WHAT IS THIRD-HAND SMOKE?
Third-hand smoke is created by tobacco smoke that lingers after a cigarette has been put out.
It’s called ‘third-hand’ because it is created once second-hand smoke has disappeared.
Third-hand smoke can stick to almost all surfaces but especially clings to fabrics.
People can be exposed to third-hand smoke particles through inhalation, ingestion or skin contact.
Third-hand smoke is thought to be particularly dangerous to young children because they are more likely to crawl on the floor and eat from their hands without washing them first – ingesting the toxins into their systems.
Third-hand smoke is ‘noxious residue’ produced by cigarette smoke that clings to virtually all surfaces after second-hand smoke has disappeared.
The study from the Laurence Berkeley National Laboratory at the University of California also found that this toxic residue becomes more harmful over time.
Co-author Lara Gundel said: ‘This is the very first study to find that third-hand smoke is mutagenic.
‘Some of the chemical compounds in third-hand 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 researchers used a variety of tests to establish if third-hand smoke breaks down DNA strands and leads to long-lasting DNA damage and gene mutation.
‘Until this study, the toxicity of third-hand smoke has not been well understood,’ continued Gundel.
‘Third-hand smoke has a smaller quantity of chemicals than second-hand smoke, so it’s good to have experimental evidence to confirm its genotoxicity.’
Previous studies have found that it can still be detected in dust and surfaces of homes more than two months after smokers moved out.
Common cleaning methods such as vacuuming, wiping and ventilation have not proven to be effective in lowering the presence of these particles.
The report added: ‘You can do some things to reduce the odours, but it’s very difficult to really clean it completely.
‘The best solution is to substitute materials, such as change the carpet and repaint.’
To generate the samples, the researchers put paper strips in smoking chambers.
The acute samples were exposed to five cigarettes smoked in about 20 minutes.
The chronic samples were exposed to cigarette smoke for 258 hours over 196 days.
During that time, the chamber was also ventilated for about 35 hours.
The researchers found that the concentrations of more than half of the compounds studied were higher in the chronic samples than in the acute.
They also found higher levels of DNA damage caused by the chronic samples.
The study said there was a 0.4 per cent conversion in human cells within the first hour of exposure and this increased ten-fold over a three-hour period.
Lead author Mohamad Sleiman said: ‘Given the rapid sorption and persistence of high levels of nicotine on indoor surfaces, including clothing and human skin, our findings indicate that third-hand smoke represents an unappreciated health hazard through dermal exposure, dust inhalation and ingestion.’
The researchers conclude in their paper: ‘Ultimately, knowledge of the mechanisms by which third-hand smoke exposure increases the chance of disease development in exposed individuals should lead to new strategies for prevention.’
The findings are published in the science Journal Mutagenesis.