April 2007 - Elimination of Silicosis

Silicosis, a form of pneumoconiosis caused by inhalation of crystalline silica dust, is marked by inflammation and scarring in forms of nodular lesions in the upper lobes of the lungs. Silicosis is characterized by shortness of breath, fever, and cyanosis (bluish skin). It may often be misdiagnosed as pulmonary edema (fluid in the lungs), pneumonia, or tuberculosis. The best way to prevent silicosis is to identify workplace activities that produce crystalline silica dust and then to eliminate or control the dust.

The Global Occupational Health Network (GOHNET) recently published a newsletter (www.who.int/occupational_health/publications/newsletter/gohnet12e.pdf) discussing the elimination of silicosis in the work place. Their recommendations and approach center around prevention and, if necessary, mitigation. The following, as provided in the newsletter, is a summary of GOHNET's prevention philosophy :

"In the field of occupational health there are few risk factors and, thus, few health outcomes that can be completely eliminated at a global level. Silicosis is a positive exception. In countries like the United States and in Europe where appropriate measures have been taken, the incidence of silicosis has decreased dramatically. It is clear that to eliminate silicosis, the main focus has to be on prevention. It is as simple as this; if occupational exposure to dust is avoided, silicosis will cease to occur. If there is no primary prevention, silicosis cannot be eliminated, just possibly mitigated. It should be kept in mind that when silicosis is detected by a chest X-ray, it is already too late; that lung will never be normal again."

Primary prevention aims at interrupting the "chain of exposure" - the process by which hazardous agents are formed/used and transmitted from their source to the receptor (worker). The hierarchy of controls is:

Control of the source - Aims at preventing or minimizing the use or generation/release of a hazardous agent. Examples of measures in this category include substitution of materials and equipment, modification of processes, wet methods, and adequate work practices.

Control at the transmission path - Exhaust ventilation should be well-designed, properly installed and operated, routinely checked, and well-maintained;otherwise it will not be efficient and may even give an undesirable “false sense of security”. Examples of inadequacies, which may hinder the performance of local exhaust ventilation systems, include insufficient air velocity at the entry (hood) thus not properly capturing and removing the airborne particles;low transport velocity in the ducts or very sharp changes of direction, causing dust to deposit; and perforation of the ducts, not noticed due to lack of proper checks and maintenance.

Control at the worker level - Includes adequate work practices, education and training, personal hygiene, and health surveillance. Good work practices are extremely important as they can eliminate or minimize hazards even at their source. Control at the worker also includes preventing dust from reaching the worker’s breathing zone by means of some form of respiratory protection, such as masks and helmets. Although a respirator may be a good solution for sporadic, temporary, or short duration tasks, it should be considered as the last option for routine, full-shift work. For certain special types of work, respirators may be needed but, then, the duration of use should be limited accordingly, particularly for the mask type with a filter.

COPYRIGHT ©2007, ISO Services Properties, Inc.

The information contained in this publication was obtained from sources believed to be reliable. ISO Services Properties, Inc., its companies and employees make no guarantee of results and assume no liability in connection with either the information herein contained or the safety suggestions herein made. Moreover, it cannot be assumed that every acceptable safety procedure is contained herein or that abnormal or unusual circumstances may not warrant or require further or additional procedure.