Saturday, January 18, 2014

How Dangerous is Second-Hand Smoking?


Exposure to secondhand smoke (SHS) is an unpleasant experience for many nonsmokers, and for decades was considered a nuisance. But the idea that it might actually cause disease in nonsmokers has been around only since the 1970s.

Recent surveys show more than 80 percent of Americans now believe secondhand smoke is harmful to nonsmokers.

What is secondhand smoke?

Secondhand smoke (also called environmental tobacco smoke, involuntary smoke, and passive smoke) is the combination of “sidestream” smoke (the smoke given off by a burning tobacco product) and “mainstream” smoke (the smoke exhaled by a smoker).

People can be exposed to secondhand smoke in homes, cars, the workplace, and public places, such as bars, restaurants, and recreational settings. In the United States, the source of most secondhand smoke is from cigarettes, followed by pipes, cigars, and other tobacco products.

The amount of smoke created by a tobacco product depends on the amount of tobacco available for burning. The amount of secondhand smoke emitted by smoking one large cigar is similar to that emitted by smoking an entire pack of cigarettes.

National Cancer Institute statement claims that there is no safe level of exposure to secondhand smoke. Even low levels of secondhand smoke can be harmful. The only way to fully protect nonsmokers from secondhand smoke is to completely eliminate smoking in indoor spaces. Separating smokers from nonsmokers, cleaning the air, and ventilating buildings cannot completely eliminate exposure to secondhand smoke. 

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Who is at greatest risk of being harmed by secondhand smoke?

Although any person who spends time around those who smoke has an increased chance of developing a smoking-related illness, certain people are extremely susceptible to the harmful effects of secondhand smoke.

These include:
* Service industry workers, such as bartenders and restaurant servers. People who work in environments where they are constantly exposed to smokers might absorb carcinogens and other harmful substances from secondhand tobacco smoke on a regular basis. This puts them at greater risk of developing the health issues addressed above.
* Pregnant women. Second hand-smoke harms not only the mother-to-be, but her unborn child as well. Smoke exposure during pregnancy increases the risk for problems such as placenta previa (low lying placenta), placental abruption (a medical emergency), as well as miscarriage, stillbirth, and ectopic pregnancy. It decreases the amount of oxygen available to mother and baby, increases the baby’s heart rate, and increases the likelihood that the baby will have a low birth weight or be born prematurely.
* Infants and children (and pets! ) Because young children and animals can't choose to leave a smoke-filled environment, this constant exposure makes them especially vulnerable to the health risks of secondhand smoke.

Infants and children who are regularly exposed to secondhand smoke have an increased chance of developing the following conditions:
* Frequent colds and respiratory infections (including bronchitis and pneumonia)
* May experience slow or incomplete lung growth and development
* Asthma and chronic coughs
* Chronic and/or recurrent ear infections
* SIDS (Sudden Infant Death Syndrome)
* High blood pressure
* Learning and behavior problems, including inattention and aggression.
* Cataracts
* Poor dental health
* Increased likelihood that the children themselves will become smokers
* Increased risk of tumors and cancer shown in cats, dogs, and birds.

Federal Government Reports

A 1972 U.S. surgeon general's report first addressed passive smoking as a possible threat to nonsmokers and called for an anti-smoking movement. The issue was addressed again in surgeon generals' reports in 1979, 1982, and 1984.

A 1986 surgeon general's report concluded involuntary smoking caused lung cancer, but it offered only weak epidemiological evidence to support the claim. In 1989 the Environmental Protection Agency (EPA) was charged with further evaluating the evidence for health effects of SHS.

In 1992 EPA published its report, "Respiratory Health Effects of Passive Smoking," claiming SHS is a serious public health problem, that it kills approximately 3,000 nonsmoking Americans each year from lung cancer, and that it is a Group A carcinogen (like benzene, asbestos, and radon).

The report has been used by the tobacco-control movement and government agencies, including public health departments, to justify the imposition of thousands of indoor smoking bans in public places.

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Flawed Assumptions

While, the governmental medical organizations’ position is clear, it always bothered me the charade, why the widespread draconian antismoking laws, implemented everywhere, has not resulted in the substantial improvement in cancer spread statistics. Why, for example, cases of allergic asthma in California have multiplied, while the smoking has significantly dropped? Is there is something wrong with the government sponsored approach?

Looking back, EPA's 1992 conclusions were not supported by reliable scientific evidence. The report has been largely discredited and, in 1998, was legally vacated by a federal judge. Even so, the EPA report was cited in the surgeon general's 2006 report on SHS, where then-Surgeon General Richard Carmona made the absurd claim that there is no risk-free level of exposure to SHS.

For its 1992 report, EPA arbitrarily chose to equate SHS with mainstream (or firsthand) smoke. One of the agency's stated assumptions was that because there is an association between active smoking and lung cancer, there also must be a similar association between SHS and lung cancer.

But the problem posed by SHS is entirely different from that found with mainstream smoke. A well-recognized toxicological principle states, "The dose makes the poison."

Accordingly, we physicians record direct exposure to cigarette smoke by smokers in the medical record as "pack-years smoked" (packs smoked per day times the number of years smoked). A smoking history of around 10 pack-years alerts the physician to search for cigarette-caused illness. But even those nonsmokers with the greatest exposure to SHS probably inhale the equivalent of only a small fraction (around 0.03) of one cigarette per day, which is equivalent to smoking around 10 cigarettes per year.

Low Statistical Association

Another major problem is that the epidemiological studies on which the EPA report is based are statistical studies that can show only correlation and cannot prove causation.

One statistical method used to compare the rates of a disease in two populations is relative risk (RR). It is the rate of disease found in the exposed population divided by the rate found in the unexposed population. An RR of 1.0 represents zero increased risk. Because confounding and other factors can obscure a weak association, in order even to suggest causation a very strong association must be found, on the order of at least 300 percent to 400 percent, which is an RR of 3.0 to 4.0.

For example, the studies linking direct cigarette smoking with lung cancer found an incidence in smokers of 20 to around 40 times that in nonsmokers, an association of 2000 percent to 4000 percent, or an RR of 20.0 to 40.0.

Scientific Principles Ignored

An even greater problem is the agency's lowering of the confidence interval (CI) used in its report. Epidemiologists calculate confidence intervals to express the likelihood a result could happen just by chance. A CI of 95 percent allows a 5 percent possibility that the results occurred only by chance.

Before its 1992 report, EPA had always used epidemiology's gold standard CI of 95 percent to measure statistical significance. But because the U.S. studies chosen for the report were not statistically significant within a 95 percent CI, for the first time in its history EPA changed the rules and used a 90 percent CI, which doubled the chance of being wrong.

This allowed it to report a statistically significant 19 percent increase of lung cancer cases in the nonsmoking spouses of smokers over those cases found in nonsmoking spouses of nonsmokers. Even though the RR was only 1.19--an amount far short of what is normally required to demonstrate correlation or causality--the agency concluded this was proof SHS increased the risk of U.S. nonsmokers developing lung cancer by 19 percent.

EPA Study Soundly Rejected

In November 1995 after a 20-month study, the Congressional Research Service released a detailed analysis of the EPA report that was highly critical of EPA's methods and conclusions. In 1998, in a devastating 92-page opinion, Federal Judge William Osteen vacated the EPA study, declaring it null and void. He found a culture of arrogance, deception, and cover-up at the agency.

Osteen noted, "First, there is evidence in the record supporting the accusation that EPA 'cherry picked' its data. ... In order to confirm its hypothesis, EPA maintained its standard significance level but lowered the confidence interval to 90 percent. This allowed EPA to confirm its hypothesis by finding a relative risk of 1.19, albeit a very weak association. ... EPA cannot show a statistically significant association between [SHS] and lung cancer."

The judge added, "EPA publicly committed to a conclusion before the research had begun; adjusted established procedure and scientific norms to validate its conclusion; and aggressively utilized its authority to disseminate findings to establish a de facto regulatory scheme to influence public opinion."

In 2003 a definitive paper on SHS and lung cancer mortality was published in the British Medical Journal. It is the largest and most detailed study ever reported. The authors studied more than 35,000 California never-smokers over a 39-year period and found no statistically significant association between exposure to SHS and lung cancer mortality.

Recent Studies

A decade ago that the British Medical Journal, published the results of a massive, long-term survey into the effects of second-hand tobacco smoke. Between 1959 and 1989 two American researchers named James Enstrom and Geoffrey Kabat surveyed no few than 118,094 Californians. Fierce anti-smoking campaigners themselves, they began the research because they wanted to prove once and for all what a pernicious, socially damaging habit smoking was. Their research was initiated by the American Cancer Society and supported by the anti-smoking Tobacco Related Disease Research Program.

At least it was at first. But then something rather embarrassing happened. Much to their surprise, Kabat and Enstrom discovered that exposure to environmental tobacco smoke (i.e. passive smoking), no matter how intense or prolonged, creates no significantly increased risk of heart disease or lung cancer.

Similar conclusions were reached by the World Health Organization which concluded in 1998 after a seven-year study that the correlation between "passive smoking" and lung cancer was not "statistically significant." A 2002 report by the Greater London Assembly agreed. So too did an investigation by the House of Lords Economic Affairs Committee.

The recent article in the Journal of the National Cancer Institute, headlined "No Clear Link Between Passive Smoking and Lung Cancer," describes a large prospective study that "confirmed a strong association between cigarette smoking and lung cancer but found no link between the disease and secondhand smoke." The study tracked more than 76,000 women, 901 of whom eventually developed lung cancer. Although "the incidence of lung cancer was 13 times higher in current smokers and four times higher in former smokers than in never-smokers," says the JNCI article, there was no statistically significant association between reported exposure to secondhand smoke and subsequent development of lung cancer. "We don’t want people to conclude that passive smoking has no effect on lung cancer," says one of the researchers, Stanford oncologist Heather Wakelee. "We think the message is, this analysis doesn't tell us what the risk is, or even if there is a risk."

Resume

Smoking is really bad for your health and takes about 5 years of your life. The worst part of it that it has the ability to make your life miserable. Secondhand smoking danger has not been scientifically proven to be harmful while applied in reasonable amounts, however, it may be not welcome in your household for many other reasons, both aesthetical and psychological. You may need to consider your smoking habits and go outside for smoke break.

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