Recent observations have shown a great decrease in the levels of atmospheric lead concentrations in cities in Japan today compared with levels in the 1950's, probably due to rigid control of lead discharge from factories and the promotion of lead-free gasoline in particular. We attempted to estimate the amount of lead inhaled and absorbed by the human body in Japan today. With the average atmospheric lead concentration in the average Japanese city today at about 0.1μg/m3, we obtained the values of 1.6 to 2.2μg/day for the amount of lead inhaled and 0.8 to 1.1μg/day for the amount of lead absorbed by the average Japanese adult.
A lysosomal enzyme, N-acetyl-β-D-glucosaminidase (NAG) is abundant in kidneys and has various isoenzymes. An increase in urinary NAG activity is found in workers exposed to nephrotoxic chemicals. Urinary isoenzyme determination is accepted as a method of identifying affected nephron lesions. We did a NAG isoenzymes determination using isoelectric focusing and the MCP-NAG method. This method was applicable to normal urine with condensation by Centricut (2500G×60min). In 17 normal urine samples, 77.5% of the total NAG was found as a NAG A form, and 22.5% as a NAG B form. These values agreed well with earlier reports. The calibration curve of NAG activity in electrofocused gels gave a good linearity over the range of 0-206U/L. The reproducibility was sufficient since the intra-assay coefficient of variation was 5.6% (n=10). The separation level of isoelectric focusing is regarded to be better than that of the electrofocusing procedure. Moreover, 15 samples can be analyzed at once. Thus, our method satisfied the requirements for separation ability, linearity, reproducibility, and time-saving. This method will be applied to workers exposed to nephrotoxic chemicals in the future.
A questionnaire study on daily life style and subjective healthiness was conducted on students, housewives and workers. About 80 percent considered themselves subjectively in “excellent” or “normal” health. The percentage of “excellent” for males was higher than for females, particularly nurses. Subjects who replied “excellent” or “normal” for subjective healthiness included the following items in daily life style: having 7-8 hours sleep every day, exercising 2-3 times a week, always having breakfast, considering nutritional balance, not smoking, and not or usually not feeling stress. The rate of unhealthiness (percentage of “not well” or “ill” replise) was in proportion to scores of unhealthiness (the sum for items considered unhealthy for daily life styles). The questionnaire can be used for both individuals and groups.
The first-order rate theory may be useful for estimation of the accumulation in the body in the experiments of consecutive administration. With this theory, the balance of lead in the human body was estimated in each case of 9, 13 and 17μg of daily lead absorption by assuming the ultimate limit of accumulation in the body is 80mg and that half-life time of hard tissues (bone, teeth) is 10 years. If 99 of the ultimate limit of accumulation is regarded as “actual ultimate limit of accumulation”, good results were obtained. The estimated parameters are following; the daily absorption of lead is 13 to 17μg, and the time to reach “actual ultimate limit of accumulation” is 60 to 78 years.