About Asbestos

The section on ASBESTOS in this website may seem a little incongruous however I have had a long association with asbestos and its dangers.

This first started in the mid 1950s when I was about ten years old with my father telling about the dangers of asbestos dust. In turn my father had been informed about the asbestos problem by my grandfather who had been a mining engineer.

In the 1950s asbestos was widely used and few people appreciated how potentially dangerous it was.

In 1968 in my first job after leaving university during an investigation into another matter I identified the extensive and high level asbestos contamination at Meremere power station. My findings were included in a report to the Electricity Dept management by the station chemist Jim Foy.

Later as Wine Chemist I found extensive contamination of wine by fine asbestos particles. This asbestos was derived from the filter pads being used in the wine industry and was frequently associated with the short cutting of filtration startup procedures.

I am now on the asbestos register for persons who have been exposed to asbestos as a consequence of their employment.

Subsequently as MOLAB Ltd I have been examining materials for the presence of asbestos and other hazardous components on be half of a number of organisations including Ceiling Technologies Ltd.

The following series of topics is related to Asbestos and/or the potentially dangerous ceiling texture coats that have been and still are widely used with little consideration for public safety.

What Is Asbestos?

There is a common perception that asbestos is just one substance The reality is that there are a number of different substances that are different kinds of asbestos. Asbestos is a particular kind of crystal. There are a number of different silicates that have as one of their crystal forms a type of asbestos.

But what make a silicate crystal asbestos?

Many crystals split easily along what is known as a cleavage plane. The most obvious example of this is mica which can be split into progressively thinner sheets. Mica has one good cleavage plane. A crystal may have more than one cleavage plane. The second plane meets the first plane at an angle. Instead of splitting into sheets like mica a crystal with two good cleavage planes splits into fibres. The more it is crushed the finer are the fibres produced. It is this splitting into progressively finer fibres that makes asbestos so useful but also so dangerous.

Crystals that split into fibres like this are known as asbestiform (or asbestos like) crystals.

The common substance calcium sulphate or gypsum can produce asbestiform crystals.

Only silicates are asbestos. The most common asbestos is chrysotile this a crystal form of the mineral serpentine. Normal serpentine splits like mica and when powdered is rather like talc. Of particular importance in NZ is the mineral tremolite. This exists in a number of different forms. One the fibres are all parallel this is tremolite asbestos. Another form consists of fine needles randomly oriented to produce a mass into locked fibres. This form is nephrite or NZ greenstone. It is this mass of interlocking fibres that give greenstone its special properties of strength and impact so important in the beautiful thin and deadly mere or war axe. Greenstone was also prized as a hammer stone to make other stone tools for good reason.

How Dangerous is asbestos?

The main dangers from asbestos are due to the effects that fine asbestos fibres have when breathed into the lung. To have any effect the fibres must enter the lung and be retained there. Fibres that are too large do not reach the lung. Fibres that are too small do not settle in the lung but remain suspended in the air and are breathed out.

The small needle like fibres that settle in the are able to penetrate cells damaging them and in many cases killing them. A single asbestos fibre has the potential to kill more than one cell. The killing of the cells produces scar tissue or plaque in the lung. This plaque reduces the efficiency of the lung.

Occasionally instead of killing a cell an asbestos fibre damages the chromosomes in the cell transforms that cell into a cell that divides and continuously multiplies. A cancer cell. The cancer mesothelioma is primarily caused by asbestos. It only takes one fibre in one cell to transform that cell into a cancer cell. This change is very rare. Each asbestos fibre in the lung can be considered to be a lottery ticket in a lottery in the winning prize is a fatal cancer.

Not a prize I would want to win.

VESICULAR GLASS as found in CEILING TEXTURE COAT

Many ceiling texture coats contain vesicular glass.

This glass may be either a natural product, pumice, or an artificial material suchas perlite.In either case the composition of material is similar. The basic material is glassymaterial produced by the melting of alkalis, sodium, potassium, and/or calcium oxides with silica. The composition can vary greatly. a higher alkali content produces a lower melting point glass.

The artificial material is produced by the melting and foaming of crude rock material. The fusion is seldom complete with particles of rock minerals frequently being present. This is also the case with natural pumice.

All glass material tends to be brittle and texture coat material often contains fine glass. The hazards associated with this glass are primarily associated with the silica content. With an incompletely fused or melted glass the glasses with a high silica present the greatest silicosis hazard.

The glass material used in textured ceilings is not a high quality completely melted glass and frequently contains undissolved silica. This silica is likely be present as the high temperature form cristabolite. Cristabolite is regarded as being much more hazardous then normal quartz. Cristabolite is an OSHA listed carcinogen. As silica and glass have much different coefficient of thermal expansion glass particles containing undissolved silica tend fragment on cooling producing dusty material.

Glasses on contact with moisture release caustic soda and caustic potash. The higher the alkali content greater the amount of alkali released. The effects of beathing fine high alkali glass dust are similar to small amounts of caustic soda or sodium carbonate dust. Irritating but not very dangerous unless large amounts are breathed.

Summary

Dust from vesicular glass is not completely innocuous.

The American OSHA recommends that all perlite should be considered to be a hazardous material.

The primary problem with the glass dust is its irritant nature.

The secondary problem is due the silica content and the form of silica present in the glass.

This risk may vary from extremely low up to a significant level depending on the individual glass material actually present.

Notes on the aging of bonding agents in textured ceiling coatings

All textured ceiling coatings consist of a variety of fibrous and coarse solid materials loosely bound into a porous matrix by a binding agent.

Two types of binding agents commonly used are portland cement or lime based, and synthetic resin binders. Frequently cement binders also have a small amount of synthetic resin added.

The binding agents are potentially susceptible to change. These changes have the potential to adversely affect the stability of the ceiling texture.

Cement and lime binders even when first applied tend to be brittle and susceptible to mechanical damage.

On aging these materials slowly absorb carbon dioxide from the air changing the chemical composition of the binder. This change is also accompanied by a change in the volume of the material. As a result of this change fine fractures develop in the binder reducing its mechanical strength.

If enough moisture is present mold growth can occur in the material.

Mold growth in addition to causing mechanical damage to texture coat also produces organic acids which can attack the cement binder.

Organic resin binders initially appear to be stable however closer examination shows that this may not be so. Organic resins are susceptible to the effects of ultraviolet light.

Ultra violet light breaks the molecular chains making up the resins causing the resin matrix to slowly break down. Where light opaque materials are present the surface of the material slowly powders off. This effect is characteristically seen in the "powdering off" of paints. Ultra violet inhibitors added to resins are consumed by the action of ultra violet light and have a limited life.

In NZ there is a seasonal variation in ultraviolet light with high intensities occurring in spring and early summer. Ordinary window glass is not completely opaque to ultraviolet light and significant levels of ultraviolet light enter our homes from this source.

There is another very significant source of ultraviolet light fluorescent lights.Fluorescent lights are ultra violet lights coated with phosphors which convert the ultra violet light generated to visible light. This conversion is not complete and significant levels of ultraviolet light leak from fluorescent lights. The problem of ultraviolet light leakage from fluorescent lights is clearly shown in the bleaching of bottled soft drinks stored too long in merchandisers.

The environmental instability of binding agents used in textured ceiling materials mean that no textured ceiling materials are stable.

In addition to powdering off brittle cement based materials are likely to fracture and release more powdered material.

Organic resin bound materials while appearing sound will powder off at the surface releasing a dust of previously bound material.

IT IS PROBABLE THAT NO TEXTURED CEILING MATERIAL CONTAINING ASBESTOS IS SAFE.

The Significance of Cement in Ceiling Texture Coats

The Significance of Cement in Ceiling Texture Coats

All textured ceiling coatings consist of a variety of fibrous and coarse solid materials loosely bound into a porous matrix by a binding agent.

The most common binding agent used is a small amount of portland cement.

Cement bound materials are brittle and are easily damaged.

Even more important the cement is susceptible to chemical attack.

In a house there are humidity variations varying from quite low due to the use of heating during winter to steam in the kitchen.

Human beings contribute moisture, carbon dioxide, and volatile organic acids to the house atmosphere by just being present in the house.

Food preparation also releases organic acids into the house atmosphere.

Carbon dioxide and organic acids directly attack cement breaking it down. This is a surface effect that is normally insignificant on large concrete and cement objects. This is not so in cement bound texture coats. The thin layers of cement on the surfaces of the particles making up the texture coat are rapidly attacked, by acids and carbon dioxide, breaking down the cement bond.

Texture coats due to their porous nature provide an ideal environment for mold and fungal growth. Mold growth within the texture coat has two main effects. Molds during their growth produce acids which attack cement. Secondly during their growth mold filaments fracture the texture coat in exactly the same way that that tree roots can split hard rock apart.

The flexing of the material caused by temperature and humidity cycling, the attack of the cement binder by carbon dioxide and acids, and the fracturing of the coat by mold growth all both singly and together cause the texture coat to break down and slowly powder off.

This break down slowly releases the other components present in the texture coat as a fine dust. This dust may be blown around and deposited through out the house. Carpets are particularly effective in catching fine asbestos dust which may be released later. In the presence of asbestos texture coats carpets, which are older and have not been well cleaned, often contain significant amounts of fine easily dispersed asbestos dust.

Human Behavior associated with asbestos

In Preparation