Prolonged exposure of soil and sediment invertebrates to toxic Polycyclic Aromatic Compounds (PACs)* has large and unpredictable effects on the life cycle of these species, concludes Dutch researcher Miriam León Paumen.
These chronic effects can be very different from the effects of short-term exposure to PACs. Therefore, assessments of soil and sediment contamination are more reliable when they are based on the effects of prolonged exposure of soil and sediment fauna to toxic substances.
The effects of Polycyclic Aromatic Compounds (PACs) on terrestrial and benthic invertebrates are used to estimate the risks of soil and sediment contamination. Effects are assessed exposing the organisms to PACs in life cycle tests. In seventy percent of cases this results in highly predictable effects on development of the exposed invertebrates. León Paumen has now demonstrated that the effects of prolonged exposure can be very different and so risk assessments based on such measurements are more accurate.
Worms, springtails and chironomids
León Paumen examined the effects of two 'standard' (regulated) and four 'new' (non-regulated) PACs on one or more generations of terrestrial and aquatic invertebrates. The animals; two species of worm, a springtail and a chironomid species were found to exhibit highly predictable arrested development in seventy percent of cases when subjected to the influence of artificially PAC contaminated soil and sediment.
However, prolonged exposure also demonstrated that large and unpredictable effects on the life cycle frequently occur, mainly due to exposure to the 'new' PACs. Moreover, a multigenerational experiment revealed that the influence of these toxic substances over several generations is unpredictable. The usual concentration-response relationships changed into an all-or-nothing response with a clear threshold value. This analysis has therefore demonstrated that gradual effects cannot be assumed in risk assessments for soil and sediment contamination.
PACs are ubiquitous in the environment and have therefore been designated as priority toxic substances by the European Union. PACs often determine the need for soil and sediment remediation. Risk limits are determined by means of a risk calculation based on short-term effects of PACs on aquatic organisms. This method is, however, disputed. León Paumen´s research has provided opportunities to improve the accuracy of risk assessments and the Dutch firm Bioclear has already used some of the techniques applied at contaminated locations.
Other participants in the project are the National Institute of Public Health and the Environment (RIVM), the Ministry of Housing, Spatial Planning and the Environment, the Water Service and Deltares, Arcadis and Bioclear. The crude oil industry (NAM and EXXONMobil) was also involved in the project due to the importance of PACs in crude oil and its combustion products.
*Polycyclic aromatic compounds, are chemical compounds that contain at least three fused aromatic rings that may include heteroatoms like N, O, and S and that may carry substituents.
The above story is based on materials provided by NWO (Netherlands Organization for Scientific Research). Note: Materials may be edited for content and length.
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