What is asbestos?
Asbestos is the name given to a group of minerals that occur naturally in the environment as bundles of fibers and can be separated into thin, durable threads. These fibers are resistant to heat, fire, and chemicals and do not conduct electricity. For these reasons, asbestos has been widely used in many industries.
There are two subgroups of asbestos: chrysotile, which has curly fibers and is in the serpentine family of minerals; and amphibole asbestos, which has straight, needle-like fibers and includes actinolite, tremolite, anthophyllite, crocidolite, and amosite asbestos. Chrysotile asbestos is the form that has been used predominantly in commercial applications worldwide (1, 2).
How is asbestos used?
Asbestos was mined and used commercially in North America beginning in the late 1800s. Its use increased greatly during World War II (3, 4). Since then, asbestos has been used in many industries. For example, the building and construction industry has used it for strengthening cement and plastics as well as for insulation, roofing, fireproofing, and sound absorption. The shipbuilding industry has used asbestos to insulate boilers, steampipes, and hot water pipes. The automotive industry uses asbestos in vehicle brakeshoes and clutch pads. Asbestos has also been used in ceiling and floor tile; paints, coatings, and adhesives; and plastics. In addition, asbestos has been found in vermiculite-containing consumer garden products and some talc-containing crayons.
In the late 1970s, the U.S. Consumer Product Safety Commission (CPSC) banned the use of asbestos in wallboard patching compounds and gas fireplaces because the asbestos fibers in these products could be released into the environment during use. Additionally, in 1979, manufacturers of electric hairdryers voluntarily stopped using asbestos in their products. In 1989, the U.S. Environmental Protection Agency (EPA) banned all new uses of asbestos; uses established prior to 1989 are still allowed. The EPA also established regulations that require school systems to inspect for damaged asbestos and to eliminate or reduce the exposure to occupants by removing the asbestos or encasing it (2).
In June 2000, the CPSC concluded that the risk of children’s exposure to asbestos fibers in crayons was extremely low (1). However, the U.S. manufacturers of these crayons agreed to eliminate talc from their products. In August 2000, the EPA responded to reports it received about the adverse human health effects associated with exposure to asbestos-contaminated vermiculite by conducting a series of tests to evaluate the extent of the risk. The EPA investigation concluded that the potential exposure to asbestos from some vermiculite products poses only a minimal health risk to consumers. The EPA recommended that consumers reduce the low risk associated with the occasional use of vermiculite during gardening activities by limiting the amount of dust produced during use. Specifically, the EPA suggested that consumers use vermiculite outdoors or in a well-ventilated area; keep vermiculite damp while using it; avoid bringing dust from vermiculite use into the home on clothing; and use premixed potting soil, which is less likely to generate dust.
The regulations described above and other actions, coupled with widespread public concern about the health hazards of asbestos, have resulted in a significant annual decline in U.S. use of asbestos. Domestic consumption of asbestos amounted to about 803,000 metric tons in 1973, but it had dropped to about 2,400 metric tons by 2005 (3, 5).
What are the health hazards of exposure to asbestos?
People may be exposed to asbestos in their workplace, their communities, or their homes. If products containing asbestos are disturbed, tiny asbestos fibers are released into the air. When asbestos fibers are breathed in, they may get trapped in the lungs and remain there for a long time. Over time, these fibers can accumulate and cause scarring and inflammation, which can affect breathing and lead to serious health problems (6).
Asbestos has been classified as a known human carcinogen (a substance that causes cancer) by the U.S. Department of Health and Human Services, the EPA, and the International Agency for Research on Cancer (2, 3, 7, 8). Studies have shown that exposure to asbestos may increase the risk of lung cancer and mesothelioma (a relatively rare cancer of the thin membranes that line the chest and abdomen). Although rare, mesothelioma is the most common form of cancer associated with asbestos exposure. In addition to lung cancer and mesothelioma, some studies have suggested an association between asbestos exposure and gastrointestinal and colorectal cancers, as well as an elevated risk for cancers of the throat, kidney, esophagus, and gallbladder (3, 4). However, the evidence is inconclusive.
Asbestos exposure may also increase the risk of asbestosis (a chronic lung disease that can cause shortness of breath, coughing, and permanent lung damage) and other nonmalignant lung and pleural disorders, including pleural plaques (changes in the membrane surrounding the lung), pleural thickening, and pleural effusions (abnormal collections of fluid between the thin layers of tissue lining the lung and the wall of the chest cavity). Although pleural plaques are not precursors to lung cancer, evidence suggests that people with pleural disease caused by asbestos exposure may be at increased risk for lung cancer (9).
Who is at risk for an asbestos-related disease?
Everyone is exposed to asbestos at some time during their life. Low levels of asbestos are present in the air, water, and soil. However, most people do not become ill from their exposure. People who become ill from asbestos are usually those who are exposed to it on a regular basis, most often in a job where they work directly with the material or through substantial environmental contact.
Since the early 1940s, millions of American workers have been exposed to asbestos. Health hazards from asbestos fibers have been recognized in workers exposed in shipbuilding trades, asbestos mining and milling, manufacturing of asbestos textiles and other asbestos products, insulation work in the construction and building trades, and a variety of other trades. Demolition workers, drywall removers, asbestos removal workers, firefighters, and automobile workers also may be exposed to asbestos fibers. However, recent studies do not support an increased risk of lung cancer or mesothelioma among automobile mechanics exposed to asbestos through brake repair (10). As a result of Government regulations and improved work practices, today’s workers (those without previous exposure) are likely to face smaller risks than did those exposed in the past.
Those involved in the rescue, recovery, and cleanup at the site of the September 11, 2001, attacks on the World Trade Center (WTC) in New York City are another group at risk of developing an asbestos-related disease. Because asbestos was used in the construction of the North Tower of the WTC, when the building was attacked, hundreds of tons of asbestos were released into the atmosphere. Those at greatest risk include firefighters, police officers, paramedics, construction workers, and volunteers who worked in the rubble at Ground Zero. Others at risk include residents in close proximity to the WTC towers and those who attended schools nearby. These populations will need to be followed to determine the long-term health consequences of their exposure (11).
One study found that nearly 70 percent of WTC rescue and recovery workers suffered new or worsened respiratory symptoms while performing work at the WTC site. The study describes the results of the WTC Worker and Volunteer Medical Screening Program, which was established to identify and characterize possible WTC-related health effects in responders. The study found that about 28 percent of those tested had abnormal lung function tests, and 61 percent of those without previous health problems developed respiratory symptoms (12). However, it is important to note that these symptoms may be related to exposure to debris components other than asbestos.
Although it is clear that health risks from asbestos exposure increase with heavier exposure and longer exposure time, investigators have found asbestos-related diseases in individuals with only brief exposures. Generally, those who develop asbestos-related diseases show no signs of illness for a long time after their first exposure. It can take from 10 to 40 years or more for symptoms of an asbestos-related condition to appear (2).
There is some evidence that family members of workers heavily exposed to asbestos face an increased risk of developing mesothelioma. This risk is thought to result from exposure to asbestos fibers brought into the home on the shoes, clothing, skin, and hair of workers. To decrease these exposures, Federal law regulates work practices to limit the possibility of asbestos being brought home in this way. Some employees may be required to shower and change their clothes before they leave work, store their street clothes in a separate area of the workplace, or wash their work clothes at home separately from other clothes (2).
Cases of mesothelioma have also been seen in individuals without occupational exposure, but who live close to asbestos mines or have been exposed to fibers carried home by family members working with asbestos (6).
What factors affect the risk of developing an asbestos-related disease?
Several factors can help to determine how asbestos exposure affects an individual, including (2, 6):
Dose (how much asbestos an individual was exposed to).
Duration (how long an individual was exposed).
Size, shape, and chemical makeup of asbestos fibers.
Source of exposure.
Individual risk factors, such as smoking and pre-existing lung disease.
Although all forms of asbestos are considered hazardous, different types of asbestos fibers may be associated with different health risks. For example, results of several studies suggest that amphibole forms of asbestos may be more harmful than chrysotile, particularly for mesothelioma risk, because they tend to stay in the lungs for a longer period of time (1, 2). All common commercial types of asbestos have been associated with lung cancer (13).
How does smoking affect risk?
Many studies have shown that the combination of smoking and asbestos exposure is particularly hazardous. Smokers who are also exposed to asbestos have a risk of developing lung cancer that is greater than the individual risks from asbestos and smoking added together (3, 6). There is evidence that quitting smoking will reduce the risk of lung cancer among asbestos-exposed workers (4). Smoking combined with asbestos exposure does not appear to increase the risk of mesothelioma (9). However, people who were exposed to asbestos on the job at any time during their life or who suspect they may have been exposed should not smoke.
How are asbestos-related diseases detected?
Individuals who have been exposed (or suspect they have been exposed) to asbestos fibers on the job, through the environment, or at home via a family contact should inform their doctor of their exposure history, whether or not they experience any symptoms. The symptoms of asbestos-related diseases may not become apparent for many decades after exposure. It is particularly important to check with a doctor if any of the following symptoms develop (6):
Shortness of breath, wheezing, or hoarseness.
A persistent cough that gets worse over time.
Blood in the sputum (fluid) coughed up from the lungs.
Pain or tightening in the chest.
Difficulty swallowing.
Swelling of the neck or face.
Loss of appetite.
Weight loss.
Fatigue or anemia.
A thorough physical examination, including a chest x-ray and lung function tests, may be recommended. The chest x–ray is currently the most common tool used to detect asbestos-related diseases. However, it is important to note that chest x-rays cannot detect asbestos fibers in the lungs, but they can help identify any early signs of lung disease resulting from asbestos exposure (2).
Studies have shown that computed tomography (CT) (a series of detailed pictures of areas inside the body taken from different angles; the pictures are created by a computer linked to an x-ray machine) may be more effective than conventional chest x-rays at detecting asbestos-related lung abnormalities in individuals who have been exposed to asbestos (14).
A lung biopsy, which detects microscopic asbestos fibers in pieces of lung tissue removed by surgery, is the most reliable test to confirm the presence of asbestos-related abnormalities. A bronchoscopy is a less invasive test than a biopsy and detects asbestos fibers in material that is rinsed out of the lungs. It is important to note that these tests cannot determine how much asbestos an individual may have been exposed to or whether disease will develop (14). Asbestos fibers can also be detected in urine, mucus, or feces, but these tests are not reliable for determining how much asbestos may be in an individual’s lungs (2).
How can workers protect themselves from asbestos exposure?
The Occupational Safety and Health Administration (OSHA) is a component of the U.S. Department of Labor (DOL) and is the Federal agency responsible for health and safety regulations in maritime, construction, manufacturing, and service workplaces. OSHA established regulations dealing with asbestos exposure on the job, specifically construction work, shipyards, and general industry, that employers are required to follow. In addition, the Mine Safety and Health Administration (MSHA), another component of the DOL, enforces regulations related to mine safety. Workers should use all protective equipment provided by their employers and follow recommended work practices and safety procedures. For example, National Institute for Occupational Safety and Health (NIOSH)-approved respirators that fit properly should be worn by workers when required.
Workers who are concerned about asbestos exposure in the workplace should discuss the situation with other employees, their employee health and safety representative, and their employers. If necessary, OSHA can provide more information or make an inspection. Regional offices of OSHA are listed in the "United States Government" section of a telephone directory’s blue pages (under "Department of Labor"). Regional offices can also be found at http://www.osha.gov/html/RAmap.html on the Internet.
More information about asbestos is available on the OSHA Asbestos Web page, which has links to information about asbestos in the workplace, including what OSHA standards apply, the hazards of asbestos, evaluating asbestos exposure, and controls used to protect workers. This page is available at http://www.osha.gov/SLTC/asbestos/index.html on the Internet. OSHA’s national office can be contacted at:
Organization:
Office of Public Affairs Occupational Safety and Health Administration U.S. Department of Labor
Address:
Room N–3649200 Constitution Avenue, NW.Washington, DC 20210
Telephone:
202–693–19991–800–321–6742 (1–800–321–OSHA)
TTY (for deaf or hard of hearing callers):
1–877–889–5627
Internet Web site:
http://www.osha.gov/as/opa/worker/index.html (workers’ page)
Mine workers can contact MSHA at:
Organization:
Office of Public AffairsMine Safety and Health Administration U.S. Department of Labor
Address:
21st Floor 1100 Wilson BoulevardArlington, VA 22209
Telephone:
202–693–9400 1–800–746–1554
Internet Web site:
http://www.msha.govhttp://www.msha.gov/codeaphone/codeaphonenew.htm(National Hazard Reporting Page)
The National Institute for Occupational Safety and Health (NIOSH), part of the Centers for Disease Control and Prevention, is another Federal agency that is concerned with asbestos exposure in the workplace. NIOSH conducts asbestos-related research, evaluates work sites for possible health hazards, and makes exposure control recommendations. In addition, NIOSH distributes publications on the health effects of asbestos exposure and can suggest additional sources of information. NIOSH can be contacted at:
Organization:
Education and Information Division Information Resources Branch National Institute for Occupational Safety and Health
Address:
Robert A. Taft Laboratories4676 Columbia ParkwayCincinnati, OH 45226
Telephone:
1–800–356–4674 (1–800–35–NIOSH)
E-mail:
eidtechinfo@cdc.gov
Internet Web site:
http://www.cdc.gov/niosh
What programs are available to help individuals with asbestos-related diseases?
Some people with asbestos-related illness may be eligible for Medicare coverage. Information about benefits is available from Medicare’s Regional Offices, located in 10 major cities across the United States and serving specific geographic areas. The Regional Offices serve as the agency’s initial point of contact for beneficiaries, health care providers, state and local governments, and the general public. Contact information for each Regional Office can be found at http://www.cms.hhs.gov/RegionalOffices on the Internet. General information about Medicare is available by calling toll-free 1–800–633–4227 (1–800–MEDICARE) or visiting http://www.medicare.gov on the Internet.
People with occupational asbestos-related diseases also may qualify for financial help, including medical payments, under state workers’ compensation laws. Because eligibility requirements vary from state to state, workers employed by private companies or by state and local government agencies should contact their state workers’ compensation board. Contact information for state workers’ compensation officials may be found in the blue pages of a local telephone directory or at http://www.dol.gov/esa/regs/compliance/owcp/wc.htm on the Internet.
If exposure occurred during employment with a Federal agency, medical expenses and other compensation may be covered by the Federal Employees’ Compensation Program, which is administered by the DOL, Employment Standards Administration’s Office of Workers’ Compensation Programs. This program provides workers’ compensation benefits to Federal (civilian) employees for employment-related injuries and diseases. Benefits include wage replacement, payment for medical care, and, where necessary, medical and vocational rehabilitation assistance in returning to work. Benefits may also be provided to dependents if the injury or disease causes the employee’s death. The program has 12 district offices nationwide.
In addition, the Longshore and Harbor Workers’ Compensation Program provides benefits to longshoremen, harbor workers, other maritime workers, and other classes of private industry workers who are injured during the course of employment or suffer from diseases caused or worsened by conditions of employment. Information about eligibility and how to file a claim for benefits under either of these programs is available from:
Organization:
Office of Workers’ Compensation ProgramsEmployment Standards AdministrationU.S. Department of Labor
Address:
Frances Perkins Building200 Constitution Avenue, NW.Washington, DC 20210
Telephone:
1–866–692–7487 (1–866–OWCPIVR)202–693–0040 (Federal Employees’ Compensation Program)202–693–0038 (Longshore and Harbor Workers’ Compensation Program)
E-mail:
OWCP-Public@dol.gov
Internet Web site:
http://www.dol.gov/esa/owcp_org.htm
Eligible veterans may receive health care at a Department of Veterans Affairs (VA) Medical Center for an asbestos-related disease. Veterans can receive treatment for service-connected and nonservice-connected medical conditions. Information about eligibility and benefits is available from the VA Health Benefits Service Center at 1–877–222–8387 (1–877–222–VETS) or on the VA Web site at http://www1.va.gov/health on the Internet.
Is there legislation to help victims of asbestos-related health diseases?
No Federal legislation has been enacted yet to compensate victims of asbestos-related diseases or to protect people from asbestos exposure. However, in 2005, the Fairness in Asbestos Injury Resolution (FAIR) Act (Senate bill 852) was introduced into Congress (15). This bill would create a national trust fund to compensate victims suffering from asbestos-related diseases. The proposed trust fund would be administered by the DOL, outside of the courts, through a claims process whereby all those with certain medical symptoms and evidence of asbestos-related disease would be compensated. Funding for the trust would come from insurance companies and companies that mined, manufactured, and sold asbestos or asbestos products. Under the bill, individuals affected by asbestos exposure would no longer be able to pursue awards for damages in any Federal or state court.
What other organizations offer information related to asbestos exposure?
The organizations listed below can provide more information about asbestos exposure.
The Agency for Toxic Substances and Disease Registry (ATSDR) is the principal Federal agency responsible for evaluating the human health effects of exposure to hazardous substances. The agency works in close collaboration with local, state, and other Federal agencies, with tribal governments, and with communities and local health care providers to help prevent or reduce harmful human health effects from exposure to hazardous substances. The ATSDR provides information about asbestos and where to find occupational and environmental health clinics. The ATSDR can be contacted at:
Organization:
Agency for Toxic Substances and Disease Registry
Address:
1825 Century BoulevardAtlanta, GA 30345
Telephone:
1–800–232–4636 (1–800–CDC–INFO)
TTY:
1-888-232-6348
E-mail:
cdcinfo@cdc.gov
Internet Web site:
http://www.atsdr.cdc.gov
The U.S. Environmental Protection Agency (EPA) regulates the general public’s exposure to asbestos in buildings, drinking water, and the environment. The EPA offers a Toxic Substances Control Act (TSCA) Hotline and an Asbestos Ombudsman. The TSCA Hotline provides technical assistance and information about asbestos programs implemented under the TSCA, which include the Asbestos School Hazard Abatement Act and the Asbestos Hazard Emergency Response Act. The Asbestos Ombudsman focuses on asbestos in schools and handles questions and complaints. Both the TSCA Hotline and the Asbestos Ombudsman can provide publications on a number of topics, particularly on controlling asbestos exposure in schools and other buildings. The Ombudsman operates a toll-free hotline for small businesses, trade associations, and others seeking free, confidential help.
The EPA Web site includes a list of EPA regional and state asbestos contacts at http://www.epa.gov/asbestos/pubs/regioncontact.html on the Internet. In addition, EPA’s Asbestos and Vermiculite home page provides information about asbestos and its health effects and links to asbestos resources, including suggestions for homeowners who suspect asbestos in their homes, and laws and regulations applicable to asbestos. This page can be found at http://www.epa.gov/asbestos/ on the Internet. Questions may be directed to:
Organization:
U.S. Environmental Protection AgencyEPA West Building National Program Chemicals Division
Address:
Mail Code 7404T 1200 Pennsylvania Avenue, NW.Washington, DC 20460
TSCA Hotline:
202–554–1404
TTY:
202–554–0551
Asbestos Ombudsman:
1–800–368–5888
E-mail:
tsca-hotline@epa.gov
Internet Web site:
http://www.epa.gov/asbestos/
Another EPA resource that may be of interest is the brochure titled Current Best Practices for Preventing Asbestos Exposure Among Brake and Clutch Repair Workers. Released in April 2007, this brochure includes work practices for both automotive professionals and home mechanics that may be used to avoid asbestos exposure. It also summarizes existing OSHA regulatory requirements for professional auto mechanics. The brochure supersedes the EPA’s existing Guidance for Preventing Asbestos Disease Among Auto Mechanics, which is known as the "Gold Book." The brochure can be found at http://www.epa.gov/asbestos/pubs/brakesbrochure.html on the Internet.
The U.S. Consumer Product Safety Commission (CPSC) is responsible for protecting the public from unreasonable risks of serious injury or death from more than 15,000 types of consumer products, including asbestos, under the agency’s jurisdiction. The CPSC maintains a toll-free 24-hour hotline where callers can obtain product safety and other agency information and report unsafe products. In addition, CPSC publications provide guidelines for repairing and removing asbestos, and general information about asbestos in the home. CPSC can be contacted at:
Organization:
Office of Information and Public Affairs U.S. Consumer Product Safety Commission
Address:
4330 East West HighwayBethesda, MD 20814
Telephone:
1–800–638–2772
TTY (for deaf or hard of hearing callers):
1–800–638–8270
E-mail:
info@cpsc.gov
Internet Web site:
http://www.cpsc.gov
Individuals can also contact their local or state health department with questions or concerns about asbestos.
Information about cancer is available by calling the National Cancer Institute’s (NCI) Cancer Information Service (CIS) at 1–800–4–CANCER (1–800–422–6237) or by visiting the NCI’s Web site at http://www.cancer.gov on the Internet. The NCI is a component of the National Institutes of Health. Information about quitting smoking, including smoking cessation counseling, is available by calling the NCI’s Smoking Quitline toll-free at 1–800–44U–QUIT (1–800–448–7848) or visiting the NCI’s smoking cessation Web site at http://www.smokefree.gov on the Internet.
Selected References
Agency for Toxic Substances and Disease Registry (April 2006). What Is Asbestos? Retrieved August 30, 2006, from: http://www.atsdr.cdc.gov/asbestos/more_about_asbestos/what_is_asbestos.
Agency for Toxic Substances and Disease Registry (September 2001). Public Health Statement for Asbestos. Retrieved August 30, 2006, from: http://www.atsdr.cdc.gov/toxprofiles/phs61.html.
National Toxicology Program. Report on Carcinogens. Eleventh Edition. U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program, 2005.
Ullrich RL. Etiology of cancer: Physical factors. In: DeVita VT Jr., Hellman S, Rosenberg SA, editors. Cancer: Principles and Practice of Oncology. Vol. 1 and 2. 7th ed. Philadelphia: Lippincott Williams and Wilkins, 2004.
Virta RL (January 2006). Mineral Commodity Summaries: Asbestos. U.S. Geological Survey Minerals Information. Retrieved August 30, 2006, from: http://minerals.usgs.gov/minerals/pubs/commodity/asbestos/asbesmcs06.pdf.
Agency for Toxic Substances and Disease Registry (June 2006). Asbestos: Health Effects. Retrieved August 30, 2006, from: http://www.atsdr.cdc.gov/asbestos/asbestos/health_effects/index.html.
U.S. Environmental Protection Agency. Health Effects Assessment for Asbestos. U.S. Environmental Protection Agency, 1984. EPA/540/1-86/049 (NTIS PB86134608).
International Agency for Research on Cancer (March 1998). Asbestos. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, vol. 14. Lyon, France: Retrieved September 6, 2006, from: http://monographs.iarc.fr/ENG/Monographs/vol14/volume14.pdf.
Agency for Toxic Substances and Disease Registry (November 2000). Case Studies in Environmental Medicine: Asbestos Toxicity. Retrieved September 6, 2006, from: http://www.atsdr.cdc.gov/HEC/CSEM/asbestos/index.html.
Laden F, Stampfer MJ, Walker AM. Lung cancer and mesothelioma among male automobile mechanics: A review. Reviews on Environmental Health 2004; 19(1):39–61.
Landrigan PJ, Lioy PJ, Thurston G, et al. Health and environmental consequences of the World Trade Center disaster. Environmental Health Perspectives 2004; 112(6):731–739.
Herbert R, Moline J, Skloot G, et al. The World Trade Center disaster and the health of workers: Five-year assessment of a unique medical screening program. Environmental Health Perspectives 2006; 114(12):1853–1858.
Schrump DS, Altorki NK, Henschke CL, et al. Non-small cell lung cancer. Cancer of the lung. In: DeVita VT Jr., Hellman S, Rosenberg SA, editors. Principles and Practice of Oncology. Vol. 1 and 2. 7th ed. Philadelphia: Lippincott Williams and Wilkins, 2004.
Agency for Toxic Substances and Disease Registry (June 2006). Asbestos: Working with Patients: Diagnosis. Retrieved August 30, 2006, from: http://www.atsdr.cdc.gov/asbestos/medical_community/working_with_patients.
U.S. Congressional Budget Office (August 2005). Congressional Budget Office Cost Estimate for S. 852, Fairness in Asbestos Injury Resolution Act of 2005. Retrieved August 30, 2006, from: http://www.cbo.gov/ftpdocs/68xx/doc6881/s852.pdf.
鸟类是地球最重要的养分搬运者之一
-
鸟类在塑造地球化学环境上的作用被低估了，它们是地球最重要的养分搬运者之一。研究人员揭示了鸟类如何通过自身的排泄物和身躯，将养分在陆地、湖泊和海洋之间搬运。这一过程深深影响着从土壤和水体的化学性质，到动植物的生长。飞行能力让鸟类能跨越广阔的距离，甚至逾越海洋和山脉等天然屏障。鸟类在处理和循环养分上也极其高效。鸟类的...
16 hours ago
