Toxicological Risks of Selected Flame-Retardant Chemicals (2000) / Chapter Skim
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2 Assessment of Health Risks from the Use of Flame Retardants
2 Assessment of Health Risks from the Use of Flame Retardants
Pages 21-34
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From page 21... ...
Risk estimates derived from this process are often vital in making informed and balanced decisions to effectively manage risks and to communicate about the significance of known or anticipated risks. The risk assessment process enables the systematic evaluation of data and the quantitative presentation of complex information.
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From page 22... ...
Although acute toxicity information was reviewed, it was not used in developing risk assessments because chronic exposure data are more relevant. The four basic steps of risk assessment process applied to FRs are hazard identification, dose-response assessment, exposure assessment, and risk characterization.
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From page 23... ...
The reversibility of adverse effects once exposure ceases can also be studied. Animal data reviewed included studies of neurotoxicity, immunotoxicity, reproductive and developmental toxicity, organ toxicity, dermal end pulmonary toxicity, and other local and systemic effects.
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From page 24... ...
The results of these studies are important in hazard identification and can provide supporting data when the animal data are inadequate or absent. Discussion The subcommittee's hazard-identification step describes the types of toxic responses, if any, that can be caused by the FR under review, the weight of the primary and supporting evidence, the scientific merits of the data, and their value and reliability for estimating human toxicity under defined conditions of exposure.
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From page 25... ...
Dose-response assessment includes the process of extrapolating adverse effects observed in experimental animal organism from high to Tow doses; it also includes extrapolating data from animals to humans. To perform such extrapolations, two fundamentally different approaches are used, one for carcinogenic responses and another for all other forms of toxicity.
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From page 26... ...
The major UFs, some or all of which may be applied for derivations of RfDs or RfCs, are described below: Interspecies Extrapolation Despite physiological similarities among mammalian species, laboratory animals are not human beings, thereby providing a clear disadvantage in estimating possible adverse human health effects from exposure to Fits. Based on both toxicological principles and empirical observations, reasons exist to support the hypothesis that many forms of biological responses, including toxic responses, can be extrapolated across mammalian species, including humans.
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From page 27... ...
Therefore, by convention, one assumes that, in the absence of clear evidence that a particular toxic response is not relevant to humans, any compound-related adverse effects found in laboratory animals tested in properly designed studies are potentially predictive of response in at least some humans. This subcommittee agrees with this convention and also adopted that approach.
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From page 28... ...
yet individuals are exposed by another route (e.g., dermal or inhalation) , the resulting differences in toxic potency are taken into account by applying a UF of 10; if evidence indicates little or no such variability, a factor of less than 10 is used.
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From page 29... ...
If an FR causes cancer in laboratory animals, the slope of the dose-response curve is used as the unit to describe carcinogenic potency and is called the cancer potency factor (also technically designated as quay (Crump 1996~. Many models have been developed to assess the effects of Tow doses of carcinogens.
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From page 30... ...
Such potency factors are, therefore, suited more to standard setting than to defining actual risks to a specific population. Quantitative estimate of risk is obtained by multiplying cancer potency factors by lifetime average dose rates.
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From page 31... ...
Risk Characterization of Flame Retardants This final step of a risk assessment process involves integration of data and analyses from the other three steps of risk assessment to determine the likelihood that groups of individuals may not experience any ofthe various forms of toxicity associated with a chemical under its known or anticipated conditions of exposure. This step includes estimations of risk to individuals end population groups and a full exposition of the uncertainties associated with the conclusions.
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From page 32... ...
The subcommittee's charge did not include evaluation of trade-offs, and it did not attempt to make such evaluation. Risk Characterization of Carcinogenic Effects The approach used by the subcommittee to characterize risks from exposure to carcinogenic FRs involves extrapolation of observations of cancer in animals at relatively high doses to much lower doses anticipated in residential settings.
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From page 33... ...
The subcommittee's upper limits of cancer estimates reflect the chance that cancer may occur and not that they must inevitably occur; however, because of limitations in knowledge about the processes of cancer causation, it is also possible that the risk may be zero and that no excess cancers above the background levels would ensue from a specified exposure. REFERENCES Brown, C.C.1987.
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From page 34... ...
1984. Principles for Evaluating Health Risks to Progeny Associated with Exposure to Chemicals During Pregnancy.
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