Health hazard identification epidemiology

Scientists skilled in epidemiology, toxicology, and related disciplines collect and evaluate all of the scientific literature containing information regarding the types of toxic effect the chemical under review has been shown to produce. Toxic effects include one or more of the many manifestations of toxicity described earlier in this book. The list of adverse health effects produced by the chemical are said to constitute its toxic hazards, and the critical review and evaluation leading to the list is the hazard identification step. A discussion of the extent to which causal associations with human disease or toxic harm have been established is an important aspect of this step. 

For classification purposes, reliable epidemiological data and experience on the effects of chemicals on humans (e.g. occupational data, data from accident databases) should be taken into account in the evaluation of human health hazards of a chemical. Testing on humans solely for hazard identification purposes is generally not acceptable. 

Hazard identification is the step in the risk assessment that qualitatively characterizes the inherent toxicity of a chemical. Scientific data are evaluated to establish a possible causal relationship between the occurrence of adverse health effects and chemical exposure. This step includes characterization of acute, subchronic, and chronic effects the potential for local versus systemic effects the influence of the route of exposure the relevance, to humans, of effects seen in animals an evaluation of the biological importance of the observed effects the likelihood of the effects occurring under certain conditions and the potential implications for public health. This step should be based on a thorough review of all the data that may provide information that is relevant to evaluating the potential chemical hazard. This may include data describing the effects on a variety of test animals, in vitro studies that characterize mechanisms of toxicity, metabolism, physiologically based pharmacokinetic studies, structure-activity relationships, short-term human studies, and epidemiological studies. Animal studies may focus on particular types of effects and may include reproductive toxicity studies,... 

Risk assessment is usually divided into four steps hazard identification, hazard characterization, exposure assessment, and, finally, risk characterization [1]. In hazard identification, agents capable of exerting negative health effects are identified. Often, the first indications of toxic potential of a compound or mixture are derived from epidemiological studies. The advantage of epidemiological studies is that extrapolation from experimental animal studies is unnecessary. On the other hand, indications from epidemiological studies show that unwanted exposure has already taken place. For marine biotoxins in bivalve mollusks, all known syndromes have been detected as a result of... 

In addition to obtaining information to perform a hazard and dose-response evaluation, an exposure assessment will need to be conducted to estimate and characterize any potential risks associated with nanomaterials. If the hazard identification process reveals that a nanomaterial is iimocuous and does not pose a potential for eliciting any adverse human health or environmental effects, it may not be necessary to conduct additional toxicological studies or an extensive exposure assessment. In cases where the hazard evaluation determines a potential for adverse effects for the nano-material, in vitro and/or in vivo studies may be conducted to evaluate the potential for systemic exposure from inhalation, oral, or dermal penetration. Such information may help to refine the exposure assessment by providing estimates of internal doses. Much of the published human toxicological and epidemiology data relate to airborne exposme to nanoparticles or ultrafine particles. However, there are additional routes by which humans can be exposed to nanomaterials that may need to be considered, including ... 

To summarize the noncancer health risk-assessment process, chemicals of concern, pathways of exposure, and exposed populations are identified in the first step of the risk assessment, hazard identification. In the second step, analysis of exposure, the doses are estimated for each population, each exposure pathway, and each chemical of concern in the form of chronic daily intakes, or CDIs. In the third step of the risk assessment, analysis of effect, noncancer health effects are estimated by comparing CDIs to reference doses, or RfDs, derived from animal toxicity studies (with input from human epidemiological studies, when available). If the CDI is greater... 

The four steps of the risk-assessment process are hazard identification, analysis of exposure, analysis of effect, and risk characterization. In the hazard identification step, the risk assessor identifies chemicals of concern, environmental pathways of exposure, and populations and subpopulations at risk. The exposure analysis develops exposure scenarios and estimates the chronic daily intake of each chemical of concern. In the analysis of effect, the risk assessor combines the chronic daily intake calculated in the exposure analysis with toxicity data from animal studies (and/or human epidemiological studies, if available) to estimate the risk of toxic effects in exposed populations, whereby risks to public health are divided into two broad categories noncancer health effects and cancer. The final step of the risk-assessment process, risk characterization, is a narrative that marshals all the evidence of risk to public health, including quantitative risk assessments and qualitative evidence of risk. The risk assessor weighs all the evidence and uses professional judgment to draw conclusions about risks. 

Toxicology and epidemiology in identification of long-term health and environmental hazards. 

---