Health risks in international container and bulk cargo transport due to volatile toxic compounds

Factors determining occurrence and severity of health effects

Additive or synergistic effects from co-exposure to the substances.

Health effects of individual fumigants

Sulfuryl difluoride (sulfuryl fluoride)

Sulfuryl difluoride is considered as a less toxic substitute for methyl bromide. However, it does have ozone-depleting as well as toxic effects including acute and chronic encephalopathy, disturbances in the olfactory function, and neuropathy with reduced nerve conduction velocity [12]. See Table 2 for limit values.

Formaldehyde

Acute intoxication is characterized by dizziness, nausea and vomiting, fatigue, feeling of drunkenness, disturbance in coordination and concentration followed by headache, malaise, hypersensitivity for noise and light, and upper airway symptoms like cough, shortness of breath, a hoarse voice and sometimes skin eruptions. Symptoms and complaints last for days or weeks [15].

More than 90% of inhaled formaldehyde is taken up in the upper airway system and leads to local irritation and neuro-cognitive effects. Severe exposure may cause additional complaints from the lower respiratory tract like shortness of breath, increased sputum production and coughing.

Formaldehyde may also impose severe long-term effects since it is carcinogenic to humans [16].

Chloropicrin (trichloro(nitro)methane, nitrochloroform)

This previously used fumigant may be added as an indicator to (odourless) methyl bromide or other fumigants due its strong odour. See Table 2 for limit values.

Health effects of preservatives and ripening inhibitors

Health effects of toxic substances released from cargo

Immediate diagnostic set-up, which requires an experienced physician in case of assumed intoxication is outlined below (see also the questionnaire in Additional file 1)

Case report: intoxications in a storage room from off gassing fumigants

In a medium sized European company, which received electronic production parts from south east Asia and South America, several employees developed signs of intoxication on three occasions within two years [30]. Six storage room workers were exposed to fumigants off gassing from shipped products. They were unloading approximately two overseas shipments a week at the time of the incident. They all worked 8 hours per day day in a storage room. Patients 1,3,4,5 and 6 unloaded the delivered items on a regular basis, and unpacked wooden pellets with paper boxes covered with plastic. Patient 2 supervised the working place. The workers were responsible for unloading and distributing the delivered items into several separate areas on different floors. Following each incident, the workers (patients 1, 3, 4, 5 and 6) noticed itchy skin, very red eyes and suffered from recurrent epistaxis, headaches and intention tremor. After the second incident, four individuals (Pat. 1, 3, 4 and 5) additionally complained about paresthesia (pins and needles in the legs), dizziness, breathing difficulties and increasing irritability. After the third incident, patient 4 was on sick leave for several weeks; patients 1 and 3 developed immediate epistaxis with a severe headache [30]. Air samples taken in the space between the packed electronic parts with trapped gas residues (in the breathing zone of the workers) showed presence of ethylene oxide and methyl bromide. Patients (n = 6, aged from 32 to 54 yrs.) were compared with a healthy control group (n = 30, with median age of 40 yrs.). Patients underwent standardized medical examination for the symptoms of fumigant intoxication as described earlier [31,27,30]. No significantly elevated bromide levels in any of the analyzed serum samples were detected. However, we detected low methyl bromide levels (0.24 μg/L) in the blood of patient 5 collected five days after the second incident (BM2). No increased levels of ethylene dichloride, chloropicrin, methyl iodine or dichloromethane were detected in the blood samples (all were below the limit of detection). Patients 1, 3, 4, 5 and 6 showed slightly increased levels of ethylene oxide in blood and two patients displayed elevated methanol levels, Patient 5 showed presence of small amounts of methyl bromide in blood [30]. In-vivo dose monitoring by means of adducts to macromolecules after exposure to methylating agents showed elevated levels of hemoglobin adducts: methylvaline and hydroxyethylvaline. The monitoring of hemoglobin adducts additionally allows to monitor past exposures and to generate extrapolated data that might enhance the risk assessment strategy. We have calculated the theoretical exposures to methyl bromide and ethylene oxide at the time of the individual incidents. Based on these data, the intoxication could be confirmed for three patients out of six (patients, 3, 4 and 5); data for patients 1, 2 and 6 did not allow any extrapolation. The clinical examination data from these patients (data not shown here) support the evidence of intoxication. No intoxication could be confirmed for patients 1, 2 and 6. Patient 2 supervised the other workers and after the first incident patients 1 and 6 were mostly engaged in other areas of the storage room with less direct contact with (newly delivered) unloaded products. Notably, after the first accident the company reorganized the storage area with a separate zone for unpacking the incoming shipment. As reported, the patients showed serious intoxication symptoms with itchy skin, very red eyes, dizziness, breathing difficulties and increasing irritability. They suffered from headache, acrotaxia, (intention tremor) paresthesia, and/or developed immediate or recurrent epistaxis. Our case studies indicate a need for an early and comprehensive prevention system including dedicated rules for the occupational hygiene and biomonitoring procedures [30].

Pilot study in China

With more than 30 years economic reform, the Chinese government is now paying more attention to the working conditions and health and safety of workers than before. However, little notice has been paid to these issues in the field of container fumigation in China [31].

Firstly, the operation of the fumigation of export containers in China is discussed in general, mainly considering the following two questions: who is operating the business and how work has been organized. It also looks at the working conditions and the health issues of workers. The research draws on a case study of a Chinese state-owned company, established in 2007, operating the fumigation of containers. It is a subsidiary company of the Provincial Administration of Inspection and Quarantine. Qualitative methods are utilised, with two first line managers being interviewed extensively and four workers being group-interviewed under the ‘supervision’ of their managers. The presence of the managers may prevent workers from expressing their concerns to some extent and hence weakens the analysis. However, available data still provide a meaningful explanation as to what is going on within that particular field.

The monopolization of the business of fumigation by the subsidiary companies is a result of special supports of the provincial agency to the subsidies. Firstly, the subsidies obtain credentials to provide training to the workers and issue them professional certificates. More importantly, the subsidies obtain credentials of operating fumigation and issues official certificates to the fumigated containers, which are highly recognized by foreign consignees. None of these credentials can be obtained by any other company. Last but not least important, these subsidies are supported financially by their parent agency. By monopolizing the business, the subsidies are faced with little competition in the market and do not have to concern much about lowering down the costs.

These peasant workers are specifically trained for fumigating containers, without many other skills. They are in a very weak position and depend on their managers for job opportunities. Because of the presence of their managers, it is possible that workers did not thoroughly express their concerns about their working condition or occupational health issues, especially the problems. However, the limited alternatives of their jobs in the labour market can be another important explanation as to why the workers express their content with their current jobs.

In conclusion, the study suggests that peasant workers are in lack of job security and basic protection, especially concerning the social insurance aspect. Their weak position due to the lack of protection and support from the society is an important issue that needs addressing. It is also important to notice that fumigation of export containers is monopolized by subsidiary companies of the Provincial Administration of Inspection and Quarantine. Without much pressure for high profits, state-owned subsidies provide relatively satisfactory working condition to their workers.

It was also seen from the case study that since the European countries improved the inspecting standards of the levels of methyl bromide in the imported containers, fumigation using toxic chemicals has been gradually replaced by heat treatment in this state-owned company. This might imply that a stricter regulation may reduce the use of using toxic chemicals in this industry and improve workers’ health and safety standard.

Pilot study in Denmark

The practice of container work was investigated in a series of semi-structured interviews with key informants including managers and safety representatives of two organizations the employees of which may be chemically exposed while handling containers [31].

Two major working populations are potentially exposed to hazardous chemicals when handling containers in Danish harbours: workers who unload freight and government officers in charge of inspecting transported goods. The practices and perceptions of workers was assessed by approaching the staff of the custom office and a container logistics company both located in Aarhus – the largest Danish container port. The selection of respondents was based on a purposeful snowball sampling method of individuals that were rich in information and experiences related to the topic. The interviews followed a template that included questions about work activities, potential chemical exposures, experienced health effects, health and safety regulations and applied preventive measures. A semi-structured face-to-face method was used to support the respondents to share their views and to gain in-depth information about the topic.

The approaches to prevention were quite different for the two populations. Group policies in the logistic company aimed to follow the vision for conducting business in a safe manner and to comply with applicable laws and regulations. The safety instructions were structured and easily available but had no stated relation to national and international regulations. In case of suspicion caused by the presence of a fumigation certificate, labeling as “dangerous goods” or closed container ventilation valves, ventilation, filter mask and gloves were prescribed. The custom office had safety instructions applying to control of containers, storage and warehousing that relate to the IMDG code, to European and Danish directives as well as to a chemical database established by the Danish occupational health service for seafarers (Seahealth).

In spite of limited knowledge about the potential health risks from exposure to fumigated containers, all the interviewees agreed on their existence. They expressed concern about frequent chemical exposure and estimated the proportion of polluted containers to be high, up to 50%. According to their experiences, 20% to 50% of the containers have a distinct perceivable odour. In contrast, they recalled that few containers were documented and labelled as previously fumigated or chemically treated. Methyl bromide was the only fumigant encountered in practice that all interviewed persons could quote. Some interviewees expressed their awareness about general industrial chemicals and noted experience with signs of exposure, such as a white powder in some containers, but could not specify the chemicals.

Most interviewees assumed that chemical exposures from transport containers may chronically damage workers’ health. Inspectors were increasingly aware of the risk, but had very limited specific knowledge. Manual workers were also rather unknowledgeable about the problem and fear was not typical among them.

Headache as the most commonly reported acute health effect was more frequently experienced in the past and tends to be related to special types of freights. Eye irritation and unspecified discomfort are also experienced occasionally. However, no interviewees recalled chronic intoxications with medically established connection to previous chemical exposures.

The interviewed managers were aware of the existence of relevant international and national regulations although they were typically not able to specify them. On the other hand, the interviewees were more knowledgeable about the local instructions of their organisations. Besides the general provisions for workplace health and safety, e.g. risk assessment, education, use of safety equipment and personal protective equipment, the local instructions, however, give insufficient guidance for several practical challenges of preventing chemical exposures during work with containers.

In practice, the preventive measures are primarily based on the attempt to identify the containers that carry occupational health risks. Although the review of documentation was reported to be the main way to get information about previous chemical treatment it was rarely seen and likely to be absent in a major proportion of fumigated containers. Apart from the documents, strange odour, the type of goods and the country of origin may create suspicion. Containers arriving from developing countries with food, footwear, furniture and other wood products were most frequently regarded as carrying chemical hazards. Equipment for monitoring of container air is available in some of the organisations only, but even if available, it can detect only methyl bromide but no other potentially harmful chemicals. In some organisations a suspicion is sufficient for applying specific preventive measures while others would require positive results of air measurements to take action.

The decision and choice of preventive measures to be used in practice tend to be left to the directly involved employees and the actions taken show considerable variation. The main preventive measure to reduce chemical exposure is passive ventilation; active ventilation is not applied in practice. The conditions of aeration are not consistently prescribed. The applied ventilation times vary between 2 and 48 hours without knowledge of whether this amount of time is sufficient. The other major way of preventing adverse health effects of chemical exposures is the use of personal protective equipment. Dust masks are usually provided to the workers, but do not prevent passage to the airways of chemical vapours. Gloves are typically provided and the use of coveralls reported by some interviewees. In practice, however, the overall frequency of wearing personal protective equipment is low.

Discussion of the pilot studies in China and Denmark

Both presented experiences from China and Denmark are likely to represent “best cases”. In China, the state monopoly of fumigation without competition permits a certain level of training and protection of workers. Even heat treatment was used when adequate. Still, the peasant workers are disfavoured by the absence of social security. The importing countries experience adequate labelling as being rare even when most containers arrive from China. In Denmark, the set standards aimed to provide full protection. Still, monitoring and ventilation practices and e.g. the use of respiratory protection were clearly inadequate. We have little information about fumigation practices elsewhere in exporting countries, but the level of protection might well be inferior compared to China. Denmark has relatively high standards relating to chemical exposure at work, and exposure levels may well be much higher in other importing countries with lower standards of protection. Some Incidents of intoxications with chemicals used for pest control in transport containers and on bulk cargo ships.

Fumigant intoxications – general

Incidents with fumigants used for pest control are reported frequently [32-35]. A lot of cases occur in the agricultural use of pesticides, and in some cases affecting both applicators and people living in the neighbourhood [36]. Some incidents occur in relation to fumigation of buildings, both public buildings and private homes [37,38]. A recent incident was reported in in January 2014 where a private home in Jerusalem, Israel, was fumigated with phosphine by a professional exterminator, and two children died. Two other children were seriously harmed but survived.(http://www.jpost.com/National-News/Family-of-6-believed-poisoned-by-pesticides-in-Jerusalem-home-toddler-dies-338999).

Fumigated transport containers

Although adverse health effects after occupational exposures to pesticides seem to occur frequently, the documentation of these incidents are often insufficient, lacking traceable description of exposure with respect to site and time, well documented exposure data, adverse health effects, clinical symptoms and not at least: publication of the incidents/cases in well-respected and traceable sources.

In particular, incidents related to opening of transport containers or fumigant intoxications on bulk cargo ships are seldom reported in scientific journals or described in public available reports. For those that are reported, the sources are variable, ranging from a few scientific papers, conference presentations to newspaper articles and short notes in organisations like Marine Accident Investigation Branch (MAIB).

To address container incidents a literature survey was conducted on PubMed in October 2014 with the following search string in the Title/Abstract field: "(toxic* OR poison* OR intoxic*) AND (fumiga* NOT fumigatus) AND container*". The search returned 43 references. Nearly 30% of all papers regarding fumigants or hazardous volatile chemicals in transport containers were by Baur and various co-partner, who started to collect the cases (see Table in Additional file 2). The PubMed search revealed only one paper with sufficient documentation of an intoxication case related to opening of transport containers: Two dock workers who opened a container in the port of Rotterdam in 2006 were acutely intoxicated, and subsequent field analysis by the fire brigade confirmed the presence of methyl bromide as the likely causative agent, although the paper did not contain any data showing the methyl bromide levels [39].

Two papers reported exposure incidents in detail. Preisser et al. described 26 patients referred to a clinic in Germany with symptoms of pesticide intoxication after opening of transport containers [29]. The authors were able to confirm the diagnosis based on typical symptoms and extensive clinical examination. Additionally by laboratory analysis ethylene dichloride, methyl bromide, phosphine and methylene chloride were identified. The predominant symptoms were headaches, concentration and memory problems, dizziness and nausea, irritation of the skin and mucous membranes and a reduced ability to do exercise. In addition to the neurological and neuropsychological impairments the analyses verified the development of reactive airways dysfunction syndrome (RADS) in 14 of 26 patients with long lasting symptoms due to their contact with fumigants.

Later Budnik et al. has performed more comprehensive exposure assessment using biomonitoring data for 164 subjects exposed to halogenated hydrocarbon pesticides (methyl bromide and ethylene dichloride) [27]. Another paper described 33 cases of presumed intoxication by transport containers [40]. The cases indicated phosphine and ethylene dichloride as the fumigants. However, the paper lacked detailed documentation of exposure data and for two of the cases there were no information of where the incident took place. A recent case report documented phosphine intoxication on board of bulk carrier in France [41].

Similar search on Web of Science added a single reference; this was a meeting abstract presenting a case report with two dock-workers being poisoned by methyl bromide as they opened a transport container. The abstract did not contain any information of location and date, but the incident most probably occurred in the Netherlands since the authors were from the National Institute for Health and the Environment in the Netherlands. No exposure data were included [42]. A Google search reveals two short notes describing patients referred to the Expertise Centre Environmental Medicine in Arnhem, The Netherlands after intoxication by container fumigants [9,40].

Fumigated bulk cargo ships

Incidents related to transport of bulk cargo on ships seem to be slightly more frequently reported in relevant publications, e.g. as Safety Flyers/Accidents Flyers by MAIB internet site (www.maib.gov.uk). A similar, systematic literature survey as for container contamination was conducted for fumigation on bulk cargo ships. A search on PubMed in October 2014 with the following search string in the Title/Abstract field: "(toxic* OR poison* OR intoxic*) AND ship" returned 223 references. Replacing "ship" with "freighter" gave 3 additional results. Another search with the string "(fumiga* NOT fumigatus) AND (ship OR crew)" in the Title/Abstract field returned 21 references. The search results identified 3 scientific papers describing incidents on board bulk cargo ships: One on a Polish ship in Vietnam, 1967 [43], one on a grain freighter on the Canadian/American East Coast in 1978 [44], and a survey on Danish merchant ships 1988–1996 carried out by the Institute of Maritime Medicine and Danish Maritime Authority in Denmark [45,46]. The latter investigation [45] showed 6 intoxication incidents due to fumigation of cargo with pesticides, 4 of these were fatalities. The oldest publication was not assessed due to difficulties in retrieving the paper.

The PubMed search was then supplemented with searches for incident reports on the web sites of International Labour Organization (ILO), the International Maritime Organization (IMO, the International Maritime Health Association (IMHA), Marine Accident Investigation Branch (MAIB), and the international maritime insurance companies Gard, Skuld and Norwegian Hull Club. The two latter companies did not have any incident reports made public, but Gard described several incidents in Gard News 204 (November 2011/January 2012). Neither ILO (http://www.ilo.org), IMO (http://www.imo.org) nor International Maritime Health Association had any publications on incidents/case reports. MAIB showed two incidents in the period from 1999 to date: One fatality with phosphine on a bulk cargo ship loaded with grain in 2007 was released by MAIB as an Accident Flyer. Another hazardous incident happened by unloading a maize cargo in 2012 without any serious injuries was released by MAIB as a Marine incident report 21/2013 (MAIB, 2013; http://www.maib.gov.uk/publications/index.cfm).

The majority of reported cases are bulk transport of foodstuffs like grain, flour etc., and nearly all of these are treated with aluminium or magnesium phosphide in solid form. The phosphide then reacts with water (as moisture in the air or in the cargo) and releases phosphine (PH₃) gas as the active pesticide. A unique feature of this way of administrating the fumigant is that the moisture/water may be a limiting factor and cause the reaction to stop, leaving solid phosphide in the cargo. When it arrives at the destination and the holds are opened, replenishment with ambient, moist air may restart the reaction liberating phosphine gas.

Summary of incidents

Concluding remarks

Both incidents with fumigated containers and bulk cargo ships are scarcely reported in the scientific literature. However, based on the literature survey and the reports referenced above it might seem as if there is a difference with regard to the severity of outcomes in the two cases: So far, there has been only limited reports of fatalities in relation to opening of transport containers (Table 4 and Additional file 2), while fumigation of bulk cargo ships has led to several fatalities, including several stowaways (Table 5). A possible explanation may be that the exposure on a bulk cargo ship may be of considerable longer duration, and that it is more difficult to escape. In addition, the fumigants may be present in the living compartments on the ship without recognised until the exposure has become fatal.

It is important to emphasise that the numbers of incidents reported in Tables 4 and 5 (and the Table in Additional file 2) may be highly underestimated since input from several representatives from both research institutions and national regulatory bodies suggest that a lot of near-accidents and intoxications with serious outcomes are never reported in public. This view was also supported by several presentations and participants at the Berlin workshop in May 22-23^rd, 2014 (http://www.eomsociety.org/index.php/meetings).

The literature surveys add to this and illustrate one of the major challenges pursuing this field: providing adequate and sufficient documentation of incidents relating to fumigated transport containers including adverse health effects, clinical symptoms, and well documented exposure data, and to make these data public available in well-respected sources.

Own requirements of individual countries

Most countries directly require all vessels in their territorial waters to comply with the IMO recommendations. The US and the Canadian Coastguards issue their own regulations and specifications (e.g., for Canada: https://www.tc.gc.ca/eng/marinesafety/bulletins-1997-06-eng.htm) and the European Union has issued regulations for the Fumigation of packaged goods only (freight container fumigation) under Regulation CE 1107/2009 and Directives 2008/40/EC, 2006/39/EC e 2003/68/EC.

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.

Labelling

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 [46] 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 [1]. 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 [25]. In Gothenburg none of the 101 randomly selected containers were labeled [47] 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 [48]. Discussions with managers and workers in an Australian study suggested that no systematic assessment of containers took place prior to entry by workers [25]).

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 [48]; (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 [25]. 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 [48]. 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.

Measurements

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.

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 [51]. 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 [51].

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 [47] 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 [48]. 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.

Ventilation

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 [47] 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 [25] 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 [47].

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 [48]. 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 [54]. Knol-de Vos [46] noted that staff wore personal PPE when opening containers in Rotterdam. Pedersen et al. [48] 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 [47].

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.