Metals are naturally present in the environment, but releases as a consequence of abandoned metals mines, industrial manufacturing, consumer uses, and recycling can pose risk to ecological quality.
Approaches for managing the risks posed to the environment from metals that take account of their bioavailability are rapidly gaining popularity, both with regulators and the regulated community. For example, bioavailable Environmental Quality Standards (EQSbioavailable) for nickel (Ni) and lead (Pb) and have recently been adopted under the EU Water Framework Directive (WFD).
We are experts in the use of bioavailability-based approaches for assessing the risk of metals in the environment with many years of experience. We can assist clients during the complete lifecycle of bioavailable standard development and implementation, including Chemical Speciation Modelling, BLM development, EQSbioavailable derivation, EQSbioavailable implementation, user-friendly bioavailability tool development, monitoring programmes and compliance assessment phases. We can also help clients develop approaches for dealing with natural (ambient) background concentrations.
Why Are Metals Different?
There are a number of differences between metals and metal compounds and organic chemicals which mean that different approaches are required for their assessment. Metals are naturally occurring, and are found at low levels in all environmental media. Some metals are also essential elements, and are required for the growth and development of almost all living organisms.
As a result of the exposure to natural levels of metals, and the essential nature of some metals, many organisms have developed mechanisms for regulating cellular levels of many metals. In addition, some organisms and communities may be able to adapt to some degree of increased exposure.
The toxicity of metals to organisms is influenced by the local conditions of waters, sediments, or soils, and this also needs to be taken into account in assessing the potential risks posed by metals in the environment. Degradation is not relevant to metals, although some metals can form solid mineral phases, reducing their availability for biological uptake, and may be an important fate process for some metals in the environment.
Approaches For Metals
Traditionally, risk assessment methods and guidance have focused on approaches which are suitable for organic compounds, and in some cases these are inappropriate for performing comparable assessments on metals. Assessment approaches which are suitable for metals may need to consider the importance of ambient background concentrations of the metal, partitioning processes which are not determined by hydrophobicity or hydrophillicity, the formation of mineral precipitates, and the bioavailability of the metal in environmental media.
Chemical speciation of metals may be particularly important in terms of their environmental fate and potential for transport, and can be an important tool in the exposure assessment of metals. Chemical speciation is similarly important in understanding the potential toxicity of metals
under any particular conditions, and Biotic Ligand Models are commonly used to take account of these bioavailability effects in the environmental
effects assessment for metals.
Please contact us if you would like to discuss the bioavailability of metals with one of our team