Guidance Values Development

This section gives an overview of the development of guidance values in general terms. 

According to the OECD/IPCS definitions listed in Annex 1 (OECD 2003)  

Guidance Value is Value, such as concentration in air or water, which is derived after allocation of the reference dose among the different possible media (routes) of exposure.  

Combined exposures from all media at their respective guidance values over a lifetime would be expected to be without appreciable health risk. The aim of a guidance value is to provide quantitative information from risk assessment for risk managers to enable them to make decisions concerning the protection of human health. 

Guidance values are developed from a standard such as, e.g., an Acceptable/Tolerable Daily Intake (ADI/TDI), and Reference Dose/Concentration (RfD/RfC). For threshold effects, the standard is derived by dividing the No-Observed-Adverse-Effect Level (NOAEL) or Lowest-Observed-Adverse-Effect Level (LOAEL), or alternatively a Benchmark Dose (BMD) for the critical effect (s) by an overall assessment factor, described in detail in Chapter 5. For non-threshold effects, the standard is derived by a quantitative assessment, described in detail in Chapter 6. 

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Examples of guidance values developed by the WHO include air quality guidelines and drinking water guidelines, and (in collaboration with the FAO) maximum residue limits (MRLs) for pesticides and veterinary dmgs and maximum levels for food additives. 

The development of health-based guidance values, which are derived from the tolerable intake, is addressed in Chapter 9. 

In the following sections, human exposure factors for ambient air (Section 7.3.1), soil (Section 7.3.2), and drinking water (Section 7.3.3) will be described. These media are used as examples, which serve to illustrate the differences in exposure factors provided by various exposure factor documents. Such differences can have a great impact on the risk characterization (Chapter 8) as well as on the development of regulatory standards and health-based guidance values (Chapter 9), and it is therefore important that the most relevant and reliable values are used for the particular situation. 

Regulatory standards, or health-based guidance values, in this chapter denoted guidance values, for exposure to chemicals in various media such as air, drinking water, sod, and food are set by various international, federal, and national bodies. This chapter will give an overview of the development of guidance values in general terms and present some examples. 

A central tool in ATSDR assessment of public health impacts is the minimal risk level (MRL) health guidance value. MRLs have been developed by ATSDR for many hazardous waste constituents, though no new MRLs have been developed for TPH. A limited number of existing MRLs can be applied to TPH assessment. Most are MRLs for individual TPH components (e.g., benzene) however, a few MRLs are available for whole petroleum products. MRLs for substances that represent the fractions defined by the ATSDR approach to assessing TPH health impacts are provided and discussed in this profile. In recognition of the likelihood that even acute exposures to fresh releases will be to fractions of a product, the information on pertinent fractions of TPH should also be consulted (particularly Sections 2.3, 6.1, 6.2 and 6.6). 

The remediation or removal of soil contaminated with asbestos from land under development is a very costly process. It is therefore essential that the laboratory be provided with samples that are of a suitable size, have been taken in a correct manner, stored correctly and are representative of the site or area from where they originated. To achieve these criteria, soil samples submitted for analysis should be in the range of 1-2 kg and be taken representatively throughout an area of potential contamination. In the case of large stockpiles awaiting classification prior to disposal or re-use, a guidance value of one sample per 250 m3 or a minimum of four samples per stockpile is generally considered acceptable. 

Notice that these principles do not explicitly define the test parameters. However, the guidance documents developed by CDHR do provide accelerated aging protocols for specific devices within their jurisdiction based on the Q,q theory for chemical reactions. So, the theory postulated by Von t Hof using the Qio value (which states that a rise in temperature of 10°C will double the rate of chemical reaction) is the most convenient method of estimating the approximate ambient storage time equivalent at a selected accelerated aging temperature, despite flie Imown limitations and concerns for use on complex and dissimilar material structures. 

In Germany, basic principles of HBM have been defined by the German Human Biomoiutoring Commission (http //www.umweltbundesamt.de/gesundheit-e/monitor/ index.htm). The Commission was established in 1992 at the Federal Environment Agency. Two kinds of guidance values in HBM have been developed the reference... 

In summary, the BSS provide radiological criteria to serve as a basis for the derivation of clearance levels but provide no definitive quantitative guidance on clearance levels. The activity concentration values developed in the following section for use in making decisions on the exemption of bulk materials may find use by regulatory bodies as a basis for the clearance of such materials. 

In April 1982, a data workshop was held to evaluate, discuss, and critique data in order to establish a consensus generic data set for the USNRC-RES National Reliability Evaluation Program (NREP). The data set contains component failure rates and probability estimates for loss of coolant accidents, transients, loss of offsite power events, and human errors that could be applied consistently across the nuclear power industry as screening values for initial identification of dominant accident sequences in PRAs. This data set was used in the development of guidance documents for the performance of PRAs. 

It is well known that the characteristics of coal differ widely according to the age of the coal formation as well as to the location of coal, etc. And the reactivity during hydroliquefaction depends on the characteristics of coals. This relationship will he a guidance to select and develop coal mines. Many parameters to indicate the reactivity of coal have heen proposed (l, 2, 2). Among these parameters, carhon content, volatile matter content, value of H/C atomic ratio, reactive macerals content, etc. are reported to he relatively closely related parameters to coal reactivity. However, these relations are usually found only in limited reaction conditions. Therefore, attempts to find better parameters still continue. 

The United Nations Globally Harmonized System of Classification and Labelling of Chemicals (GHS) includes an internationally standardized guidance procedure on Transformation/Dissolution Protocol (T/DP) for metals and sparingly soluble metal compounds (United Nations, 2007), recently validated by the OECD (Organization for Economic Cooperation and Development). To establish the acute aquatic hazard classification level of a metal-bearing substance under the GHS, data from the T/DP are compared with an acute ecotoxicity reference value (ERV) derived under conditions similar to those of the T/DP. 

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