Asbestos latency period

The replacement of asbestos fibers by other fibrous materials has raised similar health issues in relation to substitute materials. However, since lung cancer has a latency period of approximately 25 years, and since the fiber exposure levels in contemporary industries is far lower than those which prevailed half a century ago, the epidemiological data on most substitutes is insufficient. A possible exception is slag fibers for which several studies on worker populations are available over extended periods (44) some results show a substantial increase in lung cancer occurrence. Consequentiy, the toxicity of asbestos substitute fibers remains a subject of active investigation. 

Asbestos. EPA issued a proposed rule concerning identification and correction of friable asbestos-containing materials in schools. Based on data voluntarily submitted, EPA estimated that at least 8,600 public schools attended by over 3 million children contain such materials. However, EPA reportedly has no information on another 44,000 schools. Classroom concentrations of asbestos fibers in some schools have been found to approximate concentrations in homes of asbestos workers who do not have shower or laundry facilities at work. Since children exposed to asbestos will live long enough to allow the cancer latency period to elapse, the presence of friable asbestos materials in schools represents a potentially enormous public health problem. The final asbestos rule will reportedly be promulgated in the near future. (The rule was published May 27, 1982.) No other regulations regarding asbestos have been issued. 

Most studies have found Uttle pathology in the lungs of animals exposed for a few weeks to high doses of the asbestos but pulmonary fibrosis, and occasional malignant tumors do develop when the exposure and observation periods are increased (Middleton et al., 1975). This result suggests that tu-morgenicity by asbestos exposure through inhalation has a latency period but is also dose related. The effect of episodic exposure is unknown. 

Bianchi C, Giarelli L, Grandi G, et al. 1997. Latency periods in asbestos-related mesothelioma of the pleura. Eur J Cancer Prev 6 162-166. 

Latency periods for the development of asbestos-related nonmalignant respiratory effects are usually 15-40 years from the time of initial exposure to asbestos. 

The latency periods are generally 20 years or more for lung cancer and 30 years or more for mesothelioma due to asbestos exposure. 

All chlor-alkali producers should have a surveillance and monitoring program. Given the long latency period of asbestos-related diseases, employers should retain monitoring and medical records for longer than normal periods. The tabulation below shows the normal lag after the first exposure for death rates to become mathematically significant and the number of years required for death rates to reach their peaks. 

The signs and symptoms of lung cancer or gastrointestinal cancer induced by exposure to asbestos are not unique, except that a chest X-ray of an exposed patient with lung cancer may show pleural plaques, pleural calcification, or pleural fibrosis. Symptoms charaderistic of mesotheiioma include shortness of breath, pain in the walls of the chest, or abdominal pain. Mesothelioma has a much longer latency period compared with lung cancer (40 years versus 15-20 years), and mesothelioma is therefore more likely to be found among workers who were first exposed to asbestos at an early age. Mesothelioma is always fatal. 

One of the hallmarks of these work-related illnesses is the protracted latency period. This increase in projected survival times is relevant to this perspective. For example, with this increase in longevity over the past 50 years, it is reasonable to expect that workers with asbestos-related lung disease would... 

Several studies (Newhouse and Berry 1976, 1979 Nicholson et al. 1982 Peto et al. 1982) have indicated that the risk of mesothelioma from a given level of exposure to asbestos depends primarily upon the time elapsed since exposure (latency), with risk increasing exponentially with time after a lag period of about 10 years. Whereas early studies indicated that diagnosis with mesothelioma was fatal within a short period of... 

Eighty to ninety percent of patients diagnosed with mesothelioma report a history of occupational or environmental exposure to some form of asbestos (Attanoos and Gibbs 1997 Bianchi et al. 1997 Colt 1997 Roggli et al. 1997). Malignant mesothelioma is an aggressive and fatal cancer that is most often located in the pleura (90%) and sometimes in the peritoneum (6%-10%) (Attanoos and Gibbs 1997 Kelley 1998). In a review of 1,690 cases of mesothelioma associated with occupational exposure to asbestos, the authors reported that the median period of latency between initial exposure and detection was 32 years ... 

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