Hazard indices

Source Adapted from Wilkinson, C.F., Christoph, G.R., Jolien, E., et al., Reg. Toxicol. Pharmacol. 31, 30, 2000. 

HI = Expi/RfDi + Expii/RfDii + Expin/RfOm + Expiv/RfDiv 

Although the HI method is transparent, easily understandable, and directly relates to the RfD, the major disadvantage is that the RfD is not an appropriate metric to use as a POD for cumulative risk assessment, since the RfD is normally derived by using NOAELs and uncertainty factors, which are not data based, but may incorporate significant policy-driven assumptions. This issue is addressed in detail in Chapter 5. 

Use of the information in Table 10.2, scenario A, where the AF values for each compound is the same gives the following result  

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Tyler, B. J., A. R. Thomas, P. Doran, andT. R. Greig (1996). A Toxicity Hazard Index. Chemical Health and Safety 3 (January/February), 19-25. 

Aggregate the hazard for multiple chemical agents and exposure pathways as a hazard index, where appropriate. 

To assess tlie overall potential for noncarcinogenic effects posed by more dian one chemical, a liazard index (HI) approach has been developed based on EPA s Guidelines for Healdi Risk Assessment of Chemical Mixtures. This approach assumes that simultaneous subtlu eshold exposures to several chemicals could result in an adverse healtli effect. It also assumes tliat tlie magnitude of the adverse effect will be proportional to tlie sum of the ratios of the subtlireshold exposures to acceptable exposures. The non cancer hazard index is equal to tlie sum of the hazard quotients, as described below, where E and tlie RfD represent the same exposure period (e.g., subclironic, clironic, or shorter-term). 

When die hazard index exceeds miity, diere may be concern for potential health effects. While any single chemical with an exposure level greater than the toxicity value will cause die hazard index to e.xceed unity, die reader should note diat for multiple chemical exposures, die hazard index can also exceed unity even if no single chemical exposure exceeds its RfD. 

It is important to calculate die hazard index separately for clironic, subclironic, and short-temi exposure periods as described below. It is also important to remember to include RfDs for die noncancer effects of carcinogenic substances. 

For each clironic exposure padiway (i.e., seven years to lifetime exposure), calculate a sepmate clironic hazard index from die rados of the clironic daily intake (GDI) to die clironic reference dose (RfD) for individual chemicals as described below ... 

Cluonic Hazard Index = CDIi/RlDi + CDI./RfDo +...CDf/RfD, (13.3.3)... 

For each subclironic exposure pathway (i.e., two weeks to seven year exposure), calculate a separate subclironic hazard index from die ratios of subclironic daily... 

If there are specific data germane to the assumption of dose-additivity (e g., if two compounds arc present at the same site and it is known that the combination is five times more toxic than the sum of the toxicitics for the two compounds), then tire development of the hazard index should be modified accordingly. The reader can refer to the EPA (1986b) mi.xiure guidelines for discussion of a hazjird index equation that incorporates quantitative interaction data. If data on chemical interactions are available, but arc not adequate to support a quantitative assessment, note the information in the assumptions being documented for the risk assessment. 

If it is deemed appropriate to smii risks and liazard indices across padiways, the risk assessor should clemly idendfy those exposure padiway combinations for which a total risk estimate or hazard index is being developed. The rationale supporting such combinations should also be clearly stated. 

Hazard Index (exposure pathway ) + Hazard Index (exposure pathways) +. Hazard Index (exposure pathway,)... 

Note that die total exposure hazard index is calculated separately for clironic, subchronic, and shorter-term exposure periods. 

When the total hazard index for an exposed individual or group of indii iduals exceeds unity, dicrc may be concern for potential non cancer health effects. As indicated before, for multiple exposure pathways, the hazard index can exceed unity even if no single exposure padiway hazard index exceeds unity. If the total hazard index exceeds unity and if combining exposure... 

If tlie pollutant causes iui acute non carcinogenic risk, tlie inaximuin one hour concentration is used for C, and tlie acute reference exposure limit is used for tlie REL. Likewise, if tlie pollutant causes a clironic non carcinogenic risk, tlie one year average concentration is used, as is tlie clironic reference exposure limit. In tliis procedure, a Iiazard index is calculated for each pollutant separately, and tlien tlie indices are summed for each toxicological endpoint (i.e., tlie respiratory system, tlie central nervous system, etc.). Finally, tlie total hazard index is tlien compared to a value wliich is considered significant. 

The hazard index for clironic exposure to. xylene concentrations at the gas station is ... 

It is suggested then that fire hazard index , II (inflammation index), is defined by the following equation ... 

Chronic daily intake (CDI), Hazard Index (HI), and Cancer Risk (CR) for carcinogenic effects were calculated and exposures associated with HI<1 and CRdE-6 were considered negligible. 

A Fire Hazard Index. There are a number of situations where all that is needed is an indication of whether a change in a specific commercial product is beneficial or not. In these cases, one can presume that the people exposed to the fire and the building in which the fire exists are fixed. Moreover, it must be established that toxicity is the sole threat to escape, not smoke obscuration or heat. 

This chapter will review the levels and distribution of pharmaceuticals detected in both waste and river waters from the Ebro river Basin and gives an example about the use of established hazard indexes to estimate the possible risks posed by the pharmaceutical levels detected towards different aquatic organisms (algae, daphnia, and fish). Results presented in this chapter were integrated in the FP6 European Union project AQUATERRA (contract no. 505428). 

Fig. 9 Percent contribution of different compounds to hazard indexes for (a) fish in the monitoring carried out in June 2006, (b) Daphnia magna in October 2007, and (c) algae in November 2006...

D. R. Stull11 developed a rating system to establish the relative potential hazards of specific chemicals the rating is called the reaction hazard index (RHI). The RHI is related to the maximum adiabatic temperature reached by the products of a decomposition reaction. It is defined as... 

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