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Source:  National Institutes of Health

Wide Variety of Bacteria Mapped Across the Human Body

By analyzing bacterial communities in and on several people, scientists have begun to create an atlas of bacterial diversity that documents the different types of microbes that thrive in distinct regions of the human body. This research sets the stage for determining how changes in bacterial communities help to cause or prevent disease.

Our bodies play host to a wide variety of microbes, called the human microbiota, that outnumber our own cells by about 10 to 1. Many of these microbes help us stay healthy—for instance by aiding digestion or crowding out disease-causing microbes. But details about how microbial communities vary in different body regions, among people or over time are not yet well understood.

In a study funded in part by NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), Dr. Rob Knight and his colleagues at the University of Colorado, Boulder, and George Washington University, St. Louis, began to chart a baseline map of the human microbiota in healthy people. The results were published on November 5, 2009, in the advance online edition of Science.

The scientists surveyed bacterial communities in up to 27 different locations on the bodies of 9 healthy adults. Sampled regions included hair on the head, ear canals, nostrils, mouth, lower gut and 18 different skin sites ranging from foreheads and armpits to navels and feet. Swabs from these regions were collected 4 times over 3 months.

As in other recent studies of the human microbiota, Knight and colleagues identified bacteria by extracting DNA from each sample and then analyzing a bacteria-specific gene, called the 16S ribosomal RNA gene. Overall, the detected microbes belong to 22 bacterial phyla. Four phyla were dominant, representing more than 90% of the identified bacteria.

The researchers found wide variability in bacterial communities on each person and between people. The greatest diversity over time was seen on hair, nostril and ear canal sites, as well as some skin regions, especially the forearms, palm, index finger, back of the knee and sole of the foot. These regions were also the most divergent between people, as was the lower gut. The mouth had the least bacterial variability of any tested region.

The researchers also tested how well bacteria from one body region could survive on another. They transferred bacteria from the tongue to the disinfected forearms and foreheads of some volunteers and tracked them for up to 8 hours. Tongue bacteria persisted longer on the forearms than foreheads, suggesting that the oily forehead may be too harsh a habitat for some bacteria. Bacterial communities transplanted from forehead to forearms and vice versa could not survive well in the new habitats, coming to resemble the native mix rather than the transplants within hours.

“This is the most complete view we have yet of the microbial side of ourselves, one that our group and others will be adding to over the coming years,” says Knight. “If we can better understand this variation, we may be able to begin searching for biomarkers for disease.”

—by Vicki Contie

Reference:
National Institutes of Health (November 16, 2009) Wide variety of bacteria mapped across the human body.  Retrieved November 16, 2009 from http://www.nih.gov/researchmatters/november2009/11162009bacteria.htm

Zheng W, Lee SA.

Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37203-1738, USA. wei.zheng@vanderbilt.edu

PMID: 19838915 [PubMed - in process]

Resource:  National Cancer Institute

1.  
   • arsenic (a heavy metal toxin)
   • benzene (a chemical found in gasoline)
   • beryllium (a toxic metal)
   • cadmium (a metal used in batteries)
   • chromium (a metallic element)
   • ethylene oxide (a chemical used to sterilize medical devices)
   • nickel (a metallic element)
   • polonium–210 (a chemical element that gives off radiation)
   • vinyl chloride (a toxic substance used in plastics manufacture)
2. What is secondhand smoke?
3. How is secondhand smoke exposure measured?
4. Does secondhand smoke contain harmful chemicals?
5. Does exposure to secondhand smoke cause cancer?
6. What are the other health effects of exposure to secondhand smoke?
7. What is a safe level of secondhand smoke?
8. What is being done to reduce nonsmokers’ exposure to secondhand smoke?

Secondhand smoke (also called environmental tobacco smoke) is the combination of sidestream smoke (the smoke given off by the burning end of a tobacco product) and mainstream smoke (the smoke exhaled by the smoker) (1, 2, 3, 4). Exposure to secondhand smoke is also called involuntary smoking or passive smoking. People are exposed to secondhand smoke in homes, cars, the workplace, and public places such as bars, restaurants, and other recreation settings. In the United States, the source of most secondhand smoke is from cigarettes, followed by pipes, cigars, and other tobacco products (4).

 Secondhand smoke is measured by testing indoor air for nicotine or other smoke constituents. Exposure to secondhand smoke can be tested by measuring the levels of cotinine (a nicotine by-product in the body) in the nonsmoker’s blood, saliva, or urine (1). Nicotine, cotinine, carbon monoxide, and other evidence of secondhand smoke exposure have been found in the body fluids of nonsmokers exposed to secondhand smoke.

Yes. Of the more than 4,000 chemicals that have been identified in secondhand tobacco smoke, at least 250 are known to be harmful, and 50 of these are known to cause cancer. These chemicals include (1):

Many factors affect which chemicals are found in secondhand smoke, including the type of tobacco, the chemicals added to the tobacco, the way the product is smoked, and the paper in which the tobacco is wrapped (1, 3, 4).

 

Yes. The U.S. Environmental Protection Agency (EPA), the U.S. National Toxicology Program (NTP), the U.S. Surgeon General, and the International Agency for Research on Cancer (IARC) have classified secondhand smoke as a known human carcinogen (cancer-causing agent) (1, 3, 5).

Inhaling secondhand smoke causes lung cancer in nonsmoking adults (4). Approximately 3,000 lung cancer deaths occur each year among adult nonsmokers in the United States as a result of exposure to secondhand smoke (2). The Surgeon General estimates that living with a smoker increases a nonsmoker’s chances of developing lung cancer by 20 to 30 percent (4).

Some research suggests that secondhand smoke may increase the risk of breast cancer, nasal sinus cavity cancer, and nasopharyngeal cancer in adults, and leukemia, lymphoma, and brain tumors in children (4). Additional research is needed to learn whether a link exists between secondhand smoke exposure and these cancers.

Secondhand smoke causes disease and premature death in nonsmoking adults and children (4). Exposure to secondhand smoke irritates the airways and has immediate harmful effects on a person’s heart and blood vessels. It may increase the risk of heart disease by an estimated 25 to 30 percent (4). In the United States, secondhand smoke is thought to cause about 46,000 heart disease deaths each year (6). There may also be a link between exposure to secondhand smoke and the risk of stroke and hardening of the arteries; however, additional research is needed to confirm this link.

Children exposed to secondhand smoke are at an increased risk of sudden infant death syndrome (SIDS), ear infections, colds, pneumonia, bronchitis, and more severe asthma. Being exposed to secondhand smoke slows the growth of children’s lungs and can cause them to cough, wheeze, and feel breathless (4).

There is no safe level of exposure to secondhand smoke. Studies have shown that even low levels of secondhand smoke exposure can be harmful. The only way to fully protect nonsmokers from secondhand smoke exposure is to completely eliminate smoking in indoor spaces. Separating smokers from nonsmokers, cleaning the air, and ventilating buildings cannot completely eliminate secondhand smoke exposure (4).

Many state and local governments have passed laws prohibiting smoking in public facilities such as schools, hospitals, airports, and bus terminals. Increasingly, state and local governments are also requiring private workplaces, including restaurants and bars, to be smoke free. To highlight the significant risk from secondhand smoke exposure, the National Cancer Institute, a component of the National Institutes of Health, holds meetings and conferences in states, counties, cities, or towns that are smoke free, unless certain circumstances justify an exception to this policy.

More information about state-level tobacco regulations is available through the Centers for Disease Control and Prevention (CDC) State Tobacco Activities Tracking and Evaluation (STATE) System Web site. The STATE System is a database containing up-to-date and historical state-level data on tobacco use prevention and control. This resource is available at http://apps.nccd.cdc.gov/statesystem/ on the Internet.

On the national level, several laws restricting smoking in public places have been passed. Federal law bans smoking on domestic airline flights, nearly all flights between the United States and foreign destinations, interstate buses, and most trains. Smoking is also banned in most Federally owned buildings. The Pro-Children Act of 1994 prohibits smoking in facilities that routinely provide Federally funded services to children.

The U.S. Department of Health and Human Services (DHHS) Healthy People 2010, a comprehensive, nationwide health promotion and disease prevention agenda, includes the goal of reducing the proportion of nonsmokers exposed to secondhand smoke from 65 percent to 45 percent by 2010 (7). More information about this program is available on the Healthy People 2010 Web site at http://www.healthypeople.gov/ on the Internet.

Internationally, several nations, including France, Ireland, New Zealand, Norway, and Uruguay, require all workplaces, including bars and restaurants, to be smoke free.

Selected References

1. National Toxicology Program. Report on Carcinogens. Eleventh Edition. U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program, 2005. 
2. National Cancer Institute. Cancer Progress Report 2003. Public Health Service, National Institutes of Health, U.S. Department of Health and Human Services, 2004. 
3. International Agency for Research on Cancer. Tobacco Smoke and Involuntary Smoking. Lyon, France: 2002. 
4. U.S. Department of Health and Human Services. The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General. Rockville, MD: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, Coordinating Center for Health Promotion, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2006. 
5. U.S. Environmental Protection Agency. Respiratory Health Effects of Passive Smoking (Also Known as Exposure to Secondhand Smoke or Environmental Tobacco Smoke–ETS). U.S. Environmental Protection Agency, 1992. 
6. California Environmental Protection Agency, Office of Environmental Health Hazard Assessment. Proposed Identification of Environmental Tobacco Smoke as a Toxic Air Contaminant: Part B Health Effects, 2005. 
7. U.S. Department of Health and Human Services. Healthy People 2010: Understanding and Improving Health. 2nd ed. Washington, DC: U.S. Government Printing Office, 2000. 

Related NCI materials and Web pages:

• National Cancer Institute Fact Sheet 10.16, Questions and Answers About Cigar Smoking and Cancer
  (http://www.cancer.gov/cancertopics/factsheet/Tobacco/cigars)
• National Cancer Institute Fact Sheet 10.19, Quitting Smoking: Why To Quit and How To Get Help
  (http://www.cancer.gov/cancertopics/factsheet/Tobacco/cessation)
• Smoking and Tobacco Control Monograph 10: Health Effects of Exposure to Environmental Tobacco Smoke
  (http://cancercontrol.cancer.gov/tcrb/monographs/10/index.html)
• NCI’s Smoking and Cancer Home Page
  (http://www.cancer.gov/cancertopics/smoking)

For more help, contact:

NCI’s Cancer Information Service
Telephone (toll-free): 1–800–4–CANCER (1–800–422–6237)
TTY (toll-free): 1–800–332–8615
LiveHelp^® online chat: https://cissecure.nci.nih.gov/livehelp/welcome.asp

Reference:

National Cancer Institute (2009). Secondhand smoke questions and answers.  Retrieved November 2, 2009 from http://www.cancer.gov/cancertopics/factsheet/Tobacco/ETS