Occupational cancer is defined as any cancer caused either entirely or partially by exposure to an agent or situation within the work environment. These exposures involve cancer-causing substances, known as carcinogens, which workers may inhale, absorb through the skin, or ingest during their duties. Workplaces expose millions of people to substances that can alter cellular function and lead to uncontrolled cell growth. Although the proportion of all cancers attributable to occupational factors is estimated at between 2% and 8% worldwide, the total number of affected individuals is substantial, and these cancers are considered highly preventable.
Understanding the Link Between Work and Cancer
A defining characteristic of occupational cancer is the long time gap between the initial exposure and the manifestation of the disease, which is known as the latency period. This period often spans decades, making the process of linking a current cancer diagnosis back to a specific workplace exposure from twenty or thirty years earlier difficult. For instance, mesothelioma, a cancer strongly associated with asbestos exposure, commonly develops 20 to 40 years after a person’s first contact with the fibers.
The complexity of attribution is compounded because non-occupational factors, such as smoking or genetics, can also influence cancer risk. Evidence is gathered by confirming exposure to a substance classified as carcinogenic and evaluating the level and duration of that contact. A core concept in this field is the dose-response relationship, which indicates that the risk of developing cancer generally increases with both the concentration of the carcinogen and the length of time a person is exposed. Longer occupational exposure to chemical agents has been shown to have a significantly positive association with increased cancer risk.
The public health burden is substantial, with hundreds of thousands of cancer deaths globally attributed to occupational exposures each year. For example, the World Health Organization estimated that approximately 334,000 cancer deaths in 2017 were due to workplace exposures. These diseases impose significant economic costs on healthcare systems and through lost productivity. Prevention efforts are highly beneficial, as many of the carcinogens found in the workplace are well-known and their risks can be mitigated.
Identifying Major Occupational Carcinogens and High-Risk Settings
Occupational carcinogens can be broadly categorized into chemical, physical, and biological agents, and exposure to these occurs across a wide range of industries. Among chemical carcinogens, asbestos is historically significant, used heavily in construction, shipbuilding, and insulation. Inhaling its fibers is linked to lung cancer and mesothelioma, which affects the lining of the lungs and abdomen.
Other significant chemical agents include benzene, a solvent found in petroleum and industrial processes, which is strongly associated with leukemia, particularly acute myeloid leukemia. Formaldehyde, used in resins and disinfectants, is a known cause of nasal and throat cancers, affecting workers in the funeral industry and manufacturing. Fine particulate matter like crystalline silica dust, common in mining and construction, and diesel engine exhaust, which contains polycyclic aromatic hydrocarbons (PAHs), are classified as human carcinogens linked to lung cancer.
Physical carcinogens include various forms of radiation that affect workers in specific settings. Ionizing radiation exposure, such as from uranium and radon gas, is a known risk for underground miners. Non-ionizing radiation, specifically ultraviolet (UV) radiation from the sun, poses a significant cancer risk for outdoor workers in agriculture, construction, and forestry, increasing the likelihood of skin cancer and melanoma.
Exposure to complex mixtures also contributes to the occupational cancer burden. Wood dust, for instance, is a recognized carcinogen leading to nasopharyngeal cancer in those working in the wood industry. Workers in rubber manufacturing are exposed to various chemicals and toxins that increase the risk of bladder, lung, and stomach cancers. High-risk settings are diverse, encompassing construction, mining, chemical and rubber manufacturing, painting trades, and agriculture, where workers routinely encounter these hazardous substances.
Hierarchy of Controls for Workplace Cancer Prevention
The most systematic and effective strategy for preventing occupational cancer is the application of the Hierarchy of Controls, a universally recognized framework that ranks control measures from the most effective to the least effective. This approach prioritizes intervention at the source of the hazard over measures that rely on worker behavior or protective equipment.
Elimination
The highest level of control is Elimination, which involves removing the carcinogenic substance or hazardous work process entirely from the workplace. This is the most preferred solution because it ensures no exposure can occur.
Substitution
If elimination is not possible, substitution means replacing the hazardous carcinogen with a safer or less toxic alternative. For example, a less volatile solvent might be used instead of a highly carcinogenic one, or water-based products could replace solvent-based paints. Careful review is necessary to ensure the substitute does not introduce new, unrecognized risks to the workplace.
Engineering Controls
This level involves physical changes to the work environment designed to isolate the worker from the hazard. Examples include installing local exhaust ventilation systems to capture airborne contaminants at the source or using enclosed systems to handle chemicals. Isolation barriers and machine guarding are other forms of engineering controls that reduce exposure without requiring significant human interaction.
Administrative Controls
These controls involve changes to work practices and policies to minimize exposure. This includes limiting the duration of time a worker spends in a high-exposure area through job rotation or implementing stringent hygiene practices like mandatory wash stations. Providing comprehensive training on safe work procedures and hazard awareness also falls under this category.
Personal Protective Equipment (PPE)
The last and least effective line of defense is Personal Protective Equipment (PPE), such as respirators, gloves, and protective clothing. PPE is considered the final barrier because its effectiveness relies entirely on correct fit, proper use, maintenance, and the worker’s consistent compliance. While necessary when higher-level controls are insufficient, PPE should never be the primary method for controlling carcinogen exposure in the workplace.