World Health Organization Press Office
Press Release WHO/51/REV.1
September 10, 1996
The group concluded that where appropriate control measures have been applied, workplace exposures to chrysotile have been reduced considerably, and that the production and processing of chrysotile generally present less risk for persons involved in mining and manufacturing of friction materials and asbestos cement products. However, other uses of products containing chrysotile may pose health risks. Of special concern is the potential exposure to chrysotile in buildings during alterations and maintenance. Therefore, when available, substitute materials evaluated as safer than chrysotile should be considered.
The commercial term "asbestos" refers to a group of fibrous minerals that have high tensile strength, conduct heat poorly, and are fire resistant. Chrysotile is the main form of asbestos, the other two principal forms of asbestos being amosite and crocidolite. Today, chrysotile accounts for over 95% of the world asbestos trade, and chrysotile deposits are exploited in more than 40 countries. The main producing countries are the Russian Federation, Canada, Kazakhstan, China, Brazil, Zimbabwe and South Africa.
Asbestos is ubiquitous in the environment because of its extensive industrial use and the dissemination of fibres from natural sources. The asbestos minerals occur naturally as fibre bundles that may be several centimetres long. However, when manipulated, they break down into smaller fibres which may have dimensions in the submicron range. It is these small fibres that, when inhaled, can pose health risks.
Epidemiological studies, mainly on occupational groups, have established that human exposure to all types of airborne asbestos fibres may be associated with such diseases as diffuse pulmonary fibrosis (asbestosis), lung cancer (bronchial carcinoma), and primary malignant tumours of the pleura and peritoneum (mesothelioma)
The group of international experts met in July 1996 at the Geneva headquarters of the World Health Organization (WHO) within the framework of the International Programme of Chemical Safety (IPCS), a joint Programme of WHO, the International Labour Organisation (ILO), and the United Nations Environment Programme (UNEP).
According to the experts, the available published data showed that, in general, exposure levels in the production and processing of chrysotile, which were very high in the past, dropped significantly in the late 1970's and have continued to decline to present-day low levels. However, in production facilities without adequate dust control, exposure is still high.
The experts stressed that appropriate control measures should considerably reduce risks of developing asbestosis, lung cancer and mesothelioma. Data from industries where such measures have been introduced demonstrate the feasibility of keeping exposure at levels generally below 0.5 fibres/ml of air. The experts concluded that clinical manifestations of asbestosis were unlikely to develop under these conditions of exposure. The risk of lung cancer is highest in chrysotile textile production, and considerably lower in chrysotile cement production, in the production of friction products, and in mining. The question of the extent to which the mesotheliomas may be attributed to chrysotile versus other contaminating asbestos fibres sometimes present was not resolved by the group.
Some asbestos containing products pose particular concern and chrysotile use in those circumstances was not recommended. These uses include friable products. There are also large quantities of mixed asbestos still in place in many buildings and the presence of friable products has high exposure potential. Construction materials are of particular concern because the workforce involved is large and control measures are difficult to institute. It was stressed that building materials already in place may pose a risk to those carrying out alterations and maintenance. In buildings where there are control measures, exposure to chrysotile of maintenance personnel is low. However, where control measures have not been introduced, building maintenance personnel can be exposed to high levels of chrysotile and other asbestos fibres. In the general population, the risk of adverse effects from exposure to chrysotile was considered to be low.
The chrysotile evaluation once again confirmed that asbestos exposure and cigarette smoking interact to increase the risk of lung cancer. Those who have been exposed to asbestos can substantially reduce this risk if they stop smoking.
The group of experts did not identify any new information that would alter the previous evaluation by a WHO group of experts of the potential risks from exposure to chrysotile in drinking-water: there is no consistent evidence that ingested asbestos is hazardous to health (see press release WHO/17, 25 February 1994).
More than 140 IPCS contact points - collaborating centres, institutions and individuals both in
developed and developing countries - were involved in the preparation of the evaluation of chrysotile, which was reviewed by 17 experts from 10 countries: Austria, Canada, China, Croatia, Finland, Germany, Italy, Japan, the United Kingdom and the United States of America.
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