More than 500 million ocean freight container units are shipped annually
between countries and continents. Residual levels of fumigants, as well as
naturally occurring off-gassing chemicals emanating from the goods, constitute
safety risks, which may affect uniformed workers upon entering the container.
The aim of this study was to assess workers' exposure during stripping of
containers and is the first study of its kind.
First, an experimental tracer gas method was investigated to determine its
usefulness to approximate real exposures from gaseous fumigants and off-gassing
volatile organic compounds (VOCs). Nitrous oxide was injected and left to
distribute in the closed containers. The distribution of the tracer gas and
initial (arrival) concentrations of off-gassing volatiles were measured prior
to opening the containers.
Second, personal exposure (breathing zone) and work zone air monitoring of both
tracer gas and VOCs were carried out during stripping. Adsorbent tubes, bag
samples, and direct-readings instruments (photoionization detector and Fourier
transform infrared spectrometry) were used. The distribution studies with
nitrous oxide, and the high correlation between the former and VOCs (r 2 ~ 0.8)
during stripping, showed that the tracer gas method may well be used to
approximate real exposures in containers. The average breathing zone and work
zone concentrations during stripping of naturally ventilated 40-foot containers
were 1-7% of the arrival concentrations; however, peaks up to 70% were seen
during opening. Even if average exposures during stripping are significantly
lower than arrival concentrations, they may still represent serious violations
of occupational exposure limits in high-risk containers.
The results from this and previous studies illustrate the need to establish
practices for the safe handling of ocean freight containers. Until
comprehensive recommendations are in place, personnel that need to enter such
containers should, in addition to appropriate personal protective equipment,
have access to equipment for measuring contaminants and for applying forced
ventilation when necessary.
AplusA-online.de - Source: The Annals of Occupational Hygiene