Health Based Values

The TLVs and BEIs are health-based values established by committees that review existing published and peer-reviewed literature in various scientific disciplines (e.g., industrial hygiene, toxicology, occupational medicine, and epidemiology). TLVs have been recommended for more than 700 chemical substances and physical agents and there are more than 50 BEIs that cover more than 80 chemical substances. Documentations provide the rationale for the TLVs and BEIs these can be purchased via the ACGIH Web site (ACGIH 2007). 

Exposures to Environmental Chemicals for Which Health-Based Values Are Available, 20... 

As discussed in Chapter 6, communicating health-based values and other conclusions based on biomonitoring data requires a full discussion of the inherent strengths and limitations of the original data and the related risk conclusions. 

Many of the chemicals do not have specific health-based values, but because many are in similar classes of compounds, alternative approaches to evaluate toxicity, such as toxic equivalency factors, are available. 

Lack of health-based values for comparison Few health-based values (such as RfDs, RfCs, cancer slope factors, or BEIs) are available to put biomonitoring results into context... 

Interpreting data for health risk Because of lack of data and absence of health-based values, it is possible to estimate health risks posed by only a very small fraction of chemicals that can be biomonitored... 

The harmonization of the regulation of plant protection products throughout the EU has resulted in harmonized data requirements for occupational, bystander and worker exposure assessment. These requirements are outlined in Annex III of Council Directive 91/414/EEC. This annex lists product-related exposure data requirements and, consistent with the tiered approach outlined above, provides some advice as to when different data are required (Harney, 2000). An estimation of operator exposure, using, where available, a suitable calculation model, must always be made and reported. Actual exposure data must be provided where the risk assessment indicates that a health-based value is exceeded or where no appropriate calculation model exists to estimate exposure. 

Health based values and what is technically feasible. Recent discourse on the OELs that are used in practice in the coimtries of the EU, goes to some lengths to be clear that they do not represent safe levels of exposure for all workers, nor is it intended that they should set a limit below which it is unnecessary or undesirable to reduce exposures fiirther. The Scientific Committee on Occupational Exposure Limits (SCOEL) is quite clear about this, stating for example ... 

Hanson demonstrates that for exanple die change for substances overall between 1969 and 1994 corresponds to an average yearly reduction of 3.9 per cent. Most of this reduction took place in the first ten years. For carcinogens die reduction was considerably greater at 10 per cent and for solvents there was a 5 per cent reduction over the same period. This is despite the fact that Swedish OELs are not intended to be solely health based values but are set after taking into account issues of technical and economic feasibility. 

U It is unnecessary to recommend a health-based value for these compounds because they are not hazardous to human health at concentrations normally found in drinking water. NAD No adequate data to permit recommendation of a health guideline value. 

WHO (1994). Environmental Health Criteria, 170. Assessing human health risks of chemicals derivation of guidance values for health-based exposure limits. World Health Organization, Cieneva. 

The LOQ must take into account relevant health based limit values or relevant exposure levels. In SANCO/825/00 a method to calculate a relevant health based limit is given. The limit of quantitation must be equal to or lower than the concentration C, which is defined by equation (1). 

AEGL-1 values for dimethylhydrazine are not recommended because of inadequate data to develop health-based criteria and because the concentration-response relationship for dimethylhydrazine indicated that a very narrow margin exists between exposures producing no toxic response and those resulting in significant toxicity. 

The NIOSH immediately dangerous to life and health (IDLH) value (NIOSH 1994) is greater than the 30-min AEGL-3. NIOSH based their recommended exposure limit (REL) on the statement by Flury and Zernik (1931) that 45-54 ppm could be tolerated by man for 0.5 to 1 h without immediate or late effects. Although the Flury and Zernik (1931) data are based on animal studies, NIOSH did not apply a UF. 

Internationally, the BMD approach is used by the US-EPA to derive health-based limit values (US-EPA 2007a). Within the OECD (OECD 2000) and the European Union (EC 2003), the BMD approach is also mentioned as an alternative to the traditional NOAEL approach in health risk assessment but is not implemented in regulatory toxicology within the European Union. 

These two definitions reflect two sides of the same situation. In this book, the term critical effect(s) will be used for the hazard/effect considered as being the essential one(s) for the purpose of the risk characterization, e.g., for the establishment of a health-based guidance value, permissible exposure level, or Reference Dose. It should be noted that the critical effect could be a local as well as a systemic effect. It should also be recognized that the critical effect for the establishment of a tolerable exposure level is not necessarily the most severe effect of the chemical substance. For example, although a substance may cause a serious effect such as liver necrosis, the critical effect for the establishment of, e.g., an occupational exposure limit could be a less serious effect such as respiratory tract irritation, because the irritation occurs at a lower exposure level. 

Default Assessment Factors Used or Suggested for the Establishment of a Regulatory Standard or Health-Based Guidance Value for Threshold Effects... 

FIGURE 5.1 Subdivision of the 100-fold UF showing the relationship between the use of UFs (above the dashed line), and the proposed subdivisions (below the dashed line) based on toxicokinetics and toxicody-namics. (From Renwick, A.G., Food Addit. Contain., 10, 275, 1993 WHO/IPCS Assessing human health risks of chemicals Derivation of guidance values for health-based exposure limits. Environmental Health Criteria 170. Geneva, 1994. Available at http //www.inchem.org/documents/ehc/ehc/ehcl70.htm)... 

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. 

Derivation of Guidance Values for Health-Based Exposure Limits, Geneva, 1994. Available at http //www.inchem.org/documents/ehc/ehc/ehcl70.htm WHO/IPCS, Principles for the Assessment of Risks to Human Health from ... 

WHO/IPCS. 1994. Assessing Human Health Risks of Chemicals Derivation of Guidance Values for Health-based Exposure Limits. Environmental Health Criteria 170. Geneva WHO. http //www.inchem.org/ documents /ehc/ehc/ehcl70. htm... 

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. 

The health-based quality criteria derived as described above are used as the basis for the setting of quality criteria for chemical substances in soil and drinking water, and of C-values (Contribution values, the maximum amount of any pollutant a company is allowed to emit in the air) in ambient... 

HBORV Health-Based Occupational Reference Values... 

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