Second- and Thirdhand Smoke Exposure in Malta

Researchers from the University of Malta and the University of California, San Francisco have recently published studies establishing the current state of second- and thirdhand tobacco exposure in Malta. These studies, the first of their kind in Malta, contribute new international perspectives and understanding of passive tobacco smoke exposure. 

By Leta Dickinson

April 6, 2022

Malta is a small island nation located in the Mediterranean Sea. Maltese life expectancy is high, and its people live close to 90 percent of their lifespan in good health (as of a 2017 WHO report). However, one threat to Maltese health that needs more attention is passive tobacco smoke exposure – also known as second- and thirdhand smoke. The nation’s smoking rate is still around 20 %, compared to the US rate of around 14 %. 

Recently, researchers from the University of Malta and the University of California, San Francisco published three papers that, for the first time, measured and characterized second- and thirdhand smoke exposure in Malta. One study measured traces of secondhand exposure from the urine samples of schoolchildren, a second found thirdhand smoke present in house dust, and a third discovered that a cancer-causing tobacco byproduct is present in air sampled from Malta, as well as from several other countries. 

The first study measured three biomarkers, or indicators of tobacco exposure, in Maltese public-school children between nine and 11 years. The biomarkers — cotinine, 3-hydroxycotinine (3HC) and NNAL –each measure different chemicals from tobacco and last varying amounts of time in the body. When analyzed together, the biomarkers provide a more complete picture of the children’s exposure to tobacco smoke pollutants. 

Dr. Noel Aquilina, a researcher from the Department of Chemistry at the University of Malta, was the lead author for all three of these studies. He says that biologically measuring the children’s exposure, versus relying on surveys of parental smoking behavior in the home, was significant because children can be exposed to secondhand smoke in any number of places.  

“[The parents] had a questionnaire where they were asked if the kids were exposed [to secondhand smoke] at home, and only 16 % reported that they were. And so, one would expect that a relatively small proportion of the children was exposed to secondhand smoke.”

The biomarkers told a different story. At least 95% of the children had measurable levels of all three, indicating high levels of passive tobacco smoke exposure outside of the home. Dr. Aquilina suggests that this exposure may occur while parents and children walk to school or at social activities with both children and smoking adults in attendance. 

Dr. Aquilina and Professor Stephen Montefort’s team from the University of Malta’s School of Medicine were also interested in how asthma might fit into the picture, as tobacco smoke is one of the most common triggers for asthma attacks. About 11 % of the schoolchildren had parents who reported smoking at home — a clear minority. However, among these children, those diagnosed with asthma were found to have twice the levels of biomarkers as the non-asthmatic children, indicating that asthmatic children were exposed to significantly higher levels of tobacco smoke. 

“From an air quality and medical point of view, I think this is a finding which is worrying,” Dr. Aquilina explains. “One would expect that if you have asthmatic children, [your] attitude changes so health impacts due to smoking are possibly reduced.” 

The second study collected settled house dust from the five districts in Malta after at least three days without sweeping or dusting. Then, these dust samples were tested for the presence and amounts of thirdhand smoke toxins, including nicotine, nicotelline, and NNK (a cancer-causing chemical that becomes the biomarker NNAL). As one might expect, the dust in homes with smoking residents had the highest levels of pollutants. Traces of thirdhand smoke, however, were detected in every sample — regardless of residents’ smoking status and in all Maltese districts. This means that thirdhand smoke was present in dust in all homes, where it could later be picked up by young children who are exposed to these toxic pollutants. 

Although most Maltese homes have hard floors, Dr. Aquilina explains how these findings might apply more widely: “Even in three days of dust accumulating in homes, the pollutants still were easily found. [These levels were] probably not as high as in the US where the dust would go into the carpet fibers and therefore accumulate over time.”

The third and final study took air samples from 11 cities in four countries, including Malta and the US, and tested them for the cancer-causing tobacco smoke pollutant, NNK. Previous studies measuring pollutants have focused on fossil fuels sources, like traffic and industrial exhaust. The researchers hypothesized that cities with higher smoking rates would have accordingly higher NNK levels. Their findings confirmed this: The air samples from Msida, Malta, which has a smoking prevalence of around 20 %, had higher NNK levels than the sample from San Francisco, California, which has a smoking rate of about 12 %. All the samples, even those from cities with higher smoking rates, contained only a small amount of NNK, but Dr. Aquilina says that as long smoking continues, its byproducts will always be present in the air. 

“As NNK is carcinogenic,” Dr. Aquilina says, “and we cannot choose not to breathe. Even if it is a small portion of the air we breathe, we are continuously inhaling a potent lung carcinogen.” 

These three studies, together, emphasize how significant, unavoidable, and widespread of an issue passive tobacco smoke exposure is. These findings of second- and thirdhand smoke exposure in children, house dust, and ambient air in Malta clearly demonstrate that smoking is more than a personal choice. As long as smoking continues, the toxins contained within will infiltrate our bodies, homes, and air. Tobacco smoke exposure is a global issue that affects every local community. But there is also a global community to tackle it. 

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Click here to learn more about air quality.

Click here to learn more about house dust.

Click here to learn more about smoke exposure biomarkers.

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