Health risk characterization, of lead effects

Health Risk Characterization of Lead Effects in Human Populations... 

The time-dependent human health hazard characterization for lead is best summarized by chronological blocks of time and those adverse health effects that were considered of medical or scientific importance. Associated with the various levels of adverse health effect severity are body lead burdens or dose. The combination of these dose ranges, whether measured at the time or retroactively imputed as likely lead doses given current knowledge, defines the dose—response relationship, also called the dose—effect severity relationship. This topic as the third component of health risk assessment is addressed in Chapter 22. 

The second element of health risk assessment for lead is the identification of dose—response relationships for the various adverse health effects noted in the previous chapter. Dose—response relationships, like health hazard characterizations, are general in nature and independent of site-specific lead exposure scenarios. 

Risk characterization is the final step in the risk assessment process. It comprises quantitative or semiquantitative estimations, including uncertainties, of the probability of adverse health effects in people associated with exposure to the toxic agents. Risk characterization is based on the information gathered through the first three steps in the risk assessment procedure. It is important that the weight of evidence leading to the conclusions be openly discussed. Risk characterization should include a description of the primary causes of uncertainties. 

Risk assessment in human populations is broadly defined within the vocabulary of the National Academy of Science/National Research Council (NAS/ NRC) (1983) monograph on the topic as [quantitative] characterization of the potential adverse health effects from quantified exposures of humans to environmental hazards. In keeping with the NRC report s use of the term, both qualitative and quantitative risk assessments are considered when dealing with lead contamination and adverse effects in this text, although the most useful information emerged when empirical determination or modeling estimations produced a numerical outcome. Part 4 (Chapters 20—24) of this monograph presents the topic of human health risk assessment in detail. 

Lead induces numerous adverse effects involving multiple tissues, organs, and systems, but not aU of them are of equal relevance or gravity for human health nor are all of them well characterized for risk assessment purposes. Chapter 21, in much the same fashion as the rest of this monograph, does not offer an indiscriminate compendium of the universality of adverse effects but rather is a selective treatment of those toxic effects of current principal concern to lead toxicology and public health, documented as to data reliability. 

---