Although there is the potential for tollbooth workers
at the Baltimore Harbor Tunnel to be exposed to high levels
of cancer-causing air toxins emitted from the thousands of
vehicles that pass under their nose, researchers from the
Johns Hopkins Bloomberg
School of Public Health found that the tollbooth
ventilation system was effective in keeping air toxins out
of the tollbooth and away from the workers. The researchers
measured levels of volatile organic compounds and
particle-bound polycyclic aromatic hydrocarbons inside and
outside the tollbooth and found relatively high levels
outdoors and relatively low levels indoors. The study is
published in the May 1 issue of Environmental Science &
Technology.
"Tollbooth facilities represent a potential worst-case
scenario for occupational exposure to mobile source-related
air pollution, as these employees spend a majority of their
shift within an arm's length of thousands of vehicles
emitting a wide range of toxic pollutants. Yet, little has
been done to evaluate worker exposure and the protection
afforded by the indoor environment," says Amir Sapkota,
lead author of the study and a postdoctoral fellow in the
Bloomberg School's
Department of Environmental Health Sciences.
In June 2001, the researchers measured the
concentration of air toxins at a tollbooth at the Baltimore
Harbor Tunnel. They also examined traffic volume in
addition to curbside pollutant concentrations and the
concentrations inside the tollbooth. They compared air
toxin levels during the three shifts worked by tollbooth
employees — 6 a.m. to 2 p.m., 2 to 10 p.m. and 10
p.m. to 6 a.m.
The researchers found that levels of 1,3-butadiene and
benzene peaked with the morning and afternoon rush-hour
traffic. In contrast, they found that the levels inside the
tollbooth were relatively low and constant. They found,
however, that some of the chlorinated VOCs used in dry
cleaning, air deodorizers and cleaning products were
present in higher concentrations inside the tollbooth than
outdoors.
"It is wonderful to discover that the tollbooth
environment is doing what it is designed to do —
protect workers from the hazardous environment in which
they would otherwise be immersed. It is important to note,
however, that not all tollbooth workers in this country,
and especially in developing countries, are provided with
this protection," says Timothy J. Buckley, senior author of
the study and an associate professor in the Bloomberg
School's Department of Environmental Health Sciences.
The study was supported by the Johns Hopkins Education
and Research Center Pilot Project Research Training Fund,
National Institute of Environmental Health Sciences and
U.S. Environmental Protection Agency. Co-authors were
Sapkota, D'Ann Williams and Buckley.
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