Occupational Exposure to Coal, Genotoxicity, and Cancer Risk

Coal is a heterogeneous mixture containing large quantities of organic and inorganic matter, including carbon, hydrogen, oxygen, sulfur, nitrogen, and organometallic forms. The presence of mineral matter in coal may result in a number of environmental and human health problems related to its mining, preparation, and combustion. During coal mining activities, large quantities of coal dust, ashes, polycyclic aromatic hydrocarbons (PAHs), and heavy metals are released into the environment, forming a complex mixture. This mixture becomes one of the most important occupational risks for the health and safety of workers due to its synergistic, additive, and enhancing effects. Once inside the organism, this cocktail-like mixture can interact with cellular mechanisms related to the production of reactive oxygen species (ROS) and can cause damage in important macromolecules such as DNA, lipids, and proteins. In this review, human populations exposed to coal and coal burning were analyzed. Data from different studies were evaluated in relation to the effect of complex mixture exposure on DNA damage and mechanisms, and the background factors, such as gender, age, or smoking habit. The high temperatures that occur in combustion processes affect the characteristics of the resulting particles. The coal fly ash is released by combustion and its composition varies depending on the coal type and the method of collection used such as electrostatic precipitators. Compounds such as PAHs once activated by the organisms have been shown to have mutagenic and carcinogenic activity due to its ability to form adducts with purines. Moreover, metals that commonly are evaporated during the cooling process increase its toxicity. The particles when inhaled can pass from the alveoli into the bloodstream and affect extrapulmonary organs. Several studies have described the inflammatory cascade that triggers exposure to coal and coal fly ash particles; they have a complex composition capable of generating a persistent inflammatory process, resulting in diseases widely described as emphysema, bronchitis, pneumoconiosis, asthma, and cancer. Several human biomonitoring studies have been conducted evaluating the inflammatory process and the release of cytokines, polymorphisms involved in detoxification mechanisms, different biomarkers associated with occupational exposure, DNA damage, and the influence of oxidative stress in disease development. The relationship between chronic exposure to coal and coal ash particles and cancer is still widely debated. This review gave us a broad assessment about the associated mechanisms between cancer and exposure to coal and different findings around the world.