Hinz and her colleagues enlisted the help of the New Zealand customs authorities for their study. The workers used probes inserted through the rubber seals on the container doors to take gas samples from 490 sealed containers. Hinz also collected air samples himself from dozens of other containers and tracked how concentrations of compounds changed in real time as the containers were opened and the air inside was allowed to mix with fresh outside air.
The investigation revealed many evil substances. In 3.5 percent of the sealed containers, customs officials found methyl bromide, the compound that overwhelmed the Rotterdam dockers. They found formaldehyde in 81 percent of the containers and ethylene oxide in 4.7 percent, to name just a few of the chemicals. Exposure to ethylene oxide can cause a variety of uncomfortable symptoms, including nausea, vomiting, and diarrhea. Formaldehyde, a preservative, is carcinogenic and can cause internal irritation if inhaled, among other symptoms.
In their study, Hinz and her colleagues found that some of the concentrations measured appeared high enough to trigger an acute response that triggers immediate symptoms. However, Hinz says that in practice it is unusual for a worker to come into direct contact with toxic gases at such high concentrations. Instead, there is a more common but still notable risk with repeated exposure to low levels. For example, chronic exposure to these chemicals can increase the risk of cancer or cause psychiatric problems. And yet there is relatively little research on the risks of chemicals in shipping containers.
“I definitely think it needs attention, a lot more attention than it’s got,” says Hinz.
Gunnar Johanson, a toxicologist at the Karolinska Institute in Sweden who served as a peer reviewer for Hinz’s study, agrees with her assessment.
“We don’t know exactly how big the risk is, but it’s an unnecessary risk because it’s easy to address,” he says. All it needs is better ventilation.
A few years ago, Johanson and his colleagues were called in to investigate a suspicious container in Sweden. It was loaded with rice, but inside the container was also a strange blue bag filled with white powder. When Johanson analyzed the air, he found phosphine, a fumigant, in a concentration high enough to be lethal.
To protect dockers, Johanson and his colleagues designed a device that hooks up to an exhaust fan and attaches to the existing — but tiny — vents on the sides of most containers. Experiments indicate that after turning on the device, the concentration of harmful gases drops within minutes.
“We can reduce about 90 percent of the volatile contaminants in one hour,” says Johanson. The device is currently being used by the Swedish Customs Agency, he adds.
The shipping and logistics industry should be more aware of the dangers associated with exposure to noxious gases in shipping containers, says Martin Cobbald, managing director of Dealey Environmental, a UK environmental services company.
His company is frequently hired to open and aerate containers, but, he adds, “we don’t do it nearly as often and for the range of people we should be doing.”