Introduction
Work-related injury and disease, whether fatal or nonfatal, is an important cause of morbidity and mortality in all countries of the world. Most aspects of society are affected, as the injury or illness impacts not just on the injured or sick person, but also on their family, friends, and workmates. Tragically, most work-related deaths (and nonfatal conditions) are preventable and therefore should not occur, but this preventability has a positive aspect, because it means that there is an opportunity to decrease the current burden from work-related injury and illness. Understanding the scope of the problem, and how and why work-related fatal and nonfatal disorders occur, is an important first step in their prevention. This research paper aims to support this understanding by providing an overview of work-related injury and illness, focusing on fatal conditions, but including serious nonfatal conditions also. The scope covers the burden of work-related ill health in societies around the world, as well as information on the type of disorder and, particularly for injury, the circumstances in which the disorders occur.
Definitions
When considering work-related injury or illness, it is important to have a clear definition of ‘work-relatedness.’ This concept is not always straightforward and has been applied differently in different settings and by different authors. A reasonable general definition of work-relatedness is that the disorder results from a work exposure. That is, work-related exposures must have contributed as a necessary factor to the individual injury or illness.

Usually, it is clear whether or not someone is employed, but this may not be the case when the arrangements are less formal, such as family members helping out in a family business (e.g., a shop or a farm), or ad hoc work such as collecting discarded cans for recycling. These more informal arrangements occur in all societies, but are particularly common in developing countries. In the case of disease, the condition may well not become manifest until the affected person has changed jobs or retired, making the connection to work difficult to recognize or establish. Work-related disorders may even affect persons who are not employed at the time of injury or the relevant exposure. This is because persons who are not working (bystanders) can be harmed as a result of the work activity of others (e.g., a visitor to a factory being hit by a forklift truck, or a community living around a smelter affected by contaminated runof f ).

The context of the work activity is often of importance in terms of prevention and is also commonly used as the basis for inclusion or exclusion of cases. This is particularly so for work-related injury of working persons, which can be usefully divided into three groups – injuries that occur in traffic incidents on public roads in the course of work (‘work-road injuries’); other injuries that occur in the course of work (‘workplace injuries’); and injuries that occur while traveling to or from work (‘commuting injuries’). Workplace and work-road injuries are commonly combined into a single measure of work-related injuries of workers (‘working injuries’). Most injury studies include working injuries. Commuting injuries are included less consistently.
Global Burden Of Occupational Injury And Disease
Fatal Injury
Occupational injury is an important cause of mortality and morbidity throughout the world, in both developing and developed countries. The extent of the burden arising from occupational injury is difficult to determine accurately, and what information is available primarily arises from specific studies designed to assess the burden. This is true at a national and international level. Developing accurate estimates is even more difficult at an international level, but in recent years several attempts have been made. The estimates of the annual number of injury deaths of workers vary from about 140 000 to nearly 500 000, with a best estimate of about 350 000. This includes workplace and work-road deaths, but largely excludes commuting deaths, for which there are no soundly based estimates. The main problems with the global estimates are a widespread lack of data, the ‘contamination’ of injury data by the inclusion of some disease cases in some countries, and the inconsistent inclusion of homicides, suicides, and commuting deaths (Driscoll et al., 2005c).

There are no global or regional estimates of bystander injury deaths, but bystander death is an important occupational injury issue, and some idea of the scope of the problem is given by two national studies. These studies found that the number of workplace bystander deaths was between one-tenth (New Zealand) and one-quarter (Australia) of the number of workplace deaths. In Australia the number of road bystander deaths (nonworking persons killed in motor vehicle incidents on public roads in which the working vehicle was ‘at fault’) was similar to the number of work-road deaths.
Fatal Disease
As with injury, occupational disease is an important cause of mortality and morbidity throughout the world, but the extent of the burden is much more difficult to quantify. This is because most diseases can have a number of possible causative exposures or exposure circumstances and take many years to become fully developed, which makes it extremely difficult to establish a connection between work exposures and a resulting disease in an individual case. This has meant that epidemiological approaches, particularly population attributable risk (PAR) techniques, have been used. These require an estimate of the risk arising from exposure, and of the prevalence of exposure. Risk information is obtained from epidemiological studies and is probably broadly generalizable from one exposure circumstance to another. Reliable exposure information is commonly not available, or inconsistently available, for many countries. This has meant that extrapolation between countries and time periods is commonly required for national and global estimates.

As for injuries, several attempts have been made in recent years to establish global estimates of occupational disease. The estimates of the annual number of disease deaths of workers vary from about 325 000 to about 1.6 million, with the higher estimates probably the most accurate (Driscoll et al., 2005c). The recent Comparative Risk Assessment project of the World Health Organization (WHO) provided global estimates of fatal (and nonfatal) disease arising from carcinogens (Driscoll et al., 2005a), airborne exposures (Driscoll et al., 2005b), and injury risk factors (Concha-Barrientos et al., 2004). The disease estimates from the various studies have considerable uncertainty, arising in particular from missing, sparse, or old information on exposure and overall rates of death for specific diseases, and varying inclusion and exclusion criteria. There are no estimates at either national or global level of bystander disease deaths.
Nonfatal Injury And Disease
Global estimates of injury and disease usually focus on mortality, mainly because in the statistics collected by countries and institutions the mortality data are generally more comprehensive. However, nonfatal conditions can still result in considerable morbidity. Because it can be difficult to compare or combine the burdens arising from fatal and nonfatal conditions, several measures have been developed to enable this to be done. The most commonly used such measure is the disability-adjusted life year (DALY), which is a weighted estimate of the number of years lived with disability. The severity of the disability is described by the weighting. The DALY therefore represents the gap between the current situation and an ideal situation in which everyone achieves an agreed standard life expectancy in perfect health (Driscoll et al., 2005a).

On the basis of DALYs, which allow both fatal and nonfatal disorders to be included, the recently completed Comparative Risk Assessment project estimated that work-related exposures were responsible at a global level for about 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. Looking only at health-care workers, about 40% of hepatitis B and hepatitis C infections and 4.4% of HIV infections in these workers were estimated to be due to needlesticks (Concha-Barrientos et al., 2004).