Past human societies modified their environment in several ways; however, the extent of these modifications is, in many cases, poorly known. Under the Roman rule, extensive environmental changes took place, in the Western Empire in particular. During this historical period, atmospheric levels of several potentially toxic metals, such as mercury, increased substantially due to intense mining and metallurgy. These activities left behind their imprint in both the landscape and humans.
This research is focused in A Lanzada (NW Iberia) - a rural necropolis placed relatively far away from the neuralgic sources of mercury emissions during Roman period. The aim was to find out variations in mercury levels in human remains. Human (cortical) bone was analysed from skeletons covering contrasting periods of atmospheric p ollution (Roman, AD 1st-4th centuries, post-Roman, AD 5th -7th centuries). Samples from 3 types of bone (n=143; ribs, long bones and crania) as well as soils/sediments associated to the burials (n=34) were analysed. Mercury concentrations in soils were below 5 ng g-1, while the average in bone was 36±52 ng g-1, making post-depositional incorporation unlikely. Concentrations were found to be significantly different between the two periods (Roman: 54 ± 60 ng g-1, post-Romans: 21±23 ng g-1), but for type of bone, sex, age, social status or diet of the individuals they were not. Values from Roman times were moderately elevated when compared with other collections of individuals subjected to direct mercury exposition. These results agree well with the chronology of mercury pollution reconstructed from a local peatland, suggesting a predominant atmospheric source. Our study shows that, as it happens today, rural Roman populations were mostly affected by low dose chronic mercury exposure, whose levels varied with the intensity of the anthropogenic activities.