AbstractIncreasing evidence suggests that inorganic arsenic, a major environmental pollutant, exerts immunosuppressive effects in epidemiological, in vitro, and animal models. The mechanisms, however, remain unclear, and little is known about variation in susceptibilities due to age and sex. We per-formed a review of the experimental and epidemiologic evi-dence on the association of arsenic exposure and immune diseases. The majority of the studies described arsenic as a potent immunosuppressive compound, though others have re-ported an increase in allergy and autoimmune diseases, sug-gesting that arsenic may also act as an immune system stim-ulator, depending on the dose or timing of exposure. Limited
information, due to either the high concentrations of arsenic
used in in vitro studies or the use of non-human data for predicting human risks, is available from experimental stud-ies. Moreover, although there is emerging evidence that health effects of arsenic manifest differently between men and wom-en, we found limited information on sex differences on the immunotoxic effects of arsenic. In conclusion, preliminary data show that chronic early-life exposure to arsenic might impair immune responses, potentially leading to increased risk of infections and inflammatory-like diseases during childhood and in adulthood. Further investigation to evaluate effects of arsenic exposure on the developing immune system of both sexes, particularly in human cells and using concentrations relevant to human exposure, should be a research priority.