“Sandblasting” Clean Metals but Ruins Lungs

Introduction

Sandblasting or abrasive blasting is the process of softening, shaping, and cleaning hard surfaces by forcing solid particles on the surface at high speed. The finishing is similar to that of sandpaper work without causing any problems in the corners or grooves. Sand erosion occurs naturally and is caused by particles being blown by the wind or using compressed air.

Overview of the abrasive blasting process

It is a process of cleaning metal and other surfaces to remove contaminants, rust, and paint by directing a high-pressure stream of abrasive material on the surface. Generally, when sand is used as an abrasive, it is changes to a smooth level from its natural state, and the quartz content largely depends on the source of the sand. Sandblasting equipment usually consists of a chamber mixed with sand and air. The mixture travels through the hand-held tip. Nodes come in a variety of shapes, sizes, and materials.

Technically, if sand is used as an abrasive, the process is referred to as sandblasting.  The term is commonly used when other materials such as coal and metal sludge, steel shot, and garnet are used as abrasives. 

Abrasive blasting is widely used in the marine industry to make hulls, tanks, and other components remove marine growth from the bottom of ships. These operations were often carried out in the open or tightly defined areas on a vessel.

Abrasives are applied in various ways. Compressed air is used during dry abrasion eruption. Others include wet and airless blasting. In some industries, abrasive blasting operation is carried out inside closed blasting machines or chambers to reduce the exposure of aerial silica. The blasting units are provided with exhaust ventilation to control airborne emissions to the worker and the collection systems to collect abrasive materials for recycling. Abrasive blasting presents many occupational hazards to the blaster other than exposure to airborne contaminants, the abrasive material is impinged at high speeds and causes a serious physical risk to the blasting operator.  The hood or helmet, is protecting the head, neck, and shoulder. 

Overview of Silicosis

Excessive exposure to crystalline silica in the air causes severe health damage for more than 100 years. Work practices and regulatory standards have improved as knowledge of the dangers of crystalline silica has developed, Mortality rates, and spreading of lung disease found in industries involving dusty operations in the early 1900s.

Abrasive blasting operations were dangerous and provided the basis for many of the engineering control and respiratory safety requirements still in practice today. Engineering controls are often not fully effective in reducing aerial silica concentrations to safe levels; As a result, respiratory safety has always been an essential component in protecting workers. Over the past 15–20 years, quantitative exposure-response modeling, experimental animal studies, and in vitro methods have been used to understand the relationship between silica and disease exposure in the workplace. Its focus is on protecting workers who are still known to be exposed to silica in the workplace (including abrasive plasters), in light of occupational safety and health management efforts to reconsider the current permissible exposure range (PEL) for crystalline silica. Scientific review of one of the most dangerous activities involving crystal silica should provide a useful background. In the historical evolution of crystal silica and related abrasive eruption, activities recognized occupational health risks and required for respiratory protection.

In the early 20th century, changes associated with the Industrial Revolution led to the formation of airborne dust concentrations in many industrial systems. This raise was primarily due to the use of machines (e.g., drills, automatic grinders) in previously made applications by hand. The increase in lung disease among workers in ¨dusty trades¨ led to the recognition of the role of silica in the development of so-called silicosis.  Exposure occurs in a wide variety of industries. For example, silica, which is naturally present in rocks, can be eroded during mining (e.g., rock drilling, excavation) and quarrying. The abrasive blasting operations are carried out without adequate dust controls, creating the potential for exposure to aerial crystal silica, and the associated risk for the disease is significant.

There are three forms of silicosis, chronic, accelerated, and acute (NIOSH, 2002a). Chronic silicosis is considered a classic form of the disease and develop after adequate exposure for ten years or more. Chronic silicosis is simple silicosis. Acute silicosis will develop within 5 weeks to 5 years if the initial exposure concentration level of aerial silica is high. 

Abrasive Explosion Studies and Advances in Industry

Abounding Explosions at Foundries and Shipyards Foundry studies published in the 1940s and 1970s focused on the effectiveness of previously established dust controls to reduce the incidence of silicosis. One of the most important themes is to ensure that blast chambers, boxes, and rotary drums are sealed and properly maintained to prevent dust containing silica from escaping into the public work area. Staff working in the blast rooms urged to wear air-conditioning hoods and to store helmets in a separate place to prevent them from Contamination by silica dust. These recommendations are not limited to abrasive cracking using sand containing silica but also to the use of steel grid as abrasives that produces significant dust levels.

In 1950, in Great Britain use of silica sand for abrasive blasting was banned (Industries Act), followed by the Netherlands in 1956 and Belgium in 1964 (Council of Europe, 1970). Sandblasting is banned in India also as in the rest of the world. The ban on silica as an abrasive material has sparked research into alternative materials that provide a comparable surface product without the toxicity of silica. The risk of silicosis is high in workers exposed to abrasive blasting with silica, and the hazard is difficult to control. NIOSH has therefore recommended since 1974 that silica sand (or other substances containing more than 1% crystalline silica) is prohibited, as the abrasive blasting material. 

The alternative for Sandblasting 

The engineering controls commonly used in foundries are not feasible for many shipbuilding operations, and shipbuilders need to develop alternative ways to protect workers against the hazards associated with abrasion explosions. A restriction involves connecting dust-removal equipment to explosive pipes. This method was especially useful when blasting in tanks or the vicinity of a blaster hopper during shipyard hull preparation.

The most frequently recommended alternative at this time is the abrasive steel shot. However, it is acceptable that sand has superior properties such as an abrasive and, in many cases, is less expensive than some common alternatives. The cost is the main factor for most of the industries, as high levels of abrasion are in blasting operations. Furthermore, abrasives such as steel shot were known to produce metal dust, which required protective measures (supply-air respirators and abrasive blast helmets) such as silica abrasives (brand, 1943), and even now, industries are using sandblasting. Since silica sand is considered an industrial resource in the United States. Rather than banning the material, the United States sought to control industrial emissions associated with abrasive eruption activities through engineering regulations and respiratory protection. Silicosis swallows the workers.