Environmental Engineering Reference
In-Depth Information
ents. In addition to respiratory illness, a number of studies have shown a
relationship between otitis media, an ear infection that can lead to varying
degrees of hearing loss, and exposure to ETS. ETS exposure appears to
increase the incidence of fluid in the middle ear, an indication of chronic
middle ear disease.
Numerous studies have reported higher prevalence of common respira-
tory symptoms (cough, phlegm production, and wheeze) in children of
smoking parents. In a study of 10,000 school children conducted in the U.S.,
parental smoking was associated with a 30% increase in the prevalence of
persistent cough. In other studies, prevalence of chronic wheeze increased
significantly as the number of smokers in the household increased.
Although wheeze is a common symptom of asthma, the relationship
between exposure to ETS and asthma has been less well-established. In
some studies, parental smoking has been shown to be a strong predictor of
asthma in children, whereas others have failed to demonstrate a relation-
ship. Nevertheless, USEPA has concluded that ETS is a risk factor for new
cases of asthma.
Though exposure to ETS has not been established as a cause of asthma
in children, there is evidence to indicate that parental smoking increases the
clinical severity of asthma. These include symptom frequency, changes in
lung function, and emergency room visits. The USEPA estimates that 200,000
to 1 million asthmatic children in the U.S. have their asthmatic condition
worsened by exposure to ETS. Cessation of smoking by parents, or not
smoking indoors, has been reported to result in a significant decline in
asthmatic symptoms in children.
Lung function studies have been conducted on adults. In some studies,
decreased lung function (determined by spirometry) was associated with
reported ETS exposure in the home and workplace. Lung function decreased
with increased smoking rates and years of exposure. Other studies, however,
have reported no apparent relationship between presumed ETS exposure
and adult lung function.
Numerous epidemiological studies have been conducted to evaluate a
potential causal relationship between exposure to ETS and lung cancer. These
have varied in design and population size evaluated. Evidence from cohort
and case control studies does not uniformly establish a strong relationship
between increased lung cancer risk in individuals exposed to ETS; however,
most studies indicate increased risk among nonsmokers married to smokers.
Based on the biological plausibility of the association between exposure
to ETS and lung cancer and supporting epidemiological evidence, the Inter-
national Agency for Research on Cancer (IARC), USEPA, and OSHA have
concluded that ETS is a Class A carcinogen, i.e., a proven human carcinogen.
The extent of the lung cancer hazard associated with ETS is uncertain.
In 1992, USEPA published findings from a meta-analysis of 31 published
studies which predicted a 19% greater risk of a nonsmoker contracting lung
cancer when living with a smoker. A subsequent evaluation, which included
additional studies by the California Environmental Protection Agency (Cal
