Research led by scientists from Lawrence Berkeley National Laboratory, UCLA and the University of Texas identified for the first time that the toxic smoke residues that stick to surfaces and objects (also known as thirdhand smoke) increases the risk of DNA damage and may lead to mutations; thereby increasing the risk of cancers and other diseases. The study also suggested that chronic exposure causes more damage as compared to acute exposure since the smoke particles tend to accumulate over-time and transform into more harmful entities and compounds leading to extensive risk of genetic alterations.
Co-author of the study, Lara Gundel, also a Berkeley Lab scientist commented:
“ This is the very first study to find that thirdhand smoke is mutagenic. Tobacco-specific nitrosamines, some of the chemical compounds in thirdhand smoke, are among the most potent carcinogens there are. They stay on surfaces, and when those surfaces are clothing or carpets, the danger to children is especially serious.”
The results and recommendations of the study “Thirdhand smoke causes DNA damage in human cells” were published in the journal Mutagenesis.
Details of the study:
The team of researchers utilized two common in vitro assays, the long amplicon-qPCR assay and the Comet assay. The purpose of these assays is to determine the nature of genotoxicity and genetic damage. Result findings suggested that the exposure to thirdhand smoke leads to breaks in the continuity of DNA strands and higher risk of oxidative DNA damage. The two factors lead to genetic mutation. Genotoxicity is the primary patho-physiologic event that increases the risk of developing a variety of diseases that includes cancerous growth of different tissues in the body, pathological aging and premature onset of atherosclerosis.
Dr. Bo Hang, a chemist in the Life Sciences Division of Berkeley Lab and senior investigator of the study, commented:
“Until this study, the toxicity of thirdhand smoke has not been well understood. Thirdhand smoke has a smaller quantity of chemicals than secondhand smoke, so it’s good to have experimental evidence to confirm its genotoxicity.”
Thirdhand smoke produces harmful toxins when nicotine of smoke combines with nitrous acid. The chemical reaction produces carcinogenic, tobacco-specific nitrosamines, such as NNA, NNK and NNN. Nicotine also has the capability to cross-react with ozone molecules in air to form highly toxic ultrafine particles that are capable of penetrating human tissues via inhalation, ingestion or mere physical contact with scattered toxic particles.
Thirdhand smoke particles are much stubborn when compared to secondhand smoke:
The toxicity of thirdhand smoke particles is attributed to the longer half-life and difficult eradication. Various studies revealed that the nicotine toxic particles persist in air (as part of dust particles that sticks to furniture, items of daily use, and the roof or ceilings of apartments, even months after smoking residents moved out). Unfortunately, conventional cleaning methods (like wiping, mopping, vacuuming and ventilating) cannot clean or effectively remove the nicotine reduced products. Destaillats commented:
“You can do some things to reduce the odors, but it’s very difficult to really clean it completely. The best solution is to substitute materials, such as change the carpet, repaint.”
Additionally, the toxicity and genotoxic potential of these particles increase with time. The researchers studied the concentration of chemicals and toxins in the acute sample of thirdhand smoke and compared the findings with the chronic sample, identifying that almost 50% compounds of interest have a higher concentration in chronic smoke samples.
“The cumulative effect of thirdhand smoke is quite significant. The findings suggest the materials could be getting more toxic with time.”
The research concluded that:
“Ultimately, knowledge of the mechanisms by which thirdhand smoke exposure increases the chance of disease development in exposed individuals should lead to new strategies for prevention.”
Future research prospective:
Hang hopes to conduct further research in an effort to identify the complex chemical reactions that take place between NNA particles and DNA bases. NNA is a nitrosamine that is specific to tobacco smoke and is not associated with secondhand smoke. He suggested:
“It looks like it’s a very important component of thirdhand smoke, and it is much less studied than NNK and NNN in terms of its mutagenic potential.”