Environmental toxicology is an interdisciplinary science. In order to be successful at demonstrating complex chemical threats, coordinated research inputs in transdisciplinary projects are needed. Development in this respect has been favourable and the opportunities for receiving funds for transdiciplinary research have increased in recent years, especially in the form of grants from Formas. While this has given reason for satisfaction, there is reason to sound a warning regarding the over-reliance on the importance of relevance and the influence of the users of research results which is now gaining ground. Research is a creative process which, to be successful, cannot be directed but is amenable to stimulation. Large breakthroughs cannot be planned, they are the result of the imagination and instinct of the researcher and his/her ability to see patterns and deviations in data. A successful research is dominated not only by the issues which are most acute at the moment. The challenge lies also in trying to predict and identify the chemical threats of tomorrow.
No dead zone
Swedish environmental toxicology started early. As long ago as in 1954, Karl Borg presented experimental evidence that methyl mercury seed dressing has an impact on avian fauna. Sören Jensen's discovery of the PCB problem was reported in 1966. These and other Swedish original observations stimulated international research of a scope that is far in excess of our national research budgets.
A Swedish environmental toxicology and environmental chemistry research developed, the scientific development accelerated and finally there were foresighted decisions by the authorities. The cooperation among universities and the authorities which started at that time continues. Environmental toxicology and environmental chemistry results have been in demand and have been used in hazard assessment and in practical work on risk limitation. In this field, there has never existed a "dead zone" that isolates research from practice.
Testing is not sufficient
Under REACH (Registration, Evaluation, Authorisation and Restriction of Chemical Substances) the requirements for testing and hazard assessment of chemicals are tightened up. But there is much that remains to be done. The discussion that preceded REACH emphasised the need to strengthen both research and education in this field. It is therefore worth pointing out that most of today's most troublesome environmental toxicology problems have been demonstrated through research. They do not have their origin in standardised testing. When REACH will now be applied, there is reason to reflect on how well prepared we are to demonstrate new chemical threats and to prevent their development into full scale environmental and health risks.
Chemical threats escape detection
There is a widespread notion that the biological properties of chemicals are well enough known for adequate hazard limitation measures to be put in hand. In some cases, this is correct. In many cases it is wrong; lack of knowledge is a serious problem in hazard assessment. In the preparatory work on REACH the great lack of data was pointed out. It is to be hoped that the development of new and improved test methods which is now in progress will make more rapid testing possible and will result in improved danger and hazard assessments. It is to be hoped that there will be a better basis for decisions.
It must however be emphasised that most of the guideline-based test systems are simplified models of a composite biological and chemical reality. There is therefore a risk that many chemical threats will escape detection. This applies especially to those substances that in the early sensitive phase in the life of an organism give rise to serious effects which will only be manifested in the adult individual. It also applies to substances which assume a changed chemical structure and thus changed biological properties in the environment. In such situations it is difficult to demonstrate a causal relationship. It is not too daring to assert that many of the now known environmental toxicological problem substances could not have been identified with the existing standardised test systems. It is the task of research to demonstrate such biological effects which (once they are known) cannot be reproduced with the help of standardised
test protocols.
Guided missiles
Chemicals in the environment can at time release toxicity via sophisticated mechanisms. Over the years, we have detected a number of substances which, like guided missiles, home in on specific types of cells or tissues, and which through their chemical reactivity damage or kill these cells. Such substances often change shape during their journey through the body or through the food chains. They are converted into new chemical structures with changed biological properties. In a current Formas project we are studying how such a substance, the long-lived DDT metabolite MeSO2-DDE, affects the adrenal glands and testicles of foetuses and neonates. This metabolite is formed through a sequence of enzymatic conversion mechanisms which occur in different places in the body.
In animals and humans who suckle their young, the stored substance is secreted particularly effectively in the milk, which results in the young being exposed to much higher contents than the suckling female. The mother's body will in this way be detoxified by exporting the substance via the milk to the young. Once in the body of the young, MeSO2-DDE can attack and damage/kill the hormone producing cells in the adrebal gland and testicle. This is a drastic example of a complex mechanism that could not be detected in the standardised test systems that are now available.
Alternative test methods
REACH has an innate conflict of objectives between the need for increased testing and the ambition to limit animal experiments. This increases the pressure to produce alternative test methods. The animal based test methods will at the same time be improved according to the principle of the three Rs (Replace – the number of animals is minimised by replacement of animal experiments by alternative methods, Reduce – the number of animals in the tests is reduced, Refine – the tests are refined). It is obviously not acceptable if legislation results in greater animal testing of dubious value for the toxicological hazard assessment.
The overarching goal, to achieve an application of REACH which enables the performance of high quality hazard assessments that are anchored in actual conditions, remains. Great hopes attach to improved alternative test methods. The creation of genetically modified cell lines has increased the opportunities to progress further. The use of genetically sequenced test organisms (for example zebra fish) offers new options for the performance, under ethically acceptable forms, of mechanically oriented investigations of general value for threat assessment, both with regard to human health and the environment. Hazard assessment is however facing a number of problems that are either new or were given insufficient attention before. Such a problem concerns the question of how the synergistic effects of complex exposures (mixtures) are to be handled. Another concerns the question of how persistent metabolites and degradation products of chemicals formed through solar radiation are to be studied. Solutions are not likely to be glaringly obvious. As support for continued method development, testing and hazard assessment, we require vital research that makes us ready to face future challenges. Without a solid scientific base, there is a risk that work on hazard assessment will be politicised. Were this to happen, faith in chemical control would be eroded.
Author
:
Ingvar Brandt
is professor of ecotoxicology at Uppsala University
E-mail:
Ingvar Brandt@ebc.uu.se