Mercury in hair: Method development and application to population studies.

As part of the Avon Longitudinal Study of Pregnancy And Childhood, the toxic metal, mercury, is studied in order to assess whether it presents a danger to the development of children in the UK.The development and optimisation of a digestion procedure for the determination of total mercury in hair is described. The procedure chosen consists of the microwave digestion of 0.2-0.5g hair with 2 ml HNO3 and 1 ml H2O2 . The effect of washing and drying of the samples is investigated, and found not to influence analytical results when hair samples are collected after shampooing. However, freeze-drying of the samples results in the loss of 30% of mercury. The distribution of mercury along the length of a strand of hair is studied. It is shown to vary in adults (up to a factor of 7) but not in children (less than 20%). In the applications of this analytical method to population studies, the frequency of fish meals, and the age of the subject are positively correlated to the mercury levels in adults' hair (r = 0.539 and 0.513, respectively). Breast-feeding and mercury levels in children's hair are also correlated (r = 0.433). The relationship between number of fillings and mercury levels in adults' hair is not significant. No correlation was found between mercury levels in children's hair and Developmental Quotient (Griffith's scales) (r = -0.24 to 0.18).The optimisation of a coupled High Performance Liquid Chromatography - CV-AFS system for the study of mercury speciation is described. The use of KOH and microwave digestion for the extraction of mercury species was unsuccessful, and thus recommendations for future work are made.