Immunotoxicity risks, identifying

Some animal studies indicate that dietary exposure to methyl parathion causes decreased humoral and cellular responses (Shtenberg and Dzhunusova 1968 Street and Sharma 1975). A more recent, well-designed animal study that included a battery of immuno/lymphoreticular end points showed few effects at the nonneurotoxic doses tested (Crittenden et al. 1998). No adequate studies are available in humans to assess the immunotoxic potential of methyl parathion. Therefore, studies measuring specific immunologic parameters in occupationally exposed populations are needed to provide useful information. Further studies are also needed to investigate the mechanism for methyl parathion-induced immunotoxicity since this information would help to identify special populations at risk for such effects. 

Clinical data unequivocally demonstrate that immunotoxicity is associated with significant morbidity and even mortality [1], Immunotoxicity is therefore of considerable importance to the toxicologist who has the responsibility of identifying and characterizing the immunotoxic potential of chemicals and estimating the risk they pose to... 

Immunotoxicity. No information on specific immunological effects of 1,2-dibromoethane is available for humans or animals exposed via inhalation, oral, or dermal routes. Some effect on the immune system can be inferred from a report of lymphoid neoplasia associated with exposure of workers to various chemicals including 1,2-dibromoethane (Alavanja et al. 1988). Epidemiological and animal studies would be useful to investigate the immunotoxic potential of 1,2-dibromoethane. Furthermore, if 1,2-dibromoethane proves to be a potential immunosuppressant, further research into this area could help identify populations at higher risk because of pre-existing permanent immunosuppression. 

The immune system has unquestionably been identified as a potential target organ for drugs and chemicals. Therefore, the hazard exists. The assessment of the risk associated with xenobiotic-induced immunotoxicity represents one of the key challenges for this discipline in the immediate future. 

From the many exemplars listed in the tables of this chapter, it is clear that alternate systems are playing an important role in demonstrating the pharmacologic activity of immunoactive drugs. And, when an immunotoxicity has already been identified, either by conventional preclinical test systems or in clinical trials, alternate systems can enable in-depth characterization of the hazard posed by a therapy. Their role in the final step of immunotoxicology, Risk Assessment, however, is less clear. As shown in Tables 10.1-13 and 10.1-14,... 

Cardiovascular effects of Pb in humans are the subject of Chapter 13, particularly with respect to effect potency in older exposure subjects but with inclusion of other risk groups. Cardiovascular effects, while inconsistently quantified across human populations, have been identified in multiple epidemiological studies, supported by a number of experimental data sets appearing in the global literature. Chapter 14 on human reproductive and developmental impacts of lead exposures presents the more useful data across several risk groups within human populations. Chapter 15 discusses adverse effects of lead on the renal system as nephrotoxicity is considered to occur across both occupational and nonoccupational subsets of human populations and subsets within nonoccupational categories. Discussions in Chapter 15, much like those in Chapter 18 on immunotoxicity, have benefited from quite recent findings. 

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