Weight-of-evidence

A parallel effort has been the assignment of cause or risk using a WoE approach. Menzie et al. (1996) provides one of the earliest and clearest descriptions of the WoE approach to assigning causality. The usefulness of WoE has been extensively discussed in a series of recent papers (Burton et al. 2002a, 2002b, Chapman et al. 2002, Forbes and Calow 2002). Clearly this approach has proven useful. However, it requires improvement in order to address the needs of regional risk assessment. 

The WoE approach (Chapman et al. 2002) combines lines of evidence (LoE) including the presence of a proposed stressor, the ability of the stressor to cause an effect, and the observed effect in the field to establish causation. This is a powerful approach especially for systems that are limited in spatial and temporal scales, have clearly characterized stressors, and have extensive effects datasets. 

Laboratory sediment (B) toxicity data for the measured contaminants 

Nonchemical habitat alteration corresponds to observed impacts in the benthic community 

Sediments samples from the site confirm the estimated toxicity 

Risk assessors apply professional judgment to weigh the quantitative and qualitative evidence of risk. Their conclusions, narrated in the risk characterization step, provide the basis for managing toxic chemical risk within the framework of applicable laws and agency regulations and policies. 

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Mechanistic studies to identify how endocrine disrupting chemicals interact with hormone systems are required. Although population effects coupled with biomarkers of exposure are strongly suggestive of endocrine disruption, the effect could be secondary to metabolic toxicity. Establishing mechanisms may avoid the need to make decisions on a weight of evidence approach alone. 

What is the weight of evidence for use of task analysis in developing training ... 

If and then weight of evidence that Quality of training is Joint Weight (feedback x... 

If Project then weight of evidence that Staffing Levels are Weight (Project... 

The essential weakness of the correlation approach is that it lacks a linkage to molecular events. A correlation is not a cause-effect relationship. Nevertheless, with sufficient weight of evidence it becomes reasonable to seek an underlying... 

This section describes how the tj pes of to.xicity inforniation arc considered in the to.xicity assessment for carcinogenic effects. A slope factor and the accompanying weight of evidence determination are the toxicity data most commonly used to evaluate potential human carcinogenic risks. The methods the USEPA uses to derive these values arc outlined below. 

The USEPA classification system for weight of evidence is shown in Table 11.6.1. This system is adapted from the approach taken by the International Agency for Research on Cancer (lARC). 

Generally, the slope factor is a plausible upper bound estimate of the probability of a response per unit intake of a ehemieal over a lifetime. The slope factor is used in risk assessments to estimate an upper-bound lifetime probability of an individual developing cancer as a result of e.xposure to a particular level of a potential carcinogen. Slope factors should always be accompanied by the weight-of-evidence classification to indicate the strength of the evidence that the agent is a human carcinogen. Calculational details are presented below. 

A slope factor and the accompanying weight of evidence determination are the toxicity data most commonly used to evaluate potential human... 

Keywords Mendeleev Prediction Periodic Table Weight of Evidence,... 

Cytotoxics also cause cellular damage and the release of serotonin and other mediators from enterochromaffin cells. There is conflicting evidence regarding whether 5-HT3 receptors in the medulla are activated also during chemotherapy and contribute to production of emesis. Currently, the weight of evidence favours peripheral 5-HT3 receptors, with minor involvement of central receptors. 

There is a substantial weight of evidence for the cytoskeleton being responsible for the force production and control of cell locomotion. This view has not yet been accepted unanimously. However, an alternative hypothesis continues to be argued which states that membrane cycling is the motive force driving cell locomotion (Bretscher, 1987). One of the predictions of the membrane flow hypothesis is that there should be a discernible flow of lipid from the front to the rear of the cell. Lipid flow has proven very difficult to study, because of the lack of suitable methods to label single lipid molecules and the heterogenous behavior of membrane-associated proteins. The observation that particles were transported rearward when they bound... 

This chapter provides a health effects summary based on evaluations of existing toxicologic, epidemiologic, and toxicokinetic information. This summary is designed to present interpretive, weight-of-evidence discussions for human health end points by addressing the following questions. 

Calabrese EJ, Baldwin LA, Kostecki PT, et al. 1997. A toxicologically based weight-of-evidence methodology for the relative ranking of chemicals of endocrine disruption potential. Regul Toxicol Pharmacol 26 36-40. 

Cooper, R.L. and Kavlock, R.J. (1997). Endocrine disrupters and reproductive development A weight-of-evidence overview. Journal of Endocrinology 152, 159-166. 

In 1988, the Scientific Advisory Board for the EPA offered an opinion that the weight-of-evidence was on a C-B2 continuum (possible-probable human carcinogen). The cancer classification is currently under review by EPA (IRIS 1996). 

The current weight of evidence suggests that soy does have a beneficial effect on cardiovascular health however, the active component has yet to be identified. Studies have also demonstrated that dietary inclusion of phytoestrogen-rich foods can lower plasma cholesterol levels (Ridges et al., 2001). However, these data do not conclusively demonstrate that phytoesfrogens are responsible for the hypocholesterolemic effect, and it is possible that some other component in soy may be responsible (Erdman and Fordyce, 1989 Ling and Jones, 1995). 

Weight of evidence Chemical class known to lARC Croup 3 or 4... 

Weight of evidence demonstrates potential for adverse effects in humans EU Category 1 or 2 or CHS Category 1A or 1 B Evidence of adverse effects in humans ... 

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