Interaction between zinc, cadmium, and lead in scalp hair samples of Pakistani and Irish smokers rheumatoid arthritis subjects in relation to controls.

The incidence of rheumatoid arthritis (RA) has been associated with cigarette smoking. The aim of our study was to assess the trace essential and toxic metals, cadmium (Cd), lead (Pb), and zinc (Zn), in scalp hair samples of 32 Irish and 46 Pakistani smokers and non-smokers RA male patients with age range 42-56 years. For comparison purpose, the scalp hair samples of 27 Irish and 55 Pakistani non-RA male subjects of the same age group were collected. The concentrations of trace and toxic elements were measured by inductive coupled plasma atomic emission spectrophotometer and atomic absorption spectrophotometer prior to microwave-assisted acid digestion. The validity and accuracy of the methodology was checked using certified reference materials and using conventional wet acid digestion method on the same certified reference materials (CRMs). The recovery of all studied elements was found to be in the range of 97.5-99.7% of certified reference values of CRMs. The results of this study showed that the mean values of Cd and Pb were significantly higher in scalp hair samples of both smoker and non-smoker RA patients than in referents (P < 0.001), whereas the concentration of Zn was lower in the scalp hair samples of smokers and non-smokers rheumatoid arthritis patients. The deficiency of Zn and the high exposure of Cd and Pb as a result of cigarette smoking may be synergistic risk factors associated with rheumatoid arthritis.