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14 January 2015

Breast cancer: the workplace aspects are too often forgotten by researchers

An important association of public health professionals has issued an online appeal for an increase in the research resources devoted to investigating the occupational causes of breast cancer. The appeal is launched in a context of scientific controversy unleashed by the publication, at the beginning of January, of an article that might be interpreted as shifting the weighting of environmental and genetic factors in the increased level of cases of cancer observed in recent decades.

The American Public Health Association (APHA), which has some 30,000 members throughout the world, placed online at the beginning of January an appeal for recognition of the occupational nature of some breast cancers. The association denounces the lack of attention accorded to some alarming recent research findings that indicate a link between exposure to chemical agents in the workplace and the increase in rates of breast cancer. In the view of APHA, research on the occupational and environmental causes of breast cancer must become a priority: 'Until recently, women's occupational health hazards continued to be mostly invisible, studied inadequately and infrequently despite women's long-time participation in the workforce. This lack of gender perspective comes at a price: working women's health'.

The document draws attention to the presence in the workplace of a category of toxic agents that affect the hormonal system and are commonly referred to as ‘endocrine disrupters’. Substances subject to particular caution in this respect include bisphenol A – the use of which in the manufacture of food containers has been banned in France since 1 January – and phthalates. The presence of these chemicals in the workplace could, even in small quantities, prove harmful for the health of women workers.

APHA points also to the risk factors associated with work organisation, reiterating that night work has been recognised as a ‘probable carcinogen’ by the International Agency for Research on Cancer (IARC). APHA considers that research on breast cancer must be redirected towards environmental risk factors, and in particular the workplace, because 'more than half of breast cancer cases cannot be explained by traditional causes or risk factors (e.g. weight, diet, alcohol abuse, genetics).'

The organisations struggling to support workers who have fallen victim to cancer as a result of their jobs – generally manual workers – may be expected to welcome this appeal, for it has been launched concurrently with biased efforts to promote the conclusions of a study published at the beginning of January in the prestigious American journal Science.

The article in question, authored jointly by a biostatistician and a professor of oncology, hypothesises a correlation between risk of cancer and the number of stem-cell divisions to which an organ is subject during a lifetime. The researchers have analysed available stem-cell data relating to 31 types of human tissue and have observed that the organs with the most stem cells and with a tendency to more frequent division are more affected by cancer. The article created a stir extending well beyond scientific circles; press reports summarised its claims as being that ‘two thirds of cancers are due to bad luck’.

Voices were soon raised to point out the limits of these research findings. The study undertaken by scientists at the Johns Hopkins University (Maryland) took into account neither breast cancer, the most frequent form of cancer among women, nor prostate cancer, the second most frequent among men.

What is more, the authors’ interpretation of their findings gives rise to other questions, as pointed out by Laurent Vogel, a researcher in the ETUI’s health, safety and working conditions unit, who explained: 'This mode of presentation confuses causality with a merely statistical relationship. It bypasses an essential feature that certainly cannot be attributed to individual luck, for it is possible to come up with a social mapping of each form of cancer and to show important links between working conditions and the different locations of cancer in the human body.'

In response to the controversy unleashed by the article, one of the authors, Cristian Tomasetti, told the British weekly news magazine The Economist: ‘We have not showed that two-thirds of cancer cases are about bad luck. Cancer is in general a combination of bad luck, bad environment and bad inherited genes’.

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