Introduction to occupational diseases

Introduction

Occupational diseases span a broad range of human illnesses, many of which clinically and pathologically are not different from those of non-occupational origins. They are contracted as a result of exposure to risk factors resulting, at least partially, from work activities. The diagnosis of occupational diseases can rarely be established on clinical grounds alone. It is essential to reveal the link between occupation and disease because of the employers’ responsibility to prevent occupational diseases and the compensation of ill workers. However, the list of reportable occupational diseases, as well as the related compensation systems, differs from country to country, making comparisons considerably more difficult.

Definition of ‘occupational disease’

Several definitions of the term “occupational disease” exist. However, for the purpose of the Protocol of 2002 to the Occupational Safety and Health Convention of International Labour Organisation (ILO), the term ‘occupational disease’ covers any disease contracted as a result of an exposure to risk factors arising from work activity” (Article 1 (b)) ^[1]. The ILO Employment Injury Benefits Recommendation (1964, Article 6, (1)) defines occupational diseases more precisely in the following terms: “Each Member should, under prescribed conditions, regard diseases known to arise out of the exposure to substances and dangerous conditions in processes, trades or occupations as occupational diseases.” ^[2] The various definitions, however, have two main mandatory elements in common ^[3]

1. the causal relationship between exposure in a specific working environment or work activity and a specific disease; and,
2. the fact that the disease occurs among the group of exposed persons with a higher frequency rate than in the rest of the population, or in other worker populations.

The causal relationship is established on the basis of clinical and/or pathological data, occupational background and job analysis, identification and evaluation of occupational risk factors and of the role of other risk factors ^[4]. As a general rule, the symptoms are not sufficiently characteristic to allow an occupational disease to be diagnosed without the knowledge of the physical, chemical, biological and/or other risk factors encountered in the exercise of an occupation. The recognition of an occupational disease is a specific example of clinical decision-making or applied clinical epidemiology ^[4]. Deciding on the pathology of a disease is not an “exact science” but rather a question of judgement based on a critical review of all the available evidence. This should include the strength of association, consistency, specificity, time sequence or biological gradient (the greater the level and duration of the exposure, the greater the severity of the diseases or their incidence) ^[3][5]. To support the diagnosis of occupational diseases more detailed information, guidance notes including diagnostic criteria has been elaborated:

• EU Commission, Information notices on occupational diseases: a guide to diagnosis, 2009. [23]
• Diagnostic and exposure criteria for occupational diseases. Guidance notes for diagnosis and prevention of the diseases in the ILO List of Occupational Diseases, 2022. [24]

Further definitions concerning occupational and work-related diseases

Reportable occupational diseases: Occupational diseases mentioned in national lists as part of national laws or administrative provisions liable for compensation and subject to prevention measures. Reported occupational diseases are reportable diseases already passed through the legally required reporting process.
Recognised occupational disease: A recognised case of an occupational disease is a case accepted as such by a competent national authority in an administrative proceeding ^[6] [7].
Work-related diseases: All illnesses that can be caused, worsened or jointly caused by working conditions. Work-related diseases have a complex aetiology. Among their multiple causal agents, factors arising from the work and/or working environment play a role in the development of such diseases. Work-related diseases include diseases with solid scientific evidence concerning a possible occupational origin which may, however, not fulfil all given criteria for recognition of an occupational disease according to the rules of the national authorities^[8].

Historical overview

The history of occupational diseases is as old as organised economic activity. Back pain resulting from strain at work is described in an Egyptian papyrus and a case of severe lead colic was recounted by Hippocrates. Other early writers like Pliny also recognised the association between certain disorders and occupations (e.g., mercury poisoning of slaves working as miners).
During the Middle Ages, where primitive methods of ventilation and personal protection were used in gold and silver mines, common mining accidents and miners’ occupational diseases caused by dust inhalation were studied and described. Ramazzini’s description of the diseases associated with 54 different occupations (e.g., the mercury poisoning of Venetian mirror makers) provides a comprehensive account of occupational disorders (18th century).
The rapid technological progress and growth during the era of Industrial Revolution of the 19th century led to unsanitary working and living conditions. This corresponded with a rise in the number of accidents and deaths among workers caused by new machinery and exposure to toxic materials.
Percivall Pott, a London surgeon, first described occupational cancer when finding links between the prevalence of scrotal cancer among chimney sweeps and the prolonged exposure to soot ingrained into their skin. In the 20th century, the incidence of classic occupational diseases such as lead poisoning and anthrax have declined, although none have been eradicated. Furthermore, new diseases have appeared as a result of advances in technology or of changes in work or working conditions. For example: occupational deaths among radiologists as a result of occupational X-ray exposures, asbestos-related diseases or hemangiosarcoma caused by vinyl chloride monomer ^[9] [10].
The turn of the third millennium is witnessing the emergence of a different set of challenges, including work-related musculoskeletal disorders, psychosocial issues, and work-related mental health disorders ^[11].

Workers’ compensation

History and general aspects

Statutory compensation for occupational (industrial) diseases was enacted first in Germany and then in the United Kingdom in the late nineteenth and early twentieth centuries. During the twentieth century this trend continued in the vast majority of countries in Western Europe and North America. The moral basis or social philosophy underlying workers' compensation is the efficient and dignified provision of financial and medical benefits to those suffering from a disease caused by their work or injured on the job; and the allocation of the expenses to an appropriate source, i.e. the consumer. The cost of insurance is reflected in the cost of goods or services produced by the employer; thus the cost of workers' compensation liability is passed ultimately to consumers. This system is meant to preserve the injured worker's dignity and well-being by providing an income and medical care, benefits for physical and mental disablement and by keeping them off welfare. Broader coverage can also include prevention and rehabilitation as it already does in some countries.

Workers' compensation is a no-fault law: in case of an occupational accident or disease, the policyholder is to collect compensation for any loss of worker (death, ill-health) without a determination of liability. The current schemes in each country provide compensation for accidents and diseases attributed to work. However, there are important differences in coverage and funding between the different countries. Which diseases are compensated can in principle be decided by attributing the disease to an occupational exposure-effect relationship in the individual case (“individual proof’) or from a list of occupational diseases, where scientific evidence of an exposure-effect relationship in particular circumstances is sufficient to allow the “benefit of presumption”. In practice, a combination of these principles is found in the various schemes.

Compensation schemes in Europe

European compensation systems are generally based on two methods. One is modelled after the German approach, with self-governed sectoral insurance associations funded by employers' contributions. This provides a comprehensive prevention, rehabilitation and compensation service. In the second form, the state administers the system for compensating occupational diseases as part of its wider provision for social security and levies contributions from employers to finance it. In most countries these two approaches are mixed with participation of both the state and private insurance systems. In Belgium, for instance, there is a state system for occupational diseases for industrial and commercial sector workers. In Denmark, occupational diseases are insured by specific funds financed by contributions from employers. In Norway the private employers’ insurance system ‘tops up’ the funds provided by the state system. The United Kingdom Industrial Injuries scheme is a government-funded compensation scheme for employed earners providing benefits to those suffering from listed ‘prescribed diseases’. In many European countries, occupational disease insurance systems are now also involved in prevention and rehabilitation. In all European countries, compensated (reportable) diseases are covered in a list ^[12]. There is also a European Union list (European Schedule of Occupational Diseases = ESOD) ^[13]. In Sweden, only infectious diseases are listed; eligibility for other conditions is open and based on individual assessment. Finland has an indicative list, but its system does not exclude other conditions. France and the United Kingdom are, in general, more prescriptive and permit only listed diseases ^[12].

Legal aspects

ILO List of Occupational Diseases (revised 2010)

The 1996 ILO code of practice claims that each government should formulate, implement and periodically review a coherent national policy and principles on the recording, notification and investigation of occupational diseases ^[3]. As a part of this policy, a national list of occupational diseases should be established. This list should comprise, to the extent possible, the diseases appearing in the ILO list of occupational diseases. The ILO list is regularly reviewed and updated at tripartite meetings of experts convened by the Governing Body of the ILO. The national lists of occupational diseases should be reviewed and updated with due regard to the most up-to-date ILO list (most currently adopted in 2010). The list includes a range of internationally recognised occupational diseases, from illnesses caused by chemical, biological and physical agents to respiratory and skin diseases, musculoskeletal disorders and occupational cancer. Mental and behavioural disorders have also been specifically included in the ILO list. This list also has open items in all the sections dealing with all the aforementioned diseases. The open items allow the recognition of the occupational origin of diseases not specified in the list if a significant association is observed between exposure to risk factors arising from work activities and the disorders contracted by the worker. The sections and subsections of occupational diseases applied in the current list are as follows:

1. Occupational diseases caused by exposure to agents arising from work activities
   1. Diseases caused by chemical agents
   2. Diseases caused by physical agents
   3. Biological agents and infectious or parasitic diseases
2. Occupational diseases by target organ systems
   1. Respiratory diseases
   2. Skin diseases
   3. Musculoskeletal disorders
   4. Mental and behavioural disorders
3. Occupational cancer
4. Other diseases

The list is not exhaustive to include every occupational disease but rather specifies those considered common to many countries. The list should, therefore, be adapted to local circumstances, and used to help prioritise occupational diseases ^[14].

ILO Protocol of 2002 to the Occupational Safety and Health Convention, 1981

The provisions of the Protocol state that the competent national authorities shall establish and review requirements for the recording and notification of occupational diseases. The requirements shall determine among others ^[1]:

• the responsibility of employers to keep records on occupational diseases;
• the use of these records to establish preventive measures at the workplace;
• the maintenance period of these records;
• measures to ensure the confidentiality of personal and medical data;.
• the responsibility of employers to notify the competent authorities;
• to provide appropriate information to workers and their representatives concerning the notified cases.

The Protocol makes a recommendation concerning the data required for the notification, for example: on the enterprise, establishment and employer; the workplace, the circumstances of the exposure to health hazards. Each Member shall publish annual statistics concerning occupational diseases as well as the analyses thereof. The statistics shall be established following classification schemes that are compatible with the latest relevant international schemes.

Commission Recommendation concerning the European schedule of occupational diseases 2003/670/EC

Recommendation 2003/670/EC^[13] aims to improve knowledge of occupational diseases, reduce illness by stepping up prevention and support workers by making it easier for them to prove a link between their occupational activities and their illness and apply for compensation. The Member States should lay down workers´ rights to compensation in respect of all diseases which can be proved to be occupational in origin and nature. Prevention is supported, for instance, by promoting research or by target setting, which means formulating quantified targets for the reduction of the rates of recognised occupational diseases. The Recommendation highlights the meaning of research on ailments linked to an occupational activity, and of raising awareness among medical staff. Networking and information exchanging tasks are assigned to the European Agency for Safety and Health at Work concerning occupational illnesses. There are two annexes linked to the Recommendation. Annex 1 comprises 108 diseases divided in five groups according to their causative factors (chemical, physical, infectious, etc.) or the affected organs (e.g. the skin). This annex, the European schedule of occupational diseases, should be introduced into the national laws and regulations. The diseases mentioned in this schedule must be linked directly to the specific occupations, and, therefore, are liable for compensation and subject to prevention measures. Annex II of the Recommendation comprises 48 additional diseases that can be proved to be occupational in origin and nature and thereby granting the workers right to compensation ^[13]. The European Commission has published a guideline providing stakeholders key criteria for diagnosing occupational diseases listed in the Recommendation^[5]. The impact of the Recommendation was reviewed in 2013 ^[12]. The analysis produced several scenarios and suggestions for an EU-wide strategy to improve the identification and recognition of occupational diseases and to strive for a more harmonised approach between the different Member States^[12].

Regulation No 1338/2008 of the European Parliament and of the Council

The Regulation No 1338/2008 of the European Parliament and of the Council establishes a common framework for the systematic production of community statistics on public health and health and safety at work ^[7]. According to the scope of the regulation a case of occupational disease is defined as such by the national authorities responsible for the recognition of occupational diseases. In contrast, a case of work-related illness does not necessarily require recognition by an authority. The occupational diseases dataset shall be established in the framework of the specifications laid down by the European Occupational Diseases Statistics (EODS) methodology, taking into consideration the circumstances and practices in EU Member States. This common dataset shall cover the following list of subjects: characteristics of the disease of the sick person (including, gender and age), characteristics of the enterprise and workplace, the causative agent or factor. The overall aim of EODS is to obtain gradually synchronised, comparable and reliable data and indicators (for example exposure, occupation at time of exposure, severity of disease) on occupational diseases in Europe ^[15]. The 1^st results of the EODS data collection were published in 2010 but the project has been discontinued due to comparability issues. Eurostat has re-launched the collection of national data and the dissemination of aggregated data on occupational diseases in 2017. The statistics are presented on the basis of one indicator (EU Index) showing the evolution of occupational diseases over time^[16].

Current challenges

Developments in the national lists of occupational diseases: co-ordinating structure, wording and content of the lists

Most European countries have a national list of occupational diseases. These lists cover about the same content as the ESOD (European Schedule of Occupational Diseases, Annex I), although the number of specific diseases in the national lists varies from 32 to 141. The different numbers are due to the different characteristics and structures of the lists, and to the different structures of the particular diseases or groups of diseases within the lists. Only a few countries report that their lists do not include a number of diseases in the ESOD. In countries with relatively small populations and limited fields of industrial production, the national lists probably do not need to adopt all the diseases in the EU list. In almost all European countries, there is growing public interest in the structure and content of the national lists of occupational diseases and they are under active discussion. Consequently, the originally created national lists were amended on a number of occasions with new occupational diseases added ^[12]. For instance, COVID-19 associated with work-related activities has been added to the national lists in many of the EU countries since the outbreak of the pandemic in early 2019^[17].

The ESOD certainly contributed to more harmonised lists in the Member States. However, there is no general agreement on the diagnostic criteria of occupational diseases despite attempts to reach a consensus of the following items in relation to diseases listed in ESOD ^[5]:

• Minimum intensity of exposure: the minimum level of exposure that is required to cause disease. Lower exposures are unlikely to lead to occupational disease. This concept is applicable especially to toxic agents. Usually no minimum threshold dose can be defined for carcinogenic or allergenic agents.
• Minimum duration of exposure: the shortest exposure period for which a disease can occur. Periods of exposure less than this are unlikely to cause disease.
• Maximum latent period: This refers to the period after the cessation of exposure, beyond which it is unlikely that any disease can be attributed to the exposure. For example, acute myocardial ischemia occurring a year after an acute exposure to carbon monoxide is not attributable to that exposure.
• Minimum induction period: This is the shortest period from the beginning of an exposure to the beginning of a disease below which the exposure would have been unlikely to have caused the disease. For example, lung cancer developing within a year after the first exposure to asbestos is unlikely to be attributed to that exposure.

Priorities for prevention of occupational diseases at the European level

The EU OSH Strategic Framework 2021 – 2027 emphasises the need to reduce occupational diseases in the EU. Priorities identified are combatting work-related cancer, addressing occupational circulatory diseases, reducing work-related musculoskeletal disorders and limiting exposure to reprotoxic substances^[18]. Steps have already been taken by

- extending the scope of the Directive 2004/37/EC^[19] on carcinogenic and mutagen substances to carcinogens, mutagens and reprotoxic substances (CMR) (amending Directive 2022/431/EU)^[19];

- establishing and reinforcing occupational exposure limits (OELs) for carcinogenic, mutagenic and reprotoxic substances.

Further actions will take place such as raising awareness on musculoskeletal disorders (e.g. the launch of EU-OSHA's Healthy Workplaces Campaign 2023-2025 on creating a safe and healthy digital future, focusing on psychosocial and ergonomic risks), providing guidelines for protecting workers against exposure to hazardous medicinal products and imposing stricter exposure limits for substances such as lead and asbestos^[18].

The EU parliament adopted in 2022 a resolution on a new EU strategic framework on health and safety at work post 2020^[20]. In the resolution the parliament stresses the importance of ensuring proper compensation for workers in cases of occupational diseases. The parliament calls on the Commission to revise the 2003 Commission Recommendation concerning the European Schedule of Occupational Diseases with additions such as work-related musculoskeletal disorders, work-related mental health disorders, all asbestos-related diseases, all skin cancers and rheumatic and chronic inflammation. The parliament also asks the Commission to transform the recommendation into a directive after consulting the social partners; thus, creating a minimum list of occupational diseases and setting out minimum requirements for their recognition and adequate compensation for individuals concerned.

Emerging risks

Definitions and typology of new work-related diseases

Changes in work and working conditions have resulted in new occupational health risks and new occupational diseases. The same is true for every new technology with potential new risks. These risks, if not assessed and managed properly, could have serious potential consequences for human health. Proper risk assessment and health surveillance is needed to collect empirical and research data, and risk management to prevent new occupational diseases. The European Agency for Safety and Health at Work identifies such emerging risks and provides data and information to policy makers and other relevant stakeholders^[21]. Examples of emerging risks include:

• Risks previously unknown and caused by new processes / technologies / types of workplaces, or social / organisational changes. For example, nanotechnology is a key technology of the 21st century with far-reaching implications for science, industrial development and new product design.
• Work-related stress is recognised as a major obstacle to productivity in Europe. Work-related mental health is interrelated with cardiovascular diseases. Exposure to job strain, job insecurity and workplace bullying has been identified as a risk factor for cardiovascular diseases. For instance, the burden of disease of work-related depression is estimated at 528 549 DALYs for men and 344 151 for women (respectively 7862 and 1823 deaths)^[22].
• ICT & digitalisation in the world of work can reduce risks by removing workers from hazardous environments. At the same time IT & digitalisation can increase ergonomic risks due to more online working, the use of mobile devices in non-office environments and new human-machine interfaces. IT & digitalisation may also lead to more work-related stress as a result of the blurring of traditional boundaries between work and private life, permanent connectivity and the increasing use of AI to control work processes^[23].

Table 1. Categories of new work-related diseases, with examples.

Source: van der Laan ^[24] and EU-OSHA^[25]

Methodology

Detecting new occupational health risks may require different instruments – and often several complementary methods instead of using a single one – from those used for monitoring known occupational diseases.

An EU-OSHA report^[25] reviewed methodologies that can be used to identify work-related diseases. These methodologies are subdivided into Compensation-based national systems and Non-compensation-related systems. Within the compensation-based systems, there are systems that, in addition to the list of recognised cases of occupational disease, also offer the possibility of submitting a claim for a disease that is not on the list (open system). These open systems are also suitable for identifying new/emerging work- related health problems.

The non-compensation-related systems comprise data collection systems, sentinel systems and public health surveillance systems. The sentinel systems sentinel seem to be the most suitable approach. Sentinel systems are specifically designed to provide a signal on emerging work-related diseases (cases) and that will initiate interventions and prevention. The reporting of cases is based on the voluntary participation of occupational physicians who provide a more detailed exposure assessment in comparison with other methodologies. More details and examples on the sentinel approach can be found in the research reports:

• Methodologies to identify work-related diseases: Review of sentinel and alert approaches [25]
• Alert and sentinel approaches for the identification of work-related diseases in the EU [26]