The US military pumps over 700 million rounds of ammunition, or some 2,000 tonnes of lead into the environment every year during training. The metal pollutes the water supply and poisons the wildlife. So the Texas Research Institute in Austin, Texas, has developed a lead substitute whose density is comparable to lead's. Powdered tungsten is mixed with stainless steel and bonded with an epoxy resin before being cast into bullets. Although tungsten is more expensive than lead, it is denser and non-toxic. Mixing tungsten with stainless steel reduces the cost.