Mortality experience of amosite asbestos factory workers: dose-response relationships 5 to 40 years after onset of short-term work exposure.

A cohort of 820 men in a Paterson, New Jersey, amosite asbestos factory which began work during 1941-1945 was observed from 5 to 40 years after start of work. Most of the cohort had limited duration of work experience (days, weeks, months), though some men worked for several years until the factory closed in 1954. With white males of New Jersey as the control population, Standardized Mortality Ratios (SMRs) of 500 are evident for the cohort for lung cancer and for noninfectious pulmonary diseases (including asbestosis), while being almost 300 for total cancer and about 170 for all causes of death. A statistically significant SMR of almost 200 is seen for colon-rectum cancer. Mesothelioma incidence initially shows a strong relationship with advancing time since onset of exposure and then tails off. The main concern of the study is with dose-response patterns. Response is measured by the mortality for relevant causes of death, while the direct asbestos dosage was measured in two ways. One way was the length of time worked in the factory and the other was the individual's accumulated fiber exposure, calculated by multiplying the aforementioned length of time worked by the estimated fiber exposures associated with the particular job that the worker had in the factory. Whichever measure of dosage is used, it was found that, in general, the lower the dose, the longer it took for adverse mortality to become evident and, also, the smaller the magnitude of that adverse mortality.

Amosite Asbestos

Amosite asbestos is more commonly referred to as "brown" asbestos and sometimes "gray" asbestos. This form of asbestos was found and is mined in South Africa and is considered to be one of the more hazardous forms of the material, second only to "blue" asbestos. In fact, a large portion of South Africans who worked in the many asbestos mines there have been sickened with some sort of asbestos-related disease. Countless numbers have died.

From the amphibole group - which is naturally more hazardous than serpentine asbestos - amosite asbestos was, at one time, the second most prevalent type of asbestos found in building materials, accounting for about 5% of all asbestos used in factories and other commercial buildings. Its color comes from the natural presence of iron and magnesium found in this form of asbestos.

The amosite variety of asbestos was used primarily as a fire retardant in thermal insulation products, like ceiling tiles. Brown asbestos is now banned in most countries and has been for a number of years, but it can still be found in older products and structures, therefore still posing potential dangers, especially because this form of asbestos is highly friable. That means it crumbles easily when damaged, therefore releasing airborne fibers which can then be inhaled by those in the vicinity of the material.