Analysing the chemical burden

As a new legislative era dawns for chemical usage and the environment, Kirit Wadhia, ecotoxicology services manager at microbiology company NCIMB, highlights some new technological approaches.

Global economic development since the beginning of the last century has seen significant increase in the use of chemicals. Manufacturing and industrial activities have depended on chemicals to progress the advances in the creation of new products and technologies. Chemicals in the form of fertilizers, herbicides and pesticides have had a dramatic affect on agricultural practices to enhance yields in crop production.

In essence anthropogenic activity is attributable for increasing use of chemicals in one form or another. Mankind's footprint on earth is measurable in some ways by the extent of chemical usage. It is an inevitable consequence of population profile demographics, changes in the dynamics of industrial developments and geographical redistribution of wealth that the uses of chemicals and levels present in the environment have not remained static. Since the onset of the Industrial Revolution, the chemical loading in the environment has been growing at a rapid pace.

Chemicals cannot be deemed to be entirely malevolent. Particular industries, for example pharmaceutical and petroleum, have played a significant role in the 'improvement' of the quality of life. Advances in chemical analytical techniques have increased the scope to detect lower concentration levels in samples.

Automation and protocol refinements have permitted more samples to be tested in less time. In addition the most important milestone has been the recognition of the value of toxicity assessment. Toxicity has intrinsically always been an important aspect of chemical use.

Whereas previously the emphasis has been on setting limits for specific toxicants, it is now realised that there needs to be more focus on not just establishing what concentrations of chemicals should be acceptable in the environment, but actually rationalising the loading of the chemical burden and formulating environmental quality standards.

In the European Union, it is evident from the introduction of new directives that increasing use of chemicals is both a matter of concern and requires strict monitoring and control. Legislation implementing this process includes Integrated Pollution Prevention and Control (IPPC).

It is the lack of comprehensive information on the extent of chemicals that are in use and their exposure or toxicity effects that has been an issue. In this context Registration, Evaluation and Assessment of CHemicals (REACH) represents a profound step forward.

The significant advance framing the environmental regulatory perspective has been the inclusion of assessment based both on chemical analysis and toxicity evaluation. The manifestation of this development is evident with the existence now of such terminology as Direct Toxicity Assessment (DTA), Whole Effluent Toxicity (WET) and Whole Effluent Assessment (WEA) in the environmental
framework. This approach advocates complementary use of chemical analysis and ecotoxicology.

Bioassays
The salient feature of this holistic approach is the use of bioassays. These tests entail exposure of pertinent biological indicators to the test substance or sample. The use of different species considered to be relevant is advocated in the testing regime. The criteria for selection of species favours inclusion of representative organisms from different trophic levels; in other words species that constitute the food chain in the ecosystem. The strategy necessitates utilisation of single-species assays. This innately restricts the extent of testing that can be implemented owing to factors including cost.

A key milestone that paved the way to increase the scope of utilising bioassays for regulatory monitoring was the development of microbiotests. This involves performance of bioassays using techniques that enable more samples to be tested at lower cost without compromising the integrity of the testing rationalisation. It is the utilisation of microorganisms that has been the vanguard for progress. The awareness and realisation of the potential value of microbial assays is only now impacting the ecotoxicity testing arena. NCIMB Ltd pioneered the development of microbial multispecies assays for testing of chemicals and environmental samples.

The company is the custodian of an impressive collection of microbes which allowed selection of strains with diverse sensitivity to different toxicants. It is this concept of using an array of diverse strains as biological detectors or sensors that makes this innovation a viable alternative to conventional bioassays. The spectrum of sensitivity response of the array unlike other assays conveys not just a measure of the level of toxicity of the test substance, but also its toxicity profile. The multispecies system in the form of Microbial Assay for Risk Assessment (MARA) uses growth as a parameter to measure effect. New from the NCIMB stable now comes the launch of a unique innovative assay, LumiMARA, which employs naturally luminescent microbes.

This is the only system of its kind in the world and together with MARA enters the bastion of a revolutionary new generation approach for monitoring and control of chemicals.


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