Major sources of lead (7439921) exposure on firing ranges included the lead bullets from which airborne particles are released during firing and primers containing lead-styphnate (15245440). Measurements taken while shooters were firing lead bullets gave a mean lead exposure level of 110 micrograms per cubic meter (microg/m3), with 42 of the 47 exposures exceeding the OSHA time weighted limit of 50microg/m3. Control measures suggested include limiting the amount of time a person may spend in the range, the design and installation of correct ventilation systems, substituting a less toxic material for lead in bullets, such as zinc bullets, or using lead bullets completely encased in a nylon cladding or copper jacket. Use of nylon clad, zinc, or copper jacketed bullets resulted in lead airborne exposures of 41, 22, and 10microg/m3, respectively. Three of 43 samples exceeded the OSHA standard. Such redesigned bullets are said to be more expensive to use and perhaps less safe as there is evidence of zinc bullets bouncing back from bullet traps in some ranges.