Global Burden of Disease from Occupational Health Risks
The overall picture that emerges from all parts of the developing world is one of increased health and safety risks in all occupations for which data are available.
Dramatic changes in the global labor force will occur as globalization and population growth continue to affect the global economy. For example, the labor force in Latin America and the Caribbean is one of the fastest growing in the world, with 217 million workers in 2000; the number of workers is expected to reach 270 million in 2010 (PAHO 2002). The burden of disease and injury attributable to workplace risks in the formal and informal sectors is grave and will continue to rise. Inadequate data and reporting systems make capturing the effect of workplace risks problematic. Nonetheless, several recent efforts by international bodies have shed some light on the staggering burden, although in general attempts to derive evidence-based estimates are likely to systematically and significantly underrepresent the extent of the problem.
The gravity of workplace risks is seen in the recent International Labour Organization (ILO) estimate that among the world's 2.7 billion workers, at least 2 million deaths per year are attributable to occupational diseases and injuries. The ILO estimates for fatalities are the tip of the iceberg because data for estimating nonfatal illness and injury are not available for most of the globe. The ILO also notes that about 4 percent of the GDP is lost because of work-related diseases and injuries (Takala 2002).
A recent effort of the World Health Organization (WHO) has provided insight into the global dimensions of several selected occupational health risks. WHO included five occupational risk factors in its comparative risk assessment in a unified framework of 26 major health risk factors contributing to the overall global burden of disease and injury (Ezzati and others 2002, 2003; WHO 2002). The WHO comparative approach used a common statistical model that allows a reader to compare the contribution (attributable fraction) of several risk factors to a single outcome—lung cancer, for example. Stringent requirements for consistency in describing risk factors limited the number of occupational risk factors that could be included in the study. For all risk factors, it was necessary to estimate an exposed population and exposure levels for 224 age, sex, and country groups in the 14 WHO geographic regions of the world. Where possible, data could be extrapolated to age, sex, and country groups for which data were not available, based on similarities in demographic, socioeconomic, or other relevant indicators. Because knowing the existing burden of disease and injury globally was necessary, the only outcomes included were those for which WHO had rates of disease or injury for all regions calculated by International Classification of Disease (ICD) codes. Finally, estimates of the risk factor-burden relationships by age, sex, and WHO subregion were generated. Risk measures (relative risks or mortality rates) for the health outcomes resulting from exposure to the risk factors were determined primarily from studies published in peer-reviewed journals. Adjustments were made to account for differences in levels of exposure; exposure duration; and age, sex, and subregion, as appropriate. The information about each risk factor was entered into the WHO common model for comparative analysis. The resulting burden was described as the attributable fraction of disease or injury, using mortality and disability-adjusted life years (DALYs) lost, with one DALY being equal to the loss of one healthy life year—the common currency measure that includes mortality and morbidity.
Because of the requirements for global data, only five occupational risk factors could be described: risks for injuries, carcinogens, airborne particulates, ergonomic risks for back pain, and noise. The exposed worker populations were estimated using an approach based on the International Standard Industrial Classification of All Economic Activities (ISIC), an economic classification system of the United Nations that organizes all economic activities by economic sectors and relevant subgroupings (UN 2000). The ISIC system is used almost universally by national and international statistical services to categorize economic activity; therefore, it allows global comparisons. The ILO has developed economically active population (EAP) estimates by applying economic activity rates, by sex and by age group (older than age 15), to the population estimates and projections of the United Nations (ILO 1996). The EAP provides the most comprehensive global accounting of people who may be exposed to occupational risks because it includes people in paid employment, the self-employed, and people who work to produce goods and services for their own household consumption, both in the formal and in the informal sectors (ILO 2002). For the WHO comparative risk assessment, the EAP was further divided into nine economic subsectors (where people work) and seven occupational categories (what type of work people do), on the basis of country-level data for 31 countries (ILO 1995).
The absence of data in much of the developing world limited the range of occupational risk factors that WHO could measure, and the available data excluded children under age 15 who work. The WHO comparative risk assessment also excluded important occupational risks for reproductive disorders, dermatitis, infectious disease, coronary heart disease, intentional injuries, musculoskeletal disorders of the upper extremities, and most cancers. Psychosocial risk factors such as workplace stress could not be studied, nor could pesticide, heavy metal, or solvent exposures. The potential consequences of omitting just pesticides from the global burden analysis can be illustrated by the situation in Central America (PAHO 2002). The isthmus is primarily an agricultural and forested area of .5 million square kilometers, of which 40 percent is arable. Pesticide imports almost tripled from 15,000 metric tons in 1992 to 41,000 in 1998, and 35 percent of the pesticides were restricted in the exporting countries. In 2000, the subregion imported some 1.5 kilograms of pesticides per inhabitant per year, a quantity 2.5 times greater than the world average estimated by WHO. Exposures in the formal and informal sectors extend to the homes and families of the pesticide workers. Although this situation is common in developing nations, the WHO comparative risk assessment captured none of these exposures.
The ILO and WHO data provide the most current, yet still incomplete, picture of the overall problem of occupational health risks. Nonetheless, with just the few occupational risk factors studied in depth by WHO a picture emerges of the significant effect of largely preventable conditions (Ezzati and others 2004). WHO found that occupational injuries result in about 312,000 deaths per year for the world's 2.7 billion workers; this figure contrasts to the approximately 6,000 deaths per year caused by occupational injuries for the 150 million workers in the United States. As in the industrial world, high injury fatality rates in the developing world are clustered in certain sectors, including agriculture, construction, and mining. Using this metric, occupational injuries account for more than 10 million DALYs and 8 percent of unintentional injuries worldwide.
The second occupational factor WHO analyzed was the effect of exposure to workplace lung carcinogens (such as asbestos, diesel exhaust, and silica) and leukemogens (such as benzene, ionizing radiation, and ethylene oxide). WHO concluded that occupational exposures account for about 9 percent of all cancers of the lung, trachea, and bronchus and about 2 percent of all leukemias. Overall, about 102,000 deaths were attributable to these two occupational cancers and about 1 million DALYs.
Estimates of the global burden of chronic lung disease demonstrate the significant contribution of occupational exposures, which account for about 13 percent of all chronic obstructive pulmonary disease (COPD) and about 11 percent of asthma. In total, WHO found the annual worldwide burden of work-related COPD to be about 318,000 deaths per year and about 3.7 million DALYs. The occupational risk contribution to the worldwide asthma burden was about 38,000 deaths and about 1.6 million DALYs, reflecting the fact that a great deal of asthma occurs at younger ages and is not fatal. WHO found that 37 percent of all back pain worldwide is attributable to work, resulting in an estimated 800,000 DALYs, a significant loss of time from work, and a high economic loss. Worldwide, 16 percent of all hearing loss is attributable to workplace exposures, resulting in 4.2 million DALYs.
WHO made a special risk analysis of hepatitis B, hepatitis C, and HIV infections among health care workers caused by contaminated sharps, such as syringe needles, scalpels, and broken glass (WHO 2002). This analysis illustrates the general problem of high risks existing in the small worker population having exposure. WHO found that, among the 35 million health workers worldwide, there were 3 million percutaneous exposures to bloodborne pathogens in 2000. This finding is equivalent to between 0.1 and 4.7 sharps injuries per year per health worker. WHO concluded that of all the hepatitis B and hepatitis C present in health care workers, about 40 percent was caused by sharps injuries, with wide regional variation. WHO also found that between 1 and 12 percent of HIV infections in health care workers was caused by sharps injuries. The comparative risk assessment by region and type of infection indicates where special emphasis is needed (see figure 60.1). Clearly, solutions exist to these problems, as shown by the countries that have engaged in serious prevention efforts. Proper needle handling and waste management, substitutions for sharps, hepatitis B virus (HBV) immunization, postexposure prophylaxis, training, and legislative measures have been successful. Beyond the personal and workplace consequences, the potentially devastating societal impact of loss of this critical worker group can be anticipated if prevention measures are not ensured in developing countries, where the proportion of health care workers in the population is already small.
[Figure
60.1]
In total, the few occupational risk factors considered here were responsible for about 800,000 deaths worldwide in 2000. Not considered by WHO because of lack of global data are the additional 1.2 million deaths that ILO estimated are attributable to work-related risks (Takala 2002). The leading occupational cause of death was unintentional injuries, followed by COPD and lung cancer. Workers who developed outcomes related to these occupational risk factors lost about 25 million years of healthy life. Among the occupational factors analyzed in this study, injuries, hearing loss, and COPD accounted for about 80 percent of years of healthy life lost. Low back pain and hearing do not directly produce premature mortality, but they do result in substantial disability. This feature differentiates these conditions from the others analyzed in the study. Figure 60.2 provides summary results for the occupational risk factors.
[Figure
60.2]
The WHO comparative risk assessment has accounted for only about 800,000 (40 percent) of the 2 million deaths estimated by ILO to occur each year because of occupational illness and injury. Deaths attributable to a wide range of occupational exposures could not be included because of the strict requirements for global data. Missing are deaths attributable to asbestosis, silicosis, and other dust diseases; infectious diseases; cardiovascular diseases; and violence. Deaths attributable to workplace exposures to pesticides, heavy metals, solvents, and other chemicals are not included. Outcomes such as dermatitis, psychological disorders, and upper-extremity musculoskeletal disorders that cause little mortality but substantial disability are also not captured by the WHO comparative risk analysis. Additionally, the consequences of underreporting in existing systems and the dearth of record-keeping systems in the developing nations lead to substantial undercounting by both the ILO and WHO. Nonetheless, the analyses provide important insights into the immense global burden of disease and injury attributable to occupational risk factors.
