Introduction Several studies have shown that there may be concerns about exposure to dangerous substances for workers unloading sea freight containers, although safe procedures for unloading containers are usually in place to protect workers from being exposed to chemical agents. Since preliminary research has shown that less than 1% of unloaded containers are deliberately fumigated with known chemicals, it was necessary to find the root cause.

Methods Many production sites for sea freight containers are located in Asia. The first task in this study was the identification of production factories and their locations. The second task was to identify the full production cycle of the goods that are manufactured and shipped via freight containers. The third task was to gather exposure data during the production cycle and identify off-gassing post production, when loading containers for travel to Europe.

Results All tasks took about six years to complete, and identified a way to predict container air concentration on the unloading site (downstream) based on information at the production site (upstream). This algorithm is based upon site concentration measurements, lab experiments of the raw materials and unloading concentration measurements. These parameters can be applied for the full production cycle and are independent of variations in terms of production site outputs.

Discussion Safe container unloading procedures are now based on an upstream limit value, meaning that if the concentration at a production site is higher than the established limit value, the goods cannot be shipped by container, or the container is required to be ventilated at the unloading site. This case study series is a good example of how occupational hygiene principles can be used in root cause analysis and problem solving, in terms of exposures to chemical agents.