Inhaled cannabis smoke has more harmful
toxins than tobacco, scientists have discovered.
The Canadian government research found
20 times as much ammonia, a chemical linked to cancer,
New Scientist said.
The Health Canada team also found five
times as much hydrogen cyanide and nitrogen oxides, which
are linked to heart and lung damage respectively.
But tobacco smoke contained more of a
toxin linked to infertility. Experts said users must be
aware of the risks.
About a quarter of the population in
the UK smokes tobacco products, while a sixth of 15 to
34-year-olds have tried cannabis in the past year, making
it the most commonly used drug.
Previous research has shown cannabis
smoke is more harmful to lungs than tobacco as it is inhaled
more deeply and held in the lungs for a longer period.
However, it has also been acknowledged
that the average tobacco user smokes more than a cannabis
user.
Researchers from Health Canada, the government's
health research department, used a smoking machine to
analyse the composition of the inhaled smoke for nearly
20 harmful chemicals.
They also looked at the sidestream smoke,
given off from the burning tip of the product and responsible
for 85% of the smoked inhaled through passive smoking.
Concentrations
In most cases, the comparison on sidestream
smoke broadly mirrored that of inhaled smoke.
However, in the case of polycyclic aromatic
hydrocarbons, the toxin linked to infertility, the researchers
found concentrations were actually higher in cigarette
smoke.
The study also showed little difference
in the concentrations of a range of chemicals, including
chromium, nickel, arsenic and selenium.
Lead researcher David Moir said: "The
consumption of marijuana through smoking remains a reality
and among the young seems to be increasing.
"The confirmation of the presence of
known carcinogens and other chemical is important information
for public health."
Dr Richard Russell, a specialist at the
Windsor Chest Clinic, said: "The health impact of cannabis
is often over-looked amid the legal debate.
"Evidence shows it is multiplied when
it is cannabis compared to tobacco.
"Tobacco from manufacturers has been
enhanced and cleaned whereas cannabis is relatively unprocessed
and therefore is a much dirtier product.
"These findings do not surprise me. The
toxins from cannabis smoke cause lung inflammation, lung
damage and cancer."
Stephen Spiro, of the British Lung Foundation,
added the findings were "a great worry".
