[Older soil contaminations and human biomonitoring--two typical examples]

A health risk assessment of inhabitants had to be accomplished in two areas of former color production works, which had caused considerable soil contaminations predominantly with arsenic and lead.

Samples of soil, blood and urine were analysed during orientation and detail investigations according to the German soil protection laws.

The soil investigations revealed high contaminations in some parts of the two areas (maximum concentrations 550 mg arsenic/kg and 9100 mg lead/kg in residential topsoil from depths of 0-35 cm). Contrary to these findings, arsenic levels in the urine and lead levels in the blood of most of the residents were lower than the reference values for the common German population (arsenic 15 microg/L, lead 50-90 microg/L). In some cases of elevated biological concentrations, other sources of exposure could be detected like drinking tea from a tea-pot with a lead-containing glaze or drinking water from a highly contaminated garden well; interventional measures resulted in major decreases in the internal loads of these people.

The investigations clearly showed that an exposure via the pathway soil--water--human can be of serious health concern whereas older soil contaminations are seemingly of low relevance with regard to the direct contact of persons during daily life on those areas. Therefore, it is recommended to increase the soil examination values ("Prüfwerte") of the German soil protection laws by a default factor of 2 or 3 in cases of soil contaminations older than 20 years.