The hookah series part 2: elemental analysis and arsenic speciation in hookah charcoals

Abstract

The use of water pipes or hookahs to smoke tobacco formulations has gained great popularity among young people around the world, but the potential health hazards have not yet been adequately evaluated. The complexity of a multi component hookah apparatus, compared with cigarettes and cigars, makes it difficult to study under laboratory conditions. For this reason the detailed study of its components simplify the task. In this study the charcoal, which is traditionally used as the heat source, was analyzed for metal content before and after combustion. Sixteen different hookah charcoals were analyzed representing different compositions and manufacturing processes as well as different geographic origins. ICP-MS was used to measure 24 elements: Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Mo, Ag, Cd, Sb, Ba, Tl, Pb, Th, U. The total concentration ranges of toxic elements in native (un-burned) charcoals were: arsenic 14.8–10 300 ng g⁻¹, cadmium 3.3–2100 ng g⁻¹, and lead 95.2–55 600 ng g⁻¹. The mass-loss-corrected content of elements in combusted charcoals shows that most of the metals remain in the ash, with iron, cadmium and lead as exceptions. Because of the high content of arsenic in some samples an extraction and speciation method was developed to quantify four chemical forms of arsenic. Nitric acid, and phosphoric acid were evaluated as extractants used in a heating block, and ascorbic acid was used to minimize oxidation of inorganic As³⁺ to As⁵⁺. Anion exchange chromatography coupled to ICP-MS was used to carry out the separation and quantification of arsenic species. The best conditions in terms of extraction efficiencies and species conservation were 1.2 mol L⁻¹ H₃PO₄, with 0.2 mol L⁻¹ ascorbic acid. As⁵⁺ was the dominant arsenic species in charcoal. Concentrations ranged from 0.08–2.42 mg kg⁻¹, for As³⁺ and 0.46–8.36 mg kg⁻¹ for As⁵⁺. The results show high variation depending on the sample origin and composition. The possibility of volatile cadmium and lead contributions to the primary and second hand smoke by the charcoal are suggested and the high levels of arsenic suggest that for certain charcoals there may be more hazard from them than from the tobacco formulation.