From bioavailability science to regulation of organic chemicals

The bioavailability of organic chemicals in soil and sediment is an important area of scientific investigation for environmental scientists, although this area of study remains only partially recognized by regulators and industries working in the environmental sector. Regulators have recently started to consider bioavailability within retrospective risk assessment frameworks for organic chemicals; by doing so, realistic decision-making with regard to polluted environments can be achieved, rather than relying on the traditional approach of using total-extractable concentrations. However, implementation remains difficult because scientific developments on bioavailability are not always translated into ready-to-use approaches for regulators. Similarly, bioavailability remains largely unexplored within prospective regulatory frameworks that address the approval and regulation of organic chemicals. This article discusses bioavailability concepts and methods, as well as possible pathways for the implementation of bioavailability into risk assessment and regulation; in addition, this article offers a simple, pragmatic and justifiable approach for use within retrospective and prospective risk assessment

A collaborative evaluation of LC-MS/MS based methods for BMAA analysis: soluble bound BMAA found to be an important fraction.

Exposure to β-Ν-methylamino-l-alanine (BMAA) might be linked to the incidence of amyotrophic lateral sclerosis, Alzheimer's disease and Parkinson's disease. Analytical chemistry plays a crucial role in determining human BMAA exposure and the associated health risk, but the performance of various analytical methods currently employed is rarely compared. A CYANOCOST initiated workshop was organized aimed at training scientists in BMAA analysis, creating mutual understanding and paving the way towards interlaboratory comparison exercises. During this workshop, we tested different methods (extraction followed by derivatization and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis, or directly followed by LC-MS/MS analysis) for trueness and intermediate precision. We adapted three workup methods for the underivatized analysis of animal, brain and cyanobacterial samples. Based on recovery of the internal standard D3BMAA, the underivatized methods were accurate (mean recovery 80%) and precise (mean relative standard deviation 10%), except for the cyanobacterium Leptolyngbya. However, total BMAA concentrations in the positive controls (cycad seeds) showed higher variation (relative standard deviation 21%-32%), implying that D3BMAA was not a good indicator for the release of BMAA from bound forms. Significant losses occurred during workup for the derivatized method, resulting in low recovery ( < 10%). Most BMAA was found in a trichloroacetic acid soluble, bound form and we recommend including this fraction during analysis

25 years monitoring of PAHs and petroleum hydrocarbons biodegradation in soil

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPH) in sediment and soil has been monitored on seven experimental fields during periods up to 25 years. With this unique dataset, we investigated long-term very slow biodegradation under field conditions.. The data show that three biodegradation rates can be distinguished for PAHs: 1) rapid degradation during the first year, 2) slow degradation during the following 6 years and 3), subject of this paper, a very slow degradation after 7 years until at least 25 years. Beside 2-, 3- and 4-ring PAHs, also 5- and 6-ring PAHs (aromatic rings) were degraded, all at the same rate during very slow degradation. In the period of very slow degradation, 6% yr−1 of the PAHs present were removed in five fields and 2% yr−1 in two other fields, while in the same period no very slow degradation of TPH could be observed. The remaining petroleum hydrocarbons were high boiling and non-toxic. Using the calculated degradation rates and the independently measured bioavailability of the PAHs (Tenax-method), the PAHs degradation curves of all seven monitored fields could be modelled. Applying the model and data obtained with the Tenax-method for fresh contaminated material, results of long-term biodegradation can be predicted, which can support the use of bioremediation in order to obtain a legally acceptable residual concentration.</p

Validation of ISO 16751 Soil Quality - Environmental availability of non-polar organic compounds : Determination of the potentially bioavailable fraction and the non-bioavailable fraction using a strong adsorbent or complexing agent

ISO/TC190/Soil Quality has developed a standard to enable measurement of the bioavailability of organic contaminants in soil and soil like materials (ISO/TS16751), To become a full standard a validation is necessary. The validation is based on an intra laboratory validation carried out by the laboratory of Rijkswaterstaat in Lelystad (The Netherlands), and on an international interlaboratory validation study organized by WEPAL, Wageningen. Results are evaluated according ISO 5725. As decided by the responsible ISO-working group, the results support the transfer of ISO/TS 16751 into a full ISO-standard

Validation of ISO/DIS 20244 Soil quality - screening method for water content - determination by refractometry

ISO/TC190/Soil Quality has developed a standard to enable measurement of water content in soil and soil-like materials using a screening method ISO/DIS 20244. To become a full standard, the screening method required validation to show the applicability and comparability of the method in different laboratories (repeatability and reproducibility). This validation was organised by WEPAL, (Wageningen Evaluating Programs for Analytical Laboratories), which is part of Wageningen University in the Netherlands. 11 laboratories participated in the validation. Samples with comparable and known water content were distributed. Repeatability and reproducibility were calculated according ISO 5725. The measured water contents were lower than measured with ISO 11465. Probably the sucrose solution is not able to extract all water. Correction of the result using clay content and or organic matter content may be possible, but needs further investigation. The responsible ISO Working Group has to decide if and how the results can be added to ISO/DIS 20244 to become a full standard

Validation of a Horizontal Standard for the Determination of Polychlorinated Biphenyls (PCBs) in Soils, Sludge and Treated Bio-waste Using GC-MS and GC-ECD in a European Intercomparison Exercise

Project HORIZONTAL is interdisciplinary aiming at a harmonisation and horizontal standardisation of test procedures, in particular for sludge, soils and biowastes. In the context of this standardization project, a series of draft technical specification were designed upon an extensive desk study, fine-tuned after expert consultations and finally validated in international intercomparisons exercise. This report summarises the work performed within the validation study of the draft standard for the determination of poly-chlorinated biphenyls in soils, sludge and treated bio-waste using GC-MS and GC-ECD. It further explains the underlying statistical concept for the calculation of reproducibility and repeatability from intercomparisons data. In addition all single values, results of the statistical evaluation as well as background information on the validation materials used are described and explained.JRC.H.5-Rural, water and ecosystem resource

Certainties and uncertainties in accessing toxicity of non-extractable residues (NER) in soil

Background: Discussion concerning the bioavailability and ecotoxicological relevance of non-extractable residues (NER) in soil is still ongoing. Is NER formation a detoxification process or a hidden hazard? The use of radiolabelled chemicals enables detection of NER, but the identity of NER is usually unknown. Regulations require clear measurable parameters and the approach of Ortega-Calvo et al. (Environ Sci Technol 49:10255–10264, 2015) defines these. Results: Following that approach, we studied the fate of three ecotoxic, NER-forming chemicals over a period of 6 months after application to three different soils. Initial 14C experiments showed formation of NER for all chemicals. For the chemical 2,4,6-trinitrotoluene (TNT), NER-formation was reproducible in all soils. We applied a recently standardized method using Tenax® to remove the bioavailable fraction of the chemical at test start and test end. Removing the bioavailable fractions also removed toxicity. Further experiments without radiolabelled TNT clearly showed that the toxicity measured in applied soils was caused by the bioavailable chemical and not by NER. Conclusions: The tool developed can be used if the fate of the chemical including NER formation is well known and reproducible. The other selected chemicals, cypermethrin and carbendazim, showed unexpected behaviour in 14C-fate experiments. The degree of biodegradation was not reproducible for cypermethrin and unexpected losses occurred with carbendazim. This indicated a very large uncertainty when using non-radiolabelled compounds in NER experiments and thus the tool is not suitable in non-radiolabelled experiments.</p

Advances in the Development of Procedures to Establish the Toxicity of Non-Extractable Residues (NER) in Soil. LRI-ECO25

There is already a long discussion around the bioavailability and ecotoxicological relevance of Non Extractable Residues (NER) in soil. Is NER formation a detoxification process or should it be considered a hidden hazard? NER can only be established using labelled chemicals (e.g. 14C) and cannot be measured with conventional chemical analytics. Regulations ask for understandable and measurable parameters. Considered in the developed tool are three measurable parameters: 1) Chemical present in the water phase, 2) A potentially available fraction in equilibrium with the water phase. 3) The total extractable amount. NER is considered, but mentioned as non-measurable and non-bioavailable. The fates of three NER-forming chemicals were followed in a period of 6 months after addition also using 14C chemicals. For the chemical Tri-NitroToluene (TNT), NER-formation was reproducible and NER formation during aging removed toxicity. By removing the bioavailable fractions directly after spiking and after aging it was also possible to remove toxicity. The experiments showed that toxicity was caused by the bioavailable chemical and not by NER. With Cypermethrin and Carbendazim, results were less clear, because there was a large uncertainty in NER-formation. The degree of biodegradation was not reproducible for Cypermethrin and unexpected losses occurred with Carbendazim and it is not possible to draw conclusions from only a non-labelled experiments

Advances in the development of procedures to establish the toxicity of non-extractable residues (NER) in soil. LRI-ECO25

There is already a long discussion around the bioavailability and ecotoxicological relevance of Non Extractable Residues (NER) in soil. Is NER formation a detoxification process or should it be considered a hidden hazard? NER can only be established using labelled chemicals (e.g. 14C) and cannot be measured with conventional chemical analytics. Regulations ask for understandable and measurable parameters. Considered in the developed tool are three measurable parameters: 1) Chemical present in the water phase, 2) A potentially available fraction in equilibrium with the water phase. 3) The total extractable amount. NER is considered, but mentioned as non-measurable and non-bioavailable. The fates of three NER-forming chemicals were followed in a period of 6 months after addition also using 14C chemicals. For the chemical Tri-NitroToluene (TNT), NER-formation was reproducible and NER formation during aging removed toxicity. By removing the bioavailable fractions directly after spiking and after aging it was also possible to remove toxicity. The experiments showed that toxicity was caused by the bioavailable chemical and not by NER. With Cypermethrin and Carbendazim, results were less clear, because there was a large uncertainty in NER-formation. The degree of biodegradation was not reproducible for Cypermethrin and unexpected losses occurred with Carbendazim and it is not possible to draw conclusions from only a non-labelled experiments