Stopping silicosis at its source

Matthew Navea, Preferred Sands, USA, presents a treated proppant solution to help reduce onsite exposure to crystalline silica dust.

Crystalline silica is found in large quantities in the Earth’s crust in most natural sands, soils and minerals such as granite and quartz – the most common of all forms of crystalline silica. However, it is also found in manmade substances including concrete, brick, block and mortar. In its natural state, crystalline silica is relatively harmless, however when it becomes respirable – or broken down into extremely fine particles (approximately 100 times smaller than beach sand) respirable crystalline silica can be hazardous to those with prolonged occupational exposure.


Designed in collaboration with The Dow Chemical Company, DustPRO is the industry’s first treated proppant solution designed to reduce airborne silica dust particles during all sand transfer points.

According to the Occupational Safety & Health Administration (OSHA), workers in a variety of industries such as construction, masonry, foundry, manufacturing, sand mining, and oil and gas may be at risk of exposure. OSHA reports that nearly 2 million workers in the US are at risk of silica exposure, and more than 100 000 of those workers are in high-risk jobs.

In the oil and gas industry specifically, employees working with frac sand can be exposed to crystalline silica throughout the frac sand supply chain, from the sand mine to the sand terminals, all the way to the well site, and throughout the well completion process. The processes of moving and refilling silica sand through sand movers, along transfer belts and into blenders, releases dust from frac sand into the air. As frac sand contains up to 99% quartz, workers in the oil and gas industry need to be particularly mindful of their exposure to silica dust.

Without proper protection, consistent workplace exposure to dust particles can lead to the inhalation of crystalline silica, and eventually the development of silicosis, an irreversible but preventable disease most closely associated with occupational overexposure to silica dust. Silicosis occurs when workers breathe in crystalline silica, which causes inflammation and forms scar tissue in the lungs, reducing the ability to inhale oxygen. While there are three types of silicosis – chronic/classic silicosis, accelerated silicosis and acute silicosis – symptoms typically include varying degrees of shortness of breath, fatigue, chest pain or respiratory failure.

Regulatory environment

Given the known hazards of silicosis, OSHA has increased enforcement within the industry and has issued citations for alleged non-compliance. Further, the National Institute of Occupational Safety and Health (NIOSH), a division of the Center for Disease Control, has prioritised its research to investigate risks and hazards in the in the oil and gas industry, including during well completions and hydraulic fracturing operations.


Preferred Sands’ Arizona mine is located 150 miles west of Albuquerque, New Mexico and offers and advanced rail load-out system, which quadruples a typical load-out pace.

It is OSHA’s responsibility to enforce regulations that are intended to protect the health and safety of employees in industries working with silica materials. The current regulation, which dictates Permissible Exposure Limits (PELs) for crystalline silica, is based on data that is over 40 years old. The current limits are not consistent throughout industries and may not be protective enough for workers. In September 2013, OSHA issued a new proposed rule that would reduce the PEL by 50%. OSHA has indicated that promulgating this rule is one of their highest priorities and they are targeting a new rule by mid-2015.

Further, in 2010, NIOSH commissioned a ‘Field Effort to Assess Chemical Exposure Risks to Gas and Oil Workers,’ to research chemical exposure levels in the industry. With a focus on silica exposure, NIOSH visited 11 hydraulic fracturing sites across five states to collect 116 air samples in an attempt to evaluate and understand industry worker exposure to respirable crystalline silica. NIOSH found that 47% of the samples they collected exceeded OSHA’s current PELs and 79% of the samples exceeded NIOSH’s Recommended Exposure Limits (RELs). Even more surprising, 31% of all the samples NIOSH collected were 10 or more times the REL, with one sample more than 100 times the REL.

NIOSH was confident in its conclusion that workers at the well sites they tested were, in fact, exposed to inhalation health hazards, especially those working at or downwind of sand movers and blenders. NIOSH concluded that even when wearing half-mask air-purifying respirators, employees at the sites they tested would still be at risk of inhalation of crystalline silica.

The challenge

The oil and gas industry is addressing silica dust hazards by utilising engineering controls, personal protective equipment (PPE), and employee training – although according to the Center for Disease Control, personal respiratory protection on its own may not adequately protect workers from the dangers of silica dust. Likewise, engineering controls can be costly and can present additional worksite hazards, such as tripping hazards, and have not yet consistently been proven to reduce silica dust at the highest exposure areas, such as the blender and the hopper. It would seem that the simplest and most effective solution for protecting workers would be to eliminate the hazard from the source by using proppants with preventative dust-control technology.

The US is rapidly becoming a leading producer of natural gas. A 2013 study by the US Chamber of Commerce’s 21st Century Energy Institute found that nearly 1.7 million jobs had already been created from hydraulic fracturing. With so many workers exposed to silica dust, a permanent solution to the problem is needed.

The solution

In response to OSHA’s proposed rule to lower PELs and the dangers of respirable silica dust, Pennsylvania-based Preferred Sands collaborated with The Dow Chemical Company to develop a solution to reduce exposure to respirable crystalline silica in the oil and gas industry. DustPRO™ is the industry’s first silica dust control solution that uses preventative technology to tackle the problem at the source, and throughout the product lifecycle. The cost-effective, treated proppant solution was designed to reduce airborne silica dust particles during all sand transfer points, including pneumatic transfer.

DustPRO was designed to provide an alternative solution to traditional, less effective silica dust control methods. Proppant treated with DustPRO meets silica exposure limits and minimises loss of conductivity during pneumatic transfer. It helps to minimise respirable crystalline silica and fugitive dust during all sand transfer points.


Preferred Sands’ Genoa, Nebraska mine, located two hours west of Omaha, can produce any filtration, frac or other silica sand grade. The DustPRO proppant is available at all of the company’s mines across North America.

In the last year and a half, Preferred Sands has taken DustPRO from bench tests and research all the way to real world product application. DustPRO is treated sand using Preferred DC chemistry – a novel, inert polymer that is sprayed on proppant sand prior to transporting it to the well site. It uses an environmentally conscious, non-hazardous base chemistry that is compatible with frac fluids, and does not alter proppant substrate characteristics.

The treated proppant has many performance advantages over traditional mechanical silica dust control systems. In addition to eliminating the variable costs associated with mechanical dust control systems, it eliminates the need to haul bulky equipment to and from the well site and removes dozens of unsafe tripping hazards. Without additional mechanical equipment onsite, DustPRO allows for convenient, safe access to all critical equipment. Operators can schedule their job without the inconvenience of waiting for a vacuum. Finally, operations can remain uncovered, giving workers unlimited access to blender and belt areas onsite.

Real world results

Since its introduction in 2014, approximately 200 000 t of DustPRO proppant have been pumped by operators and well service companies throughout North America. The company has tested 113 personal samples from seven different hydraulic fracturing sites using the treated proppant, and found that 94% of samples taken met the current PEL and 98% of the last 53 personal samples taken met the current PEL. The geometric mean from all personal samples tested in the NIOSH study was 122 ug/mg3 compared to just 13 ug/mg3 with DustPRO samples.

Conclusion

DustPRO treated sand is a sound solution to the hazards of respirable crystalline silica that can help protect employees throughout the entire supply chain. As OSHA is on its way to implementing new PELs, the treated proppant provides a solution for companies looking to meet these exposure reductions and to more effectively manage risk. Minimising silica exposure will make for a safer and healthier work environment throughout the entire supply chain. DustPRO Application Systems are available for installation at any terminal or sand plant, and the treated proppant is available in basins across North America.


Edited for web by Cecilia Rehn

Published on 01/06/2015


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