Contact with tobacco smoke residue can have harmful effects similar to that of first- and second-hand smoke
By Marty Grossman –
The health risks associated with smoking and the use of tobacco in any form are no secret. Over the past several years, the news has gotten progressively worse with respect to the number and severity of those risks. Additional studies and surveys indicate the problems created by smoking are potentially far more serious than previously believed.
I. Researchers from the University of California Davis previously reported online, in BMC Cancer, that exposure to tobacco smoke may actually be causing a much greater proportion of cancer deaths than previously estimated.
Using data from the National Center for Health Statistics, the researchers examined cancer mortality rates among men living in Massachusetts from 1979 to 2003 and found there was a close correlation in changes in death rates from lung cancer and other cancers suggesting that the fraction of all cancer deaths attributable to smoking was 73%. The researchers said the study findings were strengthened because of the inclusion of all non-lung cancers, the use of sizeable, representative, and recent male populations, and the use of age-adjusted death rates.
Previously, a 2001 government estimate based on data from the Cancer Prevention Study II, placed the fraction at 34%, according to Dr. Bruce Leistikow, who headed the study.”
The full impact of tobacco smoke, including secondhand smoke, have been overlooked in the rush to examine such potential cancer factors as diet and environmental contaminants,” Dr. Leistikow said. “As it turns out, much of the answer was probably smoking all along.”
Previous estimates of the impact of smoke exposure on cancer death have traditionally been made using methods that are not universally applicable across population subgroups and that rely almost exclusively on self-reported smoking measures. Here, the researchers used a simpler, more representative, and less biased method for assessing the impact that involved examining the associations between mortality rates for lung and all other cancers.
The data analyzed by the researchers suggest “that tobacco smoke load is a potential cause of most prematurely fatal cancers in this population.” The findings infer that the percentage of all cancer deaths attributable to tobacco smoke exposure was 73% for all men and 74% for men ages 30 to 74.
II. Over the past several years, the significant health risks associated with exposure to second-hand smoke have become widely accepted, especially with respect to children. It appears, however, that youngsters living in, or frequenting, environments where smoking is common may also be at risk for what is now being labeled as “third-hand smoke,” which is the term being applied to toxins left on surfaces once tobacco smoke has dissipated.
These toxins can remain for hours and, sometimes, days on clothing, carpets, blankets, and many other objects. Taking precautions, such as smoking outside, to keep others out of direct contact with cigarette smoke, are proving to be less effective than previously thought.
According to a 2010 study, the residue, alone, can produce compounds that cause cancer. This is especially true of the residue left on indoor items.
The research leader, Hugo Destaillats, at Lawrence Berkeley National Laboratory in California, stated, “Certain compounds – such as ambient nitrous acid or nitrogen dioxide – are present in higher quantities indoors rather than outdoors.”
According to Jonathan Winickoff, M.D., of the Massachusetts General Hospital for Children and his colleagues in an issue of Pediatrics, these residual toxins are particularly hazardous to children who breathe near the surfaces, crawl and play on them, or touch and mouth them.
Winickoff and his team’s conclusion that the potential risks posed by third-hand smoke are lesser known to the general public is based on the results of a nationally representative survey that examined beliefs about second-hand and third-hand smoke and behavioral responses derived from those beliefs.
In November of 2005, the annual Social Climate Survey of Tobacco Control was given to 1,478 adults. An analysis of the data found:
- 18.9% of respondents were current smokers.
- 15.6% of the sample reported a smoker living in the home.
- 8.4% of nonsmokers lived with a smoker.
- 25.6% of the homes surveyed had at least one smoker.
- 93% of the respondents thought second-hand smoke was dangerous to children, including 95.4% of nonsmokers and 84.1% of smokers.
- Only 61% of those surveyed thought third-hand smoke was hazardous, including 65.2% of non-smokers and 43.3% of smokers.
- Those who did not smoke were three times more likely to ban smoking in the home than those who smoked (88.4% to 26.7%).
- There was an independent association between the belief that third-hand smoke harms children and a strict home smoking ban.
Since tobacco smoke within a home will dissipate throughout the enclosed environment, the toxins left behind are deposited on every surface and are also found in loose household dust. The toxins include volatile compounds that will, themselves, release gas into the air, according to the researchers.
The researchers labeled this residual tobacco smoke contamination “third-hand smoke” and their study is the first to examine the concept in relation to home smoking bans. They believe their findings have a possible clinical implication and concluded: “Emphasizing that third-hand smoke harms the health of children may be an important element in encouraging home smoking bans.” Moreover, “health messages about third-hand smoke contamination could be easily incorporated into current tobacco control campaigns, programs, and routine clinical practice.”
III. In a meta-analysis of 106 observational studies (published in the Dec. 17, 2008 issue of the Journal of the American Medical Association), a research team in Milan, Italy, under Edoardo Botteri, M.Sc. of the European Institute of Oncology, concluded that smoking is associated with development of colorectal cancer and the likelihood of dying from it.
In the analysis, individuals who had smoked at some point in their lives were 18% more likely to develop colorectal cancer than those who had never smoked and, in a further analysis of 17 studies, those who had smoked were 25% more likely to die from colorectal cancer than those who had never smoked. The researchers stated: “We believe that smoking represents an important factor to consider when deciding on the age at which colorectal cancer screening should begin either by lowering the age in smokers or increasing the age in non-smokers.”
These same researchers previously found that smoking nearly doubles the risk of adenomatous colorectal polyps, which are precursors to colorectal cancer. (Other studies – see IV, below − have demonstrated colorectal cancer occurs at a younger age in smokers).
In reaching their conclusions, the researchers identified 106 studies addressing the relationship between smoking and occurrence of colorectal cancer and 17 studies looking at mortality from the disease. In the pooled data from 39,779 cases of colorectal cancer, the researchers found that smoking was associated with an increase from 54.7 to 65.5 cases per 100,000 person-years and the risk was increased by 7.8% for every additional 10 cigarettes smoked per day and by 4.4% for every additional 10 pack-years. Although longer duration of smoking also increased the risk, the relationship only became statistically significant after 30 years.
In terms of mortality, smoking was associated with an increase from 35.3 deaths per 100,000 person-years to 41.3. Every additional 10 cigarettes smoked per day increased the risk of mortality by 7.4% in those who had ever smoked and by 10.6% in those who currently smoked. The risk of death increased linearly by 9.5% for every additional 10 years of smoking.
For both occurrence and mortality, the risks were greater for cancer of the rectum than of the colon. Not surprisingly, two large studies − the Cancer Prevention Study II and the Nurses’ Health Study – indicated that individuals who had quit smoking were less likely to die from colorectal cancer than current smokers.
IV. In a related analysis, Luke J. Peppone, Ph.D., of the University of Rochester, and colleagues at the Roswell Park Cancer Institute in Buffalo reported online, in the Journal of Cancer Research and Clinical Oncology, that smokers, and those with a history of exposure to second-hand smoke, should be screened for colon cancer before age 50, because they are likely to develop the disease years earlier than nonsmokers.
In the retrospective analysis of more than 3,500 patients over 40 years, the researchers found current smokers were diagnosed with the disease an average of 6.8 years earlier than those who had never smoked (age 57.4 for smokers versus 64.2 for never-smokers). Patients who had never smoked but had been exposed to secondhand smoke in the past, e.g., growing up in a house in which their parents smoked, were an average of 8.6 years younger at colon cancer diagnosis than never-smokers without that exposure. Those with both current and past secondhand smoke exposure were an average of 11.6 years younger at diagnosis.
As a result of these findings, the researchers stated: ”The implication of this finding is that screening for colorectal cancer, which is now recommended to begin at age 50 years for average risk individuals, should be initiated five to 10 years earlier for persons with a significant lifetime history of exposure to tobacco smoke.” Currently, age and family history are the only factors considered when making recommendations for colon cancer screening despite the fact that past studies have shown environmental and lifestyle factors may also be factors in predicting risk.
The amount smoked and ages at diagnosis were also found to be related. Compared with never-smokers, patients who smoked less than a pack a day, one pack a day, and more than a pack a day were diagnosed an average of 2.9, 3.6, and 4.7 years earlier, respectively. In addition, the age at which a patient started smoking was found to be relevant. Compared with never-smokers, those who started smoking before they were 17 were diagnosed 4.8 years earlier, those 17 to 21 at smoking initiation, four years earlier, and those 22 or older when they started, 2.7 years earlier.
While these conclusions should be regarded with caution because of the existence of several variables (confounders) such as body mass index, race, meat consumption, vegetable intake, non-steroidal anti-inflammatory drug (NSAID) use, and family history. It is clear that smoking, or the exposure to second-hand smoke, are anything but positive influences on health.
V. Finally, researchers in England have reported in the Journal of Clinical Endocrinology and Metabolism that smoking cigarettes during pregnancy is associated with small but potentially harmful changes in thyroid function both in mothers and their offspring.
When the mother’s thyroid does not function at its best, the results may include birth defects, such as miscarriage, premature birth, a lower birth weight and neuropsychological issues of the baby.
According to a cohort study of 2,355 pregnant women, Bijay Vaidya, Ph.D., of Peninsula Medical School at Royal Devon and Exeter Hospital and colleagues, those who smoked had lower levels of serum thyrotropin (TSH) and higher levels of free triiodothyronine (FT3) than nonsmokers, and babies born to smokers in the study also had lower serum TSH in cord blood.
The team pointed out that the magnitude of the changes in the direction of hyperthyroidism was small and additional research is needed to see if these levels of change result in adverse effects, although evidence is increasing that even minor abnormalities in maternal thyroid hormone levels during pregnancy are associated with both maternal and fetal adverse outcomes. “Therefore, finding of factors, such as smoking, which may modulate thyroid hormone levels in pregnancy, is important,” they said. “Although, the magnitude of the effect of smoking on thyroid function in our study was small, the smoking-related changes in the thyroid function extended to the fetus, suggesting these changes could have a biological impact on the fetus.”
While it is known that smoking lowers TSH levels in the general population and several studies have shown that smokers have higher serum levels of thyroxine (T4), triiodothyronine, or both, few studies have considered the potential effects of smoking on thyroid function in pregnant women and their fetuses. Thus, the team looked at thyroid hormone levels in two independent groups (1,428 women in their first trimester, and 927 women in their third trimester). The researchers also studied the relationship between maternal smoking and thyroid hormones in the cord blood of 618 full-term babies born to women in the third-trimester group.
The researchers found women who had stopped smoking because of the pregnancy had little difference in thyroid hormone levels than nonsmokers. According to Dr. Vaidya and his team, that finding suggests these smoking-related changes in thyroid hormone levels are “rapidly reversible.”
CONCLUSION: Tobacco smoke is made up of several components and 20 carcinogens that are believed to produce tumors on the lungs of laboratory animals and humans. Consequently, these carcinogens are part of the reasons some lung cancers develop.
Also, it is more obvious than ever that tobacco smoke, whether it be first-, second-, or even third-hand, poses widespread, significant, and ever increasing health risks to a large segment of the population (smokers as well as non-smokers) and particularly to children. Accordingly, you should make every effort to stop smoking if you are already a smoker and avoid any environment in which smoking is permitted. You should be especially vigilant when it comes to safeguarding children from exposure to second-hand smoke or to the residual toxins produced when tobacco smoke dissipates (third-hand smoke).