As the number of mineral elements considered dietary essentials in human nutrition increases, nutritionists have been faced with a communication challenge. On the one hand, they must communicate the importance of these elements in maintaining a high level of health; on the other hand, because many of these elements are toxic at high levels, nutritionists must caution consumers about the hazards of intakes or exposures to environmental contaminants beyond a level which in many cases is not appreciably higher than recommended intakes.