Lessons must be learned from the presented studies, especially since the fumigants are often colourless and odourless, and dangerous even at low concentrations. Since no reliable indication of the absence of toxic gases in closed import containers exist, each container has to be regarded as potentially hazardous. Therefore, such import containers should be entered only if hazardous airborne exposures are excluded, i.e. only after appropriate measurement of air samples or after appropriate aeration, where forced extraction ventilation was shown to be most effective (which necessitates some redesign of containers, e.g. by a hole in the back for applying the extraction pipe). Forced ventilation rapidly reduces toxic concentrations in the container atmosphere; however off gassing within the following hours or days from the goods, which may have absorbed toxic substances, have to be taken into consideration. Thus ventilation should be on-going in initially contaminated containers during stripping due to such off-gassing from goods.
Measuring gases has to be extended from fumigation to include volatile toxic industrial chemicals arising from the production processes. However, it is important to measure not only directly behind the container door (where concentrations may be low due to leakages), but rather to assess the levels deep inside at the bottom, middle, and top of the container. A new flat lancet facilitates this procedure.
It is difficult to measure all possible toxic substances in the container atmosphere; especially formaldehyde and phosphine are not adequately analysed by many devices. So far, no ideal portable non-expensive device is on the market.
More effectively, alternatives for fumigation (such as heat treatment, use of oxygen-depleted air) should be promoted and introduced and toxic industrial chemicals replaced by harmless substances.
The many still existing knowledge gaps, e.g. potentially structural modifications of food by fumigants and health risks for consumers, have to be taken into consideration by future research projects.
The previously mentioned severe and broad health hazards demonstrate an urgent need of common databases, which comprise all health relevant data of each container from the production site, along the transport line, till the end-user. Due to the globalized economy this has to done on national as well as supra-national scales, providing authorities as well as recipients/audience full access to them.
The first comprehensive preventive measures system – which can be considered to be a “State of the art model” – has been implemented in the harbor of Hamburg. The existing risk assessment system is a part of the daily routine to protect the controlling bodies from incidents associated with all kinds of terrorist or criminal threats in the container air and freight. The concept was developed during 2006 till 2010 on the basis of on-site experiences in cooperation with the Institute of Occupational and Maritime Medicine (ZfAM) and the State labor inspection office (Health & Safety Executive Hamburg). It contains a catalog of the minimal requirements for inspections, analyses and an evaluation system. If a potentially toxic gas group (comprising structurally related compounds) is identified by a screening measuring device, additional mandatory analytical toxicological measurements in a specialized analytical laboratory are required .
Applied preventive measures
Appropriate preventive measures for safe handling and stripping of freight containers rely on several factors such as correct labeling, knowledge and awareness among managers and workers, guidelines for safe procedures, measurements, ventilation and personal protective devices.
The first step for taking preventive action is based on the identification of containers with hazardous content. Although labeling is mandatory with warning signs accompanied with transportation documents specifying the fumigation procedures for fumigated containers, several articles and reports between the years 2002 to 2011 have described violations of these regulations. In a study from Rotterdam  only three of 303 randomly selected containers had some kind of warning sticker, although methyl bromide or phosphine were detected in 23% of the containers. In Hamburg in 2006 only 3.6% of the 2113 examined containers carried any form of fumigation hazard warning, but none of these corresponded to those required by the IMDG Code and they mostly consisted of fragments of old, presumably outdated, warning . Residual fumigants were detected in a total of 541 (26%) the containers. None of the containers had valid Dangerous Goods Transport Documentation. Safe Work in Australia found that none of 76 surveyed containers displayed any external notice that they had been fumigated, although methyl bromide was identified in 68% of them . In Gothenburg none of the 101 randomly selected containers were labeled  http://ki.se/sites/default/files/2011-1_0.pdf They argued that lack in compliance with the labeling regulations raises serious concerns as warning sign is the first, and perhaps only, message the worker receives that suggests the container atmosphere to be hazardous. A Danish study concluded that in practice, the measures applied to prevent harmful chemical exposures released from transport containers are primarily based on the attempt to identify the containers that carry occupational health risks . Discussions with managers and workers in an Australian study suggested that no systematic assessment of containers took place prior to entry by workers ).
Knowledge and awareness
The employers are obliged to inform the workers on all hazards in their work environment and provide adequate training in health and safety at work. The practice of handling containers was recently investigated in a qualitative study in Denmark based on semi-structured interviews with nine key informants, including managers and health and safety representatives of organizations that handle containers ; (for details see chapter IV. Practice of handling transport containers in exporting and receiving countries. Pilot studies in China and Denmark). They concluded that there was limited knowledge among managers, workers and even among occupational health professions about the types of chemicals that can be released from containers.
In Australia informal discussions were held with five experienced managers and 15 workers . Also in this study the numbers of workers who completed the surveys was low, and the authors argued that the results should not be used to make generalizations for broader industry or occupational groups. However, about 70% of the workers had completed specific work health and safety training on unpacking shipping containers. None of them knew much about the risks of fumes in containers but 67% knew a little. The most significant reason for not taking safety precautions was lack of training (33%), followed by lack of awareness that the container atmosphere may contain chemical fumes (29%). Thus, although most workers had received work health and safety training there was still a large degree of uncertainty regarding the risks associated with fumigated containers and their ability to identify such containers.
Guidelines for safe procedures
In addition to the international and national regulations related to container handling there are also local safety instructions from organizations and from employers (e.g. [48-52]).
In the Danish study the interviewed managers were aware of the existence of relevant international and national regulations but were typically not able to specify them . The interviewees were more familiar with the local instructions but these were reported to give insufficient guidance for several practical challenges of preventing chemical exposures during work with containers.
At present there is no single portable instrument available to detect all types of relevant hazardous substances at sufficient sensitivity. However, different approaches, including direct-reading devices and air sampling for later analysis have been used to detect selections of fumigants and toxic gases in various harbors.
The commercial company EWS in Belgium dealing with fumigation suggested that for ad hoc situations handhold technology could be used. Examples of those technologies are :
Photo ionization detector (PID) for volatile organic compounds (VOC)
Infrared (spectra) only for sulfuryl difluoride
Sensors (CO, CO2, O2, PH3)
Colorimetrical gas detector or indicator tubes, mainly for methyl bromide + 1,2-dichloroethane, benzene, toluene, chloropicrin, styrene, xylene.
Further, measurements for oxygen depletion are recommended.
Onsite measurements/samples from unopened containers should preferably be taken at the middle or top of the container and not only at the bottom of the door where concentrations are lowest . The openings in the top corners of the containers and possible leaking rubber seals around the doors may explain the observation of uneven concentrations in the container. Recently a new flat lancet was developed to facilitate onsite measurements from unopened containers. The lancet was further connected to a direct-reading instrument with detectors for VOCs, formaldehyde, hydrogen cyanide, phosphine and carbon monoxide .
In Hamburg, measurements were performed onsite with a gas detector array instrument (GDA, Airsense) by sampling through the online probe inserted into the container. After the measurements with the hand held instrument, special 1 liter air bags were filled with the air of the containers. The air bags were transported to the laboratory for analysis with gas chromatography–mass spectrometry (GC-MS), which requires a well-equipped lab and a well-trained lab technician; in addition, it is time-consuming [5,19,52,53].
Svedberg & Johanson  described that on arrival to Sweden, the fumigated and labeled containers are normally handled as all other containers, except when the Swedish Food Agency has border control campaigns during which about 20 containers per year are controlled by measurements. They also reported that as far as they knew most of the central stores and end costumers in Sweden do not have systems to control and handle potentially fumigated/gassed containers, although good examples exist. One large storehouse had a Fourier Transform Infrared--instrument in the central unit. However, they claimed that it is not realistic to require every costumer handling containers, small-sized terminals in particular, to have expensive measurement instruments, but rather rely on sufficient ventilation before entry.
Based on interviews with nine key informants in the Danish study, equipment for monitoring of container air is available in some of the selected organizations only, and even when available, the measuring device can detect only methyl bromide but no other potentially harmful chemicals . In some of these organizations a suspicion is sufficient for applying specific preventive measures while others would require positive results of air measurements to take action.
The container should be efficiently ventilated before opening when high concentrations of harmful substances have been detected or when measurements have not been done.
Containers normally have small openings in the top corners to provide limited natural ventilation. Svedberg & Johanson  evaluated different ventilation methods by tracer gas, and reported that natural ventilation (open doors) and blowing ventilation (open doors, fan blowing air towards goods) had virtually no impact on gas levels in deep container air 12 m from the doors. In contrast, forced extraction ventilation (fan sucking air via a tube inserted all the way into the container and fresh air entering via the doors) resulted in rapid washout of the gas. They concluded that unfortunately the current container design makes safe and speedy sampling and ventilation prior to opening the doors technically difficult. Ventilation must preferably be ongoing during stripping, and a ventilated container that is closed for stripping the following day must be re-ventilated.
In the Australian study  the containers were often left to ventilate naturally. The also concluded that for those containers with known high levels of fumigants, natural ventilation may require supplementation with forced ventilation to reduce the concentrations of residual chemicals to acceptable levels for unloading. Industry representatives expressed concern that ventilation systems for extracting fumigants from containers were not effective because the levels of fumigants within containers simply rose again after termination of ventilation and close up of the containers. Thus, it may be useful to set a time limit (e.g. 2 hours) after which unloading should be stopped and the container would have to be ventilated again.
The workers that performed stripping of containers in the Swedish study expressed that the containers frequently carried unpleasant odors that from time-to-time prevented stripping. Such containers were left for natural ventilation before re-entry .
The interviewed personnel in the Danish study reported that the main preventive measure to reduce chemical exposure is natural ventilation; active ventilation is not used in practice . The conditions of aeration were not consistently applied; the reported ventilation times varied between 2 and 48 hours without any knowledge of whether this amount of time was sufficient or not.
Personal protective equipment
In published articles and reports the use of PPE during container stripping has only been briefly mentioned, and it has not been described which type of protective mask or other PPE that have been used. The types of required PPE differ from one toxicant to another and it is emphasized that the correct PPE should be used. In addition, rescue strategies should be available to individuals who need to enter unventilated containers with unknown hazards [47,31].
In the Australian study one-third reported use of PPE, but they did not specify which kind of PPE they used . Knol-de Vos  noted that staff wore personal PPE when opening containers in Rotterdam. Pedersen et al.  reported that although masks are usually provided to the workers in Denmark, they are mainly dust masks that do not prevent exposure to gaseous chemicals. The also described that the decision and choice of preventive measures to be used in practice are often left to the directly involved employees and the actions taken show considerable variation. When the workers in Sweden experienced unpleasant odors, the containers were left for natural ventilation, or, alternatively, the workers were instructed to wear respiratory equipment .
WorkSafe  summarizes that consistent with the risk assessment for containers with methyl bromide mixtures, PPE considerations could include:
Elbow length chemical gloves;
Full face mask equipped with:
○ multi-gas filters; or
○ an organic vapor cartridge filter, that is designed to cover methyl bromide and chloropicrin
○ mixed gas (filter type will depend upon the brand & type of full face mask that you purchase); or
Self-Contained Breathing Apparatus (SCBA).
It is important to ensure regular training and instruction about the procedures and the maintenance and use of PPE to ensure that staffs are competent in its use. Records of this training should be maintained.