The National Conservation Guild
Indoor Air Quality Issues
Effects Of Environmental Tobacco Smoke
(ETS) on Children.
Excerpts from chapter 1 of the Environmental Protection
Agency's report entitled
Respiratory Health Effects of Passive Smoking: Lung Cancer
and Other Disorders,
EPA/600/6-90/006F. The report is dated December 1992 and was publicly
released on January 7, 1993.
Environmental tobacco smoke (ETS) in the United
States presents a
serious and substantial public health impact...
In children:
ETS exposure is causally* associated with an increased risk of
lower respiratory tract infections (LRIs) such as bronchitis and
pneumonia. This report estimates that 150,000 to 300,000 cases
annually in infants and young children up to 18 months of age
are attributable to ETS.
ETS exposure is causally associated with increased prevalence
of fluid in the middle ear, symptoms of upper respiratory tract
irritation, and a small but significant reduction in lung function.
ETS exposure is causally associated with additional episodes and
increased severity of symptoms in children with asthma. This report
estimates that 200,000 to 1,000,000 asthmatic children have their
condition worsened by exposure to ETS.
ETS exposure is a risk factor for new cases of asthma in children
who have not previously displayed symptoms.
In 1986, the National Research Council (NRC) and the Surgeon General
of the U.S. Public Health Service independently assessed the health
effects of exposure to ETS (NRC, 1986;
U.S. DHHS, 1986). Both of the 1986 reports conclude that ETS can
cause lung cancer in adult nonsmokers and that children of parents
who smoke have increased frequency of respiratory symptoms and
acute lower respiratory tract infections, as well as evidence
of reduced lung function.
Population estimates of ETS health impacts are also made for certain
noncancer respiratory endpoints in children, specifically lower
respiratory tract infections (i.e., pneumonia, bronchitis, and
bronchiolitis) and episodes and severity of attacks of asthma.
Estimates of ETS-attributable cases of LRI in infants and young
children are thought to have a high degree of confidence because
of the consistent study findings and the appropriateness of parental
smoking as a surrogate measure of exposure in very young children...
1. Exposure of children to ETS from parental smoking is causally
associated with:
a. increased prevalence of respiratory symptoms of irritation
(cough, sputum, and wheeze),
b. increased prevalence of middle ear effusion (a sign of middle
ear disease), and
c. a small but statistically significant reduction in lung function
as tested by objective measures of lung capacity.
2. ETS exposure of young children and particularly infants from
parental (and especially mother's) smoking is causally associated
with an increased risk of LRIs (pneumonia, bronchitis, and bronchiolitis).
This report estimates that exposure to ETS contributes 150,000
to 300,000 LRIs annually in infants and children less than 18
months of age, resulting in 7,500 to 15,000 hospitalizations.
The confidence in the estimates of LRIs is high.
Increased risks for LRIs continue, but are lower in magnitude,
for children until about age 3; however, no estimates are derived
for children over 18 months...
. a. Exposure to ETS is causally associated with additional episodes
and increased severity of asthma in children who already have
the disease. This report estimates that ETS exposure exacerbates
symptoms in approximately 20% of this country's 2 million to 5
million asthmatic children and is a major aggravating factor in
approximately 10%.
b. In addition, the epidemiologic evidence is suggestive but not
conclusive that ETS exposure increases the number of new cases
of asthma in children who have not previously exhibited symptoms.
Based on this evidence and the known ETS effects on both the immune
system and lungs (e.g., atopy and airway hyperresponsiveness),
this report concludes that ETS is a risk factor for the induction
of asthma in previously asymptomatic children. Data suggest that
relatively high levels of exposure are required to induce new
cases of asthma in children. This report calculates that previously
asymptomatic children exposed to ETS from mothers who smoke at
least 10
cigarettes per day will exhibit an estimated 8,000 to 26,000 new
cases of asthma annually. The confidence in this range is medium
and is dependent on the conclusion that ETS is a risk factor for
asthma induction.
1.3.2. ETS and Noncancer Respiratory Disorders
Exposure to ETS from parental smoking has been previously linked
with increased respiratory disorders in children, particularly
in infants. Several studies have confirmed the exposure and uptake
of ETS in children by assaying saliva, serum, or urine for cotinine.
These cotinine concentrations were highly correlated with smoking
(especially by the mother) in the child's presence. Nine to twelve
million American children under 5 years of age, or onehalf to
two-thirds of all children in this age group, may be exposed to
cigarette smoke in the home
(American Academy of Pediatrics, 1986; Overpeck and Moss, 1991).
With regard to the noncancer respiratory effects of passive smoking,
this report focuses on epidemiologic evidence appearing since
the two major reports of 1986 (NRC and U.S. DHHS) that bears on
the potential association of parental smoking with detrimental
respiratory effects in their children. These effects include symptoms
of respiratory irritation (cough, sputum production, or wheeze);
acute diseases of the lower respiratory tract (pneumonia, bronchitis,
and bronchiolitis); acute middle ear infections and indications
of chronic middle ear infections (predominantly middle ear effusion);
reduced lung function (from forced expiratory volume and flow-rate
measurements); incidence and prevalence of asthma and exacerbation
of symptoms in asthmatics; and acute upper respiratory tract infections
(colds and sore throats). The more than 50 recently published
studies
reviewed here essentially corroborate the previous conclusions
of the 1986 reports of the NRC and Surgeon General regarding respiratory
symptoms, respiratory illnesses, and pulmonary function, and they
strengthen support for those conclusions by the additional weight
of evidence (Chapter 7). For example, new data on middle ear effusion
strengthen previous evidence to warrant the stronger conclusion
in this report of a causal association with parental smoking.
Furthermore, recent studies establish associations between parental
smoking and increased incidence of childhood asthma. Additional
research also supports the hypotheses that in utero exposure to
mother's smoke and postnatal exposure to ETS alter lung function
and structure, increase bronchial
responsiveness, and enhance the process of allergic sensitization,
changes that are known to predispose children to early respiratory
illness. Early respiratory illness can lead to long-term pulmonary
effects (reduced lung function and increased risk of chronic obstructive
lung disease).
This report also summarizes the evidence for an association between
parental smoking and SIDS, which was not addressed in the 1986
reports of the NRC or Surgeon General. SIDS is the most common
cause of death in infants ages 1 month to 1 year. The cause (or
causes) of SIDS is unknown; however, it is widely believed that
some form of respiratory pathogenesis is generally involved. The
current evidence strongly suggests that infants
whose mothers smoke are at an increased risk of dying of SIDS,
independent of other known risk factors for SIDS, including low
birthweight and low gestational age, which are specifically associated
with active smoking during pregnancy. However, available studies
do not allow this report to conclude whether that increased risk
is related to in utero versus postnatal exposure to tobacco smoke
products, or to both.
The 1986 reports of the NRC and Surgeon General conclude that
both the prevalence of respiratory symptoms of irritation and
the incidence of lower respiratory tract infections are higher
in children of smoking parents. In the 18 studies of respiratory
symptoms subsequent to the 2 reports, increased symptoms (cough,
phlegm production, and wheezing) were observed in a range of ages
from birth to midteens, particularly in infants and preschool
children. In addition to the studies on symptoms of respiratory
irritation, 10 new studies have addressed the topic of parental
smoking and acute lower respiratory tract illness in children,
and 9 have reported statistically significant associations. The
cumulative evidence is conclusive that parental smoking, especially
the mother's,
causes an increased incidence of respiratory illnesses from birth
up to the first 18 months to 3 years of life, particularly for
bronchitis, bronchiolitis, and pneumonia. Overall, the evidence
confirms and strengthens the previous conclusions of the NRC and
Surgeon General.
Recent studies also solidify the evidence for the conclusion of
a causal association between parental smoking and increased middle
ear effusion in young children. Middle ear effusion is the most
common reason for hospitalization of young children for an operation.
Regarding the effects of passive smoking on lung function in children,
the 1986 NRC and Surgeon General reports both conclude that children
of parents who smoke have small decreases in tests of pulmonary
output function of both the larger and smaller air passages when
compared with the children of nonsmokers. As noted in the NRC
report, if ETS exposure is the cause of the observed decrease
in lung function, the effect could be due to the direct action
of agents in ETS or an indirect consequence of increased occurrence
of acute respiratory illness related to ETS.
Results from eight studies on ETS and lung function in children
that have appeared since those reports add some additional confirmatory
evidence suggesting a causal rather than an indirect relationship.
For the population as a whole, the reductions are small relative
to the interindividual variability of each lung function parameter.
However, groups of particularly susceptible or heavily exposed
children have shown larger decrements. The studies reviewed suggest
that a continuum of exposures to tobacco products starting in
fetal life may contribute to the decrements in lung function found
in older children. Exposure to tobacco smoke products inhaled
by the mother during pregnancy may contribute significantly to
these changes, but there is strong evidence indicating that postnatal
exposure to ETS is an important part of the causal pathway.
For diseases for which ETS has been either causally associated
(LRIs) or indicated as a risk factor (asthma cases in previously
asymptomatic children), estimates of population-attributable risk
can be calculated. A population risk assessment (Chapter 8) provides
a probable range of estimates that 8,000 to 26,000 cases of childhood
asthma per year are attributable to ETS exposure from mothers
who smoke 10 or more cigarettes per day. The confidence in this
range of estimates is medium and is dependent on the suggestive
evidence of the database. While the data show an effect only for
children of these heavily smoking mothers, additional cases due
to lesser ETS exposure also are a possibility. If the effect of
this lesser exposure is considered, the range of estimates of
new cases
presented above increases to 13,000 to 60,000. Furthermore, this
report estimates that the additional public health impact of ETS
on asthmatic children includes more than 200,000 children whose
symptoms are significantly aggravated and as many as 1,000,000
children who are affected to some degree.
This report estimates that ETS exposure contributes 150,000 to
300,000 cases annually of lower respiratory tract illness in infants
and children younger than 18 months of age and that 7,500 to 15,000
of these will require hospitalization. The strong evidence linking
ETS exposure to increased incidence of bronchitis, bronchiolitis,
and pneumonia in young children gives these estimates a high degree
of confidence. There is also evidence suggesting a smaller ETS
effect on children between the ages of 18 months and 3 years,
but no additional estimates have been
computed for this age group. Whether or not these illnesses result
in death has not been addressed here.
In the United States, more than 5,000 infants die of SIDS annually.
It is the major cause of death in infants between the ages of
1 month and 1 year, and the linkage with maternal smoking is well
established. The Surgeon General and the World Health Organization
estimate that more than 700 U.S. infant deaths per year from SIDS
are attributable to maternal smoking (CDC, 1991a, 1992b). However,
this report concludes that at present there is not enough direct
evidence supporting the contribution of ETS exposure to declare
it a risk factor or to estimate its
population impact on SIDS.
* Definition:
caus*al (kô-zõl) adj.
1. Of, involving, or constituting a cause.
2. Indicative of or expressing a cause.
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