Chemical Pollutants in Closed Spaces of Transportation and Storage of Non-Dangerous Goods: A Combined Qualitative Approach

Background: Several chemical pollutants can accumulate in closed spaces of transportation and storage of non-dangerous goods, leading to high concentrations. Pollutants are mainly residues of pesticides used to prevent the spread of harmful organisms in intercontinental transportation, volatile organic compounds and components of diesel engine exhaust. The objectives of this cross-sectional qualitative study were to identify and evaluate the regulations in connection with the occupational chemical exposures caused by chemical pollutants in closed environments of transportation and storage, and to survey the knowledge, attitudes and practices (KAP) of occupational health and safety professionals and logistics managers related to this global workplace issue. Methods: A comprehensive systematic search of legal instruments was carried out in international, European Union and Hungarian legislation databases. Legal documents relevant for occupational chemical exposure at workplaces were included in the study and the legal relationships between selected documents were mapped. The systematic search of legal instruments identied 4737 records, of which 16 were included in the in-depth content analysis. According to the second objective, semi-structured face-to-face interviews were carried out with occupational health and safety professionals and warehouse managers at logistics companies located in Hungary. Results: The analysis of the documents highlighted the lack of explicit regulation on prevention from exposures caused by chemical pollutants in closed environments of transportation and storage of non-hazardous materials. The 21 completed interviews revealed that the professionals had very limited knowledge about the potential presence of chemical residues in closed spaces of transportation and storage. They deemed such chemical exposure rare and the related health effects negligible. Although legislation requires the risk assessment of workplaces, the assessment is misleading if potential hazards are not identied. Conclusions: The increasing risk of rapid global spread of harmful organisms due to climate change and dense international trac results in growing need for fumigation, which, together with increasing temperature and transportation time, generates an emerging occupational and public health challenge. The revealed limitations point out that the chemical safety of transportation and storage of non-dangerous goods should be more specically regulated and responsible professionals should be better informed about such workplace hazards. Preventive measures and safety precautions and personal opinions in connection


Background
Transportation and storage of non-dangerous goods and packaging materials are essential parts of global trade worldwide. Goods and products are mainly carried by container ships, trains, trucks and airplanes in multimodal ways between countries and continents. Environmental impacts of freight transport are well-known, such as the harmful emission containing greenhouse gases (GHG), like carbon dioxide (CO 2 ), nitrous oxide (N 2 O) and other environmental pollutants [1,2,3]. However, these impacts may be underestimated in the workplace environments of transportation and storage of non-hazardous cargos, which involves a signi cant number of workers all over the world [5]. Transport vehicles have several closed spaces where the goods and their packaging materials are transported and stored for a relatively long time during intercontinental and inland transportation. Goods and packaging materials in closed spaces are protected from environmental factors, such as humidity, while the aeration of these ambiences may be inadequate to provide harmless indoor air quality. As a consequence of poor aeration, chemical pollutants can accumulate in such spaces [4,6]. Besides the inevitably occurring exhaust gases produced by the transport devices, these pollutants are mainly residues of previous chemical treatment of goods with pesticides and volatile organic compounds released from the transported and stored materials [4,5,6].
For the prevention of the spread of harmful species, including several infectious pathogens, fumigation is a widely used method of chemical treatment during intercontinental transportation. For this purpose, different chemicals are used and some of them could be extremely harmful for the workers as well as for the environment [7]. In high concentrations, all fumigants are toxic. They affect mainly the central and peripheral nervous system and the respiratory tract. Moreover, some of them may even cause cancer [8,9].

The International Standards for Phytosanitary Measures No. 15 of the International Plant Protection
Convention (IPPC) orders the fumigation of wood packing materials before intercontinental transportation [10].
The mostly used fumigants are methyl bromide, hydrogen phosphide, ethylene dichloride, chloropicrin and ethylene oxide. However, methyl bromide is phased out in conjunction with the Montreal Protocol on Substances that Deplete the Ozone Layer because it is an ozone depleting substance [11,12]. Nevertheless, methyl bromide is still allowed in cases of critical use exemptions wherever adequate alternative is not available for this purpose [13].
Nowadays, heat treatment is an alternative of fumigation. A heat treatment kiln must treat the packaging for a minimum period of 30 minutes at a constant temperature of 56ºC. The procedure is complicated and costly that makes chemical treatment favourable in practice.
An emerging problem related to global climate change and densifying international tra c is the increasing threat of spread of various pathogens resulting in a growing need for fumigation [14,15]. Therefore, a more frequent use of hazardous and environmentally harmful fumigants can be expected, in most cases without any adequate knowledge on the applied procedure, emitted chemicals and related environmental and occupational risks.
In addition to pesticides, noxious industrial chemicals can release from newly manufactured products.
They are typically volatile organic compounds (VOCs) with various health effects. The most commonly released VOCs during transportation and storage are benzene, xylene, ethyl benzene, toluene, ethanol, chloromethane, acetone and formaldehyde [5,16,17]. VOCs are typically emitted by products, which contain paint materials, solvents, lacquers, glues, wood preservatives, adhesives, etc. Moreover, road transport alone accounts for 30% of VOC emissions globally.
The exposure level of these chemical substances depends on the time of the transportation and storage, the nature of goods and the aeration characteristics of the cargo space.
Employees who work inside the closed spaces of transportation and storage of non-dangerous goods may be exposed to increased concentrations of these pollutants and posed to risk of acute and chronic health effects [16,17,18]. Furthermore, these chemicals pollute not only the workplace air but also the general environment, contributing to the global environmental challenges [19,20].
While the transportation and storage of dangerous goods are strictly regulated, the risks of shipping and warehousing of non-hazardous materials are presumably much less controlled [21,22]. A previous study in Denmark investigated the regulation of preventing harmful chemical exposures during container handling. According to the ndings, workers were potentially exposed to harmful chemical pollutants when handling transport containers and the international as well as the Danish regulations did not provide adequate guidance to conducting safe practices [18].
In Europe, the Framework Directive on Safety and Health at Work obliges employers to take appropriate preventive measures to make work safer and healthier. This directive shall apply to all sectors of activity and in every aspect related to the work. The employer is obliged to develop a coherent overall policy and comprehensive risk assessment which cover all eld of work, such as handling freight in closed spaces during transportation and storage [23].
The aim of this study was to investigate the legal background as well as the practice of preventing workplace exposures caused by chemical pollutants in closed spaces of transportation and storage of non-dangerous goods. For this purpose, the international, European Union and Hungarian national regulations and recommendations were systematically searched and assessed. The search was not restricted to occupational health and safety regulations but intended to identify and include legal documents relevant for the investigated problem from three different areas: occupational health and safety, chemical safety at work, and phytosanitary measures, which address occupational health and safety precautions for the use of pesticides in pest control.
To study the practice, a knowledge, attitudes and practices (KAP) survey was performed among occupational health and safety professionals and warehouse managers about the potential chemical pollutants and their management in closed environments at Hungarian logistics companies.

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A comprehensive systematic search of laws and policies, which directly address the prevention of chemical exposures arising from transported and stored non-dangerous goods and packaging materials, was conducted. The search was carried out on the i) International Labour Organization (ILO) and International Maritime Organization (IMO) conventions and recommendations through the organizational domains ii) the EU-law portal, and the Hungarian national legal database.
The search string applied in these databases has included the terms occupational health and safety, chemical safety, transportation, phytosanitary and container in the following syntax: ("Occupational Health and Safety") AND ("Chemical Safety" OR "Transportation" OR "Container" OR "Phytosanitary").
The rst round of the screening was based on titles and abstracts/preambles in order to identify the relevant legal instruments which deal with occupational health and safety.
For full-text screening, one inclusion criterion was applied: legal instruments must have dealt with workplace chemical exposures and/or with their prevention.
The included legal instruments underwent content analysis that had two parts: link analysis of legal instruments and their topic classi cation according to prede ned questions. The link analysis based on references and links, aimed to trace pathways between correlating legal instruments pointing out relevant ones based on their mutual correlation.
Then, eight prede ned assessment questions related to occupational chemical exposures and/or to their prevention in closed spaces of transportation and storage were used to further assess the strength of relevance of the previously identi ed legal instruments to the research topic.
The YES/NO type assessment questions were the following: Only legal instruments receiving YES answer to all the eight assessment questions were subjected to indepth content analysis that was conducted using the NVivo™ software version 11. Each paragraph, which regulates occupational chemical exposures and/or their prevention in closed places of transportation and storage, was coded in the software to extract the relevant sections in summary tables. The content was assessed by experts in occupational health and safety (SzL, BA) systematically. Decisions on legal matters were facilitated by OV.
Knowledge, attitudes and practices survey A knowledge, attitudes and practices (KAP) survey was performed by explorative face-to-face semistructured interviews. The companies were contacted with the assistance of the Association of Hungarian Logistic Service Centres. 35 Hungarian logistics companies were requested to allow the study and ensure an appointment with the company's occupational health and safety representative and/or with the warehouse/logistics manager in order to conduct semi-structured interviews in relation to workplace chemical exposures arising from the transportation and storage of non-dangerous goods.
Interviews were conducted personally at the worksites of logistics companies.
The interview guide used by Pedersen et al. [18] was developed further and adapted to the Hungarian context to guide the semi-structured interviews. Two pilot interviews were carried out during the preparatory phase of the study and the guide was modi ed according to the experiences.
The interviews collected qualitative and quantitative information on work activities in closed spaces of transportation and storage of non-dangerous goods, on their knowledge about relevant regulations and existing chemical exposures, on the perceived frequency of chemical exposures, on workers' knowledge and awareness related to the potential hazards, on symptoms claimed by the workers to be work related, on diagnosed work-related diseases and on applied preventive measures and safety precautions at the company. An interview was 45-55 minutes long. Thematic analysis of the interviews was carried out.
Preliminary codes according to the questions of the interview guide were created, then themes in the codes across the different interviews were identi ed. Finally, themes were revised and de ned [41].
Interviewees were asked to assess different aspects of the investigated workplace issue on ve item Likert-scales to provide their subjective estimations.
Notes and voice records were taken during the interviews. The estimations provided on Likert-scales were analysed by descriptive statistics using Excel and illustrated in bar charts.
According to the Hungarian regulation, only biomedical studies are subject for ethical license approval.
All survey interviews were anonymous and voluntary. Verbal consent was requested. After the transcriptions, audio les were destroyed, and personal data were removed.
The interviews followed a similar pattern. At most logistics companies, freight containers, other closed transport devices and warehouses were shown around by the interviewed professionals to get an insight in the ongoing work. Preventive measures and safety precautions applied at the companies were introduced by the interviewees with a discussion about their estimated effectiveness against the investigated occupational chemical exposures. Experiences and personal opinions in connection with the chemical pollutants arising from the transportation and storage of non-hazardous goods were noted and described.

Review of legal instruments
As a result of the systematic search of legal instruments, 4662 legal documents were identi ed through legal database search and 75 through manual search of organizational domains. 4424 records remained after duplicates were removed and 4311 records were excluded by screening title and abstract or preamble for the reason that they were irrelevant to the study's perspective.
113 full-text legal instruments were assessed for eligibility, since they dealt with occupational health and safety. 62 documents were excluded by not ful lling the inclusion criterion.
51 legal instruments dealing with workplace chemical exposures and/or with their prevention were included in the study. The ow chart of the systematic search of legal instruments is illustrated in Fig. 1.

Link analysis
The legal and content relationships between the 51 included documents were mapped to illustrate their interconnections. For the purpose of legal continuity, 7 additional legal instruments were added to the chart (illustrated with dashed frame line) but 9 legal instruments from the 51 originally considered were nally not illustrated with the reason that they are not rati ed by Hungary.
In this way, the chart includes 38 international and 11 national (separated with dashed line) legal instruments in the elds of occupational health and safety (n = 14), chemical safety (n = 26) and phytosanitary measures (n = 9) (Fig. 2).

Content analysis
The content of the 51 included documents was assessed using YES/NO type assessment questions to identify how speci cally they regulate the prevention of occupational chemical exposures in closed spaces of transportation and storage of non-dangerous goods. 16 legal instruments covered all of the eight assessment domains, i.e. having the strongest relevance to the issue of occupational chemical exposures in closed spaces of transportation and trade of non-hazardous materials (see Supplementary  table), including international, EU and Hungarian legal instruments.

Legal instruments at international level
Since the chemical safety aspects of the transportation of non-hazardous goods is not regulated alone, most of the identi ed legislations regulate the transport of dangerous goods and are non-binding conventions and recommendations. These documents specify non-dangerous goods as "Not goods of class" of hazardous materials.
The governing document is the Recommendations on the Transport of Dangerous Goods accepted by the United Nations [25].
Further recommendations are the Recommendations on the safe use of pesticides in ships [26], the Revised recommendations on the safe use of pesticides in ships applicable to the fumigation of cargo transport units [27], the Revised recommendations for entering enclosed spaces aboard ships [28] as well as the Code of Practice on Safety and E cacy for Marine Fumigation [29]. These recommendations advise preventive measures in connection with the using of fumigants, such as identifying the potential weaknesses during fumigation, correct using of personal protective equipment, actions for ventilation and aeration as well as the applying of warning signs at every fumigated places to keep workers away from the possibly harmful environments. Ensuring su cient time for the gas-free condition before entering in fumigated closed spaces is the major safety provision that can be found in all recommendations. Crew members should be trained in enclosed space safety to prevent contamination with the residues of pesticides.
There were two binding legal instruments found by the search, the International Maritime Dangerous Goods Code [30] and the European Agreement concerning the international Carriage of Dangerous Goods by Road [31].
These two documents specify in details the management and prevention of exposures caused by registered dangerous goods in closed spaces of transportation.
The two regulations also classify some non-dangerous goods as miscellaneous dangerous substances that can be harmful in "Class 9". A more detailed content summary of these regulations and recommendations is illustrated in Table 1. • Non-ammable, non-toxic gases which are asphyxiate and toxic gases (e.g. methyl bromide and chloropicrin) should be considered.
• Special provisions applicable to fumigated cargo transport units (United Nations Number 3359).
Fumigated cargo transport units containing no other dangerous goods are not subject to any provisions of these Regulations other than those of this section.
Recommendations on the safe use of pesticides on ships • Assess the risk as to whether it is safe to enter.
• Natural or mechanical ventilation is necessary.
• Warning signs marked to show that it has been ventilated and the date of ventilation.
• Ensuring su cient time for the gas-free condition before entering in the container.
• Fumigated units shall be marked with a warning sign a xed to the access door(s) identifying the type and amount of fumigant used and the date and time of fumigation.
• It is recommended to test for Phosphine and Methyl bromide as the two most common fumigants used.
• Personal monitors are also available to show the level of oxygen within the container.
Revised recommendations on the safe use of pesticides in ships • During the application of contact insecticides by any method, all personnel not directly involved should be evacuated from the areas being treated.
• Fumigation and aeration (ventilation) of spaces on board a ship should always be carried out in port.
• Fumigation and aeration (ventilation) of spaces on board a ship should always be carried out in port. Gas-free certi cate. The instructions given on the label or package itself, particularly those relating to safety and disposal of residual material, should be strictly followed.
Revised recommendations for entering enclosed spaces aboard ships • Crew members should be trained in enclosed space safety.
• Ventilation or aeration and testing the atmosphere.
• Not more than 50% of the occupational exposure limit (OEL) of any toxic vapours and gases.
• Residues on packages and spilled material.

Content summary
Code of practice on safety and e cacy for marine fumigation • Safety measures should be devised to reduce risks.
• Security measures at the time of fumigation in transit.
• Quali ed and experienced staff and being properly equipped can perform ventilation of the fumigated goods.
• Gas-detection and respiratory protection equipment at load port.
• Warning signs at all entrances.
• Oxygen-enriched or depleted atmosphere shall be considered.
• FUMIGATED UNIT and UN (United Nations) NUMBER placed on the cargo.
• Mechanical ventilation when it is necessary.
• Class 9: Miscellaneous Dangerous Goods are substances and articles which during transport present a danger or hazard not covered by other 8 classes.

Legal instruments at the level of the European Union
The directives and regulations in connection with occupational health and safety made by the European Parliament, the Council as well as the European Committee are obligatory to apply to all member states. Nonetheless, our ndings have revealed that there is no directive or regulation which directly regulates the exposures and their prevention in closed spaces caused by chemical pollutants.
However, European Union has several other measures in the eld of occupational health and safety, but no one of them contains accurate regulations which could be interpret as a guideline at workplaces.
The following ve directives indirectly regulate the investigated topic: The Directive 2006/15/EC [32] established a second list of indicative occupational exposure limit values in implementation of Council Directive 98/24/EC which can be used for the purpose of preventing high concentration of toluene, benzene and phosphine. This directive does not specify the different chemical pollutants released from transported goods and packaging materials.
The Directive 1998/24/EC [33] on the protection of the health and safety of workers from the risks related to chemical agents at work lays down general rules and directions to manage prevention but does not cover directly the topic of closed spaces in transportation and trade.
The Directive 2004/37/EC [34] on the protection of workers from the risks related to exposure to carcinogens or mutagens at work speci es particular minimum requirements in this area including limit values. In regard of released chemical pollutants in closed spaces of transportation and trade, some of them may be mutagenic and/or carcinogenic. Occupational limit values for these chemicals are determined in the directive.
The Directive 2008/68/EC [35] on the inland transport of dangerous goods lays down uniform rules for the safe international transport of dangerous goods. Transportation of non-dangerous goods is not de ned in this directive. Thus, this regulation cannot be applied on the transportation of nondangerous goods.
The Directive 2019/130/EC [36] on the protection of workers from the risks related to exposure to carcinogens or mutagens at work revises limit values established by the Directive 2004/37/EC. The directive establishes limit values for occupational exposure to diesel engine exhaust and certain polycyclic aromatic hydrocarbons (PAHs) which is an important preventive measure in case of transportation and storage since warehouse workers and truck drivers are exposed to these pollutants on a daily basis. A more detailed content summary of these directives of European Union is illustrated in Table 2. • Indicative occupational exposure limit values are health-based, nonbinding values, derived from the most recent scienti c data available and taking into account the availability of measurement techniques. They set threshold levels of exposure below which no detrimental effects are expected for any given substance. They are necessary for the determination and assessment of risks by the employer.
Council Directive 1998/24/EC on the protection of the health and safety of workers from the risks related to chemical agents at work • Activity involving chemical agents means any work, including production, handling, storage, transport or disposal and treatment of the goods and packaging materials.
• Hazardous chemical agents shall be eliminated or reduced to a minimum (e.g. volatile organic compounds and pesticides).
• Reducing the quantity of chemical agents present at the workplace to the minimum required for the type of work concerned.
Directive 2004/37/EC on the protection of workers from the risks related to exposure to carcinogens or mutagens at work • Prevention of risks, arising or likely to arise from exposure to carcinogens or mutagens at work.
• Reduce or replace carcinogens and mutagens at the place of work.
• Evacuation of carcinogens and mutagens at the source, local extraction system or general ventilation shall be applied.
• Individual or collective protection measures are obligatory.
• Means for safe storage, handling and transportation, in particular by using sealed and clearly and visibly labelled containers. • UN (United Nations) number 3359 means fumigated cargo transport unit, which can be dangerous under transporting and storing.
• Ventilation, education, warning signs and documentations are obligatory during transporting and storing of fumigated goods.
• UN (United Nations) Class 9: Various dangerous substances and materials which are not categorized, but could be harmful.  The employer is bound to conduct risk assessment in connection with chemical exposures. Nevertheless, this decree provides measures on dangerous chemicals and does not specify the regulation of chemical pollutants released from transport and trade of non-dangerous goods and packaging materials. Therefore, workers are not necessarily informed about these exposures.
The 26/2000. Decree on the protection of workers from the risks related to exposure to carcinogens or mutagens at work orders obligatory measurement at the workplace. The employer is obliged to document the occupational risks and exposures. In this decree, a paragraph takes provisions on the constantly ventilated workplace. Further provision is the elimination as well as the prevention of contamination with carcinogens.
It is important to mention that benzene and formaldehyde are human proven carcinogens but this decree does not deal with the carcinogenic substances released from non-hazardous transported goods.
The Act 44 of 2008 on Food Chain and its Authority Control disposes on the protection of plant products from harmful organisms. The regulation on fumigation as a plant protection process belongs here. Thus, this law is closely related to the investigated topic in connection with pesticide residues in closed spaces. However, this regulation contains mainly authority provisions, so exact directions on chemical exposures in closed spaces are not included.
The 43/2010. Decree on plant protection activities includes speci c regulation of occupational health and chemical safety on the use of biocidal products. This decree also orders the use of warning signs on fumigated enclosed spaces. Furthermore, it regulates the working in fumigated spaces which process requires personal protective equipment. Another speci c regulation in connection with chemical pollutants in closed spaces is the fumigation process where adequate ventilation is essential. The decree lays down provisions on the storage and transport of fumigated products in visibly labelled packages specifying with the fumigants that have been used.
The 61/2013. Decree on the inland transport of dangerous goods (known as "ADR") is applicable in accordance with the IMDG Code and the Recommendations on the Transport of Dangerous Goods.
Transportation of non-dangerous goods is classi ed as "Class 9 -Miscellaneous dangerous substances and articles" which may contain residues of previous chemical treatment with pesticides or volatile organic compounds released from the goods and packaging materials. Class 9 goods are substances and articles which during transport present a danger or hazard not covered by other 8 classes.
When goods mentioned are not subject to ADR because they are considered as non-dangerous according to this document, the consignor may enter in the transport document a statement to that effect, e.g.: "Not goods of Class ...".
A more detailed content summary of these legal instruments of Hungary is illustrated in Table 3. • Obligatory risk assessment at the workplace.
• Regulation on oxygen de cient workplace atmosphere (e.g. fumigated cargo transport unit and container).
Ministry of Health Decree 26/2000. on the protection against carcinogens related to work • Measurement obligatory of carcinogens and mutagens at workplace.
• Prevention of the release of carcinogens and mutagens.
• Elimination of the carcinogens at the source.
• Prevention of the contamination with carcinogens and mutagens.
• Limited concentrations of carcinogens at work.

Act XLIV of 2008 on Food Chain and its Authority Control
• Protection of plant products from harmful organisms (e.g. pesticides).
• Prevention of hazards from the use and storage of pesticides, including fumigants.
• Prevention of the hazards related to toxic substances on the surface of plant products (e.g. fumigated wood products).
Ministry of Agriculture Decree 43/2010. on plant protection activities • Occupational health and chemical safety regulations on the use of biocide products.
• Warning signs on the fumigated enclosed spaces.
• Working in fumigated spaces requires special personal protective equipment.
• Fumigation in enclosed space requires adequate ventilation.
• Storage and transportation of fumigated products require visibly signed packages.

Knowledge, attitudes and practices survey
Altogether, 21 semi-structured interviews were carried out with the participation of 13 occupational health and safety professionals and 9 warehouse/logistics managers. During the analysis, the following four themes were identi ed: work activities and related occupational health and safety regulations, workplace chemical exposures in closed spaces of transportation and storage, health effects caused by the chemical pollutants, and the preventive measures applied against chemical exposures. Below these themes are presented with relevant quotes provided by the interviewees.

Work activities and related occupational health and safety regulations
According to the interviewees, transport containers and closed transport devices arriving to Europe by sea are not always opened right at the entrance ports but transported to the target countries where they are nally opened and unloaded. Hence, warehouse workers are involved in the rst opening of the closed transport devices.
Concerning the process of loading and unloading transport vehicles, these tasks are carried out by forklifts used for lifting and carrying piles of goods driven by warehouse workers. Handling goods and products in warehouses is also carried out by forklifts and manual handling, which requires further workforce involved in work processes in closed environments. Workers reported to spend 8 or 12 hoursdepending on the work shift -in closed spaces of transportation and storage.
As regards of relevant legislation and guidance, the professionals speci ed some regulations (e.g. the These regulations were mainly the legal documents identi ed by the systematic search of legal instruments and standard operating procedure (SOP) instructions established by the companies.
SOP instructions are not binding legal instruments and regulate the way of work in warehouses (e.g. processes of loading/unloading goods, method of storing different materials and other quality maintaining standards). As reported by the professionals, these instructions do not include safety precautions regarding chemical pollutants, except if the cargo is de ned to be dangerous or contains harmful components that have to be handled differently from the non-dangerous shipments.
Nevertheless, professionals deemed that the binding European Union and Hungarian regulations provide rules for adequate prevention in the eld of occupational health and safety of transportation and storage of non-dangerous goods.
"There are several regulations regarding the processes of transportation and storage. Our work is regulated from different aspects. If you mean chemical safety, there are the ADR regulation as well as the Act of the Chemical Safety. These regulations cover all eld of our work when we have to handle chemicals." (Person 1)

Workplace chemical exposures in closed spaces
Interviewees have expressed their awareness about existing chemical pollutants in transport containers and warehouses but they were not able to specify them, except diesel engine exhaust per se, carbon monoxide and other "non-speci c" industrial chemical mixtures (e.g. aerosols, surface fertilizers, lubricant oils) which are believed naturally occurring under these working circumstances.
"It depends on the type of the cargo. I believe that the shipping company makes everything that provides adequate chemical safety during the transportation. However, containers have strange odour sometimes that can be the consequence of the released chemicals or pesticide residues.
What can we do? We leave the containers ventilated outside and after the unloading of goods we have to wash them out, otherwise they will send them back." (Person 2) An additional exposure claimed by the interviewees is diesel engine exhaust emitted by forklifts and cargo trucks, which emission can contribute to the air pollution inside the warehouses. Nowadays, electric forklifts are more common in practice but the continuously working engines of trucks at loading dockse.g. for running the trucks' air-conditioning system -can pollute the air inside the warehouses.
"When the truck drivers are waiting at the loading docks they are using the truck's engine in some cases. They are visitors at the companies, so they are not allowed to leave the truck and walk into the warehouse. Of course, the diesel engine exhaust can pollute the air inside the warehouse and we can smell the odour of the diesel exhaust. I would say that it can be a common problem." (Person 3) As reported by some professionals, transport devices can be fumigated without a label about the applied chemical treatment as well as they can be contaminated with potentially harmful volatile organic compounds, although this scenario is thought to be very rare in everyday practice at Hungarian logistics companies. Based on the respondents' experiences and estimations, less than 1% of the closed transport devices are labelled as previously treated with fumigants or other chemicals. The fumigant methyl bromide (MeBr) was familiar for the majority of the interviewees; however, they noted that it is phased out from usage.
"If a container is labelled as fumigated or other documents related to chemicals are attached, I tell the workers: after I check the chemical safety datasheet, open it and leave the container ventilated by the air for 20-30 minutes. They will know that it means that the entrance into the container is forbidden. However, this happens very rarely." (Person 4) "Methyl bromide was used decades ago. I remember that times. Now, I think that these kinds of chemicals are not used anymore. The heat treatment of wood pallets is applied for this purpose. I do not know whether other chemicals exist for fumigation. The transport document includes everything that we have to know about the cargo. If the cargo can be dangerous the shipping company will inform us." (Person 5) There is no agreement among the professionals on the frequency of chemical exposures arising from previous fumigation or released from the transported goods and packaging materials, but the majority assumes that such kind of exposures do not or very rarely occur in warehouses (Fig. 3a).
"No, there are no harmful chemicals in the workplace air. We do not handle dangerous cargos." (Person 6) "Of course there are many pollutants in the warehouse's air. This is inevitable. We do not store dangerous goods so we do not have information about the pollutants since we do not have air quality monitoring system. I do not know how they in uence our health." (Person 7) A few occupational health and safety professionals at the logistics companies expressed their opinion that quantitative information about these chemical pollutants are necessary for the better understanding of this workplace issue. Regarding the warehouse managers, they were convinced that the work environment in a warehouse is not harmful and the goods do not emit hazardous chemicals.
Potential health effects caused by the pollutants Potential health effects of pesticide residues from previous chemical treatments of transport devices and volatile organic compounds emitted by goods are believed negligible or moderately harmful to warehouse workers according to the respondents (Fig. 3b).
Reported symptoms claimed by the workers to be caused by occupational chemical exposures are mainly upper airway and skin irritation; however, workers report these health problems occasionally and the symptoms are believed to the side effects of dust and diesel engine exhaust, as well as to the limited use of protective gloves and respiratory protective equipment. Other symptoms reported by the workers were mainly headache, numbness or heaviness in arms or legs, feeling of general exhaustion and trembling of hands. These symptoms were believed by the professionals to be related to other work-related and nonwork-related causes (e.g. lifting of heavy parcels, alcohol consumption) but not to workplace chemical pollutants.
As regards the workers' awareness about the pollutants, the interviewees expressed their opinion that workers are well informed about chemical risks during the occupational health and safety trainings, but they seemed to be not con dent about the effectiveness of the education. The estimated knowledge of workers on chemical exposures was mainly inadequate (Fig. 3c). According to the interviewees, the workers are not concerned about the chemical exposures and related health effects (Fig. 3d).
"When we keep occupational health and safety trainings for the workers, we inform them about the chemicals which can occur in the warehouses. But they are just warehouse workers. They will not be worried about chemicals just if they know that the cargos arriving to the company can be dangerous. In this case, they are prepared to conduct adequate safety precautions. Otherwise, they are not worried regarding their health." (Person 8) A few occupational health and safety professionals were sure that some diseases, which occurred in the last few years at the companies (e.g. asthma, non-speci ed lung disorders and lung cancers), were caused by the "non-speci c" chemical pollutants. However, information on diagnosed occupational diseases could not be collected.
"It is di cult to state that lung disorders happened at this company in the past were related to the work. However, as a professional, I know that there are many environmental and occupational factors that can in uence our and the workers' health. Allergy or asthma is a relatively common problem among warehouse workers, but more than half of them are smokers and don't use the dust masks. Of course, these factors can contribute to work-related diseases that will never be diagnosed as occupational disease. We would measure the exposure in order to get objective information about the chemicals and after this we could investigate the association. We know nothing about these exposures." (Person 9)

Preventive measures applied against chemical exposures
The applied preventive measures are mainly determined by the documentation of cargo. If the transport device is labelled as fumigated, the review of the relevant documentation is always carried out precisely. Closed transport devices are opened carefully when they are labelled as treated with chemicals. Speci c preventive measures in closed transport devices and warehouses were not reported, but the majority of the interviewees stated that general dust masks used by the workers and passive ventilation are enough to provide harmless working environment.
"The loading docks are opened almost all day long so the natural aeration provides enough fresh air inside the warehouse. Sometimes, when the air is dusty, we make draught with opened doors." (Person 10) As regards the winter season, the interviewees were not sure whether the closed loading docks due to the low temperatures outside and the heating inside the warehouse could contribute to the accumulation of chemical pollutants in closed working environments.
Speci c respiratory protective equipment apart from dust masks or passive ventilation are not applied in these work environments in Hungary (Table 4). Passive ventilation is indirectly carried out when the loading docks are opened in warehouses, but it may not provide enough to reduce chemical concentration to a safe level.
In case of transport containers occupational health and safety representatives claimed that aeration is not necessary since the containers are not loaded with dangerous chemicals and not labelled as fumigated.
Active ventilation (mechanical extraction) Not used in practice in warehouses in case of nondangerous goods.

Respiratory protection
Dust masks are rarely used and do not provide adequate protection regarding pesticide residues and volatile organic compounds. Limited use due to discomfort of wearing.
Protective gloves Used in practice in case of non-dangerous goods.
Protective clothing Not used in practice in case of non-dangerous goods.
Other speci c PPE Not used in practice in case of non-dangerous goods.

Discussion
Workers involved in handling non-dangerous goods can be exposed to chemical pollutants accumulated in high concentrations in closed spaces of transportation and storage [5,16,17]. These chemicals can have acute and chronic health effects, among them cancer [8,9]. Regarding the occupational health and safety of chemical exposures in transportation and storage of non-dangerous goods, there is no direct legal instrument that is binding and could be applicable at such workplaces.
While this eld is strictly regulated in case of transportation of dangerous goods [21,22], the workers have to face the risks arising from the potentially accumulated chemical pollutants released in closed spaces from goods and packaging materials, which are not classi ed as hazardous products [18].
In addition, fumigation also carries health risks not only the fumigation is being conducted but also later trough the contamination with pesticide residues [24,38,39].
Detailed occupational health and safety recommendations and regulations on fumigation exist and describe the risks of opening closed spaces during transportation and storage, such as the Revised recommendations for entering enclosed spaces aboard ships [28] and the Code of Practice on Safety and E cacy for Marine Fumigation [29].
In regard the Recommendations on the Transport of Dangerous Goods [25] and the IMDG Code [30], "Class 9" provides a minimal framework to prevent occupational chemical exposures released from goods and packaging materials during loading and unloading non-dangerous cargos. Nevertheless, these two documents are not binding if the transported goods are de ned as non-hazardous. In the European Union, the European Agreement concerning the International Carriage of Dangerous Goods by Road [31] regulates the transportation of miscellaneous goods similar to the IMDG Code [30] but leaves a wide spectrum to interpret the meaning of non-dangerous goods. Therefore, these binding legal instruments are not speci c enough to prevent and manage occupational chemical exposures in case of nondangerous products.
In Hungary, all the occupational health and safety legislation is harmonized with the EU regulations. Hungary does not have independent and speci c regulations on transportation and storage of nondangerous goods.
The legal instruments identi ed and investigated in this study mention the term "closed space" at some places but do not provide complex framework to manage the risks arising from the occupational exposure to chemical pollutants. Several chemicals that can accumulate in closed spaces, such as benzene, formaldehyde and different pesticides, have to be considered in connection with their potential harmful effects [8,9,37].
It can be concluded in general that the studied legal documents have minimal and mainly indirect requirements in connection with the safety precautions against occupational chemical exposures in closed spaces of transportation and storage of non-hazardous goods and a signi cant proportion of the risk management depends on the knowledge and dedication of the employer as well as the employees.
Similarly to the ndings by Pedersen et al. [18] and Baur et al. [40], our study has revealed that the occupational health and safety professionals and warehouse managers have insu cient knowledge about the chemical pollutants and the applied health and safety practices at the logistics companies cannot adequately manage the potential occupational chemical exposure that is a "side effect" of the transportation and storage of non-dangerous goods. While the respondents were familiar with the risks arising from the handling of dangerous goods, the investigated problem seems to be underestimated among the professionals.
This qualitative analysis provides a comprehensive picture relevant to the chemical safety of handling non-dangerous goods and the methodology applied in the study is disposable for further studies on the legislation and practice of various aspects of environmental and occupational health of transportation and trade of non-hazardous materials.

Conclusions
The international and Hungarian legislations do not specify the risks and management of occupational chemical exposures arising from transported and stored non-hazardous goods and packaging materials.
Workers are potentially exposed to harmful chemicals during opening, inspecting or unloading of closed spaces where the concentration of various harmful chemicals can be high. Similarly to the handling of dangerous goods, personal protective equipment, air quality monitoring system and comprehensive risk assessment that considers chemical pollutants could be applied to prevent potential harmful effects.
Ensuring appropriate air quality with adequate ventilation of closed spaces, which may be natural or arti cial, can also be an effective precaution.
Based on the ndings, current regulations are not speci c enough to consider and handle the risks of occupational chemical exposures in closed spaces of transportation and storage of non-dangerous goods.
Occupational health professionals, employers and workers have to be well informed about this workplace issue to be able to conduct safety provisions effectively. Policymakers should establish adequate legislative framework which directly addresses the investigated problem.
More detailed guidelines and practices of workplace chemical risk assessments in this particular setting are imperative to accomplish effective prevention. The uncertainty about the exposure to chemical pollutants in the practice of transportation and storage of non-dangerous goods warrants an urgent need for the quantitative measurement of such exposures so that objective information can be applied in detailed risk assessment of these workplaces.
Professionals must be reached with comprehensive scienti c information and employees provided with adequate occupational health and safety trainings at logistics companies.
In parallel with the occupational health problems, the chemical pollution during transportation of nonhazardous goods interrelates with environmental issues in multiple ways, too.
Climate change and the threat of spread of harmful species, among them pathogenic organisms, are expected to result in an increased use of pesticides for fumigation of goods as well as, due to the rising average temperature, the closed spaces of transportation and storage will be warmer that intensi es the release of volatile organic compounds leading to not only more polluted indoor air but also outdoor air and consumer products. The studied problem is one of the many examples for an effort that is made to decrease the likelihood of global spread of harmful organisms which creates an emerging occupational and public health challenge.
A complex approach will be required to set limit values and de ne preventive measures for the chemical safety of transportation of non-dangerous goods, which also count with the problems arising from changing climate, in order to ensure an environmentally sustainable logistics together with the protection of workers' and consumers' health.

Declarations
Ethics approval and consent to participate Not applicable.

Consent for publication
Not applicable.  Estimations on ve item Likert-scales given by the interviewees related to chemical pollutants

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