Mesothelioma risk from asbestos

While lung cancer and mesothelioma are generally associated with chronic exposure to asbestos, there are several studies that indicate that short-term exposures are also of concern. For example, it has been noted that workers exposed to asbestos for only 1-12 months had an increased risk of developing lung cancer a number of years later. In animals, mesotheliomas developed in two rats exposed to high concentrations of amosite or crocidolite for only 1 day. These data are not extensive enough to define the dose- or time-dependency of health risks from short-term exposure to asbestos, but the data do indicate that short-term exposures should not be disregarded. 

Using a predictive model developed from mesothelioma data from studies of asbestos insulation workers (Peto et al. 1982), asbestos textile workers (Peto 1980), amosite factory workers (Seidman 1984), and asbestos-cement workers (Finkelstein 1983), EPA (1986a) estimated that continuous lifetime exposure to air containing 0.0001 f/mL of asbestos would result in about 2-3 cases of mesothelioma per 100,000 persons. The corresponding cumulative lifetime exposures associated with excess risks of 10 " -10 are shown in Figure 3-1. Cumulative exposure levels of 0.031, 0.0031, 0.00031, and 0.000031 f-yr/mL represent excess mesothelioma risks of 10" , 10 , 10, and 10 ", respectively. Appendix D provides further details on the derivation of these risk estimates. Currently (in 2001), EPA is in the process of reviewing their cancer risk estimates for asbestos fibers. 

Comparative Toxicokinetics. Available data Ifom ehronic rat inhalation bioassays show similar asbestos-induced respiratory effects to those in humans assoeiated with oeeupational exposure to asbestos (pulmonary fibrosis, lung cancer, and pleural mesothelioma), but the use of the rat data to predict human health risks from exposure to airborne asbestos has a number of areas of uneertainty, including those associated with interspecies differences in lifespan, airway morphometry, and breathing patterns. The development of rat and human lung retention models that incorporate species differences in anatomical and physiological parameters influencing deposition and clearance of asbestos fibers may decrease the... 

Analyses of trends in mesothelioma mortality in Britain and Western Europe (Peto et al. 1995, 1999) indicate that the worst-affected birth cohort is men bom around 1945-1950 (1/150 were projected to die of mesothelioma), whereas similar analyses of trends in the United States (Price 1997) indicate that the worst affected cohort is the 1925-1929 male birth cohort (with an estimated lifetime risk of 2/1,000). These trends mirror trends in raw asbestos consumption and a reduction in workplace airborne asbestos levels, with maximum exposure in the United States from the 1930s to the 1960s and in Britain and Western Europe in the 1970s (Peto et al. 1995, 1999 Price 1997). NIOSH (1999) has reported that age-adjusted mortality rates for malignant neoplasm of the pleura in U.S. males showed a decline during the 1987-1996 period from 3.61 per million in 1987 to 2.87 per million in 1996. 

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... 

A chest X-ray cannot detect the asbestos fibers themselves, but it can detect early signs of lung disease caused by asbestos from relatively heavy exposure. The most reliable test for asbestos exposure is the detection of microscopic asbestos fibers in pieces of lung tissue removed by surgery (invasive test). The use of biological markers, such as tissue polypeptide antigen, may play a useful role in the early detection of mesothelioma in individuals at risk. 

People of central Turkey who live in an area rich in erionite Irequently suffer from lung cancer and mesothelioma. It is not yet known definitely, if the risk of cancer from exposure to other fibrous materials is considerably lower than that of exposure to asbestos. But the existing data seems to show that the risk of health problems, due to exposure to fibers other than asbestos is less. 

As noted above, exposure to asbestos has been linked to an increased risk of lung cancer, mesothelioma, gastrointestinal cancer, and asbestosis among occupationally exposed workers. Adequate screening tests to determine an employee s potential for developing serious chronic diseases, such as a cancer, from exposure to asbestos do not presently exist. However, some tests, particularly chest X-rays and pulmonary function tests, may indicate... 

Traditionally the construction industry s high level of injury accidents has received the attention of enforcement, media publicity and management action. Arguably, the size of that problem has led to a neglect of the less tangible consequences of occupational hygiene and health problems, apart from well-publicised topics such as asbestos. There is little general awareness of just how big the occupational health risks are in construction compare the numbers already discussed for conventional injuries with the fact that mesothelioma, a form of cancer linked specifically to asbestos exposure, kills around 1400 people... 

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