Background

In 1989, the International Agency for Research on Cancer (IARC) classified commercial painting as a cause of occupational exposure in painters to Group 1 carcinogens for lung and bladder cancer [1]. The IARC reaffirmed the increased risk of lung and bladder cancer among painters after verifying the conspiracy on potential carcinogens and work processes in commercial painting in 2010 [2]. In Korea, spray paint was included on a list of potential carcinogens in 2013. The Korea Occupational Safety and Health Agency (KOSHA) and Occupational Lung Diseases Institute have performed several epidemiologic investigations on lung cancer and hematologic malignancy among painters. The investigating teams have suggested that seven cases out of ten investigated cases demonstrate a positive relationship between painting processes and lung cancer.

Comprehensive consideration is necessary to establish guidelines for criteria to evaluate the work-relatedness of cancer risks in painters in Korea. These guidelines should be based on the most reasonable information presently available, taking into account epidemiologic research on the assessment of potential carcinogen exposure among painters in Korea and other countries, and compensation data in Korea. Until now, this type of comprehensive evaluation has not been performed in Korea. Therefore, the aim of the present research is to perform a comprehensive review and to suggest criteria for the provision of compensation for occupational neoplasm among painters in Korea.

Review

General characteristics of painting

Painting is the application of specific synthetic materials to the surfaces of products or buildings to protect the objects from corrosion and dirt or to generate cosmetic appeal [1, 2]. The general purposes of painting are protection and plastering. Electrical conduction, semi-conduction, contamination control, fire-retardation, temperature sensing, and magnetic painting are further classified as specific purposes of painting [1, 2].

Paint is comprised of various components with varying purposes. The components of paint are pigments and extenders (fillers), binders (resins), solvents, and additives. Pigments affect the color, viscosity, durability, and chemical properties of paint. Extenders are able to fill in gaps and improve the physical properties of coatings. The main roles of binders are to facilitate the hardening or adhesion of coatings. Solvents are used to mix the components of paint by dissolving binders. If painting is intended to meet specific purposes of construction, such as the application of biocides or ultraviolet stabilization, then additives are adapted. The typical components of paint are summarized in Table 1 [3].

Table 1 The category and type of major components in paints
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Literature review of occupational exposure among painters in Korea

The Korean Journal of Occupational and Environmental Medicine (Annals of Occupational and Environmental Medicine), the Korean Journal of Preventive Medicine, the Korean Journal of Industrial Health, official reports from KOSHA, and existing epidemiologic investigation reports have been reviewed to estimate the previous exposure status of commercial painters to paint carcinogens in Korea. A total of 31 articles were reviewed and are summarized in Table 2.

Table 2 Literature review for potential exposure while painting process in Korea 1989-2010
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The presence and relative levels of polycyclic aromatic hydrocarbons (PAHs), benzene, hexavalent chrome, crystalized silica, asbestos, and other carcinogenic agents have been examined and estimated in the context of commercial painting processes [3]. According to a 1995 report on the level of exposure to chrome in factories reporting patients with nasal septal perforation, the level of chrome exposure among the employed spray painters was below the permissible exposure limit (PEL) of 0.5 mg/m3 at recorded measurements of 0.246 mg/mg3 in the morning and 0.318 mg/m3 in the afternoon [4]. Research on exposure levels to hazardous materials in paints at five domestic shipyards in 1999 shows that lead chromate and zinc potassium chromate were detected in 8% of paints [5]. The component analysis of that research also reveals that silicon dioxides were detected in 27 samples (8.8%) of painting materials, including extender pigments. In other findings, the geometric means of exposure ranges of asbestos were 1.6 fibers/cm3 and 2.45 fibers/cm3 in automobile repair and ship repair processes, respectively [6]. However, asbestos remains undetected in the products of automobile manufacturing companies after 1998 [7].

Scientific evidence for carcinogenicities

The IARC classifies the occupational exposures of commercial painting as Group 1 carcinogens for lung cancer and bladder cancer [1,2,3]. Existing epidemiologic studies show consistent causal relationships between occupational exposure in painters and cancers including lung and bladder cancer [3]. A meta-analysis that includes 17 cohort and linkage studies and 29 case-control studies shows that the meta-relative risk (meta-RR) for lung cancer is 1.34 (95% confidence intervals (CIs): 1.23-1.41) [3]. The results of additional meta-analysis including 11 cohort and record-linked studies and 28 case-control studies show a meta-RR for bladder cancer of 1.24 (95% CI: 1.16-1.33) [3]. However, the IARC does not assert that specific components of paints (such as chromate, PAH, benzene, and other agents) significantly increase the incidence or mortality from lung cancer or bladder cancer. The IARC indicates that no data on cancer in experimental animals are available [2]. The working group that has established a special section for “occupational exposure for painters” declares that occupational exposure hazards for painters per se include Group 1 carcinogens for lung and bladder cancer. In addition, the official report contains evidence of other relevant data about specific chemicals in common components of paint (e.g., cadmium, PAH, aromatic azo dyes, and other components) [2].

The Industrial Injuries Advisory Council (IIAC) for occupational cancer risks in commercial painters (among other industrial groups) is the official advisory council for assisting the UK government on prescribed industrial diseases [8]. The IIAC report includes a comprehensive review of epidemiologic data indicating occupational cancer risks and evaluating whether the risks for certain occupational cancers are more than doubled in painters compared to the general population [8]. The council also considers the study design of British doctors Doll and Hill in terms of their criteria on causation [9, 10] in epidemiologic studies published since 1972. The IIAC review team considers occupational cancer risks for lung and bladder cancer in commercial painters in particular (as opposed to the risks of these occupational cancers in paint manufacturers, for example) in the overall cohort study [8]. In fact, according to the literature, the elevated risks in occupational lung and bladder cancer in painters are not doubled in cases of either lung [11,12,13,14,15,16,17,18,19] or bladder cancer [14,15,16,17,18,19] relative to these risks in the general population. Reports of the IIAC specify that crucial confounding factors, such as smoking, might be one reason for the elevated incidence of lung and bladder cancer among painters.

Epidemiologic investigation of claimed cases in Korea

Epidemiologic investigation for the work-relatedness of lung cancer in commercial painters in Korea has been performed in a total of 10 cases (Table 3). Seven painters were approved by investigation board in KOSHA. Significant exposure to potential carcinogens such as hexavalent chromate, asbestos, and crystalized silica has been provided as evidence of the work-relatedness of occupational cancers including lung and bladder cancer in commercial painters.

Table 3 The epidemiologic investigation for the work-relatedness by KOSHA and Occupational Lung Diseases Institute from 2000 to 2012
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Discussion

Issues for considering the work-relatedness of cancer in painters

Means of occupational exposure mainly involve the inhalation of gases and vapors from paint components (solvents, additives, pigment dust, and binders), as well as dermal absorption or ingestion [3]. The term professional painters typically does not include paint-product manufacturers or bystanders, but refers only to workers that brush or spray paint onto objects. In interpreting the job of commercial painting, several tasks are involved that should be defined in addition to the painting itself, including clean up and preparation. Accordingly, each task should be evaluated for potential exposures. Although painters engage in the entire process, the act of painting is regarded as the main means of exposure to various hazardous materials [3]. Based on the documentation of the IARC, occupational cancer is restricted to lung cancer and bladder cancer in the present review [1,2,3]. The IARC declares that the epidemiological evidence on occupational exposure in painters does not specify potential carcinogenic agents in paint [2]. Occupational exposure for painters encompasses the potential carcinogenic risks for lung cancer and bladder cancer. This perspective should be discussed in estimating the relationship between occupational exposure among painters and occupational cancer in Korea on an individual basis. Potential carcinogens, such as hexavalent chromate [4], asbestos [20], crystallized silica [5], and PAH from coal tar [21,22,23] are found in paint. In addition, exposures within specific industries (such as shipbuilding and construction) should be taken into account. Another consideration in evaluating exposure evidence is the period of exposure. Based on our literature review, coal tar, crystalized silica, and hexavalent chromate were used in workplace paints in Korea until late 1990 [4,5,6]. Up until the 2000s, the usage of coal tar paint was found in the metal industry [21,22,23]. Unfortunately, paint containing hexavalent chromate is still currently used in Korea.

Conclusion

Established guidelines according to exposure periods, types of industry, and periodical features of the risks of occupational exposure for painters are currently undefined for occupational lung cancer and bladder cancer among painters in Korea. In addition, no country has defined specific guidelines for occupational cancer among painters. Therefore, total work duration, potential carcinogens in paint, mixed exposure to paints across industries such as construction and shipbuilding, exposure periods, latent periods, and other factors should be considered on an individual basis in investigating the work-relatedness of certain types of cancer in commercial painters.