Health risk assessment uncertainty

Selgrade, M.K., Use of immunotoxicity data in health risk assessments Uncertainties and research to improve the process, Toxicology, 133, 59, 1999. 

The Interdepartmental Group on Health Risks from Chemicals (IGHRC) in the United Kingdom has published a document entitled Uncertainty Factors Their Use in Human Health Risk Assessment by UK Government (IGHRC 2003). The document intended to lay out the principles used in the United Kingdom. 

Source Modified from KEMl, Human health risk assessment. Proposals for the use of assessment (uncertainty) factors. 

FIGURE S.6 Schematic illustration of the traditional setting of an acceptable level of exposure (ADI) by dividing the NOAEL from an animal study by an assessment factor (AF). The two dose-response relationships have identical NOAEL. If a uniform assessment factor is applied, there will be an adequate MOS at the ADI for effect b but not for effect a. (Modified from KEMI, Human health risk assessment. Proposals for the use of assessment (uncertainty) factors. Application to risk assessment for plant protection products, industrial chemicals and biocidal products within the European Union. Report No. 1/03, Solna, Sweden, 2003. 

IGHRC. 2003. The Interdepartmental Group on Health Risks from Chemicals. Uncertainty factors Their use in human health risk assessment by UK Government. Leicester Institute for Environment and Health, University of Leicester, http //www.silsoe.cranfield.ac.uk/ieh/pdf/cr9.pdf... 

Refinements of the RfC have utilized mechanistic data to modify the interspecies uncertainty factor of 10 (Jarabek, 1995). The reader should appreciate that with the inhalation route of exposure, dosimetric adjustments are necessary and can affect the extrapolations of toxicity data of inhaled agents for human health risk assessment. The EPA has included dosimetry modeling in RfC calculations, and the resulting dosimetric adjustment factor (DAF) used in determining the RfC is dependent on physiochemical properties of the inhaled toxicant as well as type of dosimetry model ranging from rudimentary to optimal model structures. In essence, the use of the DAF can reduce the default uncertainty factor for interspecies extrapolation from 10 to 3.16. 

Johnson, B.B., and P. Slovic. 1995. Presenting uncertainty in health risk assessment Initial studies of its effects on risk perception and trust. Risk Anal. 15(4) 485-494. 

Finley BL, Paustenbach DJ. 1997. Using applied research to reduce uncertainty in health risk assessment Five case studies involving human exposure to chromium in soil and groundwater. Journal of Soil Contamination 6(6) 649-106. 

Johnson BB, Slovic P (1998) Lay views on uncertainty in environmental health risk assessments. Journal of Risk Research, 1(4) 261-279. 

Assess the quality of the study and if the study is considered well-conducted , then nse the data as is, and cite incomplete recovery as an uncertainty in the human health risk assessment using this value. This third approach is consistent with how other mammalian kinetic studies (e.g. metabolism studies) are evaluated. 

There is an emerging body of evidence that suggests person-to-person differences in exposure play an important role in the variability and uncertainty associated with risk assessments for chemicals (and other agents). The traditional or standard default approaches used in human health risk assessment often do not effectively evaluate interindividual variation and may underestimate the impact of chemical exposures on particular groups of individuals. Traditional approaches must be refined to adequately account for temporal variation in factors that contribute to complex aggregate exposure patterns (e.g., chemical-specific exposure media concentrations and time-activity interactions by humans) involving multiple, intermittent exposures. 

Public health risk assessments used in considerations of food safety are intended to make predictions, particularly quantitative, of plausible negative impacts. Obviously depending on the underlying scientific information, some predictions are more reliable than others, and the extent to which predictions are reliable should be taken into account in the public health decision process. In order to accomplish this, the characterization of risk must contain a statement about the degree of uncertainty. 

Thompson KM, Burmaster DE, and Crouch EAC (1992) Monte Carlo techniques for quantitative uncertainty analysis in public health risk assessments. Risk Analysis 12 53-63. 

Bogen, K. T. (1990). Uncertainty in Environmental Health Risk Assessment, Garland Publishing, New York. 

Uncertainties. In any hazard or risk assessment it is extremely important that uncertainties be expressed. Frequently the uncertainties are expressed only in statistical terms. It is important that the uncertainties also be expressed in biological terms. Statistical modeling or modeling statistics has become very popular in health risk assessments, particularly for "low dose" extrapolations. As previously stated, there are no mathematical models with a biological basis for reproduction or developmental hazard evaluation. 

In addition to the graphic approach for toxicity data and the verification of uncertainty factors, other areas are under study such as route-to-route conversion, high-dose to low-dose extrapolation, approaches to assess the health risk from less-than-lifetime exposures, and refinement of risk assessment approaches for chemical mixtures. All of these areas represent progress in the methods used for risk assessment of single chemicals and chemical mixtures. With the new risk assessment guidelines currently being developed, the U.S. EPA can move forward to better and more consistent health risk assessments. 

Human health risk assessment is performed using the endpoints of tubular pigmentation and the developmental effect. As a result, the MOEs are 1.5 x 10 and 2.2 x 10 , respectively, which are larger than the uncertainty factor of 1,000 (short-term study x interspecies difference x individual difference) in tubular pigmentation and that of 100 (interspecies difference x individual difference) in developmental effect. Consequently, it is determined that there is no significant human health risk of SCCPs. 

The RBA results for different test materials demonstrate that As in most soils and mine wastes is not as well absorbed as soluble As. Because As in test materials is less extensively absorbed than soluble As, use of default toxicity factors for assessing human health risk will lead to an overestimate of hazard. Therefore, application of site-specific RBA estimates is expected to increase the accuracy and decrease the uncertainty in human health risk assessments for As. 

Kumar A, Xagoraraki I. Human health risk assessment of pharmaceuticals in water an uncertainty analysis for meprobamate, carbamazepine, and phenytoin. Regul Toxicol Pharmacol 2010 57(2-3) 146-56. 

There are many calculation formulas and parameters in risk assessment model and the reliability and accuracy of these factors wUl affect the accuracy of evaluation results, namely the uncertainty of risk assessment. In this paper, the uncertainty in the process of human health risk assessment of formaldehyde in textiles comes from the following aspects ... 

For the overwhelming majority of substances encountered in industry, there are not enough data on toxic responses of humans to directly determine a substance s hazard potential. Frequently, the only data available are from controlled experiments conducted with laboratory animals. In such cases, it is necessary to extrapolate from effects observed in animals to effects likely to occur in humans. This extrapolation introduces uncertainty and normally requires the professional judgment of a toxicologist or an industrial hygienist with experience in health risk assessment. 

The output of the analysis phase of an ecological risk assessment consists of an exposure profile and a stressor-response profile (Eigure 9.1). The profiles include estimates of uncertainty, which, as in human health risk assessments, are a constant and essential ingredient of ecological risk assessments. The exposure and effect profiles, together with their associated uncertainty estimates, set the stage for the final phase of the risk-assessment process. 

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