Arvo building, Yellow Hall F025, address: Arvo Ylpön katu 34
Doctoral defence of MHS Kishor Hadkhale
The field of science of the dissertation is Epidemiology.
The opponent is Adjunct Professor Jukka Takala (Tampere University of Technology). Professor Eero Pukkala acts as the custos.
The language of the dissertation defence is English.
Occupations associated with the risk of bladder cancer
Bladder cancer is ninth most common type of cancer worldwide. It is more common in men than women and usually arises after the age of 60 years. Smoking is the most common risk factor but occupational factors are estimated to cause up to one fifth of all bladder cancer cases in industrialized countries. In this doctoral thesis work, Kishor Hadkhale aimed at identifying work related factors associated with the risk of bladder cancer.
The study was based on the Nordic Occupational Cancer (NOCCA) study and the Canadian Census Health and Environment Cohort (CanCHEC). NOCCA covers all Nordic working age population who participated in one or more population censuses from 1960-1990, altogether about 15 million individuals. Census records provided information on demographic variables such as employment history, and these records were linked to national cancer registries. The follow-up started from the earliest census and continued up to 2005. Likewise, there were about 2.7 million individuals in Canada and this study utilised the data from the linkage of 1991 Canadian population census, Canadian mortality database and historical tax information files. Nearly 150,000 cases in the Nordic countries and more than 8,000 cases of bladder cancer were diagnosed in the Canadian study.
In the Nordic countries, the risk of bladder cancer was significantly higher than the average for the tobacco workers (57% higher), chimney sweeps (48% higher), waiters (43% higher), hairdressers (28% higher), seamen (22% higher), and printers (21% higher). Significantly low risk was found among farmers (30% below average), forestry workers (25% lower) and gardeners (22% lower). The results were quite different between the Nordic countries and Canada. In both studies, similar increased risk was found only among sales workers. Teachers and agricultural workers had lower risk of bladder cancer in both studies.
The third part of Kishor Hadkhale’s work estimated the number of men smoking in NOCCA data in different occupations based on how many had the lung cancer cases. When this estimated smoking information was adjusted with the risk of bladder cancer, the risk variation between the professions decreased. However, in some professions such as chimney sweeps, waiters, hairdressers, cooks and stewards and printers, the risk was not only due to smoking. The fourth study evaluated the relationship between exposure to chemical solvents at workplaces and risk of bladder cancer in four Nordic countries (excluding Denmark). Census based job titles of the cancer cases and controls were linked to a job exposure matrix (NOCCA-JEM) to estimate the quantitative cumulative exposure. This study showed marked increase in risk of bladder cancer among those exposed to trichloroethylene (23% higher risk than unexposed group), toluene (20% higher risk than unexposed group) and benzene (16% higher than unexposed group).
This study supports the view that occupation is associated with the risk of bladder cancer and smoking is the most important risk factor. Additionally, exposure to solvents at workplace appeared to play an important role. NOCCA is the largest study on occupational cancer incidence in the world and CanCHEC is the largest comparable Canadian study. The large number of cancer cases with a decade long occupational history of the participants provided a unique opportunity for this doctoral dissertation to find out the association between occupation and risk of bladder cancer in a way that has not been possible before.
The dissertation is published in the publication series of Acta Universitatis Tamperensis; 2435, Tampere University Press, Tampere 2018. The dissertation is also published in the e-series Acta Electronica Universitatis Tamperensis; 1948, Tampere University Press 2018.