By Virginia Baldwin Gilbert
Of The Post-Dispatch

Copyright 2000, St. Louis Post-Dispatch

June 7, 2000

Investigators have discovered that at least 15 workers at Mallinckrodt Inc.'s nuclear medical products plant in Maryland Heights were exposed to unacceptably high levels of radiation during the past five years.

The investigation has raised questions not only about how Mallinckrodt workers have been handling radioactive materials, but how they have been monitored for exposure.

Moreover, the findings could have implications for worker safety at hospitals and nuclear pharmacies across the country.

"We have talked informally to our competitors and some of our customers, letting them know what we found," said Roy Brown, director of regulatory compliance for Mallinckrodt.

Once the investigation is completed, Brown said, the company plans to send a letter to customers and competitors with more detail.

An estimated 14 million nuclear medical procedures are performed in the United States each year. They are used to diagnose conditions in the heart, lungs and other internal organs as well as to diagnose and treat cancer and other diseases.

The Nuclear Regulatory Commission announced last month that it was investigating procedures at the plant, located in two industrial buildings at 2703 Wagner Place and 11480 Warnen Road, after Mallinckrodt executives notified the agency of a worker's high radiation exposure.

The worker's error had exposed his left index finger and thumb to 2,000 rems of radiation - 40 times the maximum exposure limit for fingers for an entire year.

"It's one of the highest occupational radiation exposures I've heard of," said James Cameron, the commission's senior investigator for the region. Cameron has been with the NRC for 12 years.

Further investigation has turned up 33 other instances of overexposure to Mallinckrodt employees at the plant since 1995. The reason: improper procedures that exposed workers' fingers or thumbs to high radiation.

The NRC and state public-health investigators will hold a public meeting June 23 to release their report. This will mark the second time in three years that the commission has found serious enough safety problems at the company to warrant a public meeting.

The NRC will determine fines in a second phase that begins after the public meeting.

Mallinckrodt's Maryland Heights production facility - which consists of two buildings around the corner from each other - is one of the largest manufacturing plants of diagnostic and therapeutic radiopharmaceuticals in the United States.

It is the largest materials licensee regulated by the Nuclear Regulatory Commission, which also regulates nuclear power plants as well as hospitals and nuclear medicine clinics that handle radioactive material. The Maryland Heights plant and a small research lab in Hazelwood are the corporation's only facilities in the region where radioactive mat erial is handled.

Nearly 300 people work in the two buildings; about 100 of them are radiation workers. Those workers exposed to higher than maximum allowable levels last year have been transferred to areas away from even small amounts of radiation, NRC officials said.

The NRC and Mallinckrodt would not disclose the workers' identities.

According to preliminary documents from the NRC and Mallinckrodt, the cases discovered thus far involve employees handling radioactive material without proper shielding. Further, some of the exposures were overlooked for years because they were not detected by monitoring devices.

The most recent incident that prompted the investigation involved a worker using a "glove box" - a steel box with lead glass windows to shield a worker's body from radiation.

Only the hands go into the box, and those are covered with gloves. Gloves prevent contamination, such as picking up radioactive dust and carrying it home. But they do not protect from radiation, which goes through the gloves.

On March 31, a worker picked up a piece of radioactive material (molydenum-99m) with gloves instead of forceps. The ring monitoring badge he wore on his right hand registered a higher than expected exposure.

While investigating the elevated monitor reading, plant officials discovered potentially much higher exposure on the left hand, which did not have a monitor. They notified the NRC.

After re-creating the worker's actions, NRC officials estimated the worker's exposure at 1,300 to 2,000 rems for about 50 seconds in a 30-minute period. The total maximum allowable exposure to a worker's fingers for an entire year is 50 rems.

The second, and most pervasive exposure problem at Mallinckrodt occurred when workers hand-labeled vials of radioactive liquid destined to be injected into patients for diagnostic procedures. Some of the workers used their thumb - on their unmonitored hand - to hold the vial while it was unshielded.

Monitors worn as rings were too far away to pick up the much higher amount of radiation to which the workers' fingertips were exposed through their gloves.

"No one recognized the significance of the surface dose rates on the containers," Cameron said. "When you get very close to the surface of an unshielded container, the dose rates go up high."

Mallinckrodt asked a supplier to develop a fingertip monitoring badge, which it has been using for about a week, Brown said. Mallinckrodt will share data from the experimental monitor with the NRC and the industry, he said.

The third problem investigators found occurred in a sterility lab, where a sample number of vials is set aside for quality-control testing. The deviation from procedure found in this lab has the most implications for medical staff elsewhere who fill syringes with radioactive liquid, using shields for both the vial and the syringe.

Some Mallinckrodt workers were turning the vial upside-down and holding the vial with their thumb while they withdrew liquid into the syringe. That caused the vial to come out of the shield slightly and exposed their thumbs to radiation that gloves didn't block and ring monitors couldn't measure.

Thus far, the joint Mallinckrodt-NRC investigation has found no incidents as severe as the 2,000-rem exposure that occurred in March. But they have found employee exposures ranging from 53 rems a year, just three over the maximum allowed, to 591 rems a year, more than 11 times the limit.

Two workers were overexposed in each of four years. Six workers were overexposed in each of three years, one in each of two years and five for one year.

The radiation was both gamma and beta rays. Beta penetrates the upper layers of the skin only; gamma radiation goes deep into internal organs. The worker whose exposure started the investigation suffered beta radiation penetration of his skin. Mallinckrodt and NRC investigators agree: Had the worker been zapped by 2,000 rems of beta radiation over his whole body, he'd be dead.

But like more conventional serious burns, if a dose like that is just on the fingers, it might blister - but not kill.

A doctor called by Mallinckrodt examined the worker and said he suffered little beyond initial redness.

Judging from the dose alone, various health officials said the worker may have pain for several months and perhaps permanent scarring. But without examining the worker, whom officials will not identify, few medical professionals would comment on possible long-term effects.

The exposure limit for workers is intentionally set low because they could be exposed to radiation more often, said Brown, the Mallinckrodt executive.

Perhaps the best way to distinguish between a dose acceptable for workers and one for patients is by using the example of dental X-rays.

A patient sitting in the dentist's chair has the X-ray machine pointed at his head, while the technician walks around the corner to reduce her exposure. The patient gets a bigger dose, but usually just once or twice a year. The technician does many X-rays a day and must take care not to accumulate exposures.

"We have regulations (such as the annual exposure limits) for a reason," said Mark Griffon a health physicist and a consultant for the Paper, Allied-Industrial, Chemical and Energy Workers International Union, based in Nashville, Tenn.

"When you see a problem persist over time like that, it makes you wonder about the effectiveness of control," Griffon said.

The NRC fined Mallinckrodt $27,000 in 1997 when a worker's thumb was exposed to radiation through a faulty glove. That incident also included contamination - the worker carried radioactive material out of the control area, into his car and into his home, which had to be decontaminated.

As a result of the contamination in 1997, Mallinckrodt changed some procedures and installed more monitoring equipment. And it was put on two years of "escalated enforcement," that is, more scrutiny and inspections.