What is Toxicology Risk Assessment?

Toxicology risk assessment is the process of evaluating a substance’s potential risk to human health. Expert toxicologists must apply a particular set of methods to make these determinations. The U.S. EPA has published detailed risk assessment guidance in the United States, which serves as the procedural foundation for most toxicology risk assessments. In addition, the EPA has its institutional certification program. These institutions certify a person’s competence in risk assessment.

Dose-response Evaluation

Dose-response data in toxicology risk assessment are critical for assessing the risks associated with a substance or a mixture of substances. These data are often presented as a range of values, which can change as newer and better data become available. Screening-level risk assessments are generally suitable for a range of contaminants, exposure routes, and emission sources and can help to set priorities for future research. More detailed risk assessments may be needed to support regulatory decisions about a single source and should consider dose-response relationships in more detail.

Dose-response relationships describe a relationship between exposure to a chemical and the resulting adverse health effects. They are often used to determine the exposure range or concentration necessary for adverse effects to develop and to evaluate the potential impact of exposures on human health. They can be derived from cell or study data and are commonly used to support chemical risk assessments and regulatory actions.

Exposure Assessment

In toxicology, exposure assessment is a crucial first step in risk assessment. It involves estimating the amount of a substance a human population is exposed to. Exposure assessment includes factors such as the frequency, duration, and magnitude of exposure. It also addresses the adverse or beneficial effects of exposure to a particular substance. Some defaults used in exposure assessment are time-weighted average dose and assuming that a person weighs 70 kilograms and lives for 70 years.

In the absence of human data, exposure assessment uses an extrapolation method, which involves dividing the experimentally determined NOAEL by a safety factor. This factor takes into account inter and intraspecies variability and uncertainty. Ten factors are used to compensate for inter-individual variation in substances with chronic human exposure. In the absence of human data, a factor of 100 is used. Finally, the margin of safety is applied to determine an acceptable exposure level for human exposure.

Cancer Risk Determinations

Toxicology risk assessments use cancer risk estimates to decide whether to take public health actions. Such estimates aren’t necessarily representative of cancer cases in a community. In addition, these estimates use a hypothetical scenario to illustrate the concepts behind cancer risk determinations. However, they still have some critical limitations. Cancer risk estimates must be based on reliable scientific data to be effective.

The methodology for calculating risk is similar for non-carcinogens. The exposure is divided by an appropriate acute or chronic value to calculate the average individual risk. In addition, hazard indices are used to compare a particular dose level to a reference dose. Finally, the difference between the resulting hazard indices is used to calculate a risk descriptor for a given substance.

Institutional Certification Programs

Taking a course in toxicology can be beneficial for many reasons. For example, graduates of a program in toxicology are well-equipped to manage toxicological risk assessments and formulate recommendations for the safe use of products. Such training may also help a graduate find employment in pharmaceuticals, environmental toxicology, or pesticide testing. In addition, statistical modeling skills are helpful, and risk assessments are taught in BIOL 105 and 106. ENG 217W also offers a training course in toxicity modeling.

Toxicology assessments are the foundation of safety decisions. For this reason, training the next generation of toxicologists should ensure they have a comprehensive set of complementary competencies. In addition, it is essential to ensure that trainees understand how toxicology data and knowledge are translated into policy and decisions. In short, these programs can help to ensure that the future of toxicology research is safe. 

TTC Approach

TTC is an acronym for Toxicological Threat Characterisation. It is a scientifically sound and pragmatic methodology for assessing toxicological risks from substances with well-known structures, low levels of exposure, and sparse toxicity data. This approach is being used in the EU to comply with legislation that requires the submission of toxicity data on certain active substances in plant protection products and food additives. However, the TTC approach is based on scientific data and is not intended to replace the traditional toxicity assessment.

In assessing the risks of certain chemicals, the TTC method has been used for decades. The method is based on the Carcinogenic Potency Database, compiled between 1984 and 1997. In that time, 477 substances were studied. These chemicals were classified into 18 groups, each with an estimated hazard of causing cancer. During the early 2000s, carcinogenicity was deemed the most sensitive endpoint for toxicology. Currently, the TTC method is used to assess new chemicals’ risks.

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