Modern-Day Environmental Risk Assessment

Montreal (Quebec), Canada. Email: reza@scientis.ca

The limitations of government and private industry have created a significant problem for efficient use of the resources by the decision-makers. Consequently, there is a great need for consistent decision making in program development that could include both the governmental and industrial agencies. In the environmental sector, more specifically Ecological/Environmental Risk Assessment (ERA), the role of tools that can provide information on hazards of pollutants in the environment and to human health has become necessary and significant.

It is estimated that over 70,000 chemicals have been produced commercially in U.S., with some 15,000 in significant amount (1). Many of these chemical substances have the potential to be released into the environment where they could have adverse effects. As a result, the number of people interested in using Chemical Ranking and Scoring (CRS) tools that serve with a diversity of goals in government and industry has become significantly more. Chemical ranking and scoring are preliminary screening tools for risk management by providing practical information on environmental hazards, human health, exposure, and risk of chemicals. Therefore, they play an important role in the impact assessment stage of Life-Cycle Assessment (LCA), by evaluating the impact of chemical releases on human health and the environment in addition to serving as tools for waste minimization activities. Therefore, the needs for agreement and valid CRS methods or ERA procedures are becoming more important. Consensus is needed for consistency among various regulatory agencies at state, national, and international level and across regulatory programs for air, water, sediment, and soil.

Many risk assessment systems have been developed in the past. The structures of these systems vary widely, with no consensus on their scientific and technical framework. Environmental risk assessment systems have been applied in a variety of ways with one major key advantage that they can conserve resources by setting priorities among risk reduction programs, assessment of alternative chemicals for industrial processes, and/or identifying and prioritizing chemicals for further study or risk assessment.

In addition to chemical pollutants, biotechnology is changing our lives in many ways. High yielding genetically engineered crops that are herbicide and pest resistant, new pharmaceuticals and vaccines, or transgenic plants and animals are being created. Naturally existing or transgenic microbes are used to clean up pollution. As a result, environmental concerns are being extended from impact of chemicals to impact of biotechnology; therefore, the higher complexity of environmental risk assessment (Figure 1) requires more than what the traditional methods have to offer. The future systems must be designed to minimize the complexity of risk assessment by combining the impacts of chemicals and biological systems including their metabolic by-products that could be the result of different metabolic pathways present in naturally existing or Genetically Manipulated Organisms (GMOs). These processes should characterize the risk independently or in combination of different impacts.

In general, risk assessment has been based on aquatic environments and organisms. However, since 1990s the approach has been extended to include the soil environment and its organisms. Soils vary widely with regard to geology, hydrology, climate, fertility, and physical attributes. The geo-physico-chemical properties of soil are important in determining the fate of contaminants in a soil profile. When contaminants are introduced onto the surface of a soil, a number of physical, chemical and/or biological phenomena impact their removal or fate in the environment. The primary processes involved in contaminant fate are decay, advection, dispersion, biodegradation and adsorption/desorption. Soils play an important role in attenuating the toxic effects of a contaminant through binding and sorption properties and also in providing a solid, physical support to help protect and stabilize microorganisms and their cellular components.

Degrading microorganisms add another dimension to an already complex soil system. Soil is a heterogeneous and structured environment that is composed of multitude of microhabitats and small environmental changes can alter their microbiological composition significantly. Type and concentration of chemicals on surfaces of soil particles could influence the fate of microorganisms in a soil matrix. Bacterial growth and cell yield could be stimulated in presence of higher nutrient concentrations. Due to ecotoxicological impacts of contaminants, microbial populations may change continuously. As the contaminants are transformed through biological or chemical processes, the microbial populations in parallel change and adapt to the new conditions.

Species interact and/or depend on each other in a multitude of ways within ecosystems. The natural cycles of energy and material from the producers to various forms of consumers create strong symbiotic interactions in many different ways. In soil, microorganisms can either be free-living or associated with other organisms, such as plants. There is growing evidence that the degradation rate of hazardous organic compounds in the rhizosphere is greater than in root-free soil due to increased microbial activity. Microbially produced surface-active compounds such as fatty acids, lipids, peptides and polysaccharides, may interact with interfaces and affect the adhesion and deadhesion of existing and/or introduced microflora and/or the bioavailability of the contaminants. Therefore, the biodegradation of chemicals in soils depends upon the chemical, physical, microbial, and climatic characteristics of a particular soil. Changes in temperature and moisture could have a great impact on the soil environment and its microflora.

Environmental risk assessment has become an important part of environmental protection programs and it is based on the estimated risk from the relationship between exposure and effects. However, the estimated risks accompany varying degrees of uncertainty. In recent years, there has been some consensus on some criteria and standards. The risk assessment framework by USEPA (Figure 2) has been the backbone to many risk assessment programs for both chemical and biological agents (2,3). Although this general standard framework has served the decision-makers well, it has been faced with some indirect problems, which have limited its applicability in many instances or have created uncertainty in environmental risk assessment. These problems arise from lack of available data that could among many more parameters include all or any of the following: bioavailability, mixture toxicity, metabolic transformations, toxicologically active forms of polluting agents, multiple uptake routes, multiple exposures and more recently, data on impact of biotechnology and application of genetic engineering.

The limitations are the source of uncertainty in the analysis compartment of the framework. However, the other source of uncertainty is the outcome of the compartments, which involve human decision making such as problem formulation, communication, or management. Even though, the problem might seem small when individual personal decisions are considered but it may become significant if the judgement and decisions of many different managers are considered, collectively. With limited resources and a multitude of polluting agents to deal with, it is necessary that the complexity of the problem be adequate so the uncertainty could be reduced to a point where a rational decision with minimal risk can be made.

As a result, the answer to the needs of today’s decision-makers, is creation of tools to assess the risk of Chemical, Biological, Genetic Engineering, and Treatment technologies that are used in any industrial, environmental or agricultural practices. The solutions must offer efficient, low cost and rapid processes for Governmental, Industrial, Agricultural and Academic groups and citizens.

With the interest and convergence of different disciplines with the environmental sector and the rapid advances in the information technology, today, it is possible to create a series of computerized tools to allow us to face the challenges involved in environmental risk assessment. These systems would be capable of conducting risk assessment that would include multiple stressors, medium, organisms, ecosystems and many more parameters that would be based on sound scientific evidence, which would satisfy the environmental, industrial and governmental decision-makers at every level and to be efficient socio-economically. The approach to developing these systems must be progressive and multi-tier to include different parameters with the same set of standards which would apply to any case that is applied globally (Figure 3).

To improve the ERA systems to global standard tools, it is necessary for us to increase our knowledge of abiotic, biotic and functional diversity to understand better the desired makeup of ecosystems. Because of the complexity and variability of natural systems, ERA systems must be simple and friendly to the users and need to be highly accessible at the global level.

REFERENCES

1)   Swanson, M.B., Davis, G.A., Kincaid, L.E., Schultz, T.W., Bartmess, J.E., Jones, S.L. and George, E.L. 1997. A screening method for ranking and scoring chemicals by potential human health and environmental impacts. Environ. Toxicol. Chem., 19 (2), 372-383.

2)   Proposed Guidelines for Ecological Risk Assessment. 1996. U.S. Environmental Protection Agency. http://www.epa.gov/ORD/WebPubs/ecorisk/.

3)   Hass, C.N., Rose, J.B. and Gerba, C.P. 1999. Quantitative microbial risk assessment. John Wiley & Sons Inc., Toronto, Canada.

Figure 1. Levels of complexity in environmental risk assessment of different processes.

Figure 2. The ecological risk assessment framework, with an expanded view of each phase. Within each phase, rectangular boxes designate inputs, hexagon-shaped boxes indicate actions, and circular boxes represent outputs (2).

Figure 3. The progressive development of environmental risk assessment tools to include global parameters to achieve an ERA system for any industrial, environmental or agricultural treatment.

Figure 1

Figure 2

Figure 3

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