Biological monitoring of mercury vapour exposure by scalp hair analysis in comparison to blood and urine.

The reliability of human scalp hair as an indicator of mercury vapour exposure is contentious. In this study mercury concentrations in hair were compared with those in blood and urine of 20 dental students during their first "occupational" exposure to mercury vapour. Samples were collected before, at the end of the technical course of operating dentistry which lasted 6 weeks, and 3 months later. Mercury was measured by cold vapour atomic absorption spectrometry. In all biological media studied, mercury levels significantly (P < 0.05) reflected exposure to mercury vapour. After the time period without exposure mercury content decreased. Hair mercury levels were correlated to those in erythrocytes at sampling times 1 and 3 (r = 0.686 and r = 0.492) and to the frequency of fish consumption at sampling time 1. It is concluded that hair may be used as an indicator of internal uptake of mercury provided that it was not externally exposed to mercury vapour. In cases of occupational exposure to mercury vapour, hair is an useful tool for monitoring external exposure.