Immunotoxicity: the risk is real.

Several papers published over the last year represent significant progress in closing the gap between rodent immunotoxicity data and human risk and indicate that, at least for the developing immune system, the concern raised by rodent data is justified. The studies reviewed here show that suppression of immune responses in rodents is predictive of suppression of immune responses in humans and that there is a relationship between immune suppression following developmental exposure to the toxicants and enhanced risk of infectious or neoplastic disease in humans. The three cases highlighted here are remarkable in that they all deal with real-world environmental exposures that represent different media -- air (cigarette smoke), water (arsenic), and food (polychlorinated biphenyls [PCBs]) -- and constitute very real risks. Moreover, the arsenic and PCB studies actually demonstrate a quantitative relationship between human exposure and immune suppression. There is evidence that in utero exposure to cigarette smoke and arsenic but not PCBs is associated with increased risk of allergic disease as well. There is clearly potential for designing studies that could address both issues.