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Occupational cancer is a result of exposure to hazardous chemical, physical and biological agent (carcinogens) during the time. Occupational carcinogen is every chemical, physical and biological agents from workplace that increases the risk of malignant disease among the exposure workers.
In 1775 Sir Percival Pott, one of the leading British surgeons, was first who described the occurrence of occupational cancer i.e. remarkably high occurrence of scrotal cancer among chimney sweeps. He ascribed extremely difficult work conditions of these usually young boys who entered the chimneys and were in constant contact with the combustion products to the scrotal cancer, although he could not explain the cause of the disease. Pott’s detail description of these terrible work conditions initiated social measures: however, only 60 years later the law was introduced that banned young boys to enter the chimneys and clean them. Later, by the end of nineteenth century cases of lung cancer among miners in metal mines were reported in Germany. However, extensive studying of occupational cancers has started in 1950s.
How do we determine that the malignant disease is occupational?
Many agents that are proved carcinogens were first discovered at workplaces, where workers can be exposed to the numerous hazardous agents. Concentrations of these agents are much higher than in the environment, they are measured regularly, workers have similar characteristics, they have long-term exposure to carcinogens, therefore epidemiologists and physicians can easier establish the work-related cancers.
There are several specialized institutions in the world that estimate carcinogenic risks from different agents, but todays we are mostly relaying on the List of carcinogenic agents produced by the International Agency for Research on Cancer in Lion, the World Health Organization agency. Their series of monographs provide the most systematic evaluation of carcinogenic risk for humans exposed to numerous agents. The monographs have been published since 1972, and so far, 123 monographs have been released that evaluated all together 1013 different agents. The risk is assessed based on the experimental studies on animals, laboratory (in vitro) tests, and epidemiological studies, whose results are crucial and necessary condition for the recognition of causality.
Agents that were evaluated by the International Agency for Research on Cancer are classified in the following way:
Group 1 – carcinogenic for humans – 120
Group 2A – probably carcinogen for humans – 82
Group 2B – possibly carcinogenic for humans – 311
Group 3 – not classifiable as to its carcinogenicity to humans – 499
Group 4 – probably not carcinogenic for humans -1
Workplace exposure to carcinogens
Workplace agents with sufficient evidence of their carcinogenicity include chemicals and mixtures, physical and biological agents, as well as some industrial processes. It is not always easy to assess that an agent is occupational carcinogen. Most workplace carcinogens exist in the environment as well, and vice versa. It is well known that asbestos can be found in mines during its exploitation, but also in other industries, such as construction, shipyards, and automobile industry in the past, due to its excellent characteristics. However, as asbestos is widespread in the environment, it is hazardous for people in everyday life. Similar can be said for benzene and radon, for example. On the other hand, sunlight and second-hand smoke are primarily environmental hazards; however, workers can be exposed as well. All workers who are working in the open air (sailors, constructions workers, etc.) are exposed to long-term sun radiation. Hospitality workers, in the countries that no smoking ban exist inside the hospitality premises, have long-term exposure to tobacco smoke.
For some workplace carcinogens there is no doubt that they are related to the development of malignant diseases. For example, exposure to vinilhloride monomer can induce rare liver cancer (liver angiosarcoma) and benzidine urinary bladder cancer. However, there are some industrial processes where the higher occurrence of malignant diseases has been observed, but no specific agents have been identified, such as lung cancer in painters, urinary bladder cancers in aluminum production or different cancers in rubber industry.
The List of carcinogenic agents includes the following:
– natural fibers: asbestos, silica from quartz, wool and wood dust,
– metals: arsenic, nickel, cadmium, hexavalent chromium, inorganic lead, etc.,
– solvents: benzene, trichlorethylene, etc.,
– reactive chemical agents: ethylene oxides, 1,3-butadien, formaldehyde, vinyl chloride monomer, second-hand smoke, etc.,
– mineral oils, petrochemicals and combustion by-products, diesel engine exhaust, scale oils, tar, etc.,
– polycyclic aromatic hydrocarbons (benzo[a]pyrenes),
– aromatic amines: 2-naphthylamine, 4-aminobiphenyl
– insecticide Lindan
– physical agents: ionizing radiation (all types, radium, radon, etc.), sunlight
– biological agents: Hepatitis B virus, Hepatitis C virus, HIV
Most frequent malignant diseases related to workplaces
As a consequence of exposure to workplace carcinogens, lung cancer is the most prevalent, followed by cancer of urinary bladder, leukemia, skin cancer, malignant mesothelioma, nasal cavity and paranasal sinus cancers, etc. Cancers related to the workplace exposure clinically do not differ from cancers of other causes. The diagnosis and treatment are same. However, the type and localization of cancer must be specific for the certain exposure. Moreover, there must be temporal relation, i.e., latency period between exposure and development of cancer; in the case of occupational cancers it can be shorter than usual.
Estimation of the percentage of cancers that are attributable to occupational exposure varies between 3% and 10%. Considering the mortality from all occupational diseases, cancers at the second place and are responsible for 26% of all deaths.
How to prevent occupational cancer?
All occupational cancers can be prevented. The most efficient way is to eliminate all hazardous (carcinogenic) agents and industrial processes from work environment and replace them with others that do not cause malignant diseases. Often, this is not possible, therefore, the emphasis must be on maximal reduction in concentration of carcinogens or exposure time, along with regular measurements at workplaces and inspection controls. In some cases, such as for volatile chemicals and ionizing radiation, this can be achieved by installing enclosed production systems. On the critical workplaces where all this measure cannot be applied, it is necessary to reduce the number of workers and enable their regular workplace rotation. All employees must have adequate personal protection devices. It is also necessary to regularly inform all workers on all risks at work and their prevention. The employers’ obligation is to provide regular and legal preventive health check-ups.
