Blood nickel and chromium levels in association with smoking and occupational exposure among head and neck cancer patients in Tunisia

Chronic exposure to chromium (Cr) and nickel (Ni) has long been recognized as being capable to increase head and neck cancer (HNC) incidence among exposed human populations. This study represents the first biomonitoring of Cr and Ni exposure in Tunisia and focuses on a possible association with HNC risk. The aim of the present study was to evaluate the concentrations of Cr and Ni in the blood of HNC patients and controls. Metals blood levels of 169 HNC patients and 351 controls were determined using a Perkin-Elmer Analyst 800 Atomic Absorption Spectrometer. Mean blood levels of Cr and Ni in HNC cases (52.15 and 111.60 mu g/L, respectively) were significantly higher than those of controls (37.04 and 30.50 mu g/L, respectively). Cases' blood levels of Cr and Ni were significantly higher than those of controls after controlling for the other risk factors of HNC, including smoking, shisha consumption, occupational exposure, and nearby environment (P < 0.05). Among these risk factors, smoking and occupational exposure presented the most significant association with HNC (odds ratio (OR) = 6.54 and 7.66, respectively, P < 0.001). Cr and Ni levels in blood sample of cases and controls that are smoker/occupationally exposed were higher than that of non-smoker/non-occupationally exposed (P < 0.05). Smokers who are occupationally exposed present the most significant association with HNC (OR = 25.08, P < 0.0001). High levels of blood Cr (OR = 2.09) and high levels of blood Ni (OR = 8.87) were strongly associated with HNC after other potential confounders were controlled (P = 0.004 and P < 0.0001, respectively). This study suggested a potential role of Cr and Ni in the mechanism of HNC development.