Exposure to lead has been reported to produce a number of acute and chronic health effects, including damage to the central nervous system, cardiovascular system and immune system, even at very low levels and through multiple exposure routes. Warfighters also can be exposed during air and ground training at installations. This becomes a concern not only for the military, but for the community in and around the installations as well. Lead can enter groundwater when emitted from fired rockets and missiles settles to the soil. Lead may be released in wastewater from production facilities from equipment wash-down, clean-up or energetic production, if not properly treated. Workers at rocket and missile propellant manufacturing or load-assemble-pack (LAP) facilities may be exposed to lead through inhalation or accidental ingestion. Fines and training restrictions may be levied on installations if levels of lead in ambient air exceed the National Ambient Air Quality Standard (NAAQS) limits or if operational exposures exceed the occupational exposure level (OEL) for lead.
Lead beta-resorcylate (LBR), lead oxide and various lead-copper complexes can be found in the range of one to ten percent by weight in many extruded double base and MS propellants as burn rate modifiers. Nitramines (e.g., RDX and HMX) are used in MS propellants to increase performance. Extruded propellants are typically used for aviation applications (e.g., Hydra or Zuni) and castable MS propellants are typically used for high performance, close-range rockets and missiles, such as the Tube-launched, Optically tracked, Wire-guided missile (TOW) and the Javelin missile, because they leave little to no visible signature. The TOW and Javelin rockets are fired in close proximity to the warfighters (i.e., shoulder or vehicle launched) and present a unique exposure risk. Warfighters need to train with rocket and missile propellants that contain lead to mimic realistic operational environments. This introduces an inhalation risk in ambient air for warfighters and the population around training installations.
Current stabilizers incorporate aromatic amines or aromatic urea derivatives such as DPA, 2- NDPA, Akardite II and ethyl centralite, pNMA, and pNEA in propellant formulations. Research has been performed internationally for newer and better stabilizers. Epoxidized oils, a class of stabilizers with plasticizer properties (no nitrosamine formation), various substituted phenols, citrates, etc. have all been studied. While these stabilizers are effective, it has been found that the effectiveness is short-lived and the shelf-life of formulations often comes into question. There is the potential for EU REACH Authorization or Restriction of N-nitrosamine forming materials.