This system works very well most of the time. But even nature’s defense in unusual circumstances can fail. For instance, smoking slows and can eventually stop the movement of cilia.

Dusts are different in the way they affect the lungs and the difference lies in the dust itself. Where does it come from? What is it made of? Different kinds of dust may affect the body in the following ways:

• Little apparent damage. Certain dusts such as carbon, iron or tin cause no damage.
• Irritation. Asbestos fibers, for example, may set up a reaction that results in scarring of the lungs. This usually results only after many years of steady exposure to asbestos fiber.
• Cellular and chemical reaction. This is believed to be the case with silicosis, with quartz dust triggering a direct chemical reaction within the lungs resulting in fibrosis (scarring). Also scavenger cells in the lungs pick up the silica particles with release of a scar producing substance.
• These types of reaction injure the lungs in various ways – but the disease process in its later stage results in the symptom of shortness of breath and at times, coughing.

Why does one man get a dust disease while his friend who works in the same plant does not?

There are many answers. A worker can become ill because:

• He may have a different kind of job, one in which there is much more dust at face level; or his own protective devices may not be as good. At times the worker may not wear protective equipment when needed.
• He may have worked more years at his job; or maybe he puts in more overtime. So the total dust load is a real factor.
• He may breathe through his mouth, which offers much less protection than breathing through the nose.
• He may not be in good general health, and have a chronic, or long-lasting, infection in the bronchial tubes or lungs.

Other factors that help decide whether or not a worker comes down with a dust disease are: the percentage of harmful material, such as the percentage of silica in the total dust exposure; the size of the dust particle – smaller particles are more likely to enter the deeper parts of the lung without being caught in the sticky mucus in the air passages; and, as always, the individual differences in the way human beings react to dust-susceptibility.

It is often hard to predict the course of a dust disease. Some workers may suffer little from the disease – even in its most advanced stage – and eventually die of other causes. This is true of silicosis more than asbestosis. But other workers who breathe in harmful dusts over a long period of time may develop serious impairment of function.

At the beginning, there may be no symptoms. Shortness of breath is the first symptom. It usually begins some years after the beginning of exposure to the harmful dust.

A cough comes next. With extensive scarring of the lung there may be chest pains. The dust deposits, which have slowed up the normal transfer of oxygen into the blood stream, may result in blueness of the lips and ear lobes, in late stages of the disease.

Complications – the development of other illnesses – are a serious threat to persons with a dust disease.

Tuberculosis is still a problem for silicosis patients, but less than years ago when tuberculosis was common. The quartz dust reacting in the lungs makes the silicotic worker more susceptible to TB.

Pneumonia, pulmonary heart disease and lung cancer are complications that often go with a dust disease. Chronic bronchitis and emphysema are frequently seen in workers exposed to dust but these two diseases are really related to the cigarette smoking habit. In the asbestos worker Iung cancer is much more likely to occur in the smoker.

Treatment for dust disease is difficult.

Shortness of breath and coughing can often be helped. And infections such as tuberculosis or pneumonia can be treated with drugs. For emphysema a combination of medicines with regulated exercise may make breathing easier. Cessation of smoking will help the worker with bronchitis in particular.

How serious a dust disease is very often depends on how much dust is inhaled. Therefore, the best treatment obviously is to limit the exposure to the harmful dust.

A change of occupations may be important for younger men whose illness is in an early stage. On the other hand, men near retirement age may be told they can continue work if the amount of dust they breathe is reduced.

Whatever is to be done, a doctor can give advice after a complete study of the patient and his working conditions.

The cost of dust disease in sickness and death, in broken families and broken hopes – let alone the money lost – has been very large.

There is, nevertheless, a great deal of hope. Over the past 15 or 20 years the dust level has been reduced in many jobs. Credit for this reduction must be shared by many – including management, labour, governmental and industrial commissions and the worker.

Experts who have studied dust diseases believe that they can be prevented.

Each dust-producing job must be studied carefully – to decide the best method of protection. New industries, new materials, and new processes must be constantly checked to limit dust in the working environment to a minimum.

Sometimes the dust level can be reduced by such means as: adequate ventilation; use of face masks, the piping of clean air into a closed hood over the worker’s head or removal of dust by suction as it is produced; the wetting down of materials before they are worked on. The switching from a harmful material to one that does not cause disease is an ideal to be achieved if possible.

In other cases, reducing the dust level can be extremely difficult, expensive, and time-consuming. That it can be done has been shown by the authorities concerned in the handling of plutonium. Methods have been found to effectively protect the workers from this dangerous substance.

Silicosis is the most common and important dust disease. It results from inhaling silica, or quartz dust, into the lungs. Silicosis is a potentially serious disease and it has been since man first worked in stone.

The disease has been known by many other names – miner’s phthisis, potter’s asthma, grinder’s rot, stonecutter’s disease – depending upon what job is involved.

All types of mining which result in the release of silica from hard rock can produce silicosis if the worker is exposed to a significant amount of silica for a long period of time. This includes the mining of gold, lead, zinc, iron, and copper, as well as anthracite coal and some bituminous coal.

Other jobs that have led to silicosis are foundry work, sandstone grinding, sandblasting, pottery, and china making and granite carving.

Silicosis develops in direct proportion to the amount of silica breathed in, and the length of time the worker is exposed to it.

Most doctors believe that silica slowly dissolves within the lungs, and produces a chemical reaction that poisons the cells. After a while, this reaction causes great damage and scarring of the Iungs. Complicating diseases such as tuberculosis and pneumonia may develop.

Despite the seriousness of the disease, better methods of protection – and more of them – have greatly reduced the death rate.

On-the-job prevention of silicosis, along with increased research into better treatment methods and possible cures, remain a challenge of the future.