The Role of Toxicology in Risk Assessment and Sediment Evaluations

Toxicological science plays a central role in protecting public health and the environment against environmental risk. It does so directly by providing tools to prevent the development and release of toxic chemicals and indirectly through its impact on risk assessment. Toxicology and risk assessment are closely related, with risk assessment largely resting on two core toxicological principles: dose response and hazard identification.

Dose response is the basis of toxicology. It is firmly grounded in Peracelsus’ founding toxicological principle that asserts, “Dose makes the poison,”[i] and it considers an organism’s response to a concentration of chemical exposure. Hazard identification is concerned with identifying those chemicals that have the potential to cause harm and understanding their effects on people and their natural surroundings. The principles of toxicology are used to evaluate various facets of environmental health, including the health of sediments.

Additionally, risk assessments are conducted to evaluate potential exposure and characterize the associated risk. Exposure assessment aims to capture information about chemical dose, such as who or what was exposed and for how long. Risk characterization is the process of describing the risks of exposure to human health and the environment. When coupled with a firm understanding of likely dose responses to potential hazards, risk assessments are powerful tools that provide toxicologists with the data required to thoroughly evaluate sediment toxicity.

Of primary concern in most sediment evaluations is the toxicity of contaminants present. Contaminated sediments in water bodies may affect ecosystems, resources, and human health, so it is important to understand their potential impacts on the people and environment that may be exposed to them. Several factors influence our understanding of sediment toxicity, including how the physical characteristics and composition of sediments may impact their toxicity and how toxicity is defined, perceived, measured, and interpreted.

In typical sediment assessments, the toxicity of test sediments is compared with reference standards and conditions (typically comprising a battery of organism models with varying sensitivities) to measure potential chemical impacts. The results of the comparisons against reference standards are used to assess whether chemicals in the sediment pose hazards to humans and the environment, and toxicity test results inform decisions about how to manage and treat contaminated sediment.

Sediment toxicity is only a symptom indicative of an ecological response and potential environmental harm, but what it means depends on the situation. Regardless, the severity of sediment toxicity is best measured and assessed quickly to minimize negative impacts on the environment and organisms that live within it.




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