por Diana Bradley
, Staff Writer | November 13, 2012
From the October 2012 issue of HealthCare Business News magazine
Companies that still utilize lead in shielding must have safety precautions in place. If not handled carefully or contained properly within wall structures, it can be an environmental hazard. This is especially true when being stored outdoors in an unprotected space where the materials are exposed to the elements and could potentially leach into the soils and ground water, according to David Farrell, CEO and president of Veritas Medical Solutions, a company that specializes in radiation shielding in medical and industrial settings.
Proper training is the primary way to protect workers handling lead materials. Unsafe handling – for example, not wearing gloves —can lead workmen to ingest the toxin, picking up lead oxides.
“If [workers] then handle food prior to washing their hands, or in other ways allow the oxide contaminates to enter the body, elevated levels of lead can be found in the individuals,” Farrell explains. “Another common example includes workers momentarily placing their cigarettes on a piece of lead, picking them up, and inhaling.”
In many cases, when lead-based medical shielding is installed in a larger hospital, a construction manager may run the project, and they will have their own health and safety program. But to ease any worries about lead, companies like NELCO have implemented their own strict program.
“If we are cutting lead in the field, a cutting booth contains the lead, and an air filtration system is on site so no one in the area can breathe in toxins,” says NELCO’s Lewis. “The individual working on that lead is also required to wear an appropriate respirator so their exposure is limited.”
From a physics perspective, lead shielding also has problems when used in high-energy X-ray shielding, notes Steven Johnston, director of physics at Veritas. In those cases, the high-energy X-rays or photons can cause the lead to become a source of neutron radiation, which further needs to be appropriately shielded by something else. In fact, most of the neutrons produced in the treatment room are produced in the head of the accelerator where the photons are interacting with the lead casing and the other high Z materials surrounding the linac head.
“Lead is a terrible shielding material for attenuating neutrons,” says Farrell. “While photons are effectively attenuated with very dense materials such as lead or steel, neutrons [from medical linear accelerators] are generally moderated [slowed] with hydrogenous materials, and captured with the introduction of materials with a high neutron cross section such as boron, lithium or cadmium.”