13 Occupational Carcinogens (Cancer-Causing Agents) and Occupational Cancers

JAMA published a study using occupational exposure to carcinogens (cancer-causing agents) as an assessment target. Data from the Global Burden of Diseases, Injuries, and Risk Factors (GBD) 2017 were used to estimate the level of exposure. The burden of specific cancers attributable to occupational carcinogens was thus assessed individually and collectively by sex, age, and location. Global and regional estimates of 13 occupational chemical carcinogens were made from the beginning of 1990 to the end of 2017, and cancer burdens attributable to each occupational carcinogen were reported in terms of deaths and DALYs (1 DALY means 1 healthy year of life lost).

The Burden of Occupational Cancer

Occupational exposure to carcinogens has been reported to be associated with a substantial disease burden at global, regional, and national levels, and occupational diseases are receiving increasing attention worldwide.

According to a study conducted by the Global Burden of Disease (GBD), approximately 348 thousand cancer deaths in 2016 (including laryngeal, nasopharyngeal, breast, lung, ovarian, mesothelioma, and leukemia) resulted from occupational exposure to 14 carcinogens.

It is estimated that more than 80% of cancers are associated with environmental factors, including external causes (chemical, physical, and biological) and internal causes (genetic, immune, and endocrine).

Among these factors, a high-risk occupational environment plays an important role in the occurrence and progression of tumors. Well-known occupational tumors include asbestos-related lung cancer and mesothelioma, benzene-related bladder cancer, and coal-tar-pitch-related skin cancer. Lung cancer accounts for the largest proportion of occupational cancers.

This recent JAMA study summarized the outcomes of occupational carcinogens (Occupational Carcinogens – Ocs) and was updated several times at global and national levels. To date, no studies have been published that investigate the cancer burden associated with occupational exposure, individually and collectively, for specific cancers.

The map visualizations below show Cancer Deaths and DALYs Attributable to Occupational Carcinogens for All Ages and Both Sexes in 195 Countries (2017 data)

The study shows that exposure to occupational carcinogens is responsible for cancer-related deaths and DALYs globally, and that the associated cancer burden varies greatly between regions according to age, sex, and social development. The individually attributable cancer burden for each occupational carcinogen varied widely, with asbestos and silica exposure associated with the heaviest cancer burden worldwide. Most carcinogens were primarily associated with lung cancer.

Overall, based on GBD 2017, this research identified 13 occupational carcinogens associated with 7 cancers. Consistent with previous studies, this research also identified lung cancer as the cancer type most affected by occupational carcinogens and asbestos as the carcinogen responsible for the greatest number of deaths and DALYs.

Other Supporting Studies

Other studies have reported that exposure to such occupational carcinogens continues in many high-income countries, particularly asbestos, silica, and diesel engine exhaust. However, occupational carcinogen exposures in middle- and low-income countries may be even less controlled and more widespread because of a lack of automatic monitoring equipment and personal protection at work.

Asbestos Exposure and Cancer

For more than the past 30 years, several high-income countries have taken steps to minimize exposure to occupational carcinogens, particularly asbestos. The asbestos industry began to grow in the 20th century, first in Western Europe and then in low-income countries. However, a study conducted in 1960 showed that asbestos exposure was associated with the development of malignant tumors. Since then, European countries have spent a long time controlling the demolition of asbestos-containing structures and restricting asbestos production and transport. Although many European countries had precautionary bans on the disposal of blue asbestos, asbestos use was not banned from 1960 to 1993. Even after asbestos exposure has stopped completely, asbestos-attributable cancer deaths are expected to continue for another 4 to 5 years.

Silica Exposure and Cancer

The silica-related cancer burden ranks second after asbestos. From 2007 to 2017, there was an increase in both case numbers and age-standardized rates. Silica is widespread in nature, and silica-containing materials are frequently used, making it the most common among occupational carcinogens. Workers are exposed to silica in various production activities: quarrying and mining, pottery or ceramics, foundries, and various construction and manufacturing tasks.

Epidemiological studies of the relationship between silica exposure and lung cancer are mainly based on industries including mines, quarries, and granite production sites. A cohort study of the relationship between silica exposure and lung cancer was conducted with 58 677 German uranium miners from 1946 to 2003, and an association between silica exposure and lung cancer was specifically confirmed.

A cohort study conducted in China reported that long-term exposure to silica levels was associated with increased overall and cause-specific mortality. The need to control airborne silica levels and use personal protective devices in practice should therefore be emphasized.

Exposure to asbestos and silica mainly increased the burden of tracheal, bronchial, and lung cancers. Asbestos is also known to increase malignant mesothelioma risk.

Formaldehyde Exposure and Cancer

The occupational carcinogens attributable to leukemia are benzene and formaldehyde. Occupational benzene exposure can occur in many industries, including petroleum, chemical production, and manufacturing, and even in shoemaking, painting, printing, and rubber manufacturing. Formaldehyde is an important industrial chemical, and more than 2 million workers in the United States are exposed to it. Formaldehyde exposure may also occur in everyday life because it is a component of tobacco smoke and is found in household products such as furniture, particleboard, and carpets.