Endometrial cancer is an increasingly common form of cancer in developed countries. There are both genetic and environmental risk factors associated with the development of endometrial cancer, and changing the environmental risk factors may be the easiest way of reducing the incidence of endometrial cancer. Pesticides – mixtures of chemicals used in agriculture to protect crop growth – are known to cause certain cancers, but it is unclear if they can cause endometrial cancer. A recent study in Spain found that occupational exposure to pesticides is associated with endometrial cancer.

The study took place from 2017 to 2021, with researchers administering a questionnaire to 180 women with endometrial cancer. To create a control group to compare these women to, researchers also administered the questionnaire to 218 women admitted to hospitals who didn’t have endometrial cancer. The researchers asked about lifetime occupational history, demographic information, tobacco consumption, physical activity, family history of diseases, reproductive factors, and other information.

The researchers systematically coded all respondents’ occupations based on a job exposure matrix (JEM) for Spanish working conditions. A JEM is a list of occupations that provides estimated exposures to a variety of harmful chemicals for each one, respectively. Using a JEM allowed the researchers to estimate respondents’ exposure to pesticides based on their occupations. This was a clever way of creating a history of each person’s occupational exposure to pesticides, whereas collecting their current environmental or biological data would not have been able to capture their accumulated lifetime exposure. The three categories of job titles considered to be exposed to pesticides were: agricultural, poultry, and livestock activities; cleaning staff; and manufacturing and lumber industries. Using the JEM, and estimated occupational exposure to pesticides, the researchers performed statistical tests to determine if occupational exposure was associated with endometrial cancer.

Occupational exposure to pesticides was associated with two times greater odds of developing endometrial cancer than not having occupational exposure. Exposures that happened further in the past were associated with cancer, as were exposures that happened before the age of 32. Surprisingly, increased cumulative exposure was not associated with endometrial cancer. Working in agricultural, poultry, and livestock activities was associated with four times greater odds of developing endometrial cancer. Working as cleaning staff was not associated with endometrial cancer, which could be because the intensity and frequency of exposure in these jobs may be lower.

Cancers like endometrial cancer can be difficult to study because it can take a long time for the disease to develop after someone gets exposed to a cancerous chemical. Once the disease develops, collecting environmental or biological samples from the patient’s time of exposure is not possible. This study got around these limitations by using a job exposure matrix to estimate exposure to pesticides throughout women’s entire working lives. Of course, these exposures are only estimates, their use of personal protective equipment in each job was unknown, and researchers could not know what other potential cancer-causing chemicals respondents may have been exposed to.

Regardless of the limitations, this study is valuable because diseases related to women’s reproductive systems are less studied compared to many other diseases. It is also the first study to show an association between occupational pesticide exposure and endometrial cancer.

New regulations and increased use of personal protective equipment may explain why exposures further in the past were more associated with endometrial cancer. However, the results of this study demonstrate that these improvements may not be enough to keep workers safe when they come into contact with pesticides. Endometrial cancer can now be added to a growing list of diseases associated with pesticides, and more should be done to protect workers and the public from these chemicals.

For more information, CHEJ has previously written about chemicals that have been used in pesticides and herbicides such as atrazine, benzene, ethylbenzene, glyphosate, and pentachlorophenol.