Amplitude and phase response of ventilation (V_E), carbon dioxide output (VCO₂) and oxygen uptake (VO₂) during sinusoidally varying work load for periods (T) of 1-16 min were studied in six healthy men. The relationships between these parameters and aerobic capacity (VO₂max, ATVO₂) were also examined. The results and conclusions obtained were as follows:
(1) The relationship between the period (T) of exercise and amplitude response of VO₂, VCO₂ and V_E was well described by first-order exponential models. However, the relationship between the period of exercise and the phase shift (phase responses of VO₂, VCO₂, and V_E) was better described by complex models comprising a first-order exponential function and a linear equation. This can be explained by Karpman's threshold theory.
(2) High negative correlations were observed between the steady-state amplitude (A) of phase response or the time constants (r) of amplitude response and VO₂max, and ATVO₂. Significantly high negative correlations for all gas exchange parameters may be more rapid in individuals with greater aerobic capacity.
(3) A close relationship between the response of VCO₂ and V_E was demonstrated by a higher correlation coefficient than that between VO₂ and VCO₂ or between VO₂ and V_E. This can be partly, but not completely, explained by the cardiodynamic theory.

The incidence of fluorosis, believed to arise from the burning of coal, has been frequently reported in the highlands in the southern part of China. With a lot of rain and a climate of low temperature, the hilly region produces coal and inhabitants use it as a fuel for cooking and heating. The fossil fuel used by them is mostly powdery. It is mixed with dirt and rolled up into bolls. In that way,the people make the briquettes that burn a long time.Ordinary houses have no chimneys to belch forth smoke, so that it stagnates indoors for a while. Soot and smoke, before flowing out via the openings in the roof shingle of the loft, spoils farm produce stored there. Because the smoke contains high concentrations of fluoride derived from coal and dirt, it is believed that eating farm produce exposed to the smoke is one of the major factors for fluoride poisoning. Many researchers have thus far analyzed farm products for fluoride content and confirmed that high levels of fluoride were contained in their samples.In the present study, we measured fluoride concentrations in some samples of corn and capsicum produced in a rural area of Sichuan, China on one hand and on the other examined the water-solubility of fluoride. Furthermore, screening tests for chronic endemic dental fluorosis were performed on students to survey the fluoride contamination in the past as compared with the present state.Incidentally, indoor air-borne fluoride concentrations in this area averaged out at0.047mg F/m3 (15 times as high as the mean in a community that was free of fluoride contamination). The fluoride content of the drinking water from a spring in the nearby hill, measured with use of a fluoride-specific electrode method,was within the range from 0.2 to 0.3μg/ml.
Fluorides ; Fluoride measurement ; China ; Coal ; Levels

A China-Japan joint project was carried out to study the incidence of fluorosis caused by coal burning in China from 1995 to 1997.
The health survey covered a control area and two flourosis areas. In those research areas, drinking water was not polluted with fluorides. The survey was designed to analyze the health status of people exposed to fluorides and evaluate the relationships between the dose and incidence of fluorosis. The concentration of airborne pollutants in both indoor and outdoor air was measured. The concentration of fluoride in the urine was analyzed and definite diagnoses for dental fluorosis and skeletal fluorosis were determined.
As a result, the incidence of coal burning fluorosis was confirmed in studied areas. Moreover, the fluorosis was caused not only by the direct inhalation of the airbone fluorides in indoor air but also by the intake of cereals polluted with fluorides. Fluoride was contained in both coal and soil. Therefore the mixture of coal and soil used for the adjustment of fire energy contributed to the air pollution to a great extent. The typical polluted crops were red pepper, corn and potato. An extremely high concentration of fluoride in the urine of residents in the polluted areas was detected.