Appendix 2: Asbestos

What is asbestos?

Asbestos is a term used to describe naturally occurring fibrous hydrated silicates of which there are six common varieties.

The figure below shows the different types of asbestos.

Amosite (brown asbestos) and crocidolite (blue asbestos) have straight needle-like fibres which naturally split in their long axis producing very fine fibrils (thin fibres). In contrast chrysotile, (white asbestos) has softer curlier hair like fibres, which make them useful for weaving and have been used to make asbestos cloth for centuries.

When these fibres are inhaled they behave in different ways in the lungs.

Chrysotile (magnesium silicate) fibres slowly lose magnesium, which leaches out in the body fluids making the fibre more easily digested by scavenger cells (macrophages). This reduces the body burden of the asbestos dust and has lead to the view that white fibres are less harmful.

Crocidolite (iron-sodium silicate) fibres are straight and rigid, can split longitudinally, are more resistant to body fluids so that they survive unchanged in the body for up to 40 years or more, and the fine fibrils can migrate through the lung tissue to the lung lining (pleura).

Amosite (iron magnesium silicate) fibres are longer making it useful for insulation and again the fibres remain unchanged in the body for years.

The uses of asbestos

The word asbestos was first coined by the Romans in the first century AD, but by that stage the material had already been in use for at least 2000 years. Archaeological evidence from Finland has shown that a type of asbestos was used to strengthen clay pots over 4000 years ago. The Roman writer Plutarch described in the first century AD a cloth woven from asbestos fibres that could be cleaned by immersion in fire, and when the Vvenetian explorer Marco Polo returned from the East 1200 years later he too described a fire suit he had seen there.

However, it was not until the late nineteenth century that asbestos began to be used on a large scale in the manufacture of many different items. From the 1880s it was used increasingly in the textile industry to produce incombustible products, also gland packings and other linings for machinery. The different types of asbestos had some remarkable properties - with their resistance to heat, friction and chemical decomposition combined with their fibrous nature; and as the industrial age - particularly the development of the automobile - gathered momentum early this century, asbestos began to be used in an increasing range of applications. World War I saw asbestos being used as thermal insulation in naval vessels and by the 1920s the substance was firmly established as a vital ingredient in the manufacture of friction clutches and brake linings.

Coinciding with this increased use was the discovery of large reserves of white and blue asbestos in Russia, Canada and South Africa. Reserves of both were also found in Australia. Asbestos became popular as the reinforcing material in asbestos cement products, including wall claddings and roofing materials, pipes and other building materials. At the same time it was used more and more in its raw state as an insulation material in buildings, around boilers, and as a fire retardant around structural steelwork.

The post-war years were the heyday of asbestos use in New Zealand and around the world. Each of the three main types of asbestos - white, blue and brown - were sprayed, and spread in what seemed to be an ever-increasing range of applications throughout industry, as part of machinery components, and, to a lesser extent, in homes. A Uunited Kingdom report in the late 1970s estimated that about 3,000 manufactured products contained asbestos in one form or another. The same report said there were over 21,000 people in the Kingdom alone employed in the manufacturing of products which contained some degree of asbestos, and about the same number employed in processes which were subject to the asbestos regulations of the time.

Asbestos use in New Zealand

Until just before the Second World War asbestos really only found its way into New Zealand in the form of manufactured items. Since that time, the only asbestos containing products that have been manufactured in any quantity in this country were asbestos cement building materials, such as roofing and wall claddings, pipes and other moulded products.

There have been two plants producing asbestos cement products. The first was established in 1938 at Penrose in Auckland, by the Australian company James Hardie Ltd. A second factory, operated by the local company Fletcher's, was established in the Christchurch suburb of Riccarton in 1943. Depending on the item being manufactured, they were made of a mixture of Portland cement, sand, and usually between 5 and 15 percent of either chrysotile, amosite or crocidolite -the asbestos acting as reinforcing because of its fibrous nature and its high tensile strength. The types of asbestos used varied. The bulk was the white variety, chrysotile, which was cheaper and more easily worked. Because the "best" blue crocidolite from South Africa was more expensive, it tended to be used only in products requiring greater heat tolerance or strength (such as in pipes expected to contain higher pressures or temperatures). A lesser quality crocidolite from the Wittenoom mine in Western Australia was also used to some extent. Amosite, or brown asbestos was imported from Rhodesia (now Zimbabwe) and was only ever used in small quantities. The Auckland plant produced asbestos cement products until 1987 although from 1983 asbestos had been phased out of sheet products and included only in pipes. At peak production in the mid 1970s the Penrose plant employed up to 600 employees at any one time.

The Christchurch plant, called Durock Industries, operated until 1974. Estimates of the numbers employed over the life of the factory vary between 900 and 2000 and are confused by the fact that large numbers of casual workers were employed.

Another major use of asbestos was as the raw material for insulation products. This saw the various types of asbestos mixed with a binder and sprayed around boilers, pipes, ducts and other places where insulation against heat, or sometimes noise was needed. From the 1950s until the 1970s thousands of tonnes of asbestos were applied in this way, most notably in the power stations built in the period, but also in railway workshops, shipbuilding and maintenance and other large-scale industrial applications. Sprayed asbestos was also used extensively as a fire retardant for protecting structural steelwork. Uusually the insulation material was applied by contractors who mixed asbestos from the bags or sacks it had been imported in, before spraying the mixture on to chicken wire reinforcing. been banned.

Other workplaces where asbestos was used included railway workshops boiler rooms, and in fact most of the country's major industrial complexes where insulation against heat was required. Some of the industrial applications were less obvious. For example, asbestos was commonly used in the brewing industry to filter beer from the 1920s until the early 1970s, and it was dropped into wine to act as finings and clarify the finished product. Another unusual use for blue asbestos was as a filtering component in gas masks of British manufacture that were standard issue for troops and others from the first World War until after the Second World War. An inner core of asbestos was surrounded by woollen wadding, and the item was standard issue to all New Zealand troops in danger of gas attack.

Before the Second World War, asbestos was not imported in its raw state in sufficient quantities to appear in the import statistics. With the beginnings of local manufacturing and the increase in post-war construction, more than 2,000 tonnes were being imported annually by the late 1940s. This continued throughout the 1950s with peaks of up to 5,000 tonnes in some years. Uusage increased dramatically during the 1960s and until well into the 1970s with 5,000 tonnes being a minimum amount that was imported through those years, and the average being closer to 8,000 tonnes. Imported asbestos peaked in 1975 at 12,500 tonnes, although as recently as 1983, 3,000 tonnes were imported.

Throughout the 40 years asbestos was imported in large quantities, about two-thirds of the amount imported was chrysotile from Canada, with the balance being made up of different types from Australia, South Africa or, to, a lesser extent, the Uunited States.

Asbestos was only ever mined in small quantities locally, as chrysotile from a single mine near Takaka from the early 1950s until the early 1960s. It was of a low quality and had to be mixed with the imported material. In the late 1960s sizable deposits were surveyed near Dusky Sound, but for various reasons these were never exploited. Since 1984 the importing of blue and brown asbestos has been banned.

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