Memorandum by British American Tobacco
THE TOBACCO INDUSTRY AND THE HEALTH RISKS
OF SMOKING (TB 28)
ENVIRONMENTAL TOBACCO
SMOKE
240. The terms of this Committee's inquiry
encompass the "harmful effects of smoking". Many contend
today that, in addition to presenting risks to the smoker, tobacco
smoke can be a cause of disease in non-smokers exposed to other
people's smoking. Environmental tobacco smoke (ETS) has been claimed
to be both a human carcinogen, a cause of non-malignant respiratory
disease, a cause of heart disease, and a contributing factor in
the incidence of many other conditions in non-smokers.
241. British American Tobacco believes smoking
to present a real and serious risk of disease in smokers. We believe,
however, that the claim that ETS exposure (or "passive smoking")
is a cause of chronic disease is not supported by the science.
It has not even been established that ETS exposure increases the
risk of non-smokers developing lung cancer or heart disease.
242. Although many scientists agree that
the evidence that ETS presents a health hazard is inconclusive,
there is increasing pressure today for health-based regulation
of smoking in public places and the workplace. British American
Tobacco accepts that some non-smokers may dislike the smell of
tobacco smoke and find ETS annoying. Because ETS is not, in our
opinion, a risk factor for the development of chronic disease,
we support the sensible accommodation of the preferences of smokers
and non-smokers alike. Great steps have been made in this direction
in the UK, through the voluntary approach; that is, by allowing
managers and users of public places, employers and employees,
to agree appropriate levels of smoking control, without the interference
of indiscriminate, unfair and costly regulation.
243. ETS is a mixture of the smoke released
from the burning end of a cigarette and the smoke exhaled by a
smoker between puffs. This smoke quickly mixes with the ambient
air and becomes highly diluted. In all normal circumstances, ambient
air always contains a large number of substances, whether or not
smoking has taken place. Such substances can include dust, pollen,
bacteria, fungi, trace chemicals from vehicle emissions and other
sources of "pollutants", as well as emissions from cooking
and heaters. Research suggests that the types of substances found
in indoor air are generally similar, with or without the presence
of ETS.
244. It is difficult to measure real-life
ETS exposure for three reasons:
— ETS is highly diluted and therefore,
in real-life situations, there is very little in the air to be
measured;
— Many chemicals in ETS are likely
to be present in the air anyway, from other sources; and
— ETS is a complex and constantly changing
mixture, and the measurement of an individual chemical marker
cannot, therefore, be extrapolated directly to indicate total
ETS exposure.
245. Where scientists have measured ETS
in real-life environments, results suggest that exposure is extremely
low. For example, a recent study reported that, on average, in
the course of a year, non-smokers have an exposure to ambient
nicotine less than the amount delivered to a smoker from just
five cigarettes (at 12 mg tar: 1 mg nicotine per cigarette) (Jenkins
RA et al, Determination of Personal Exposure of Non-Smokers
to Environmental Tobacco Smoke in the United States, Lung
Cancer, 14(1, Suppl), p 195, 1996).
246. Measuring uptake of ETS by non-smokers
presents its own problems. The most commonly used markers are
nicotine and its metabolite cotinine, which can be analysed in
subjects' body fluids. Subjects do vary, however, in the rate
at which they metabolise body fluids, and in any case, nicotine
and cotinine are not quantitative markers for exposure to other
components of ETS.
247. Few of the epidemiological studies
on which claims about ETS and chronic disease are usually based
even attempted to measure ETS exposure or uptake in the study
populations. Exposure was usually estimated by administering questionnaires.
Aside from the comparative unreliability of individuals' memories,
known by epidemiologists as "recall bias", the questionnaires
were often administered not to actual members of the populations,
but to surviving family members, thus increasing recall unreliability
and introducing possible sources of bias.
248. Of these statistical studies, almost
50 have examined the incidence of lung cancer in women who say
they have never smoked, but who are married to smokers ("spousal"
studies). A significant majority of these studies have failed
to report an overall statistically significant increase in risk.
Where a statistically significant association was reported, the
magnitude of relative risk reported was so small (ie, typically
below 2.0), that it would be regarded as too weak, by normally
accepted epidemiological standards, to form any basis for public
health policy (US National Cancer Institute, "Dirty Water",
Reason, 28(1), p 52, 1996).
249. The positive trend in such studies,
although it generally falls short of statistical significance,
might be explained by a combination of factors. For example, non-smokers
living with smokers may tend to have different lifestyles and
diets than those living with wholly non-smoking households. It
is also unclear that all studies have adjusted at the appropriate
rate for the likelihood that some self-reporting never-smokers
are in fact former or current smokers.
250. Some attempts have been made to combine
the results of the studies, using a method known as meta-analysis.
The results of such meta-analyses have been unpersuasive. The
United States Environmental Protection Agency (EPA) was accused
of altering "confidence levels" in the original published
papers, and of bias in its study selection, in order to generate
a statistically significant result in their meta-analysis. Such
criticisms were upheld by a US Federal Court in North Carolina
which vacated the EPA's conclusions on ETS and lung cancer, the
judge commenting that the EPA had "changed its methodology
to find a statistically significant association" (Flue-cured
Tobacco Cooperative Stabilisation Corporation et al v United
States Environmental Protection Agency and Carol Browner, Order
and Judgement of District Judge Osteen in the District Court for
the Middle District of North Carolina, p 81, 17 July 1998).
251. One of the largest and most recent
studies, undertaken by the International Agency for Research on
Cancer ("IARC"), a body funded by the World Health Organisation,
combined results from several European countries. This study,
however, reported no overall statistically significant increase
in risk of lung cancer from ETS in any of the situations where
people were exposed to ETS. These included exposure at home; or
at home and at work combined; or during childhood; or in public
settings; or through exposure in vehicles.
252. Small increases in relative risk are
sometimes reported in percentage terms. A relative risk of 1.2,
for example, is often popularised as 20 per cent increase in risk,
giving an impression that if 100 people were exposed to the risk,
20 of them would contract the disease. This is highly misleading.
A 20 per cent increase in a number which is nearly zero produces
a number which is still nearly zero. A relative risk has to be
seen in the context of the base incidence of the disease in the
population. So, for example, a relative risk of 1.2 for a disease
with a non-exposed population incidence of 10 per 100,000 would
mean that the incidence in the exposed population would be 12
in 100,000. If the relative risk is not statistically significant,
as was the case with the IARC study (which reported a non-statistically
significant overall relative risk for living with a smoker of
1.16) then the increased incidence of the disease could equally
be zero.
253. The data generally on ETS exposure
at work is even less conclusive than the spousal data. Only one
of many published studies has reported an overall statistically
significant increase in risk. Similarly, most studies which have
looked at ETS exposure in social settings and during childhood
do not report an overall statistically significant increase in
risk of lung cancer.
254. The epidemiological data on ETS and
heart disease is similar in nature. Most studies do not report
statistically significant increases in risk. The most substantial
pools of data on this subject are the two databases of the American
Cancer Society's Cancer Prevention Study, and the database of
the US National Mortality Followback Survey. Combined, these sources
are ten times larger than all other studies taken together. Analyses
of these datasets have reported no overall association between
ETS and heart disease.
255. Epidemiological studies of the relationship
between ETS exposure and respiratory disease in non-smoking adults,
taken overall, do not show an increase in risk. Clinical studies
of the reaction of adults highly sensitive to ETS (eg asthmatics)
have had difficulty in prompting a measurable response.
256. There is a large body of research on
ETS exposure and respiratory disorders on children. It is hard
to analyse overall, as there is great disparity in study design,
age ranges of subjects, the symptoms measured and methods of diagnosis.
There are quite a number of reports of statistically significantly
increased risk of respiratory disorders in pre-school age children
exposed to ETS. It is unclear to what extent this increase is
an artefact of other factors more statistically common in smoking
households, such as diet, housing conditions and quality of pre-natal
care. The pattern of increased risk is not consistently replicated
for children of school age, suggesting that a real effect, if
one exists, is short-term.
257. Although smoking by parents has been
associated in some studies with an increased risk of "cot
death" (sudden infant death syndrome), a long list of other
risk factors have also been reported. Some recent studies have
reported that incidence of "cot death" has been reduced
by up to 50 per cent where parents have followed government advice
not to put their child to sleep in the "prone" position.
However, no one yet fully understands the reasons or mechanism
behind this syndrome.
258. British American Tobacco's view is
that it is right that parents and other adults be particularly
sensitive to the needs of young children, especially infants,
for a clean, comfortable environment. It makes sense not to smoke
around infants, especially in poorly ventilated environments and
not to smoke around young children for long periods.
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