The first officially reported case of occupational cancer in Korea was a case of mesothelioma at an asbestos thread factory in 1993. A 56-yr-old non-smoking woman employed at the factory for 18 yr was officially approved by the COMWEL and was compensated by the IACI (21). After the first reported compensation case, between 1992 and 1999, out of 379 claims for occupational cancer, only 22 cases were confirmed as occupational disease by the Occupational Safety and Health Research Institute (Table 1) (22). The 31 lung cancer cases associated with pneumoconiosis reported until 1999 that were compensated according to the PPPW Act are not included in Table 1, which only included cases to be conduct professional and specific examination for the work-relatedness by occupational physician and occupational hygienist of OSHRI. However, Table 2 included all cases to be decided based on PPPW Act, the result of special examination for the work-relatedness, or the self process of COMWEL.

From 2000 to 2009, out of 1933 claims, the COMWEL approved 253 cases as occupational cancer (23). Sixty-one of these were compensated according to the PPPW Act. From January 2010 to October 2012, out of 544 claims, the COMWEL approved 266 cases as occupational cancer (Table 2). After 2000, the number of claims increased rapidly. Especially after 2010, the number of compensated cancers also increased because the social awareness for occupational cancers or carcinogens such as asbestos or benzene improved and the claims from various high risk jobs such as miners, masons, construction workers, painters, welders, and so on, which would be influenced by social issue for the occupational cancer in semiconductor industry or communal claims by metal union. Respiratory cancers, especially lung cancer, were the most common cancers compensated for by the IACI. Between 2000 and 2009, occupational cancer types included respiratory (n=107), lymphohematopoietic (LHP) (n=35), malignant mesothelioma (n=28), and digestive tract cancer (n=74) (23). Between January 2010 and October 2012, occupational cancer types included respiratory (n=226), LHP (n=5), malignant mesothelioma (n=19), and digestive tract cancer (n=2). Cancers originating from digestive tract cancer abruptly decreased after the late 2000s, because hepatocellular carcinoma related to workload or stress in healthy hepatitis B virus carriers were rejected in court, and the specific criteria for recognition of liver disease was amended in 2003 (24).

Between 1999 and 2005, lung cancer related to asbestos exposure (62.3%, 33 out of 53 cases) and LHP cancer related to benzene (84.4%, 43 out of 50 cases) was the most common cause of occupational cancers (5, 25, 26). Between 2000 and 2009, construction (n=15) was most common industry among compensated cancers, followed by shipbuilding (n=11), and other metal product manufacturing (n=10). The most common occupation among compensated cancers was metal molders, welders, and related trades workers (n=16), followed by miners, shot firers, stone cutters, and carvers (n=14) (Table 3) (23).

After the early 1990s, the number of claims and compensations has increased, but the origin of cancers awarded compensation is still limited to 2 organs, namely the lung and LHP system. The major carcinogens are asbestos and benzene. Among compensated lung cancer cases, the most probable carcinogens were asbestos (45%), hexavalent chromium (30%), and crystalline silica (19%) (27). In case of LHP malignancies, the most probable carcinogens were pure benzene (27.5%), impurity of benzene in a mixture (56.9%), and ionizing radiation (8.0%) (26). With these data in mind, the existing criteria and scope for occupational cancer required amendment with respect to the causative carcinogens and the target cancer type.

The prior Korean criteria included only 10 agents and were very outdated compared with the ILO occupational disease list or the IARC list of Group 1 carcinogens. Skin cancer was the first cancer included in ILO Convention No. 42 in 1934. Mesothelioma due to asbestos was included in the occupational disease list in Convention 121 in 1980. On Recommendation No. 194 in 2002, the ILO added 15 carcinogens to the list including asbestos; benzidine and its salts; bis-chloromethyl ether; chromium VI; coal tars and coal tar pitches; beta-naphthylamine; vinyl chloride; benzene; toxic nitro and amino derivatives of benzene or its homolog; ionizing radiation; tar, pitch, bitumen, mineral oil, anthracene, or related compounds; coke oven emissions; nickel; wood dust; and other carcinogens. At this time, an association between specific occupational cancers caused by specific carcinogens was not included. In 2010, arsenic, beryllium, cadmium, erionite, ethylene oxide, and hepatitis B and C viruses were included on the ILO occupational cancer list (8).

The IARC reviewed the entire Group I carcinogenic agents list between 2006 and 2010, and 113 agents were included as Group I carcinogens. Since these agents cover both occupational and environmental exposure, Siemiatycki et al. (28) proposed 28 agents and 12 occupations or industries as definite occupational risk factors and we listed other additional occupational carcinogens updated after the review of IARC.

In the European occupational cancer lists including those of Austria, Belgium, Denmark, Germany, Finland, France, Italy, Luxemburg, Portugal, Spain, Swiss, and the EU. Finland included the fewest agents (n=17) and Germany, Denmark, and Luxemburg included >40 agents. Lung cancer due to chromate, asbestos, or nickel and malignant mesothelioma due to asbestos were included in the list of occupational cancers in all countries.

The prior criteria for recognition of occupational cancer according to the Enforcement Decree of the IACI Act included only 11 agents, for example soot, tar, pitch, asphalt, mineral oil, paraffin, vinyl chloride, chrome or its compounds, benzene, asbestos, and hepatitis virus. Except for hepatocellular carcinoma due to occupational exposure to hepatitis B or C virus, which was included in the criteria in 2003, other carcinogens and their target cancers have not ever been amended after since the 1980s'. Table 4 shows the presented agents on the occupational cancer lists of the ILO, and European countries, those suggested by Siemiatycki et al. or us based on the IARC list, and the Korean criteria of occupational carcinogens before 2013.

Table 5 shows the prior criteria and considerations of carcinogen exposure in Korea. Originally, cancer caused by soot, tar, pitch, asphalt, mineral oil, or paraffin was incorrectly identified as epithelial cancer, but needed to be amended as skin cancer. In addition, myelodysplastic syndrome is not cancer, but is a hematologic malignancy, and the epidemiologic evidence for larynx cancer caused by chrome exposure was insufficient. Vinyl chloride exposure as a cause of human hepatocellular carcinoma had sufficient evidence. In case of ionizing radiation, as a definite cause of cancer was not included in prior criteria, which only included acute radiation injury-related diseases. Therefore, the previous list had 3 main problems. First, the number of covered agents was smaller than those of the international lists. Second, the target cancer or the name of the agent was not clear. Third, a reconsideration of exposure duration or cumulative exposure level was needed; however, this was not included in the current amendment because this would require a national consensus across professional review boards considering various situations of exposure in Korea.

The main points of this amendment were as follows: First, the type and number of carcinogens should match those of international levels, considering the lists of the ILO, EU, and IARC, with the occupational cancer list of the ILO taking first priority. Second, the priority order of the list should be decided by the carcinogen exposure possibility in Korea. Third, the criteria should include matches between specific carcinogens and target cancers, as evidenced by clinical data from the IARC.

We, who suggested the list of carcinogens and its target cancers for recent amendment and directly participated in the policy making process of amendments to the scope and criteria, selected 28 agents and 11 industries to extend the criteria of occupational cancer according to the results the previously described review of the occupational cancer list of the ILO, the EU, and the IARC classification, and the exposure possibility in Korea to identified risk factors. Aflatoxins, 4-aminobiphenyl, arsenics, ultraviolet-emitting tanning devices, benzidine, beryllium, beta-naphthylamine, 1,3-butadiene, cadmium, crystalline silica, diesel engine exhaust, erionite, ethylene oxide, formaldehyde, leather dust, nickel compounds, passive smoking, polyaromatic hydrocarbons (PAHs), radon, shale oil, solar radiation, strong inorganic acid, 2,3,7,8-tetrachlorodibenzo-para-dioxin, trichloroethylene, ortho-toluidine, wood dust, anti-cancer drugs or immunosuppressants, and sulfur mustard were included in reviewed list of agents. Occupations or industries included the rubber industry, painting magenta production, coal gasification, aluminum production, auramine production, isopropyl alcohol manufacture using strong acids, underground hematite mining, iron and steel founding, coke production, and coal-tar distillation.

Coal gasification, coke production, and coal-tar distillation were reviewed with respect to PAHs. These industries could be matched to causative agents in a Korean-based exposure situation. Occupational cancer risk of the rubber industry could be explained by exposure to aromatic amines or solvents. The magenta, aluminum, auramine, isopropyl alcohol, or hematite production industries are rare in Korea. PAHs, crystalline silica, and strong inorganic acid could explain the occupational cancer risks of the iron and steel founding industry. As a result, painter was the only occupation/industry added to the amended criteria.

It was not possible to determine the exposure to passive smoking, solar radiation, ultraviolet-emitting tanning device, and solar radiation between environmental exposure and occupational exposure. In Korea, exposure to aflatoxins, sulfur mustard, erionite, shale oil, and 2,3,7,8-tetrachlorodibenzo-para-dioxin is unlikely and was classified as low risk. Measuring the exposure level of leather dust, strong inorganic acid mist, PAHs, 4-aminobiphenyl, and ortho-toluidine was very difficult. Diesel engine exhaust and trichloroethylene were recently upgraded by the IARC and information concerning exposure measurements, epidemiological evidence, or cases in Korea was limited. Anti-cancer drugs and immunosuppressant exposure are usually important to patients. In total, 13 agents and 1 occupation among 39 considerable agents and industries were assigned as priority add-ons to the amended scope and criteria specific for Korea.

We also suggest classifying the system of occupational cancer into an agent- and organ-oriented systems according to the specific criteria for the recognition of occupational diseases according to the Enforcement Decree of Labor Standard Act (LSA) and the Enforcement Decree of IACI Act. Therefore, on the basis of the scope of occupational cancers of the LSA, on which all the agents were listed without target cancer, agents were listed with target cancers based on organ oriented system named cancer on the specific criteria of the IACI Act. Especially, regarding some agents such as benzene, asbestos, or chrome, the considerations related with exposure duration or level persisted unless there were definite evidences.

As a result, 14 agents and occupation matched with 12 target cancers were added to the list including X-rays or γ-rays; arsenic and its inorganic compounds; nickel compounds; cadmium and its compounds; beryllium and its compounds; wood dust; benzidine; beta-naphthylamine; crystalline silica; formaldehyde; 1,3-butadiene; radon-222 and its decay; spray painting; ethylene oxide. Asphalt and paraffin were removed because of the ambiguity of chemical characteristics that could be masked by other agents. The descriptions for some agents were revised to enhance the clarity of the characteristics of the agent; tar was revised to coal tar, pitch was revised to coal tar pitch, chrome was revised to hexavalent chrome, mineral oil was revised to untreated mineral oil, and hepatitis virus was revised to hepatitis B and C virus.

Target cancers, especially those related with ionizing radiation, such as cancers of the salivary glands, esophagus, stomach, colon, bone, breast, kidney, thyroid, ovary, nasopharynx, and bladder were incorporated. Table 6 presents the scope of occupational cancers according to the Enforcement Decree of the LSA, July 2013 and the specific criteria for the recognition of occupational diseases according to the Enforcement Decree of the IACI Act, July 2013.