Background
Silicon dioxide or silica (SiO2) is a naturally occurring mineral formed by combining silicon and oxygen atoms. When silica molecules line up and create a repeating three-dimensional pattern, crystalline silica is formed.
Silicon is one of 107 or so chemical elements know to exist in the universe. Chemical elements consist of only one kind of atom, cannot be separated into simpler substances by ordinary chemical methods and singly or in combination constitute all matter in the universe. Silicon is the second most abundant element in the Earth’s crust (Oxygen is the most abundant). Taken together, the two elements constitute approximately 75% of the Earth’s surface and everyday thing located on it. Far beyond forming sand, glass, crystals or computer chips, silica is an essential nutrient that plants and animals extract from nature to survive. It can be found in every location from every era and is indispensable for human existence on the planet.
According to the National Institute for Occupational Safety and Health (NIOSH), out of the seven forms or polymorphs of crystalline silica, the three most common in the workplace are quartz, tridymite, and cristobalite. Quartz is the second most common mineral in the world, behind feldspar. Because of its abundance in nature, (alpha) quartz is the form most commonly associated with crystalline silica.
Shipyard Applications
Crystalline Silica (quartz) is a major component of industrial sand and granite. Maritime dry-abrasive blasting operations using silica sand and silicon carbide have generally been phased out as most shipyards have switched to other cleaner and more efficient blasting media.
Newer technologies, like the sponge jet and ultra-high pressure water blasting (UHP) systems result in a cleaner surface profile, significant particulate matter (PM) emissions reduction and considerably cleaner work environment for employees.
With all blasting operations, containment and proper personal protective equipment (PPE) substantially reduces exposure.
Health Impacts
Occupational exposures to respirable crystalline silica can be associated with the development of silicosis, lung cancer, pulmonary tuberculosis, and airways diseases. Airborne exposure primarily occurs when dust containing crystalline silica particles is inhaled.
Silicosis is a scarring and hardening of lung tissue, which results when particles of crystalline silica are inhaled and become embedded in the lung. The three types of silicosis (chronic, accelerated and acute) differ by respective latency periods. The body’s natural immune system removes dust particles through the mucociliary escalator or the lymphatic system. Inhaled particles (<10 µm aerodynamic diameter) are removed by phagocytic cells called macrophages.
SCA Involvement
Two SCA-member shipyards, VT Halter Marine, Inc. of Pascagoula, MS and Bollinger Shipyards, Inc. of Lockport, LA participated in the Occupational Safety and Health Administration’s (OSHA) SBREFA process. Named the Small Business Regulatory Enforcement Fairness Act (SBREFA) of 1996, the Act requires Federal Agencies to comply with small entity requests for information or advice about compliance with statutes and regulations within OSHA’s jurisdiction, including interpretation and application of the law to specific sets of facts supplied.
OSHA Involvement
OSHA regulates crystalline silica under their Hazard Communication Standard (HCS - 29 CFR 1910.1200). Effective March 11, 1994, HCS requires all employers to inform employees of the hazard of substances in the workplace and the steps necessary to avoid harm. The standard requires businesses that use materials containing 0.1% or more crystalline silica to follow federal guidelines concerning hazard communication and worker training.
On May 2, 1996, OSHA established a Special Emphasis Program (SEP) to reduce and eliminate the workplace incidence of silicosis from exposure to crystalline silica. The SEP incorporated most industries where the likelihood of silica exposure exists, including SIC 3731 (Shipbuilding and repair).
According to the SEP, the exposure limit for the maritime industry in 29 CFR Parts 1926 and 1915 is measured using an impinger sampling method, expressed in terms of millions of particles (of dust) per cubic foot (MPPCF). The impinger method of counting dust particles is obsolete, and comparative sampling has established that the formula of 250/[(% quartz) + 5] which sets the mppcf exposure limit described in the maritime and construction standards is equivalent to the general industry PEL of: 10 mg/m(3) / (% Quartz) + 2.
OSHA maintains a Safety and Health Topics page on crystalline silica located at: http://www.osha.gov/SLTC/silicacrystalline.
What’s New
In August, 2003, OSHA proposed a comprehensive regulation to measure crystalline silica in the workplace. OSHA is currently working to develop a standard that revises the current Permissible Exposure Limit (PEL). The Agency indicates that they will analyze the data from the SBREFA process to develop a final decision for the rule.
In December 2004, the Maritime Advisory Committee on Occupational Safety and Health (MACOSH) requested OSHA develop guidance documents on the regulation. OSHA indicates that they are currently working on the documents.
A peer review of the risk assessment is scheduled to be completed by spring 2005. No timetable has been given on OSHA’s final decision about whether to move forward with the rulemaking.
Winter 2005/2006
OSHA indicates that they plan to complete a peer review of the health effects and risk assessment by April 2006.