Boatyard workers after chronic exposure to lead exhibited a nearly 9-fold higher lead level, reduced phagocytic activity, elevated interleukin-4, reduced interferon-γ, dysregulated subpopulations of Treg and Tc cells, and decreased cell-mediated immunity, increased death rate due to brain and lung cancers, indicating the profound effect of lead poisoning on immunity (45). This evidence concerns the gene IL4 and lung cancer.