Date of Award

3-2020

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Systems Engineering and Management

First Advisor

Jeremy M. Slagley, PhD

Abstract

Hexavalent chromium is a corrosion inhibitor found in the primer of most aircraft platforms across the Department of Defense (DoD), from fighter jets to transports. It is also known to cause cancer in humans. Currently, the Occupational Safety and Health Administration (OSHA) legal exposure limit is 5 μg/m3 for workers exposed to hexavalent chromium. A non-regulatory scientific body has recently recommended lowering this exposure level over a factor of ten and sampling with a different sampler that collects particles with the same efficiency as the nose during inhalation. This inhalable sampler collects more particles than the one currently used to comply with OSHA law. An early estimate of the cost of adopting this non-regulatory exposure standard is $900M over five years across the DoD, due in no small part to the likelihood that workers would need new, more restrictive personal protective equipment. Before adopting this new standard, two open points exist: based on DoD processes, is the inhalable sampler necessary and what impact to the sampler efficiency occurs if the flow rate is increased. To answer the first question, real world abrasive blasting processes were sampled and analyzed for particle size distribution. For the second aim, the mass concentrations of samplers operating at their design 2 L/min flow rate were compared to the mass concentrations reported by samplers operating at 6 L/min. From the abrasive blasting processes sample analysis, it was determined use of the inhalable sampler is justified. A 30% positive bias was found when comparing the higher flow rate to the lower flow rate mass concentrations. If the DoD adopts the new recommendation, it is likely over-reporting of hexavalent chromium concentrations in the workplace will occur.

AFIT Designator

AFIT-ENV-MS-20-M-242/243

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