Water Quality Standards

Barium occurs as a number of compounds in the earth's crust and is used in a wide variety of industrial applications, but it is present in water primarily from natural sources. In general, food is the principal source of exposure to barium; however, in areas where barium concentrations in water are high, drinking-water may contribute significantly to total intake. Intake from air is negligible.

Although an association between mortality from cardiovascular disease and the barium content of drinking-water was reported in an ecological epidemiological study, these results were not confirmed in an analytical epidemiological study of the same population. Moreover, in a short-term study in a small number of volunteers, there was no consistent indication of adverse cardiovascular effects following exposure to barium at concentrations of up to 10 mg/litre in water. There was, however, an increase in the systolic blood pressure of rats exposed to relatively low concentrations of barium in drinking-water.

A guideline value of 0.7 mg/litre (rounded figure) was derived using the NOAEL of 7.3 mg/litre from the most sensitive epidemiological study conducted to date, in which there were no significant differences in blood pressure or the prevalence of cardiovascular disease between a population drinking water containing a mean barium concentration of 7.3 mg/litre and one ingesting water containing barium at 0.1 mg/litre, and incorporating an uncertainty factor of 10 to account for intraspecies variation. 

This value is close to that derived on the basis of the results of toxicological studies in animal species. A TDI of 51 µg/kg of body weight was calculated, based on a NOAEL of 0.51 mg/kg of body weight per day in a chronic study in rats and incorporating uncertainty factors of 10 for intraspecies variation and 1 for interspecies variation, as the results of a well-conducted epidemiological study indicate that humans are not more sensitive than rats to barium in drinking-water. The value derived from this TDI based on 20% allocation to drinking-water would be 0.3 mg/litre (rounded figure).

The guideline value for barium in drinking-water is 0.7 mg/litre.