The World Health Organization's
study is a textbook example of the right
way to conduct an epidemiological
study. Unfortunately for them, it
yielded unexpected results.
World Health Organization conducted a
study of Environmental Tobacco Smoke
(ETS) and lung cancer in Europe.
is commonly referred to as Second
Hand Smoke (SHS). The two terms are
was a case control study using a
large sample size.
purpose of the study was to provide a
more precise estimate of risk, to
discover any differences between
different sources of ETS, and the
effect of ETS exposure on different
types of lung cancer.
study was conducted from twelve
centers in seven European countries
over a period of seven years.
participants consisted of 650
patients with lung cancer and 1542
control subjects. Patients with
smoking related diseases were
excluded from the control group. None
of the subjects in either group had
smoked more than 400 cigarettes in
of the study centers interviewed
family members of the participants to
confirm the subjects were not
study found no statistically
significant risk existed for
non-smokers who either lived or
worked with smokers.
only statistically significant number
was a decrease in the risk of
lung cancer among the children of
study found a Relative Risk (RR) for
spousal exposure of 1.16, with a
Confidence Interval (CI) of .93 -
1.44. In layman's terms, that means
to the ETS from a spouse increases
the risk of getting lung cancer by
Where you'd normally find 100
cases of lung cancer, you'd find 116.
number is not statistically
real RR can be any number within the
CI. The CI includes 1.0, meaning that
the real number could be no increase
at all. It also includes numbers
below 1.0, which would indicate a
protective effect. This means that
the number 1.16 is not statistically
RR of less than 2.0 is usually
written off as an insignificant
result, most likely to be due to
error or bias. An RR of 3.0 or higher
is considered desirable. (See Epidemiology 101
for more details.)
study found no Dose/Response
relationship for spousal ETS
exposure. See Epidemiology
102 for more information.
RR for workplace ETS was 1.17 with a
CI of .94 - 1.45, well below the
preferred 2.0 - 3.0, and with another
CI that straddled 1.0.
RR for exposure from both a smoking
spouse and a smoky workplace was
1.14, with a CI of .88 - 1.47.
RR for exposure during childhood was
0.78, with a CI of .64 - .96. This
indicates a protective effect!
Children exposed to ETS in the home
during childhood are 22% less
likely to get lung cancer, according
to this study. Note that this was the
only result in the study that did not
include 1.0 in the CI.
The WHO quickly buried the report.
The British press got wind of it and
hounded them for weeks.
March 8, 1998, the British newspaper
The Telegraph reported "The
world's leading health organization
has withheld from publication a study
which shows that not only might there
be no link between passive smoking
and lung cancer but that it could
have even a protective effect."
Finally, the WHO issued a press
release. Although their study showed
no statistically significant risk
from ETS, their press release had the
misleading headline "Passive
Smoking Does Cause Lung Cancer - Do
Not Let Them Fool You." (I say
"misleading" because it
would be impolite to call it an
paragraph four they admitted the
facts: "The study found that
there was an estimated 16% increased
risk of lung cancer among nonsmoking
spouses of smokers. For workplace
exposure the estimated increase in
risk was 17%. However, due to small
sample size, neither increased
risk was statistically significant."
Fact: The press
release doesn't mention the one
statistically significant result from
the study, that children raised by
smokers were 22% less likely to get
WHO tried to blame the results on a
small sample size. However, the in
the Journal of the National Cancer
Institute, where the results were
published, the researchers clearly
state: "An important aspect of
our study in relation to previous
studies is its size, which allowed us
to obtain risk estimates with good
statistical precision..." It
should also be noted that a larger
sample size wouldn't have changed the
numbers significantly, just narrowed
the CI a bit.
An abstract of the study is
The WHO's press release is located
This article, from the
British Wall Street Journal,
discusses this study and the EPA
FORCES has lots
of links to articles and editorials
on this subject.
(If the links above don't work, go