Exposure to carcinogenic factors in the workplace

It has previously been estimated that about 3% of all the reported cancer cases in Norway for men and 0.1% for women could be attributed to exposure to carcinogenic reagents at the workplace. Based on data from the Nordic Occupational Cancer Study, a recent report presents the cancer incidence data for various occupational groups and discusses the aspects of work which may increase the risk of developing cancer.

A recent report entitled Occupation and cancer in Norway (Eggen et al, 2009) describes aspects of work that may lead to the development of cancer and highlights the incidence of cancer among workers in various occupations. Exposure to carcinogenic factors differs significantly between occupations and workplaces, directly affecting the risk of developing cancer. The report evaluated cancer risk in view of both direct exposure to carcinogenic factors at work and lifestyle habits that could be seen as work related. Historically, more men than women have been working in occupations with a higher risk of exposure to carcinogenic factors, consequently making them more vulnerable to developing cancer. This is also reflected in the general distribution of work-related cancer among Norwegian workers. Large distortions still exist in the gender distribution both within and between occupations.

About the study

The report is based on data from the Nordic Occupational Cancer Study (NOCCA), a Nordic cooperation project investigating the occurrence of cancer and exposure to work-related carcinogens among Nordic workers (Pukkala et al, 2009 and Kauppinen et al, 2009). In the NOCCA project, levels of exposure for Norwegian workers were calculated for four different time periods using the methods described by Kauppinen et al (2009), and the exposure was compiled with regard to the number of employees within the different occupations for these periods. In order to estimate the occurrence of cancer, 2.6 million workers were divided into 53 relatively homogenous occupations and the occurrence of new cancer cases in these groups was monitored for the period 1961–2005. The observed number of cancer cases in each group was then compared with the expected number calculated from the stratum-specific years together with the incidence rates for the national population. The results were presented as a standardised incidence ratio (SIR), defined as the observed number of cases divided by the expected number.

The authors of the report based their assessment of carcinogenic risk on classifications of chemicals, complex mixtures, occupational exposures, physical and biological agents and lifestyle factors as defined by the International Agency for Research on Cancer (IARC).

Key findings

Types of cancer and occupations most affected

The report mainly focused on the incidence of selected work-related cancers, such as lung cancer, mesothelioma, sinonasal cancer, bladder cancer and laryngeal cancer among different occupations. According to the findings, lung cancer is the most frequent work-related form of cancer. It has previously been estimated that 18% of the lung cancer, 83% of the mesothelioma, 30% of the sinonasal cancer, 2% of the bladder cancer and 6% of the laryngeal cancer incidence among men could be attributed to work-related exposure to carcinogenic factors; these figures are based on Nordic estimates for 2000 (Dreyer et al, 1997). The incidence of these cancers was found to be especially high among construction workers and craftworkers, while increased risks were also evident in some occupations in manufacturing and service industries.

Gender differences

Among men, plumbers had a particularly increased risk of developing mesothelioma. An elevated incidence of lung cancer was found in occupational groups in the construction industries and among craftworkers. Women appeared in general to be less vulnerable to work-related exposure to carcinogenic factors, probably due to a lower proportion of women working in occupations with the highest risk of exposure. However, an increased risk of developing lung cancer was found among female painters and decorators, motor and engine operators and also for some female-dominated occupations like hairdressers and textiles workers. An increased risk of work-related mesothelioma was not found among female workers.

Impact of lifestyle factors

Occupational groups often share similarities in lifestyle – for example, smoking and drinking habits. These lifestyle factors are well-known carcinogens and can often be the underlying reason for an observed increased risk of cancer among an occupational group. This was especially the case for male and female waiters, who have a significantly higher risk of developing lung cancer. This could be attributed to the fact that a larger proportion of daily smokers can be found among waiters, compared with the general population. Similarly, people in occupations that are known to have a lower proportion of daily smokers – for example, farmers or doctors – were found to have a lower risk of developing lung cancer.

Women in occupations that require a high level of education were found to have an elevated breast cancer incidence, which could be due to these women on average being older when having their first child.

Commentary

Almost 26,000 new cases of cancer were registered in Norway in 2007, 14,000 of which were attributed to men and 12,000 to women. It is estimated that about 3% of all cancer cases for men and 0.1% for women could be attributed to exposure to carcinogenic factors at the workplace. Thus, the social partners in Norway have for decades focused on the introduction of preventive measures at the workplace. However, the period of time from a person’s exposure to carcinogenic factors to the development of cancer could be very long and sometimes last for decades. The effects of banning carcinogenic reagents or defining new dangerous reagents may therefore not be seen for a long time.

Overall, exposure to carcinogenic factors in Norwegian workplaces has been substantially reduced over the past couple of decades. Therefore, a decline in work-related cancers in Norway may be anticipated.

References

Eggen, T. et al, Yrke og kreft i Norge [Occupation and cancer in Norway], 2009.

Pukkala et al, E., ‘Occupation and cancer – follow-up of 15 million people in five Nordic countries’, Acta Oncologica, Vol. 48, No. 5, 2009, pp. 646–790.

Kauppinen, T. et al, ‘Construction of job-exposure matrices for the Nordic Occupational Cancer Study (NOCCA)’, Acta Oncologica, Vol. 48, No. 5, 2009, pp. 791–800.

Dreyer, L., Andersen, A. and Pukkala, E., ‘Avoidable cancers in the Nordic countries. Occupation’, APMIS Supplementum 76, 1997, pp. 68–79.

Bjørn Tore Langeland, Department of Occupational Health Surveillance, National Institute of Occupational Health