Toxic and irritant pollutants from aged secondhand smoke
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: Nonsmokers’ exposure to toxicants can take place in environments contaminated with secondhand smoke (SHS) through dermal uptake, hand-to-mouth intake and inhalation of sorbed toxicants that are re-emitted to the gas phase. Such indirect pathways are particularly relevant to long-term exposures in residences, where smoking takes place on a regular basis and indoor surfaces are loaded with SHS. We need to better understand the chemical composition of SHS and its temporal evolution in order to assess this exposure. SHS “aging” involves complex physicochemical transformations that include chemical reactions as well as partitioning between various environmental media: the gas phase, aerosol particles and indoor surfaces. While the most volatile components are easily removed by ventilation, non-volatile or semi-volatile (“sticky”) chemicals tend to sorb to indoor surfaces. Nicotine is a distinct SHS-specific persistent indoor pollutant. It sorbs almost quantitatively to indoor materials, and is slowly re-emitted over extended timescales of weeks to months. During that period, sorbed nicotine is susceptible to react with atmospheric chemicals yielding toxic byproducts. Its reaction with nitrogen oxides and HONO may generate tobacco-specific N-nitrosamines (TSNAs), which are among the most potent carcinogens. Due to their low volatility, TSNAs are not easily removed by ventilation and can accumulate in the indoor environment.
 
 
 
 
 
 
 
 Very little is known about the effects of aging on SHS toxicity. We hypothesize that certain reactions taking place between persistent SHS pollutants (such as nicotine) and atmospheric reactive species (ozone, nitrogen oxides and nitrous acid) can be a long-term source of carcinogenic and/or irritant pollutants. Atmospheric reactive chemicals are ubiquitous in indoor air and are the drivers of SHS aging reactions. The goal of this project is to study chemical reactions that are likely to yield harmful pollutants during aging of secondhand tobacco smoke (SHS). For that purpose, we investigate the following two processes:
 
 
 
 
 
 1. Formation of highly carcinogenic tobacco-specific N-nitrosamines (TSNA) from reaction of sorbed nicotine with nitrogen oxides and nitrous acid. A detailed chemical characterization is achieved by isolating these reactions in a bench-scale test chamber. 
 
 
 
 
 
 2. Formation of formaldehyde, other irritant carbonyls and ultrafine aerosol particles from reaction of sorbed nicotine and other SHS components with ozone. This study is carried out using whole SHS in a realistic full-size environmental chamber. Tobacco smoke is generated with a smoking machine in the LBNL room-sized 20-m3 environmental chamber, and subsequently exposed to ozone. 
 
 
 
 
 
 At the completion of this study we expect to obtain a quantitative evaluation of exposure to TSNA, formaldehyde and other carcinogenic and irritant pollutants generated in SHS aging. This study will also contribute to improve our understanding of the chemical mechanisms of formation of harmful pollutants during SHS aging. That information is key to assess long-term cancer and non-cancer risks associated with chronic exposure of nonsmokers to aged tobacco smoke.