In context to risk assessment, risk can be defined as the probability of destructive effects to human health or to ecosystems resulting from exposure to an environmental stressor. Any physical, chemical, or biological object that can induce an adverse response is called a stressor. Stressors may unfavorably affect specific natural resources or whole ecosystems, such as plants and animals, as well as the environment to whom with which they interact. Risk assessment is done to illustrate the nature and extent of health risks to humans (e.g., residents, workers) and ecological receptors (e.g., birds, wildlife) from chemical pollutants and other stressors that may be present in the environment. We determine environmental risk assessments principally
Based on this, the occurrence and extent of human and ecological exposures that may occur as a consequence of interaction with the contaminated medium, both now and in the future, is evaluated by the risk assessor. This evaluation of exposure is then shared with information on the in-built toxicity of the chemical to predict the possibility, nature and degree of the adverse health effects that might take place. In real life, information on one or more of key data, needed for risk assessment calculations , is usually limited. This means that risk assessors have to make estimations and use judgment when carrying out risk calculations, and hence all risk estimations are indefinite to some extent. For this reason, a reasonable and open presentation of the uncertainties in the calculations and a categorization of how dependable the resulting risk estimates really are, is a key part of all noble risk assessments .It is an iterative process to develop a risk assessment which involves researchers identifying and filling data gaps in order to make a more sophisticated assessment of the
In the situation of chemical stressors, the process observes the existing scientific data for a given chemical and creates a weight of evidence to characterize the bond between the chemical agent and the negative effects. Exposure to a stressor may cause several different adverse effects in a human such as formation of tumors, propagative defects, or other effects. Clinical studies, that are statistically controlled on humans, offer the best evidence linking a stressor to a resulting effect. However, such studies are not available frequently since there are important ethical concerns which are associated with human testing of environmental hazards. On the other hand, epidemiological studies include a arithmetical evaluation of human populations to observe whether there is an relationship between exposure to a stressor and a human health effect. The main advantage of these studies is that they include humans , whereas their weakness is due to not having accurate exposure