What is Silica Gel and How Does it Work?

Introduction/ General Information 

Silica, whose chemical formula is based on silicon dioxide (SiO 2 ), is a chemical that is significantly hazardous. The physical structures of this chemical hazard are both amorphous and crystalline; with the latter being found abundantly in the crust of the earth. It is estimated that approximately three million workers in the United States are exposed to this mineral substance. Silica is both odorless and grayish in color. The vapor pressure and molecular weight of silica which stand at 0 mmgHg and 60.1 respectively are its key properties. Although there are other routes through which the exposure to silica can occur, its main exposure is through inhalation, especially at the respirable size of less than 10 um (Glenn, 2008). 

Associated Diseases 

Owing to the fact that inhalation is the main route of exposure; silica is bound to cause various respiratory complications and diseases. Exposure to this substance is often associated with diseases such as lung cancer, silicosis, chronic obstructive pulmonary disease, as well as pulmonary tuberculosis. Although silicosis has been recognized as a distinct disease since the nineteenth century, the prevention efforts for this disease continue to the present day because of its worldwide occurrence. Therefore, workers with a high level of exposure to this substance have a relatively higher mortality risk from silicosis as compared to workers with low or no exposure to crystalline silica. According to the International Agency of Research on Cancer (IARC), the occupational exposure to respirable crystalline silica is cancerous to humans and could lead to the development of tracheal and bronchial cancers (Glenn, 2008). Exposure to both crystalline silica and silicosis is also associated with emphysema and bronchitis. The other diseases that may be associated with the exposure to crystalline silica include renal diseases such as glomerulonephritis, and autoimmune diseases such as rheumatoid arthritis and systemic sclerosis. 

OSHA Exposure Limits 

OSHA provides employers with permissible exposure limits for various substances, including crystalline silica, to ensure the safety of worker in both industry and maritime occupations. The current permissible limit of exposure for this substance is fifty micrograms per cubic meter of air for an eight-hour work shift. This limit is applicable to all relevant industries (OSHA, n.d). 

Sampling Methods/ Requirements 

In addition to the OSHA final limit on exposure to this mineral substance, there are other requirements in the sampling process of this substance. These requirements include air sample pumps, filter cassettes, and size-selective respirable dust samplers. It is also a requirement to follow the established protocols during the sampling process. The sampling method involves the use of a cyclone loaded with cellulose membrane filters where the respirable silicon dust is precipitated. 

Recommended Control Methods 

For workers using saws of any blade diameter, especially those handheld, the saw equipment should be connected to a water delivery system that supplies water to the blade in a continuous stream. The water delivery system should spray water at the point of impact of the saw, drill, jackhammer, or any other handheld equipment. When the power saws are used to cut fiber-cement board, they should have a dust collection system and maintained in accordance with the instructions of the manufacturer. The dust collection system used for equipment such as saws, drills, and chipping tools must have a filter with ninety-nine percent or greater efficiency (NIOSH, n.d). 

Required Regulatory Programs (under OSHA) 

Since silica has been established to be carcinogenic to humans, there is a need to control exposure to this substance. The required regulatory programs for exposure to this substance involve recommendations for employers in various relevant sectors to establish and implement written plans on how to control the exposure to silica. Such a plan should identify the tasks where exposure is involved as well as the steps taken to protect workers who perform those tasks. This plan should also include a restriction of access to areas of work where high exposure to silica is likely to occur (OSHA, n.d). 

A competent individual should be designated to implement the plan formulated here. In addition to that, Employees should be trained on how to limit exposure. Employers should also restrict activities that expose their employees to silica in places where there are alternatives. It is also a requirement under OSHA regulatory programs to adjust housekeeping practices in order to achieve maximum control of silica dust. Under OSHA, however, these regulations or medical tests to employees are not required from companies whose reading of the silica dust generated from their operations fall below twenty five micrograms per cubic meter of air (OSHA, n.d). 

Employee Testing 

It is a requirement for employers to provide medical exams such as lung function tests and X-rays to workers who put on a respirator for at least thirty cumulative days per year. These exams should be provided every three years. In addition to that, records of how employees have been exposed to this substance, as well as the medical treatment administered should be kept (Glenn, 2008). 

Conclusions 

Silica is predominantly found in its crystalline form around the world as an ubiquitous dust. Various industries and occupations that have the potential exposure to this mineral include quarrying, mining, glass manufacture, cement production, and tunneling among others. Exposure to the crystalline form of silica is associated with several diseases including COPD, pulmonary tuberculosis, and lung diseases. With the exposure limit to this substance set by OSHA at fifty micrograms for an eight-hour shift, there are regulations, control requirements, as well as regular medical tests that should be followed to limit the effect of this hazardous substance. 

References 

Glenn, D. D. (2008). Sandstorm: Current Issues Surrounding Silica. Professional Safety , 53 (2), 37-42. 

NIOSH (n.d.). Silica . Retrieved on 26 August 2019, from www.cdc.gov/niosh/npg/npg0552.html 

OSHA (n.d.). Overview of Silica . Retrieved on 26 August 2019, from http://osha.ga/dsg/topics/silicacrystaline/