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In
order to see the effects of smoking on fertility and sperm
quality, researchers from the mutagenesis section of Health
Canada’s environmental and occupational toxicology division,
with colleagues from McMaster University, studied the spermatogonial stem cells of mature mice that had been exposed
to cigarette smoke for either six or 12 weeks. What the team was looking for
was to see the alterations in a specific stretch of repeated portions of
DNA, called Ms6-hm, which does not contain any known genes.
The smoking mice were exposed to two cigarettes per day, the equivalent
based on blood levels of tobacco by-products of an average human smoker. The
team then found that the rate of Ms6-hm mutations in the smoking mice were
1.4 times higher than that of non-smoking mice at six weeks, and 1.7 times
that of nonsmoking mice at 12 weeks. The results of the study have been
published in the June 1 issue of Cancer Research.
Lead author of the study Carole Yauk said, “We were looking at male germline
mutations, which are mutations in the DNA of sperm. If inherited, these
mutations persist as irreversible changes in the genetic composition of
off-spring.” She added, “We have known that mothers who smoke can harm their
fetuses, and here we show evidence that fathers can potentially damage
offspring long before they may even meet their future mate.”
This, according to the team, suggests that damage is related to the duration
of exposure. “So the longer you smoke, the more mutations accumulate and the
more likely a potential effect may arise in the offspring,” Yauk said.
Males, whether they are mouse or man, generate a constant supply of new
sperm from self-renewing spermatogonial stem cells. Reacting to the study,
associate professor of anatomy at AIIMS Dr Rima Dada told TOI that smoking
damages the DNA by mimicking tissue inflammation and increasing free radical
production. “The over 200 known carcinogens present in tobacco cause
testicular tissue to inflammate with the free radical level inducing the
damage to the sperm,” she said.
THE FUTURE MAY GO UP IN SMOKE
While tobacco kills about
4.9 million people every year globally, an alarming 1 million of them are
from India. Each day, 55,000 children in India start using tobacco and about
5 million children under the age of 15 are addicted to it.
India loses at least $7.2 billion per year as
healthcare expenditure due to tobacco consumption. Tobacco consumption is
linked to 25 diseases — cardio-vascular problems, cancer and diabetes being
the major ones
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