A University of California, Riverside-led study shows that third-hand smoke causes
hyperactivity and significant damage in the liver and lungs, and delays the healing of wounds.
Just as deadly
Do not smoke and do not allow yourself to be exposed to
smoke because second-hand
smoke and third-hand smoke are just as deadly as first-hand smoke, says a
scientist at the University of California, Riverside who, along with
colleagues, conducted the first animal study of the effects of third-hand smoke.
Read: Second-hand smoke affects brain
While first-hand smoke refers to the smoke inhaled by a
smoker and second-hand smoke to the exhaled smoke and other substances
emanating from the burning cigarette that can get inhaled by others, third-hand
smoke is the second-hand smoke that gets left on the surfaces of objects, ages
over time and becomes progressively more toxic.
"We studied, on mice, the effects of third-hand smoke
on several organ systems under conditions that simulated third-hand smoke
exposure of humans," said Manuela Martins-Green, a professor of cell
biology who led the study. "We found significant damage occurs in the
liver and lung. Wounds in these mice took longer to heal. Further, these mice
Study results appear in PLoS ONE.
The results of the study provide a basis for studies on the
toxic effects of third-hand smoke in humans and serve to inform potential
regulatory policies aimed at preventing involuntary exposure to third-hand
Third-hand smoke is a potential health threat to children,
spouses of smokers and workers in environments where smoking is, or has been,
allowed. Contamination of the homes of smokers by third-hand smoke is high,
both on surfaces and in dust, including children's bedrooms. Re-emission of
nicotine from contaminated indoor surfaces in these households can lead to nicotine
exposure levels similar to that of smoking. Third-hand smoke, which
contains strong carcinogens, has been found to persist in houses, apartments
and hotel rooms after smokers move out.
The team led by Martins-Green found that the mice exposed to
third-hand smoke in the lab showed alterations in multiple organ systems and
excreted levels of a tobacco-specific carcinogen
similar to those found in children exposed to second-hand smoke (and
consequently to third-hand smoke):
• In the
liver, third-hand smoke was found to increase lipid levels and non-alcoholic
fatty liver disease, a precursor to
cirrhosis and cancer and a potential contributor to cardiovascular
• In the
lungs, third-hand smoke was found to simulate excess collagen production and
high levels of inflammatory cytokines (small proteins involved in cell
signaling), suggesting propensity for fibrosis
with implications for inflammation-induced diseases such as chronic
obstructive pulmonary disease and asthma.
wounded skin, healing in mice exposed to third-hand smoke showed many
characteristics of the kind of poor healing observed in human smokers who have
gone through surgery.
in behavioural tests the mice exposed to third-hand smoke showed hyperactivity.
"The latter data, combined with emerging associated behavioural
problems in children exposed to second- and third-hand smoke suggests that with
prolonged exposure, they may be at significant risk for developing more severe
neurological disorders," Martins-Green said.
Although the potential risks attributed to third-hand smoke
exposure are increasing, virtually nothing was known about the specific health
implications of acute or cumulative exposure – until now.
"There is a critical need for animal experiments to
evaluate biological effects of exposure to third-hand smoke that will inform
subsequent human epidemiological and clinical trials," Martins-Green said.
"Such studies can determine potential human health risks, design of
clinical trials and potentially can contribute to policies that lead to
reduction in both exposure and disease."
Her research team was surprised to find that the damage
caused by third-hand smoke extends to several organs in the body.
"More recently we have found that exposure to
third-hand smoke results in changes that can lead to type II diabetes even when
the person is not obese," Martins-Green said. "There is still much to
learn about the specific mechanisms by which cigarette smoke residues harm
non-smokers, but that there is such an effect is now clear. Children in
environments where smoking is, or has been allowed, are at significant risk for
suffering from multiple short-term and longer health problems, many of which
may not manifest fully until later in life."
Research has shown that children living with one or two
adults who smoke in the home, where second- and third-hand smoke are abundant,
are absent 40% more days from school due to illness than children who did not
live with smokers.
The first complete ban in the world on indoor smoking in all
public spaces – including bars and restaurants – occurred in 1990 in San Luis
Obispo, California. Earlier this month, UC Riverside joined the rest of the
University of California campuses and facilities by going smoke- and
tobacco-free. No tobacco use of any kind is allowed on campus property, a
policy that extends to electronic cigarettes.Read more:
third-hand smoke can be a killer
third-hand smoke is bad for babies
third-hand smoke is dangerous