A urine contaminant concentration per se has uncertain meaning for human health because of dilution by hydration. However, the estimation of the health-related daily intake dose of pollutant (mg/kg/day) that equilibrates with a spot urinary concentration of a pesticide residue or metabolite, or other analyte, can be made using creatinine-corrected toxicant levels (mg analyte/mg creatinine) multiplied by an estimate of the subjects' expected creatinine excretion rates (mg creatinine/kg/day). The objective was to develop a set of equations predicting a person's expected daily creatinine excretion (mg/kg) as a function of age, gender, race and morphometry, from birth to old age. We review the creatinine excretion literature where infants, children and adults provided 24 h total urine samples for creatinine analysis. Equations are developed for infants (r3 years), children (3-18 years) and adults (Z18 years) that match at 3 and 18 years. A series of equations that estimate daily creatinine excretion (mg/day) are developed that are piecewise continuous from birth through infancy through adolescence and through adulthood for males and females, and Black and White races. Complicating factors such as diet, health status and obesity are discussed. We propose that these equations, with caveat, can now be used with measured urine concentrations to consistently estimate the corresponding equilibrium intake doses of toxicants at ages from birth to 92 years for the healthy non-obese. We recommend that this system of equations be considered for future development and reporting of applied doses in mg/kg/day of pollutants and toxicants that are measured in urine samples, as in the National Health and Nutrition Examination Survey.

The Third National Health and Nutrition Examination Survey gathered health and job data from a sample of the US population. Researchers collected urine samples from a subset of subjects and analyzed it for 12 pesticide residues or metabolites (ie, analytes). They investigated the relationship between the industries and jobs reported and the analytes detected in the urine samples. The authors found an association between several jobs and the concentration for one or more pesticide analytes above the 90th percentile. They applied a job exposure matrix to categorize subjects on their potential for job exposures to pesticides. For the detected analytes, the subjects with the highest potential for occupational exposures to insecticides were more likely to have an analyte concentration above the 90th percentile and to have an average analyte concentration score 30% higher than that of subjects reporting jobs with the lowest exposure potential. These findings indicate that occupational exposure may not be a major source of pesticide exposure among the general population.