We often hear that asbestos is dangerous, but what does that mean? What health conditions are caused by exposure, and how much exposure is necessary for asbestos to be a danger?
Why is Asbestos Dangerous?Exposure to asbestos dust and fibers can result in cancer, lung disease, as well as other conditions. Unfortunately, there is no known level of exposure that is considered safe. While the use of asbestos has been banned in the U.S., exposure is still common, as there are exceptions to the ban, and as asbestos is still present in many older buildings and homes. In fact, asbestos-related health conditions continue to increase worldwide. People most at risk include those who are exposed on the job, but those who decide to take on do-it-yourself projects in homes containing asbestos insulation may also be at risk.
Before describing asbestos-related health conditions, let's define a few terms. The pleura are membranes that surround and protect the lungs. Another term that is often referred to is the mesothelium. The mesothelium is the protective lining that surrounds organs in the chest and abdomen, and is divided into 3 regions. The pleura (which surrounds the lungs as noted above,) the pericardium (which surrounds the heart,) and the peritoneal mesothelium (the protective tissue that surrounds the organs in the abdomen.)
Cancers Caused by Asbestos ExposureActivists have done a good job in making the public and policy makers aware of the risk of one type of lung cancer – mesothelioma – caused by asbestos exposure. For those who question whether their efforts to raise their voice and ask for change when their health is at risk, this is an excellent example of how individuals can indeed make a difference.
There have been discussions about different fiber sizes and forms having different risks, but for the purpose of this discussion we’ll look at the overall picture. Cancers caused or thought to be caused by asbestos include:
Malignant mesothelioma – Mesothelioma is a cancer the begins in any of the areas where mesothelium is found as noted above, but commonly occurs in the pleura (the membranes around the lungs.) It is an aggressive cancer, with only 5 to 10% of people surviving 5 years beyond their diagnosis.
Lung cancer – Lung cancers other than mesothelioma are also increased by exposure. Both non-small cell lung cancer and small cell lung cancer are increased.
Ovarian cancer – Less well known is the increased risk of ovarian cancer. In a review of studies to date it was thought that occupational exposure to asbestos increased ovarian cancer risk by around 70%.
- Other cancers – Studies thus far have been mixed, and it’s uncertain whether or not asbestos exposure increases the risk of laryngeal cancer (cancer of the throat,) or colorectal cancer.
Medical Conditions Caused by Asbestos ExposureLess well known, but an even greater problem, is lung disease related to asbestos exposure. Some of these conditions include:
- Asbestosis – Asbestosis is a condition in which pulmonary fibrosis (scarring) occurs due to asbestos exposure. This condition, in addition to causing symptoms on it’s own, further increases the risk of lung cancer. This is discussed further below under “what level of exposure is dangerous.”
- Pleural plaques.
- Pleural thickening.
- Pleural effusions - Some people exposed to asbestos develop a build-up of fluid between the membranes that line the lungs. This has been called benign asbestos-related pleural effusions (BAPEs).
What Level of Exposure is Dangerous?A common question is, "how much asbestos do I need to be exposed to be at risk?" The answer is that there is no level of asbestos exposure that is safe. But a few studies have helped to answer the details in that question.
One study was done looking primarily at people with asbestosis. This was a large study that compared almost 2400 male insulators (who were thus exposed to asbestos,) to a group of over 54,000 people who had not had such an exposure. Overall, lung cancer was responsible for the death of 19% of the insulators (ordinarily, 1 in 14 people will die from lung cancer.) The risk of death varied considerably depending upon exposure alone, the development of asbestosis, and the co-risk factor of smoking, and since a table is worth a thousand words, the results are as follows:
- Asbestos exposure in non-smokers – There were 3.6 times as many cases of lung cancer.
- Asbestosis in non-smokers – The risk was 7.4 times that of the general population.
- Smoking without asbestos exposure – This risk of lung cancer in those who smoke was 10.3 times that of the general population in this study.
- Asbestos exposure plus smoking – Exposure to asbestos combined with smoking made the likelihood of lung cancer 14.4 times the average.
- Asbestos exposure, asbestosis, plus smoking – If people were exposed to asbestos, developed asbestosis, plus smoked, the results were grave. The risk of lung cancer was 36.8 times higher than the general population.
We can look at asbestos exposure in another way to get the big picture, and to further outline the problem for those in industry. It’s been estimated that 170 tons of produced and consumed of asbestos correlates with 1 death from mesothelioma.
An important question is how important the length of exposure is -- in other words, are those who are exposed for 30 years more likely to be affected than those exposed for 5 years? We don't have studies that outline the exact risk over time, but it's likely that the longer someone is exposed, the greater their risk of asbestos-related disease. That said, there are some people who have developed mesothelioma with an exposure time of only a few days.
How is Asbestos a Danger?How asbestos damages the body is likely a combination of fiber type and size, lung clearance, and genetics. A few theories have emerged. In one, it’s thought that asbestos fibers may directly have a toxic effect on the cells lining the lungs, causing inflammation which leads to scarring. Part of the damage may also relate to the body’s reaction to the presence of asbestos fibers, as the body secretes inflammatory substances such as cytokines and growth factors in response to the foreign substance. New evidence suggests that the presence of asbestos causes direct DNA damage to cells, which in turn can result in cell abnormalities and cancer.
Asbestos Safety and ProtectionThe best way to avoid asbestos-related health problems is to practice safety first. What does this mean?
For workers who are exposed to asbestos, there are rules in place to protect yourself. Familiarize yourself with safety precautions, as well as your rights as an employee. Here are a few sources to get you started:
- From the U. S. Department of the Labor: Better Protection Against Asbestos in the Workplace
- From the Environmental Protection Agency: Protecting Workers from Asbestos
- From the Occupational Safety and Health Administration: OSHA Asbestos Fact Sheet
For those concerned about asbestos in their homes, or who are considering home remodeling project, the Consumer Safety Commission provides information on where it is found, what should be done about asbestos in your home, and how to manage asbestos problems in this article:
What Can You Do if You’ve Been Exposed?There isn’t currently a lung cancer screening test recommended for people who have been exposed to asbestos, as there is for smokers, but it may be worth talking to your doctor. A study done in 2007 suggested that low-dose CT screening for asbestos workers may be at least as useful in detecting lung cancer in the early stages as it is for heavy smokers. That’s significant considering that later guidelines in 2013 found that screening people with a 30 pack-year history of smoking who were between the ages of 55 and 74 could reduce lung cancer deaths by 20%. Certainly if you have been a smoker in addition to being exposed to asbestos, a conversation with your doctor is a good idea.
The Agency for Toxic Substances and Disease Registry (ATSDR) has developed screening guidelines for asbestos-related disease including cancer as well as lung conditions. These guidelines recommend that you see a physician who is familiar with asbestos-related disease. (I can’t emphasize how important this is as some physicians rarely work with people exposed to asbestos.) Another problem with those who have been exposed to asbestos is that CT screening frequently reveals “false positive” tests – meaning that something may appear abnormal when it is indeed okay. For example, in one study, over half of asbestos workers had at least one abnormality noted on a CT scan.
In addition to screening and asbestos protection, perhaps the most important thing anyone can do is refrain from smoking. There are also other things you can do that may lower your risk. If you have any concerns, make sure to check these out.
Camargo, M. et al. Occupational exposure to asbestos and ovarian cancer: a meta-analysis. Environmental Health Perspectives. 2011. 119(9):1211-7.
Centers for Disease Control and Prevention (CDC). Asbestosis-related years of potential life lost before age 65 years – United States, 1968-2005. Morbidity and Mortality Weekly Report. 2008. 57(49:1321-5.
Centers for Disease Control and Prevention. Agency for Toxic Substances and Disease Registry. Clinical Screening Guidelines for Asbestos-Related Disease. http://www.atsdr.cdc.gov/asbestos/medical_community/working_with_patients/docs/clinscrguide_32205_lo.pdf
Chapman, S. et al. Benign asbestos pleural diseases. Current Opinions in Pulmonary Medicine. 2003. 9(4):266-71.
Environmental Protection Agency. Asbestos. Updated 06/28/13. http://www2.epa.gov/asbestos
Fasola, G. et al. Low-dose computed tomography screening for lung cancer and pleural mesothelioma in an asbestos-exposed population: baseline results of a prospective, nonrandomized feasibility trial – an Alpe-andria Thoracic Oncology Multidisciplinary Group Study (ATOM 001). Oncologist. 2007. 12(10):1215-24.
Goodman, M. et al. Cancer in asbestos-exposed occupational cohorts: a meta-analysis. Cancer Causes and Control. 1999. 10(5):453-65.
Homa, D., Garabrant, D. and B. Gillespie. A meta-analysis of colorectal cancer and asbestos exposure. American Journal of Epidemiology. 1994. 139(12):1210-22.
Jamrozik, E., deKlerk, N., and A. Musk. Asbestos-related disease. Internal Medicine Journal. 2011. 41(4):372-80.
Liu, G., Cheresh, P., and D. Kamp. Molecular basis of asbestos-induced lung disease. Annual Reviews in Pathology. 2013. 24(8):161-87.
Markowitz, S. et al. Asbestos, asbestosis, smoking, and lung cancer. New findings from the north American insulator cohort. American Journal of Respiratory and Critical Care Medicine. 2013. 188(1):90-6.
Occupational Safety and Health Administration. Asbestos. Accessed 07/20/13. https://www.osha.gov/SLTC/asbestos/
Przakova, S. et al. Asbestos and the lung in the 21st century: an update. The Clinical Respiratory Journal. 2013 May 27. (Epub ahead of print)
Roberts, H. et al. Screening for malignant pleural mesothelioma and lung cancer in individuals with a history of asbestos exposure. Journal of Thoracic Oncology. 2009. 4(5):620-8.
Tossavainen, A. Global use of asbestos and the incidence of mesothelioma. International Journal of Occupational and Environmental Health. 2004. 10(1):22-5.
Wender, R. et al. American Cancer Society lung cancer screening guidelines. CA: A Cancer Journal for Clinicians. 2013. 63(2):102-7.