Jutta Jahnel

Comparison of the Enzyme-Inhibition Effect of Different Humic Substances in Aqueous-Solutions

Abstract The enzymatic cleavage of the amide bond of l -leucine-4-nitroanilide by the proteolytic enzyme Pronase E releases 4-nitroaniline. The production of this molecule can be observed by the increasing UV absorption of the solution. A decrease in the rate of hydrolysis reaction was obtained in the presence of different humic substances isolated from water, sediment and soil. This result indicates that humic substances influence enzyme activity by interacting with the applied enzyme. A mathematical relation between the concentration of humic substances and their inhibition effect was used to calculate an effective concentration for which 50% of the maximum effect was observed. The obtained concentration was defined as the EC 50 value. The EC 50 values of the investigated humic substances were in the range 153 mg l −1 to 6360 mg l −1 . The amounts of humic substances used in the experiment were higher than in most aquatic environments. However, in bog water or interstitial water of sediments and soils such large amounts of biologically and ecologically relevant natural organic matter can be expected.

Zielvorgaben für Pflanzenschutzmittelwirkstoffe und andere Schadstoffe in Oberflächengewässern

In der vorliegenden Arbeit wurden fur ausgewahlte gefahrliche Stoffe Vorschlage fur Zielvorgaben zum Schutz der aquatischen Lebensgemeinschaften erarbeitet. Die vorgeschlagenen Zielvorgaben wurden auf der Grundlage der Leitlinien zur Ableitung von Zielvorgaben der Internationalen Kommission zum Schutze des Rheins (IKSR) ermittelt. Zur Ableitung einer Zielvorgabe sollten im Regelfall okotoxikologische Untersuchungen aus vier Trophiestufen der Gewasserbiozonose mit den typischen Vertretern Bakterien, Algen, Kleinkrebse und Fische herangezogen werden. Die Wirkungsdaten wurden in Zusammenarbeit mit dem Umweltbundesamt (UBA) okotoxikologischen Datenbanken entnommen. Um der Unsicherheit der Ubertragung der an wenigen Organismenarten gewonnenen Laborergebnisse auf reale Gewasserverhaltnisse Rechnung zu tragen, wurde das niedrigste akute bzw. langerfristige Testergebnis fur die empfindlichste Art mit einem Ausgleichsfaktor multipliziert. Fur sieben Pestizide wurden Zielvorgaben vorgeschlagen, die unterhalb einer Konzentration von 0.1 μg/L liegen. Demnach sind die okotoxikologisch basierten Vorgaben noch strenger als der nach der Trinkwasserverordnung vorgesehene generelle Grenzwert fur Pestizide von 0.1 μg/L. Andererseits wurden fur die uberwiegende Anzahl der betrachteten Stoffe hohere Werte abgeleitet. Die grose Spannbreite der Werte fur die Zielvorgaben zeigt sehr deutlich, dass gerade bei der Stoffgruppe der Pestizide keine einheitliche Konzentration als Qualitatsanforderung fur Gewasser genannt werden kann, sondern dass die einzelnen Pestizide sehr unterschiedliche Wirkungen auf die Gewasserbiozonose zeigen. Quality Targets for Pesticides and Other Pollutants in Surface Waters Surface waters are not only adversely affected by industrial and municipal wastewaters but also by diffuse sources. For the control of the ecological water quality, so-called quality targets are set. The quality targets are threshold concentrations for hazardous substances related to the protected goods like water ecosystems, drinking water supply, sediments, or fishing. In this paper, quality targets for the protection of aquatic life in surface waters were derived on the basis of a concept developed by the International Commission for the Protection of the Rhine (Internationale Kommission zum Schutze des Rheins – IKSR). The quality targets for the selected hazardous substances, which mainly belong to the chemical class of pesticides, were calculated using ecotoxicological results for species of bacteria, algae, fish, and small crustaceans, as the four trophic standards of the water ecosystem. In cooperation with the Federal Environmental Agency (Umweltbundesamt – UBA) the effect data were taken from ecotoxicological data bases. According to the concept of the IKSR, the lowest test result for the most sensitive species was multiplied by an assessment factor. This proceeding concerns the difficulty in describing the complex interactions in water ecosystems with toxicity data of single laboratory experiments for a few organisms. For seven pesticides quality targets below 0.1 μg/L were proposed. These results show that the ecotoxicologically based quality targets might be even lower than the limit values for pesticides in drinking water of 0.1 μg/L. But for most of the substances the determined values are significantly higher. The great concentration range of quality targets demonstrates distinctly that one standard concentration for all pesticides could not be given with regard to the different effects on aquatic organisms.

Risk assessment of nanomaterials and nanoproducts - adaptation of traditional approaches

Different approaches have been adopted for assessing the potential risks of conventional chemicals and products for human health. In general, the traditional paradigm is a toxicological-driven chemical-by-chemical approach, focusing on single toxic endpoints. Scope and responsibilities for the development and implementation of a risk assessment concept vary across sectors and areas and depends on the specific regulatory environment and the specific protection goals. Thus, risk assessment implication is a complex task based not only on science based knowledge but also on the regulatory context involving different parties and stakeholders. Questions have been raised whether standard paradigms for conventional chemicals would be applicable and adequate for new materials, products and applications of nanotechnology. Most scientists and stakeholders assume that current standard methods are in principle applicable to nanomaterials, but specific aspects require further development. The paper presents additional technical improvements like the complementary use of the life cycle methodology and the support of risk-based classification systems. But also aspects improving the utility of risk assessment with regard to societal impacts on risk governance are discussed.

Chapter 3.2 – Addressing the Challenges to the Risk Assessment of Nanomaterials

Risk assessment is a primarily evidence-based process employed by agencies, industry, and scientific communities to evaluate public health and environmental issues of concern. Moreover, it has become a dominant policy tool for informing regulatory and technological decisions and setting priorities for research and funding. Yet risk assessment also depends on the sociocultural and regulatory contexts of the issues. Different approaches have been adopted for assessing the potential risks posed by conventional chemicals and products for human health. In general, the traditional paradigm is a hazard-driven chemical-by-chemical approach, focusing on single toxic endpoints. Scientific committees currently anticipate a substantial change in this standardized process due to the demands for a reduction in animal testing. Questions have also been raised about the applicability of this general chemical-based form of risk assessment in the specific case of nanomaterials (NMs). Most scientists and stakeholders assume that the current standard methods are in principle applicable to NMs, but that specific aspects require further development. This paper presents possible technical improvements and additional supporting tools. Nanospecific risk assessment, however, also faces a number of substantial challenges and uncertainties. This leads to considerable scientific, political, and public scrutiny and an apparent decision-making gridlock. To improve its utility, the current understanding of risk assessment has to be moved toward an integrated form of assessment within increasingly participative and transparent processes.

Formation of Haloforms in Drinking Water

The drinking water industry is required to ensure effective disinfection while minimizing the formation of disinfection by-products (DBPs). A multitude of data exists for the occurrence and the health effects of DBPs, primarily for trihalomethanes (THMs) and other chlorination by-products. The consumption of chlorinated drinking water has been linked to cancer and to a variety of adverse reproductive outcomes. Chloroform, the main THM identified in chlorinated water, is a probable human carcinogen. A significant proportion of the mutagenicity in chlorinated drinking water is attributed to the hydroxyfuranone MX. Different approaches have been applied to investigate the reactions of chlorine and other oxidants like ozone, chloramine and chlorine dioxide during the water treatment process. Especially the influence of precursors like natural organic matter (NOM) is an important subject of current research. Nevertheless, the reactions and products have not yet been clearly identified even with the aid of newly developed analytical tools. In the water treatment practice the three general approaches for the reduction of DBPs are to control their formation by using alternative disinfectants, to remove them after formation, or to remove their precursors. For this purpose the characterization of NOM is important to optimize the removal process, including coagulation, adsorption and membrane technologies.

Epigenetics—New Aspects of Chemicals Policy

Epigenetics is the study of the natural processes that regulate the differentiation of cells and tissues, and are of significance in the development of organisms. This means it is able to offer a specific perspective on how various factors and stressors in the environment control gene activity. For instance, chemicals such as hormonally active ‘endocrine disruptors’ leave behind traces in the epigenetic code that not only trigger illnesses, but can also be passed on from generation to generation. These epigenetic mechanisms of action are not taken sufficiently into consideration in the use and regulation of chemicals. Although the evaluation of hormone disrupting effects due to endocrine disruptors is covered by various product-specific European regulations, neither an unambiguous regulatory definition nor specific toxicological testing strategies have been in place to date. As a result of this, the protective measures provided for in the existing legislation remain vague. It has not been possible up until now for the state to monitor the use of these substances in everyday products. How society deals with the consequences of the influence epigenetic mechanisms have due to anthropogenically conditioned changes in the environment constitutes an interdisciplinary challenge for the academic community, policymakers and ethicists. The European Parliament has adopted a resolution on the protection of public health from endocrine disruptors in which it demands precautionary action because risks to the environment and human health cannot be ruled out. This means epigenetics has arrived as a topic on the current political agenda in the context of the impact assessment and regulation of substances with epigenetic mechanisms of action.

Epigenetik – neue Aspekte für die Chemikalienpolitik

Die Epigenetik erforscht naturliche Regulationsprozesse der Zell- und Gewebsdifferenzierung, die bei der Entwicklung von Organismen von Bedeutung sind. Sie ermoglicht dadurch eine spezifische Sicht auf die Steuerung der Genaktivitat durch verschiedene Faktoren und Stressoren aus der Umwelt. So hinterlassen Chemikalien wie die hormonell wirksamen ‚Endokrinen Disruptoren‘ Spuren im epigenetischen Code, die nicht nur Krankheiten auslosen, sondern auch uber Generationen weitervererbt werden konnen. Diese epigenetischen Wirkungsmechanismen werden bei der Verwendung und Regulierung von Chemikalien nicht adaquat berucksichtigt. Zwar ist die Bewertung hormonstorender Effekte durch endokrine Disruptoren Bestandteil verschiedener produktspezifischer Verordnungen, doch gibt es bisher weder eine eindeutige regulatorische Definition noch spezifische toxikologische Teststrategien. Dadurch bleiben bestehende Rechtsvorschriften in ihren Schutz-Masnahmen unkonkret Eine staatliche Uberwachung der Verwendung dieser Substanzen in Alltagsprodukten ist bisher nicht moglich. Der gesellschaftliche Umgang mit den Folgen der Beeinflussung epigenetischer Mechanismen durch anthropogen bedingte Veranderungen der Umwelt ist eine interdisziplinare Herausforderung fur Wissenschaft, Politik und Ethik. Das europaische Parlament fordert in einem Gesetzesvorschlag uber den Schutz der offentlichen Gesundheit vor endokrinen Disruptoren ein vorsorgeorientiertes Handeln, da ein Risiko fur die Umwelt und die menschliche Gesundheit nicht auszuschliesen ist. Somit ist das Thema Epigenetik im Kontext der Folgenabschatzung und Regulierung von Substanzen mit epigenetischen Wirkmechanismen auf der aktuellen politischen Agenda angekommen.

Technology Assessment Beyond Toxicology – The Case of Nanomaterials

The chapter of Fleischer, Jahnel and Seitz points out that the current concept of toxicological risk assessment in the field of nanotechnology (in particular that referred to manufactured particulate nanomaterials (MPNs)), which is based on conventional expert-based chemical risk assessment procedure, is too narrow. We analyse various proposals, such as the recent ones made by the International Risk Governance Council based on the considerations of societal impacts and needs, which recommends the inclusion of concern assessment in the process (concerns of the general public and the stakeholders). After having discussed the methodological challenges of a broadening of the concept of risk assessment, they discuss the results from the Eurobarometer 2010 as well as from particular public engagement exercises and focus groups. In the paper the authors call for a wider concept, developing further the idea of concern assessment: this approach should allow for a plurality in perspective, actors and different kinds of knowledge adequately considering societal impacts for understanding risk in a broader sense than experts.