Occupational Diseases in Korea

Diseases caused by chemical agents

Lead poisoning has been the most common occupational diseases caused by chemicals. An outbreak of lead poisoning was clustered around storage battery workers in 1982. The blood lead level was more than 40 µg/dL in 75% of the total 234 workers (12). Workers with lead poisoning showed anemia, neurologic diseases (13), renal dysfunction (14), and neurobehavioral changes (15). Since 2000, less than 5 cases whose blood lead level exceeds 40 µg/dL, have been reported.

Nasal septal perforation was found in plating workers exposed to chromium mist. In 1988, the prevalence rates of nasal septal perforation and ulceration of mucosa of the plating workers were 31.7% and 10.5%, respectively out of 627 workers, according to a cross-sectional study (16). Since the late 1990s, nasal septal perforations are rarely found. Nasal septal perforations were also found in welders who were exposed to welding fumes that included hexa-valent chromium (17).

Mercury poisoning occurred in the thermometer and fluorescent lamp manufacturing industry in the early 1990s (18). There was a debate over the possibility of cadmium poisoning in a worker who worked in a zinc galvanizing factory (19). After then, there were many cases of misdiagnosed cadmium poisoning because of the low quality of analyzing biological samples. Hence, the quality control program for biological monitoring was adopted in 1995 (20). Proteinuria was found in workers at a cadmium smelting factory and battery recycling factory; a renal biopsy subsequently showed interstitial fibrosis (21).

The first report of manganese poisoning were attributed to ore crushing work (22). Increasing signal intensity in Magnetic Resonance Imaging (MRI) was found in welders (23). Some cases of Parkinson syndrome due to manganese exposure in welders were accepted for compensation; however, increased signal intensity does not necessarily translate into manganese poisoning (24). The Pallidal index on MRI is the most effective predictor of neurobehavioral performance in workers exposed to manganese because it reflects the target organ dose of occupational manganese exposure (25). Signal intensity on MRI is an effective predictor of the neurobehavioral performance of manganese exposed workers (26).

The outbreak of carbon disulfide poisoning (27) in the early 1990s was the most serious occupational disease in Korea, which eventually led to approximately 1,000 cases of compensation by 2009. The signs of carbon disulfide poisoning were retinal microaneurysm (28), renal glomerulosclerosis (29), multiple cerebral infarction (30), peripheral neuropathy (31), ischemic heart disease, mental diseases, impotence (32), etc.

Various health effects caused by organic solvents have been reported (33). They are demyelinating lesion of the brain by toluene based solvents (34), neurologic diseases by acetonitrile, peripheral neuropathy by acrylamide (35), temporary strabismus by optic nerve palsy by phosphorus trioxide, cerebellar ataxia by mixed solvents, amyotrophic lateral sclerosis by solvents and metals (36), Mobitz type 2 ventricular bundle branch block by toluene based organic solvents, premature ventricular beats caused by trichloroethylene, and cardiomyopathy by carbon monoxide. Bone marrow suppression by ethylene glycol monoethyl ether acetates was found in painters at a shipyard (37). Neurologic diseases caused by methyl bromide were found in fumigation workers (38, 39). Workers exposed to methyl bromide showed high signal intensities in the medulla oblongata and paravermian of cerebellum in MRI or polyneuropathy in a nerve conduction velocity study.

In 1995, reproductive problems were reported for the first time in workers exposed to 2-bromoprophane at an electronic supplier factory (40). The workers were exposed to a level exceeding the occupational exposure level of Korea.

Toxic hepatitis occurred in workers exposed to dimethylformamide, which is used to produce synthetic fiber or synthetic leather (41). Several cases of toxic hepatitis developed to fatal fulminant hepatitis (42, 43). Toxic hepatitis occurs usually within 2-4 weeks after exposure. A liver function test is mandatorily performed on workers who are newly engaged to work of being exposed to diemthylformamide, within 4 weeks of the initial assignment to the task. Severe toxic hepatitis with erythematous skin diseases caused by trichloroethylene were reported (44-46).

In 2005, 8 Thai migrant workers developed peripheral neuropathy. They were exposed to 150-200 ppm of n-hexane (47). Peripheral neuropathy by n-hexane is continuously reported in the IT industry (48) because it is non-irritant and easily removes blemishes from plastic products.

OSHRI reported conjunctivitis by chlorine in a worker at a swimming pool, conjunctivitis by organic solvents, acid and alkali, naso-lachrymal duct obstruction by resin dust, and macular degeneration by methanol. Macular degeneration was also reported in welders (49).

Diseases caused by physical agents

NIHL is the second common occupational diseases. Annually 200-300 cases are compensated. Sudden hearing loss was reported after exposure to high level of noise (50). Approximately 10 cases of disease by vibration are compensated in a year. Handarm vibration syndrome was reported in workers using a grinder that produced hand transmitted vibration (51, 52). Heat related diseases such as heat stroke were also reported (53). Diseases caused by compressed or decompressed air (54, 55) have been continuously reported.

Biological agents and infectious or parasitic diseases

Occupational infectious diseases increased. In 2009, the number increased to 427 cases, which was 3 times more than that of 2008. They were mostly tsutsugamushi disease which occurred among public service laborers who performed landscape gardening (56). Tuberculosis is a common infectious disease among health care workers (57, 58). Seroconverted viral hepatitis after needle stick injury among health care workers is generally accepted as occupational disease although their seroprevalence rates were not different from those of the general population (59).

Although farmers are not included in the IACI, brucellosis can be found among farmers (60).

Respiratory diseases

The most common occupational respiratory disease is coal workers' pneumoconiosis that occurs most often in coalminers. The amount of compensated cases of pneumoconiosis from 1991 to 2009 were 19,127. However, the total cases of pneumoconiosis since 1972 could be approximately 40,000 if we consider the 24,754 cases from 1972 to 1990 when more than 95% of compensated cases were pneumoconiosis. The compensated cases of fatality by pneumoconiosis from 1998 to 2009 were 4,864. The case of pneumoconiosis will continue to decrease as most mines were closed in the early 1990s and only several mines are active as of 2010. Tuberculosis, emphysema, bronchitis, bronchiectasis, and cor-pulmonale accompanying with pneumoconiosis are also conditions that can be compensated for. Pneumoconiosis is also reported by welders (61) and foundry workers (62).

Occupational asthma is the second most common occupational respiratory disease in Korea. Toluene diisocyanate (TDI) (63, 64) is the most common causative agent followed by reactive dyes (65). Occupational asthma caused by various agents such as chromium (66), antibiotics and digestives (67), latex (68), grain dust (69), flour (70), and citrus red mite in citrus farmers (71) were also reported. Occupational asthma caused by colophony is rarely reported even though it is one of the most common causative agents in the UK.

OSHRI reported metal fume fever by zinc fume, chronic obstructive lung diseases by waste materials, hypersensitivity by TDI, idiopathic interstitial lung disease by styrene, eosinophilic pneumonia by nickel, acute respiratory failure in a welder, and diffuse interstitial lung diseases by organic solvents.

Skin diseases

Occupational dermatitis is a common workplaces problem (72), but rarely reported because it is not a serious disease. Most skin diseases were contact dermatitis, vitiligo by hydroquinone, and dermal pigmentation by 2,5 hexandione (73). Contact dermatitis, chloroacne, chemical burns by fluoric acid, and hand eczema were common in the semiconductor industry (74).

Musculoskeletal disorders

WR-MSDs were first reported in the late 1980s in telecommunication workers (75, 76). Since then, many cases of WR-MSD were claimed; most of which were attributed to the assembly processes in the manufacturing industry and they were expanded to the service industry. In 1998, records from a university hospital showed that 34.7% of carpal tunnel syndrome were work-related; however, less than 1% filed for compensation (77). The occupation of patients were various and included restaurant workers, assemblers, manual workers, farmers, fishermen, health care workers, and construction laborers. In 2005 according to analysis for the cause of occupational diseases (78), 73.9% of MSD excluding back pain cases were reported in the manufacturing industry. The main cause of MSD was due to awkward position (50.2%), strenuous forces (28.2%), and repetitive work (16.8%).

The number of occupational back pain disorders has changed widely depending on the classification system. Occupational back pain was mostly classified as an accidental injury because workers usually described the onset of symptoms as abrupt. These cases have been included in occupational diseases since 2006. Herniated intervertebral disc was the major back pain disease (67.5%).

Mental and behavioral disorders

Stress related mental disorder can be accepted as occupational diseases. Post-traumatic stress disorder can develop after a serious industrial accident (79). Conductors of underground subway trains have experienced panic disorder after serious train-passenger accidents (80). Under special conditions, suicide by workers who have a confirmed mental disorder (such as depression) can be compensated.

Asbestos

The first case of mesothelioma caused by asbestos was found in a female worker in an asbestos textile factory in 1993 (86). Since 1972, asbestos was widely used after Korea changed roofs from rice sheaves to asbestos corrugated roofing slates. The total amount of asbestos use was estimated at 2,026,963 tons (87). The annual cases of mesothelioma are approximately 40 to 50 in Korea and continuously increasing (88); however, few cases were accepted as occupational cancer (83). The incidence of mesothelioma remains relatively low compared to other industrialized countries and it may be caused by delayed peak period of consumption. However, another reason would be the different way of use - in the case of Korea, asbestos was rarely used in spraying and for thermal insulation.

Benzene

Benzene was not used in Korea for manufacturing glue because of the late industrialization. Glue, adhesive, and solvents that contained mainly toluene were widely used. However, solvent based chemicals contain benzene as an impurity. The first cancer caused by benzene (officially recognized in 1998) was myeloid dysplastic syndrome of a worker at a tire manufacturing factory, who used adhesives that contained benzene as an impurity (89). After that, many cases of leukemia were reported in different industries (90). In 2000, it was estimated that 200,000 workers could be exposed to benzene at work, which meant that many cases of benzene induced leukemia could have occurred. Recently, leukemia cases that occurred in the semiconductor industry have gained public attention. However, there was no convincing evidence of an increased incidence of leukemia in the semiconductor industry by the epidemiologic investigation performed by OSHRI (91).

Cerebro-cardiovascular disease

CVD was compensated as an occupational disease since 1994 when its diagnostic criterion was established (amended in 2008). Two conditions are required to be accepted as WR-CVD. One is a disease entity and the other is pre-existed working condition such as long working hours or job stress.

This diagnostic criterion of work-related CVD was established due to social pressure. CVD was not on the list when the IACI Act was established in 1963. Most cases of claimed CVD were not accepted as work-related, which led many workers and relatives to go to the courts in the early 1990s. The court accepted CVD as work-related if the workers proved that they suffered from long working hours or job stress. Consequently, the diagnostic criteria for work-related diseases expanded in 1994 and WR-CVD cases have rapidly increased due to the generous application procedure in conjunction with the increased workload after the economic crisis in 1998.

From 1996 to 2009, 20,143 cases were accepted as WR-CVD. The number of compensated cases peaked in 2003 and gradually decreased due of active prevention activities for life-style diseases such as hypertension or hyperlipidemia at workplaces. The number of compensated cases has sharply decreased since 2008, after amendments of the diagnostic criterion. In 2008, the expenses for CVD accounted for 9.5% of total expenses for compensation.