Interaction of Occupational Toxic Metal Burden with HIV Status and Increased Cancer Risk

Aims: This study aimed to investigate the effects of HIV infection and occupational exposure on the concentrations of selected toxic metals and essential trace elements such as zinc in relation to the carcinogenic process.

Study Design: Comparative cross-sectional study.

Place and Duration of Study: Participants were recruited from two local government areas (Calabar municipal and Calabar south) and one secondary health facility in Calabar, Nigeria from April 2017 to February 2018.

Methodology: Study participants comprising 248 adults (191 males, 57 females, aged 18-65 years) were divided into four groups based on HIV status and occupational exposure to toxic metals: HIV-positive exposed (HPE; n=62), HIV-positive unexposed (HPU; n=66), HIV-negative exposed (HNE; n=60), and HIV-negative unexposed (HNU; n=60). The HIV-positive and HIV-negative groups had similar occupations, ages, and other characteristics. Blood cadmium (Cd), lead (Pb), mercury (Hg) and selenium (Se) were measured by inductively coupled plasma optical emission spectrometry (ICP-OES), while serum zinc (Zn) and copper (Cu) were determined using atomic absorption spectrometry.

Results: Lead, cadmium, and mercury were significantly elevated in HPE (14.92 ± 0.54 μg/dl, 0.25 ± 0.01 μg/L, 1.93 ± 0.08 μg/L respectively) compared with the HNU (11.07 ± 0.48 μg/dl, 0.17 ± 0.01 μg/L, 0.76 ± 0.05 μg/L), p<0.01, respectively. Zinc, a well-known antioxidant, p53 activator, and cell cycle regulator, was significantly lower in the HPE than in HPU, HNE, and HNU (p=0.02, p<0.01, p<0.01 respectively). Toxic metal exposure and HIV-positive status were associated with increased Pb and Hg levels as well as decreased Zn, suggesting additive effects.

Conclusion: Occupationally exposed HIV-positive individuals exhibited a higher toxic metal burden and a lower zinc level, both of which are important determinants of genome instability and may exacerbate DNA damage as well as impair DNA repair, raising cancer risk. Further studies with a larger sample size may fully elucidate the mechanisms underlying the interaction between HIV infection and occupational toxic metal exposure.