Occupational epidemiology is a subdiscipline of epidemiology that focuses on investigations of workers and the workplace. Occupational epidemiologic studies examine health outcomes among workers, and their potential association with conditions in the workplace including noise, chemicals, heat, or radiation, or work organization such as schedules. The need for evidence to inform occupational safety regulations, workers' compensation programs, and safety legislation motivated the development of public health policy, occupational epidemiology methods, and surveillance mechanisms. Occupational epidemiological research can inform risk assessments; development of standards and other risk management activities; and estimates of the co-benefits and co-harms of policies designed to reduce risk factors or conditions that can affect human health. Occupational epidemiology methods are common to methods used in environmental epidemiology.
History Occupational hazards have long been recognized. For Hippocrates recommended other physicians consider patients' vocational backgrounds when diagnosing and treating disease, and Bernardino Ramazzini in 1700 outlined many occupational diseases in his book De Morbis Artificum. There are several examples from the 19th century onwards of hazard recognition proceeding to systematic epidemiology studies. In one example, premature mortality was reported among gold and silver miners in the Erz Mountains in Germany as early as the 16th century. It was initially thought to be the result of consumption, but it was subsequently determined to be silicosis, and studies from 1879 through the 1930s uncovered the association of miners' deaths with lung cancer and nonmalignant respiratory diseases. Other examples include cancer among chimney sweeps, asbestos-related diseases, and the variety of occupational diseases found among factory workers in the early 1900s. Occupational health risks were initially observed by case series reports of apparent disease excesses or clusters. Although the case series approach provided a good indicator of occupational hazards, they are not adequate on their own to assess a wide spectrum of health outcomes that may not be closely related to workplace exposure. The development of retrospective, cohort design allowed for a more comprehensive study of the cases. Desire to improve the cost-efficiency of studies led to the use of case-control studies. Other methods later used in occupational epidemiology include cross-sectional and longitudinal studies.
Early disease of concern recognized in the workplace
Coal Workers' Pneumoconiosis The classic and preventable lung disorder of the mining industry, pneumoconiosis is commonly known as “black lung disease” and due to long term exposure to coal dust. This condition has been identified since 1775 and has been officially listed as an occupational disease since 1980 by the ILO List of Occupational Diseases. Coal Workers Pneumoconiosis (CWP) develops when coal dust accumulates over time in the respiratory system and creates dark spots of trapped coal dust particles called coal macules. CWP typically takes at least 10 years to develop after initial exposure and as the scarring continues to worsen, oxygen may be prevented from reaching the blood which subsequently puts stress on other organs, such as the heart and brain. The CDC and NIOSH examined and assessed trends in premature mortality attributed to CWP from 1999 to 2016, which are the most recent years for which complete data is available and calculated years of potential life lost to life expectancy (YPLL). From 1999 to 2016, people aged 25 and older with CWP lost more years of life relative to their life expectancy than expected. This suggests that there has been increased CWP severity and rapid disease progression and highlights the importance of strengthening prevention measures to prevent premature CWP-associated mortality. The Coal Workers’ Health Surveillance Program (CWHSP) was established by the Federal Coal Mine Health and Safety Act of 1969. The mission of this program is to detect lung disease early in coal miners to subsequently prevent progression to severe lung disease. CWHSP provides U.S. coal miners with black lung screening opportunities at no cost to miners and are available when miners initially begin employment and at periodic intervals throughout their careers. The Mine Safety and Health Administration (MSHA) announced that they will give coal miners with black lung disease the right to work in areas with lower dust levels without reduced pay, discrimination, or termination. In 2014, MSHA landmark respirable dust rule went into effect with phase III in 2016, which decreased allowable exposure to respirable coal mine dust, which is the most effective means of preventing CWP caused by excessive exposure to such dust.
Occupational exposures The ability to identify, measure and model workplace exposures is a key step in the prevention of occupational illness. Occupational epidemiologists collaborate with industrial hygienists through field investigations that seek to identify and assess hazard exposures in the workplace. Depending on the type of work being done, many modes of exposure exist--droplet exposure through air, consumption, and injection are three occupational examples. The exposures experienced by a miner would differ from a nurse, but both fall under the jurisdiction of occupational epidemiology. Specific exposures associated with disease may be encountered in or near the workplace: compounds such as carbon monoxide leading to carbon monoxide poisioning and pesticide molecules leading to pesticide poisoning are two. After identifying such exposures, occupational epidemiologists use data analysis skills to create models illustrating a dose-response relationship. This leads to an understanding of how much, if any, exposure is safe. Data on both the amount of occupational disease and the level of exposure to a particular hazard will be collected and compared to discern whether there is a correlation.
Types of studies
Case series Typically occupational epidemiological investigations begin with the observation of an unusual number of cases of disease among a group of workers. When the investigation does not go further than what is referred to as identifying a disease cluster, the study is referred to as a case series report.
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