Work-related diseases cause great losses to employees, companies and society at large. The work-related attributable fraction (AF) of many diseases may be considerable although it does not always mean that the disease is also recognised as an occupational disease. About 26% of low back pain has been estimated to be work-related  and 3.2% to 4.6% of all cancer deaths are due to occupational exposure. Different methods have been developed for the evaluation of economic costs to companies and society. Disease-adjusted life years (DALYs) are often used as a measure to estimate the burden of occupational and work-related diseases.
The term burden of disease (BOD) can be defined as the total, cumulative consequences of a defined disease or a range of harmful diseases with respect to disabilities in a community. These consequences include health, social aspects and costs to society. The gap between an ideal situation, where everyone lives free of disease and disability, and the accumulated current health status is defined as the burden of disease . It is a statistical measure indicative of premature death and loss of healthy life years through disabling disease and is often measured by disability-adjusted life years (DALYs). In addition to diseases, also work-related accidents contribute to BOD, causing premature death and serious injuries decreasing the quality of life. Work-related diseases and accidents are responsible for costs to individual employees, employers, companies, insurance companies and to the society at large.
According to EU-OSHA a work-related disease is any illness caused or made worse by workplace factors. This includes many diseases that have more complex causes, involving a combination of occupational and non-work-related factors . Many common diseases are partly caused by occupational factors, even though this is not the main cause for the disease. A distinction can be made between occupational disease and work-related disease, namely:
- An occupational disease is a case of disease recognised by the national authorities as being caused by a factor at work. Occupational diseases are illnesses primarily caused by a physical, chemical or biological factor at the workplace. Their attributable fraction is more than 50%. Occupational diseases can have temporary or permanent consequences. There are some differences between the recognition schemes of the EU countries in this respect which makes comparison between countries difficult. Examples of occupational diseases include noise-induced hearing loss, repetitive strain injuries, asbestosis.
- Work-related diseases (WRD) comprise occupational diseases and also other diseases, whose aetiology is partly affected by work-related factors, but their attributable fraction is less than 50%. These kinds of diseases include musculoskeletal disorders (MSDs), cardiovascular diseases, many respiratory diseases, mental health disorders and many types of cancer.
- An occupational accident is defined as a discrete occurrence in the course of work which leads to physical or mental harm . In the worst-case scenario, it represents a fatal occupational accident. Occupational accidents may cause occupational injuries.
- Occupational injury is bodily damage resulting from work.
Due to the great variety of workers' compensation systems in the EU, different definitions are used for occupational accidents and diseases resulting in different practices for reporting and recording these cases.
The attributable fraction (AF) takes into account both the relative risk of becoming ill from an exposure and the proportion of workers exposed to it. The calculation of burden of disease is carried out on the basis of disease and cause of death registers and epidemiologic studies of specific exposed groups. Attributable fraction (AF) is defined as the fraction of diseases (morbidity or mortality), which could have been avoided by removing the exposure or some other risk factor. Often the term population attributable fraction (PAF) or population attributable risk is used, when studies/evaluations refer to the whole population . The attributable fraction can be calculated using the following formula presented originally by Levin :
AF = [p x (RR-1)]/[(p x (RR-1) + 1], where
p = proportion of exposed population,
RR = relative risk of exposed population compared with the whole population (to a specific disease/outcome)
When using Levin's formula for calculating the attributable fraction, one should be aware that this formula is sensitive to various confounders. The relative risks obtained from epidemiologic studies may be influenced by several confounders such as individual lifestyle factors (e.g. smoking frequency, alcohol consumption, physical fitness, obesity) and exposure to other occupational factors. These factors depend on the study design, and the health outcomes and exposures under study. They are difficult to eliminate completely, although they are duly taken into account in most epidemiological studies.
The AF not only takes into account the relative risk of the disease but also the proportion of subjects exposed within the population. For instance, the fraction of lung cancers attributable to asbestos in a country is determined by the proportion of people exposed to this agent . The data visualisation tool based on the joint estimates of the World Health Organisation (WHO)/International Labour Organisation (ILO) joint methodology for estimating the work-related burden of disease and injury includes AF according to country and illness.
Disability-adjusted life years (DALYs)
DALYs have often been used as a measure of the burden of disease. The concept has been mainly developed within the WHO and World Bank. DALYs offer the possibility to take into account both premature mortality and the decreased quality of life due to a disease. DALY (Disability Adjusted Life Years) for an illness or health condition are calculated as the sum of the YLL (Years of Life Lost) due to premature mortality in the population and the YLD (Years Lived with Disability) for people living with the health condition or its consequences .
DALY = YLL + YLD
The YLD for a particular cause in a particular time period, is estimated by multiplying the number of incident cases in that period (I = number of cases attributable to exposure) with the average duration of the illness (L) and a weight factor (DW) that reflects the severity of the disease on a scale from 0 (perfect health) to 1 (dead) .
YLD = I * DW * L
DALYs attributable to a specific (occupational) risk factor or disease can be calculated by multiplying the disease specific DALYs of the country by the country's attributable fraction (AF) for the risk factor of interest.
The EU-OSHA report the value of OSH (2019) used different approaches for calculating the societal costs of work-related injuries and diseases . The bottom-up model uses data on the number of occupational accidents and diseases and estimates of the costs of each case. The cost estimates include direct costs, indirect costs and intangible costs and are based on extensive data sources such as healthcare costs, market output losses due to absenteeism and insurance administration costs. The top down model uses an approach that attributes a monetary value to DALYs. The result of each of the approaches is a monetary value (€) which can be expressed as a % of the Gross Domestic Product (GDP).
The WHO has been the forerunner in studies concerning the global burden of disease. The World Bank commissioned the first Global Burden of Disease (GBD) study in 1993 and the study quantified the health effects of more than 100 diseases and injuries for eight regions of the world in 1990 . Since then, the WHO has steadily improved the methodologies and metrics and also widened the scope to include more diseases and countries. The Global Burden of Disease study 2019 provides estimates of incidence, prevalence, mortality, YLLs, YLDs, and DALYs due to 369 diseases and injuries, for two sexes, and for 204 countries . All data and publications can be accessed on the website of the Institute for Health Metrics and Evaluation.
Within the GBD, health risks are classified into categories including occupational risks which allows analysing the contribution of occupational risks to the global burden of disease. In one of the first studies on the work-related burden of diseases, Fingerhut et al. (2005) concluded that five occupational risk factors accounted for an estimated 37% of back pain, 16% of hearing loss, 13% of chronic obstructive pulmonary disease, 11% of asthma, 9% of lung cancer, 8% of injuries, and 2% of leukemia worldwide and that almost all cases of silicosis, asbestosis, and coal workers’ pneumoconiosis were work-related . Another early study by Driscoll et al. (2005) evaluated the global burden of occupational diseases due to occupational carcinogens . The estimates on the work-related burden of disease are produced within the framework of the global Comparative Risk Assessment in which exposure to a specific occupational risk factor is linked to the specific attributable burden of one specific health outcome .
Not only the WHO but also the ILO has been compiling and analysing data from various sources since the late 1990s to produce Global Estimates of Occupational Injuries and Diseases. Examples of such estimates are available in the study of Takala et al. (2009)  and in the ILO report for the World Congress on Safety and Health at Work in 2014 . The ILO estimates have been based on two distinct processes, one for occupational injuries and the other on work-related diseases. The estimates for occupational injuries rely on reliable statistics from representative groups of countries that are used as 'proxy' countries to cover missing data. The estimates on work-related diseases are made by combining data on attributable fractions with WHO mortality tables  .
Since the ILO and WHO used different methods, their studies yielded different results . In 2016 both agencies made an agreement to develop a joint estimation methodology and produce a comprehensive set of estimates of work-related burden of disease: the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury (WHO/ILO Joint Estimates). The WHO/ILO Joint Estimates have been produced for 41 pairs of occupational risk factors and health outcomes. Examples of such pairs are Occupational exposure to benzene and Leukaemia and Occupational ergonomic factors and Back and neck pain. Several risk factors are linked with more than one health outcome, e.g. Occupational exposure to asbestos is paired to Larynx cancer but also to Mesothelioma. The estimates are produced within the comparative risk framework . Combining information on prevalence of exposure to a defined risk factor with information about the increased risk of the incidence of mortality from a defined health outcome among people exposed to the risk factor, allows the calculation of the population attributable fraction (PAF) for this pair of risk factor/health outcome . Based on the PAFs estimates are made of the numbers of deaths and DALYs for each health outcome attributable to its respective occupational risk factor. All estimates are available for the years 2000, 2010 and 2016, reported at country, regional and global levels, and are fully disaggregated by sex and age group. The results show that, globally in 2016, risk factors at the workplace caused the loss of 90 million (DALYs) and the deaths of 1.9 million people. Figure 1 depicts the contribution in percentage of each of the occupational risk factors to the total number of work-related deaths (inner circle) and DALYs (outer circle). The figure shows that the occupational risk factor with the largest number of attributable deaths is exposure to long working hours . More details on the data and on the pairs of risk factor/health outcome are available in the Global Monitoring report jointly published by the WHO and ILO . Infographics and a data visualisation tool can be accessed on the WHO website .
Figure 1 – Proportions of total attributable deaths and DALYs by occupational risk factor (183 countries, 2016)
The EU-OSHA website provides a data visualisation tool on the value of OSH to society . The tool highlights the key findings of a project carried out by the ILO, the Finnish Ministry of Social Affairs and Health, the Finnish Institute of Occupational Health, the Workplace Safety and Health Institute in Singapore, the International Commission on Occupational Health and EU-OSHA. The project aimed at developing worldwide estimates of the costs of work-related injuries and illnesses, covering all world regions and offering more specific data at EU member state level. The costs to society are shown in monetary terms and as a percentage of Gross Domestic Product (GDP). In addition at EU-level the distribution of DALYs amongst the main work-related causes is provided (cancer, circulatory illnesses, musculoskeletal disorders and injuries) .
The results (2017) show that work-related injuries and illnesses lead to the loss of 3.9% of all work-years worldwide and 3.3% in the EU. This loss of working years corresponds to a global cost of about 2.680 billion and 476 billion for the EU. In total, 123.3 million DALYs are lost globally due to work-related injuries and illnesses of which 67.8 million are lost due to fatal injury or illness and 55.5 million are lived with disability. In the EU, 7.1 million DALYs are lost of which 3.7 million are due to fatal injury or illness and 3.4 million are lived with disability .
The burden of work-related disease and injury differs between genders. According to the WHO/ILO Global monitoring report  the death rate per 100 000 working-age males was 51.4 while for women it was 17.2 (per 100 000 working-age women). Similarly, the DALY rate per 100 000 working-age males was 2361.1 compared with the DALY rate 911.2 per 100 000 working age females . These differences are mainly related to differences in the labour market and the different occupations traditionally held by men and women. Men tend to work in high-risk occupations such as those in industry, mining and construction. Women work more often in health and education, real estate, hotels and restaurants, and other service sectors, such as cleaning .
Findings of studies on gender differences in occupational hazard exposures  show that men are exposed to noise, vibration, medical radiation, physically demanding work, UV radiation, falls, biomechanical risks and chemical hazards while women are exposed to wet work, bullying and discrimination, work stress, and biological agents. Even when men and women work in the same occupations, there are differences. Men are more likely to be exposed to physical hazards, except for women in health care occupations and exposure to prolonged standing. Women compared to men in the same occupations are more likely to experience harassment . Women workers are also more frequently exposed to MSD-related physical risks including lifting, handling or moving persons,repetitive movements at work, awkward postures and prolonged static standing or sitting, all of which are often directly related to the prevalence of MSDs .
The burden of disease studies provide key information to guide policies and prevention strategies. Risk prevention and management activities in companies and in society should be directed more towards long term limiting illnesses and diseases, which would reduce considerably disability adjusted life years. For example, the prevention of lung cancer and other cancers is important. About 40% of cancer cases in the EU are preventable . Reducing exposure to work-related carcinogens remains a priority both in the "Europe beats cancer" plan  and in the EU Strategic Framework on Health and Safety at Work 2021-2027 . Workplace prevention strategies and measures have been set out in the Directive 2004/37/EC of 29 April 2004 on the protection of workers from the risks related to exposure to carcinogens, mutagens or reprotoxic substances at work (reprotoxic substances were added to the scope of the directive by in 2022) . The Directive has undergone major updates from 2017 onwards by introducing binding occupational exposure levels (OELs) for more than 40 known carcinogens. Several impact studies have accompanied these amendments and have made use of burden of disease data to demonstrate the benefits of reducing exposures at work. Examples are the studies on trichloroethylene and other substances , on inorganic arsenic compounds incl. arsenic acid and its salts  and on formaldehyde . Specifically on asbestos-related risks, the EU Commission is taking steps towards an asbestos-free future including further reducing the health risks of workplace exposure to asbestos. In 2022 the Commission issued a proposal for amending Directive 2009/148/EC on the protection of workers from the risks related to exposure to asbestos at work . The proposal includes a reduction in the exposure limit of asbestos at work from 0.1 f/cm³ to 0.01 f/cm³. The study analysing different policy options in preparation for the proposal used data on the burden of asbestos-related diseases to make comparisons and socio-economic impact assessments .
However, it should be noted that burden of disease (BOD) studies to some extent mainly reflect the effects of occupational exposures in past decades  and it remains therefore important to combine the results of BOD-studies with findings on emerging risks to support workplace policies. The work from EU-OSHA’s European Risk Observatory and the European Survey of Enterprises on New and Emerging Risks (ESENER) provide key data to ensure safe and healthy workplaces in the future.
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