Question - What are so-called HMTA’s?
Answer - HMTAs are “heavy metal tungsten alloys”. The cited article notes that HMTAs are “a category of tungsten-based substances containing 90 to 98% by weight tungsten (W) in combination with nickel (Ni), iron (Fe), copper, and/or cobalt (Co). Due to their impressive ballistic properties (high density, strength, and stiffness) and a belief that tungsten and its alloys were relatively inert (based on studies investigating pure tungsten or tungsten carbide), HMTAs have been the leading candidates to replace depleted uranium and lead in military munitions.” (Roedel EQ et al. Pulmonary toxicity after exposure to military-relevant heavy metal tungsten alloy particles. 2012 Tox Applied Pharm 259: 74-86)