Leisure time activities related to carcinogen exposure and lung cancer risk in never smokers. A case-control study
Introduction
Lung cancer is an important public health problem in developed countries and also in developing world (Jemal et al., 2011). It is the cancer with the highest mortality rates in males and the second cancer in incidence for females (Malvezzi et al., 2013, Ferlay et al., 2010). Tobacco consumption is its main risk factor (Lopez et al., 2006), followed by residential radon exposure (Ruano-Ravina et al., 2012, World Health Organization, 2009), whereas other important risk factors are occupation (Alberg et al., 2007) and diet (Dosil-Díaz et al., 2007, American Institute for Cancer Research and World Cancer Research Fund, 2007).
Occupation is also a risk factor for lung cancer. It has been estimated that more than 20% of all EU workers are exposed to carcinogens at work (Kauppinen et al., 2000). Some occupations employing a high number of workers that have been associated with lung cancer are carpenters and construction workers, painters (Guha et al., 2010) and those working in heavy industries (coke oven workers, steel funding, rubber workers or shipbuilding among others (Villeneuve et al., 2012)). Occupations such as carpenters or painters entail the exposure to many carcinogenic substances i.e. glues, lacquers, stains, organic solvents, wood dust or some types of paints. Some leisure time activities, such as model building, painting and artwork, furniture refinishing or wood working, among others, share with some occupations the exposure to these carcinogens. Lungs are the target organs for the aforementioned substances. These leisure time activities are usually performed for years and users are not conscious about the potential risks of these exposures.
The carcinogens employed in these leisure time activities may enter the body by ingestion, can be absorbed through skin or by inhalation. Inhalation is the main entry of these substances when practicing these hobbies. Noxious exposures via inhalation may come from aerosol mist to fix drawings or from varnishes; from paint, chemical or wood dust, powders, dry pigments, from gases emitted by liquid painting mediums or from solvents. The respiratory tract and lungs are directly exposed to carcinogens. Bearing this fact in mind, a feasible biological assumption could be stated since the carcinogenic effect found for the lung would be much higher than the corresponding one for other internal organs. Furthermore, some of the inhaled substances, although not being carcinogenic, may act as pulmonary irritants, facilitating the carcinogenic effect of well-known carcinogens (Pérez-Ríos et al., 2010).
Subjects participating in model building, painting/artwork or furniture refinishing activities are exposed to multiple noxious agents and deal with different toxic materials and exposures simultaneously. Wood working or carpentry, through wood dust composition, may also encompass exposure to multiple chemicals agents, some of them with known carcinogenic effects (e.g. formaldehyde) which are used to treat wood and in the manufacturing of wood products (Barcenas et al., 2005). The complexity of these combined exposures limits the individual assessment of each of these substances.
Previous studies have observed that the practice of leisure time activities, where individuals are exposed to potential carcinogens, increases the risk of lung cancer (Ruano-Ravina et al., 2002, Prini-Guadalupe et al., 2012). None of the available studies have analyzed this possible relationship among never smokers, and information regarding the length of exposure was not available. We should highlight that studying exclusively never smokers minimize the possibility of confusion bias due to tobacco consumption.
The objective of this work is to assess the relationship between leisure time activities where individuals can be exposed to carcinogenic substances and the risk of lung cancer in a case-control study performed exclusively in never smokers.
Section snippets
Design, subjects and setting
A multicenter, hospital-based, case-control study was designed for this research, involving eight hospitals in Galicia and Asturias (North-West of Spain). The participating hospitals were: Arquitecto Marcide Hospital, A Coruña University Hospital, Santiago de Compostela University Hospital, Pontevedra Hospital Complex, Vigo University Hospital, Ourense University Hospital Complex, University Hospital Lucus Augusti and Central University Hospital of Asturias. The recruitment area covers a
Results
Rejections to participate among cases and controls were extremely low (<5%). A total of 513 never smokers were finally included, 191 cases and 322 controls. Table 1 shows the sample description. There were no appreciable differences on gender and age between cases and controls and also in the proportion of participants who had worked in a risk occupation for lung cancer. 62 individuals performed the studied leisure risk activities (14.1% of cases vs. 10.9% of controls), 28 of them for more than
Discussion
The hypothesis that certain leisure time activities might pose a risk for lung cancer is supported by the results of this study. Never smokers performing activities or hobbies that imply the exposure to proved or suspected carcinogenic substances such as model building, painting/artwork, furniture refinishing or wood working/home carpentry for more than 10 years have a 2-fold risk of lung cancer compared with those not practicing such activities. To our knowledge, this is the first study
Funding source
This research has been funded by a competitive research grant of the Xunta de Galicia: 10CSA208057PR “Risk factors of lung cancer in never smokers: a multicenter case-control study in the Northwest of Spain.” The funding source did not have any role on the design or interpretation of the results.
Ethics
All participants were required to sign a written consent for participating in the study. The research protocol was approved by the Galician Clinical Research Ethics Committee (2010/295).
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