Simulation of average energy expenditures and related inhalation rates for the US population

Inhalation rates (rVe) for determining intakes of air pollutants generally must be estimated because it is difficult to make direct inhalation measurements in free-standing populations. The key to quantifying rVe is to estimate the oxygen consumption rate (rO2) required to sustain an individual's total daily energy expenditure (TDEE) and then to convert rO2 to rVe using the ventilatory equivalent for oxygen (VQ). To estimate TDEEs for U.S. population cohorts, nonlinear equations that predict TDEE were developed using data derived from doubly labeled water metabolic studies involving 222 groups with a total of 6,027 subjects. Monte Carlo sampling of lognormally distributed body weights, VQ values, and error terms of the TDEE predictions were then used to simulate average TDEE and rVe for U.S. population cohorts. The maximum TDEE value for males was 13.5 MJ/day, which occurred within the 19-29 year age cohort, and for females it was 10.4 MJ/day at ages 18-19 years. Analyses of the relationship between the body mass index (BMI) and physical activity level (PAL = TDEE A center dot resting metabolic rate) showed that PAL is not very sensitive to changes in BMI. The highest daily inhalation rates for males and females were 17 and 13 m(3)/day, respectively, and estimated breathing rates for active (nonresting) hours were about a factor of two greater than for inactive (sleep/resting) periods. Finally, it was shown that efforts to control obesity in the USA have the potential for reducing inhalation rates due to the decreased oxygen/energy requirements of lower body weights.