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Chemistry LibreTexts

Introduction

Cigarette smoking is the leading cause of premature death in the US. Although preventable, it still causes the death of more than 400,000 Americans annually.5 Nicotine and polycyclic aromatic hydrocarbons (PAHs) present in cigarette smoke are commonly known to be psychoactive and carcinogenic compounds, and have been well studied.5 However, the presence of heavy metals like cadmium (Cd) and lead (Pb) in cigarettes has not garnered as much attention. The chemical composition of the tobacco leaf is affected by both agricultural practice and curing method: cadmium and lead content in tobacco and smoke have been correlated with the content in the soil in which the tobacco was grown and in the fertilizer applied, but heavy metals in the air can also be important.3 The Fourth National Report on Human Exposure to Environmental Chemicals from the US Centers for Disease Control and Prevention (CDC) highlighted the finding that higher urinary cadmium from cigarette smoke could be the cause of several kidney diseases and low bone-mineral density.5 Both cadmium and lead are listed by the US Environmental Protection Agency (EPA) as toxic air pollutants: Pb is a criteria air pollutant under the NAAQS with a specified limit of 150 ng/m3, Cd is carcinogenic and the Oregon Department of Environmental Quality has established a benchmark concentration of 0.6 ng/m3 based on an inhalation unit risk analysis provided by the US EPA.6

In the experiment described here, levels of cadmium and lead in cigarettes were measured using Anodic Stripping Voltammetry (ASV) after a nitric acid extraction. This provided an introduction of ASV (a well-known trace electroanalytical technique) into the undergraduate instrumental analysis laboratory for upper division chemistry major students at Portland State University (PSU). Common methods of measuring the level of cadmium and lead include atomic absorption spectroscopy (AAS), inductively coupled plasma - atomic emission spectrometry (ICP-AES) and ASV.7,8,9 Compared with other elemental analytical methods, ASV is a simple, relatively low cost, highly sensitive and efficient method that can be carried out in a single student laboratory period. ASV also requires less volume of solution and generates less heavy metal waste than some other methods and hence is more environmentally friendly and less costly.

While doing this experiment, students get hands-on experience with instrumentation and sample extraction while applying their skill and knowledge to investigate a real-world problem with connections to environmental health related issues. Findings of this experiment (i.e., the presence and concentration of cadmium and lead) serve as direct evidence to students of the harmfulness of cigarette smoking. The students work in teams of two or three and develop journal quality lab reports, allowing them to practice teamwork and technical and non-technical scientific communication. A fairly obvious extension of the approach is suggested that would allow for a strong Active Learning component and an expansion of both the student involvement/control and the scope of the experiment.