Assessing Heavy Metal Burden Among Cigarette Smokers and Non-smoking Individuals in Iran: Cluster Analysis and Principal Component Analysis

Smoking is one of the major causes of mortality and numerous diseases, both directly and indirectly. The role of smoking as a significant risk factor is already known in several human diseases such as cardiovascular diseases, lung cancer, and chronic obstructive pulmonary disease. We aimed to compare the toxicity of heavy metal levels in the two groups of cigarette smokers and non-smokers in Birjand during 2018. In this case-control study, 70 smokers were enrolled as the case group and 70 individuals with no history of smoking as control group. The cases were selected from among those who smoked 10 cigarettes per day without a drug use history. Heavy metal concentrations were collected in participants' serum samples. Cluster analysis and principal components analysis were employed to compare heavy metal toxicity between the groups. The duration of smoking and the number of cigarettes consumed per day were 14.36 ± 12.75 years and 11.32 ± 7.23, respectively. The concentration of thallium (Ti), arsenic (As), manganese (Mn), and copper (Cu) was significantly higher in the smoker group than that in the non-smoker group (p < 0.05). Lead (Pb), cadmium (Cd), and cobalt (Co) are among the most important metals accumulated in smokers' blood, and 21.6% of our study's total data was associated with them. Cluster analysis in the smoker group, including A1 (Cd), A2 (Co, Pb), B1 (Ti), B2 (mercury (Hg), As, chromium (Cr), iron (Fe), nickel (Ni), and zinc (Zn)) and C (Mn and Cu). In our study, cluster analysis showed a different grouping of elements in patient and control groups. Lead, cadmium, and cobalt were the most critical metals accumulated in the blood of cigarette smokers.