Databases Toxicology

Keywords Environmental and risk assessment models, Life-cycle Impact assessment models, Physicochemical and toxicological database... 

In Table 3, a selection of physicochemical and toxicological databases is shown. These databases are selected according to the existence of quality controls and their free online availability. 

Table 3 Physicochemical and toxicological databases Database Description...

Criteria now recommended for protection of various species include the following dietary loadings, in mg/kg FW ration, of <0.05 for human health, <0.05 for livestock, <1 for honey bees, and <5 for poultry seawater concentrations <0.1 pg/L for estuarine crustacean larvae and, for all aquatic life, restricted or prohibited use of diflubenzuron in saltmarsh mosquito breeding areas and on agricultural lands less than 5 km from coastal areas. No criteria are available or proposed for protection of avian and mammalian wildlife against diflubenzuron, probably because of an incomplete toxicological database. 

The assessment factors generally apphed in the estabhshment of a tolerable intake from the NOAEL, or LOAEL, for the critical effect(s) are apphed in order to compensate for rmcertainties inherent to extrapolation of experimental animals data to a given human situation, and for rmcertainties in the toxicological database, i.e., in cases where the substance-specific knowledge required for risk assessment is not available. As a consequence of the variabihty in the extent and nature of different databases for chemical substances, the range of assessment factors apphed in the establishment of a tolerable intake has been wide (1-10,000), although a value of 100 has been used most often. An overview of different approaches in using assessment factors, historically and currently, is provided in Section 5.2. 

Adequacy of the toxicological database relevance, validity, reliability children... 

The overlap of areas covered by the FQPA factor and those addressed by the traditional UFs was recognized, and it was concluded that the current UFs, if appropriately applied using the approaches recommended in the review (i.e., US-EPA 2002), will be adequate in most cases to cover concerns and uncertainties regarding the potential for pre- and postnatal toxicity and the completeness of the toxicology database. In other words, an additional UF is not needed in the RfC/RfD methodology because the currently available factors are considered sufficient to account for uncertainties in the database from which the reference values are derived (and it does not exclude the possibility that these UFs may be decreased or increased from the default value of 10). 

In the hazard assessment, it is important to evaluate the toxicological database with regard to its adequacy. The adequacy of a study includes its validity and its relevance. The relevance refers to what has been studied in relation to what is needed for the hazard and risk assessment, and the validity refers to how the study was performed, e.g., conforming with a particular test guideline. The validity and the relevance of a study, or a whole database, has to be considered in relation to the reliability and thus the confidence. The data for hazard assessment are described in detail in Chapter 3. 

US-EPA (1993) stated that in addition to the standard factors (for inter- and intraspecies differences, less than chronic duration studies, and LOAEL-to-NOAEL extrapolation), an extra factor should be included if the total toxicological database is incomplete, i.e., the so-called modifying factor (ME). It was stated that the magnitude of the MF depends upon a professional assessment of scientific uncertainties of the study and database not explicitly accounted for by the standard factors, e.g., the completeness of the overall database and the number of species tested. The default value for the MF is 1. 

In the hazard assessment, it is important to evaluate the toxicological database with regard to its adequacy, i.e., the overall confidence regarding the quality, completeness, and consistency of the database should be considered. 

There are no specific guidance criteria available for the selection of the index compound. US-EPA (1986) has suggested that the index compound should be the member of the group that is the best studied and has the largest body of scientific data of acceptable quality. This will be associated with a low AF and lead to the lowest combined risk. However, this has been criticized for using data on well-studied compounds to improve the acceptability of compounds that have poor toxicological databases. 

Overall, the toxicology database of OCs and BFRs in the Philippines are very limited the current literature is incomplete and often conflicting. Many animals—including whales, dolphins, seals, birds, and humans— have already been found to be contaminated with these substances, and the levels appear to be increasing in the developed countries, whereas in the developing countries such as the Philippines not much studies has been carried out and needs detailed studies on the present scenario. 

In order to assess risk to individuals following dermal exposure to a pesticide, dermal absorption data are often required to convert dermal deposition data to estimates of systemic exposure. These estimates of systemic exposure are then compared with the No Observed Adverse Effect Levels (NOAELs) from oral toxicity studies or limit values (for instance. Acceptable Operator Exposure Levels (AOELs)) derived from these oral data (Bos et at., 1998 Rennen et al 1999). As noted in the introduction, oral studies are generally used because the toxicology database is typically focused on the oral route of exposure. 

Tiered approaches to dermal exposure and risk assessment have been developed (OECD, 1997 de Heer et al, 1999 Harney, 2000 EC, 2002). Although the number of tiers differ depending on the specific approach, common to all approaches is the sequential refinement of the value used for dermal absorption in the risk assessment. For example, in a Tier 1 risk assessment, a conservative value of 100 % dermal absorption is often used. If required, a more refined default may be justifiable, based on a number of considerations such as the physico-chemical properties of the substance and the toxicological database. Use of dermal absorption data would be the third tier. Biological monitoring data would be a potential fourth tier, if required. 

If the results of a preliminary risk assessment, using a Tier 1 approach, do not generate acceptable risk levels, an examination of the physico-chemical properties of the substance, as well as the toxicological database of the product, may yield a justification for a lower dermal absorption default. A weight-of-evidence approach should be used, e.g. both the physico-chemical information and the toxicological database should support the reduced default. 

The toxicological database may also yield information which will assist in characterizing dermal absorption. For instance, in an analysis of dermal absorption studies, Zendzian concluded that severe dermal irritants did not show evidence of saturation of dermal absorption (Zendzian, 2000). As such, a reduced default for severely irritating or corrosive materials seems inappropriate. 

Drew AK, Whyte IM, Bensoussan A, Dawson AH, Zhu X, Myers SP. Chinese herbal medicine toxicology database monograph on Herba Asari, xi xin. J Toxicol Clin Toxicol 2002 40(2) 169-72. 

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