Study finds 28 trace metals in tobacco smoke

Research into tobacco smoke has been conducted for many years, revealing a variety of pollutants, including toxic metals. However, which of these metals are classified as second- or third-hand smoke has remained a mystery to the research community. The problem is that many of the metals found in tobacco smoke can also come from industrial or natural sources of indoor and outdoor air pollution.

Now, a recent study by scientists at Lawrence Berkeley Lab has identified 28 trace metals in tobacco smoke. The results, published in the journal Environmental Science & Technology Letters, provide new evidence of the long-term health effects of second- and third-hand smoke. Second-hand smoke is the smoke emitted by a burning cigarette. Third-hand smoke is the harmful tobacco residue that settles on indoor surfaces after a cigarette goes out.

"It is important to quantify trace metals from second- and third-party smoke because some trace metals are present in other sources of indoor and outdoor air pollution. For more than a decade, our group has studied toxic organic pollutants emitted by smoking. Now, we are also interested in completing the picture of smoke's permanent legacy by assessing how trace metals may contribute to tobacco's health burden," said Hugo Destaillats, the study's principal investigator and a senior scientist in the Indoor Environment group at Berkeley Lab's Energy Technologies Area.

In experiments in a chamber simulating room conditions, the team from the Indoor Environment group collected samples of aerosol particles for 43 hours after six cigarettes were smoldered. To characterize second-hand smoke, they used Teflon filters to capture the freshly emitted aerosol immediately after smoldering. They then took additional samples over longer periods to characterize tertiary smoke.

Co-author Wenming Dong, a postdoctoral fellow in Berkeley Lab’s Earth and Environmental Sciences Area (EESA), used advanced triple quadrupole inductively coupled plasma mass spectrometry (QQQ ICP-MS) in EESA’s Aquatic Geochemistry Lab to detect significant levels of 28 trace metals in secondary and tertiary smoke. These included toxic metals such as cadmium, arsenic, chromium, beryllium, and manganese.

To better understand how trace metals may contribute to the chemical composition of second- and third-party smoke, the researchers used experimental results from the chamber study to predict trace metal concentrations in a smoker’s home and in non-residential scenarios, such as smoking bars, at various air exchange rates. In nearly all of the modeled scenarios, they found that predicted indoor air concentrations of cadmium, arsenic, and chromium exceeded California’s cancer risk guidelines. They also found that some of these metals exceeded the state’s reference levels for chronic non-cancer exposure.

Berkeley Lab researchers note that this study is a first step in understanding how tobacco smoke may contribute to overall indoor trace metal exposure, and that more work is needed to advance methods to eliminate second- and third-hand smoke pollutants.

"In smoking environments, these trace metals are found in indoor air as well as on surfaces and in dust particles, and people can be exposed to them through pathways such as dermal absorption and ingestion," said Xiaochen Tang, a researcher in the Energy Analysis and Environmental Impacts Division at the Energy Technologies Area of Berkeley Lab and the study's first author. "We focused our analysis on inhalation of airborne metal pollutants, so our results represent only a subset of total exposure. Given the persistence of trace metals in the environment, it is important to better understand the effectiveness of ventilation, cleaning, and vacuuming as mechanisms for removing these pollutants."