Arsenic in Danish and Swedish Mesolithic and Neolithic human bones - diet or diagenesis?

Arsenic has previously been measured in a bone sample of a c. 5-year-old Mesolithic child from Nivaagaard in Denmark yielding an anomalously high value of 13 μg/g. In the present work we show that other individuals at a nearby site also exhibit elevated arsenic levels, whereas individuals from other Mesolithic sites in Denmark are found to have quite low As-concentrations. Several attempts to reveal the source of the arsenic are reported: A railway track near the site, where the railway sleepers were suspected to have been impregnated with As leading to transport or diffusion of As into the adjacent soil; Several food items, the remains of which were found at the site, and one food item not preserved in the excavation, i.e. seaweed. Finally, it is shown that the most likely explanation of the elevated arsenic levels in human bones at Nivaa is diagenesis.