system and muscles, respectively, are more vulnerable than enolase isozymes under treatment with n-hexane, and may possibly serve as a specific indicator to evaluate the neurotoxic effects. Further research would be worthwhile to elucidate the role of the specific S-100 protein in evaluating the neurologic damage induced by various industrial chemicals.

Asbestos fibers in human pulmonary and extrapulmonary tissues

The association between asbestos fibers in human lung tissues and those in other extrapulmonary organs was studied by analysing three autopsied cases, one of whom had a high pulmonary asbestos burden, one an intermediate burden, and one a low burden. The amount, types and sizes of asbestos fibers in the tissues of lung, liver, spleen, pancreas, kidney, and gastrointestinal tract were identified and measured by transmission electron microscopy equipped with an energy dispersive X-ray analyser. The following results were obtained: 1) The concentrations of asbestos fibers in extrapulmonary organs tended to increase with that in lung tissues. 2) The types of fibers identified in lungs were approximately consistent with those in other organs. 3) A relatively large range of fiber length was observed in both lungs and other organs. The findings extend and support previous light microscopic studies comparing asbestos bodies in various organs, and may imply that persons with high levels of asbestos in their lungs are also likely to have the same types and high levels of asbestos in their other tissues.

Relationship between chlordane and its metabolites in blood of pest control operators and spraying conditions

Chlordane has been widely used to protect soil and house foundations against termite infestation. Pest control operators (PCOs) are occupationally exposed to chlordane. The relationship between chlordane and its metabolites in blood of PCOs and spraying conditions were investigated. Chlordane and its metabolites were detected in the blood of some chlordane-exposed PCOs, but not in that of the controls. Trans-nonachlor and the metabolites oxychlordane and heptachlor epoxide were detected in the blood of PCOs. Total concentration of chlordane and its metabolites in blood (trans-nonachlor + oxychlordane + heptachlor epoxide) was less than 5.6 ppb (mean: 0.89 ppb). The concentration of chlordane and its metabolites in blood of chlordane-exposed PCOs was significantly correlated with the number of spraying days and the amount of chlordane sprayed, particularly with a large correlation coefficient (r = 0.81, P less than 0.001) with the spraying days in the three months prior to the medical examination. The concentration of chlordane and its metabolites in blood is considered to be a useful indicator of biological monitoring for chlordane exposed workers (PCOs).

[A nationwide survey on the use of organic solvents in Japan]

A total of 1,179 organic solvent products used as thinners, paint, degreasers, inks, adhesive and others, were collected nationwide from factories of various sizes and kinds in Japan, and analyzed by gas chromatography. Solvent components per sample, frequency of each solvent component, and contents of each component were analyzed and classified by use. Paints, inks, and adhesives which contained nonvolatile substances were analyzed by head space techniques. Seventy-seven percent of all samples, 93% of paints, 85% of thinners, 73% of adhesives, and 52% of degreasers contained mixed organic solvents. The average numbers of solvent components per sample were 4.14 (max. 13) in thinner, 3.29 (max. 7) in paint, 2.23 (max. 5) ink, 2.19 (max. 6) in adhesive, 1.71 (max. 6) in degreaser, when gasoline was excluded. Toluene, xylene, methylalcohol, isopropylalcohol, ethylacetate, methylethylketone, industrial gasoline were widely used in the above-mentioned products. Toluene was the most popular component in the solvent products, excluding degreasers. Many kinds of solvent components were used in thinner and paint. However, toluene, xylene and industrial gasoline were their main components and contents per sample were very high. Acetates, alcohols, ketones and glycols were frequently detected in solvent products, but their contents per sample were relatively low, because these solvent components were usually used as subordinate solvents. The chlorinated hydrocarbons such as trichloroethylene, tetrachloroethylene and 1,1,1-trichloroethane, and industrial gasoline were the most popular components in degreasers. 1,4-dioxane was detected in a relatively large number of the samples, but its content per sample was very low, because it is usually used as an additive to 1,1,1-trichloroethane. Toluene was the most popular component in ink solvents, too. In addition, isopropylacohol, methylalcohol, methylethylketone were frequently detected in inks. Toluene was also the most popular component in adhesives, and n-hexane was also frequently detected in them. In order to prevent poisoning by industrial solvents, special attention should be paid to toluene and xylene, which are frequently and largely used for wide purposes, trichloroethylene which is largely used as a degreaser and has a severe toxicity, n-hexane which is frequently used in adhesives and has a high volatility and severe neurotoxicity, and other popular and toxic solvents. The severely toxic solvents such as benzene, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane and carbon disulfide were detected in few samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes of n-hexane neurotoxicity and its urinary metabolites by long-term co-exposure with MEK or toluene

It is well known that the neurotoxicity of n-hexane may be modified upon co-exposure with other organic solvents. In order to elucidate this mechanism further, rats were exposed to 500ppm n-hexane, 500ppm n-hexane plus 500ppm methyl ethyl ketone (MEK), 500ppm n-hexane plus 500ppm toluene, or air only for 8h per day for 33 weeks. The body weight, motor nerve conduction velocity (MCV) and distal latency (DL) were determined before exposure and after 4, 8, 12, 16, 20, 24, 29, and 33 weeks of exposure. From each group one rat was histologically examined after 33 weeks of exposure. To establish a relationship between the n-hexane neurotoxicity and changes in biotransformation, urinary metabolites (2-hexanol, methyl n-butyl ketone (MBK), 2,5-hexanedione, 2,5-dimethylfuran, and gamma-valerolactone) were measured by gas chromatography on the first exposure day, and after 1, 2, 4, 8, 12, 16, 20, 24, 29, and 33 weeks of exposure. The total amounts of metabolites of n-hexane in the urine significantly decreased upon co-exposure of n-hexane, with MEK as well as with toluene, in comparison with those of animals exposed to n-hexane alone. 2,5-Hexanedione, which is considered the ultimate neurotoxic metabolite of n-hexane, also decreased. Electrophysiological and histological studies did not reveal statistically significant differences between any two groups among the four groups. It is considered that the present results might explain the combined effects of n-hexane and toluene which decrease n-hexane neurotoxicity, but do not explain those of n-hexane and MEK. Therefore, other mechanisms of the combined effects of n-hexane and MEK should be studied.

[Vibration hazards in quarry workers]

Vibration hazards were surveyed in a population of quarry workers using chipping hammers and to a lesser extent, rock drills. Sixty-nine male quarry workers, aged 49.1 +/- 8.7 and exposed to vibration for 16.4 +/- 5.1 years, were surveyed in 1981-82. They were exposed to vibration for about 2-4 hours per days, mainly under a piece-work pay system. They had a high prevalence of Raynaud's phenomenon (36.2%) and numbness in upper extremities (53.6%). It is considered that the high prevalence was mainly due to large vibration levels in chipping hammers and rock drills and long daily exposure time. The attacks of Raynaud's phenomenon were found predominantly in the left hand, which held chisels, whereas the restriction of motion in the elbow was predominantly in the right arm which pushed chipping hammers. The same 49 male quarry workers in this population were also surveyed in 1976-77 and the prevalence of their complaints between 1976-77 and 1981-82 was compared. The prevalence of Raynaud's phenomenon was the same, but the frequency of the attacks increased between the two periods. The prevalence of other complaints such as numbness, pain and chills in the upper extremities also increased. Between 1976-77 and 1981-82, the prevalence of Raynaud's phenomenon, numbness, and pain in the upper extremities increased in the population of quarriers exposed to vibration for above 2.6 hours per day and 200 days per year, or 600 hours per year. On the other hand, the prevalence of these complaints mostly decreased in the population of quarriers with less exposure.