A small, light and inexpensive pocket flicker (P. F.) apparatus for measuring fatigue was designed, fabricated and tested. The apparatus, being composed of a light emitting diode and a variable resistor with a scale, is so compact that it can be carried in a shirt pocket. Thus, critical fusion frequency (CFF) values can be easily determined at a working place and the load involved is small when compared to other physical fatigue measurements and earlier CFF apparatuses. Moreover, the apparatus is so inexpensive that it can be widely used.
To compare the performance of the P. F. apparatus with earlier apparatuses, the following experiments were performed. CFF values were measured at the same time with the pocket type apparatus, blinking type apparatus and sector type apparatus and the results were compared. The subjects were 13 males and 5 females with their age ranging from 21 to 52 years. The total number of measurments was 132.
The CFF values measured with these three apparatuses showed a significant correlation. The correlation coefficient between the CFF values measured with the sector type apparatus and blinking type apparatus was high, but the slope of the regression line was not one. Hence, in comparing the values measured with another apparatus, we should be aware of the differences between these data. The correlation coefficients between the CFF values measured with P. F. apparatus and with sector type apparatus or blinking type apparatus were not higher than those between the CFF values measured with sector type apparatus and blinking type apparatus. As the standard deviation of the CFF values measured with the P. F. apparatus was higher than that calculated from other apparatuses, the CFF values measured with the P. F. apparatus are less accurate than those measured by other apparatuses. The results of these experiments suggest that the P. F. apparatus is an effective tool for measurement of fatigue. However, some problems (durability and precision) must be resolved before its practical use and therefore improvements should be made by further experiments.

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The effects of benzene and its metabolites, phenol and hydroquinone, on natural killer (NK) activity in mouse spleen cells in vitro were studied. NK activity was evaluated by the specific release percentage of ⁵¹Cr from labeled YAC-1 cells after YAC-1 cells (target cells) were incubated with spleen cells (effector cells) of mice at ratios of effector cells to target cells (E/T) of 100/1, 50/1, and 25/1. Benzene was shown to inhibit NK activity at concentrations of 1×10^-5 M5×10^-5 M, phenol at concentrations of 1×10^-75×10^-5 M and hydroquinone at concentrations of 1×10^-6 M1×10^-5 M. Phenol and hydroquinone depressed NK activity in a dose-dependent manner.
This study demonstrated that NK cell function of mouse spleen was depressed by exposure to benzene and its metabolites in vitro. Hydroquinone and phenol have very potent toxicity for suppression of immunosurveillance.

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A physiologically based pharmacokinetic model was developed to describe the transfer of organic solvent vapors in the human body. The model was composed of seven tissue compartments, i.e., lungs, vessel-rich tissues, vessel-poor tissues, muscles, fat tissues, gastrointestinal tissues, and liver, each being interconnected by the blood flow system. Transfer of organic solvents was expressed in the form of simultaneous differential equations, which were then solved numerically on a personal computer using a simple spreadsheet program. The simulation of pharmacokinetic behavior of trichloroethylene with this model was found to be in general agreement with the experimental data. The usefulness of physiological simulation model to elucidate some toxicokinetic aspects of human exposure to organic solvent vapors are discussed.

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The relationship between external dose and internal dose of trichloroethylene (Tri) was analyzed by using a physiological simulation model. The external dose of Tri was represented by the time-weighted average (TWA) concentration in inhaled air or by the product of exposure concentration and exposure duration, and the internal dose by the area under the curve (AUC) of Tri blood concentration or by the cumulative amount of total trichloro compounds (TTC) in urine. If TWA concentrations were equal, the internal doses were also equal irrespective of whether Tri exposure was continuous, intermittent, or random. Both AUC of Tri and cumulative amounts of urinary TTC increased linearly with increase of Tri concentration in inhaled air up to 100 ppm. The increase at exposure concentrations between 100 and 500 ppm was non-linear. At concentrations above 500 ppm where Tri metabolism was saturated, AUC increased linearly again but much more sharply than the increase at concentrations below 100 ppm. In contrast, the increase of cumulative amounts approached a plateau along with Tri exposure concentration. If the exposure concentration was below the level when saturation of Tri metabolism did not occur, equal products of Tri concentration and exposure duration resulted in almost the same internal dose. In general, however, the AUC of blood concentration in a high-concentration, short-duration exposure was larger than that of a low-concentration, long-duration exposure, whereas the cumulative amount of TTC was larger in the latter than in the former.

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Toxicokinetic behaviors of trichloroetylene were analyzed by using a physiological simulation model and the effects of physical activity (work load), body fat content and alcohol consumption on the uptake, distribution and excretion of this solvent were studied. This simulation study was not intended to predict the exact kinetic behavior of trichloroethylene in man, but to show how a physiological pharmacokinetic model is used to elucidate some aspects of individual differences in the kinetics of organic solvent vapors in human exposure. The following results were obtained:
1. Physical activity of 50 W during exposure greatly increases the blood concentration of trichloroethylene and the urinary excretion of its metabolites, whereas the activity after exposure exerts only a marginal influence.
2. Body fat content substantially affects the kinetic behavior of trichloroethylene only when the blood flow through fat tissue is assumed to increase according to the increase in body fat volume. In general, both blood concentration of trichloroethylene and urinary excretion rate of its metabolites are higher in slim men than in obese men during exposure, and the relationship is reversed between obese and slim men after exposure.
3. Ethanol-induced inhibition of trichloroethylene metabolism causes a marked change in the kinetic behavior when trichloroethylene exposure level is low, whereas the greater is the effect of ethanol-induced enhancement of metabolism, the higher the exposure level.

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In the investigation of the exposure conditions to organic solvents of workers in 35 waste water treatment facilities, it was found that these workers treated various kinds of solvents. Almost all of the facilities treated chloroform, acetone, n-hexane, methanol and carbon tetrachloride. The average exposure concentration of the workers was, however, low.
Exposure concentration to organic solvents (chloroform, xylene and carbon tetrachloride) was evaluated in one of the facilities. The average concentration of the respective solvents in the workers did not exceed the threshold limit value of Japan, but the concentration calculated on the basis of combined exposure exceeded the threshold limit value. On the other hand, high concentrations of organic solvents were detected in the room where the solvents were introduced but not in the working rooms, indicating that the workers engaged in waste water treatment were mainly exposed to organic solvents in the former room where they sorted and mixed the solvents and placed them in the incinerator.
In conclusion, improvement in working conditions and health care for workers engaged in waste water treatment facilities should be made in order to prevent workers from becoming intoxicated by organic solvents.

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Developmental effects of single prenatal trimethyltin exposure were examined in THA rats. Pregnant rats were injected on gestational day 12 with single dose of trimethyltin chloride (TMT) ip at either 0, 5, or 7 mg/kg.
Significant differences between treated and control offspring rats could not be observed in terms of body weight, pinna detachment, incisor eruption, eye opening, surface righting, cliff avoidance, pivoting, negative geotaxis and auditory startle. Spontaneous motor activity and open field behavior in the rats were also not affected by TMT. In Sidman avoidance test, however, the avoidance rate of the treated offspring rats was lower when compared to that of the controls.
These results suggest that prenatal TMT administration disrupts learning acquisition.

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