11/14/2008

Health Hazard Evaluation Report on Baggage Screeners Now Available

Between November 2002 and March 2003, the US-American National Institute for
Occupational Safety and Health (NIOSH) received three health hazard evaluation
(HHE) requests from Transportation Security Administration (TSA) employees at
the Cincinnati, Honolulu, and Baltimore airports. The employees expressed
concerns about a variety of potential exposures including diesel exhaust, dirt,
dust, noise, and hazardous items found in baggage. In addition, a concern
common to all three requests was exposure to x-rays from carry-on baggage and
checked baggage screening machines.

During a basic characterization phase, the researchers observed poor work
practices such as employees reaching into the Explosive Detection System (EDS)
machines to clear bag jams and employees covering up the emergency stop
buttons. The researchers inspected and measured radiation exposure rates for
281 EDS machines. The researchers observed that EDS machines at several
airports exhibited a flaw that could be a source of unnecessary radiation
exposure to TSA baggage screeners operating these machines. Radiation could
leak out of the main gantry housing the computer-aided tomography (CAT) scanner
through gaps between the entrance and exit baggage conveyors that appeared
because the conveyor belt tunnels on most standalone units were not bolted to
the gantry. Workers who frequently have to push odd-sized baggage up the
entrance conveyor of the standalone machines are potentially exposed to the
radiation present in the gap between the gantry and conveyor belt tunnel. The
researchers recommended taking six machines offline because the potential
exposures to workers from these machines were equal to or greater than 500
microRoentgen per hour (R/hour), the Food and Drug Administrations Performance
Standard for cabinet x-ray systems.

Occupational radiation measurements over a 6-month period from 854 TSA
employees included 4024 results from dosimeters worn on the chest (as an
estimate of exposure received by the whole body) and 3944 results from
dosimeters worn on the wrist. Approximately 89% of the occupational whole body
exposures and 88% of the occupational exposures to the wrist were below 1
millirem (mrem).

None of the participants doses in this evaluation exceeded the Occupational
Safety and Health Administration (OSHA) permissible exposure limit of 1250 mrem
per calendar quarter for individuals present in a restricted area (an area
where access is controlled by the employer for purposes of protecting
individuals from exposure to radiation or radioactive materials). Furthermore,
no doses exceeded 25% of the OSHA quarterly limit which would require employee
monitoring.

The median estimated 12-month cumulative occupational whole body dose during
the period of observation was zero at four of six airports. The highest median
estimated 12-month cumulative occupational doses (whole body and wrist)
occurred at LAX (14.7 and 15.5 mrem); the other airport with a non-zero median
estimated 12-month cumulative dose was BOS (0.4 mrem each for whole body and
wrist). Doses for only two out of 854 individuals exceeded the 500 mrem/year
estimated cumulative occupational dose, which is the monitoring threshold of
the Nuclear Regulatory Commission, and only 13 exceeded an estimated cumulative
whole body or wrist dose of 100 mrem/year, which is the monitoring threshold of
the Department of Energy. However, because the sample of airports may not be
representative, and the study participants were volunteers, these results may
not generalize to the entire TSA workforce.

Given the strengths and weaknesses of this study, the need for a routine
radiation dosimetry program for TSA screeners can neither be justified nor
refuted at this time. Approximately 90% of the doses that screeners received
were below 1 mrem, but some doses were at levels that warrant further action.
Therefore, additional monthly or quarterly dosimetry targeted at specific
airports for at least a year may be useful to evaluate the high doses reported
in this evaluation. The number of airports and the specific airports for this
targeted monitoring are left to the discretion of the TSA. Selection criteria
could include airport size, machine type, and orientation of machines (in-line
versus standalone). It is recommended that the dosimetry program be managed by
a health or medical physicist. To address weaknesses of this study, the
researchers also recommend that TSA make participation in the dosimetry program
mandatory.

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AplusA-online.de - Source: National Institute for Occupational Safety and Health (NIOSH)