Mice exposed to household fabrics contaminated with third-hand tobacco smoke showed changes in biological markers of health after only one month, a
recent study found. After six months, the mice showed evidence of liver damage and insulin resistance, symptoms which usually precede the development of type 2 diabetes.
A landmark study in 2011 by Georg Matt of San Diego State University showed that
nicotine levels were still elevated in house dust in non-smokers’ homes two months after the previous smoking tenants vacated. Even
infants in a neonatal intensive-care unit in the US, with a strict no-smoking policy, had chemical markers of tobacco exposure in their urine after a visit from a parent who smoked.
The new mouse model study investigated the effects of third-hand smoke exposure over time on animal health (the first study to do so). The researchers, from the University of California, Riverside, used a smoking machine to create third-hand smoke contaminated household fabrics in mice cages, including curtain material, upholstery and carpet. Once the fabrics showed levels likely to be found in smokers homes, the mice were placed in the cage and monitored over a period of six months.
After just one month, the mice showed changes in markers of health in the blood serum, liver and brain tissues. The range and severity of the changes on the health of mice got progressively worse the longer they were exposed.
After four months, the mice showed increases in factors related to oxidative stress and liver damage. Fasting glucose and insulin levels increased with third-hand smoke exposure and, after four months, the mice already had a increased risk of type 2 diabetes.
The speed at which third-hand smoke residues cause measurable health effects in the mice is surprising. How the health effects observed in mice translate to humans, though, remains an open question.