March 16, 2015: What exposures occur during refining?

Crude oil is a complex mix of hydrocarbons benzene, sulfur, nitrogen, chromium, toluene, and xylene. Crude oil is used to make fuel and other petroleum products.and is refined to produce gasoline. It is during the refining process that exposures occur that can cause toxicity.

Workers can be exposed to toxins during drilling, pumping, treating, transport by pipeline, ship, rail, and storage.  For example, volatile components at well heads, pumps, or through vents in storage tanks and ship’s tanks, create a potential for exposure via inhalation. Crude oils with high concentrations of sulfur can result in inhalation of hydrogen sulfide gas, particularly in confined spaces, well head and storage tanks. Inhalation of benzene, toluene, and xylene can also occur.  Human epidemiology data revealed inadequate evidence for carcinogenicity, and therefore crude oil is not classified as carcinogenic.


Typically, crude is transferred to a refinery distillation unit (see diagram below) that separates the crude into different petroleum products. During these processes, carbon monoxide, polycyclic aromatic hydrocarbons (PAH), petroleum asphalt, petroleum coke, chlorine, chromium, and other products are produced and are potential toxins.


Petroleum products have negative impact on the environment and on human health. As petroleum products burn as fuel, they emit gases into the atmosphere, which are potential sources of global warming. Some of these gases emitted include carbon dioxide, carbon monoxide, sulfur dioxide, nitrogen oxides, volatile organic compounds, and particulate matter.


Petroleum industry operations present wide varieties of exposure. Chemicals and chemical mixtures have not been fully characterized for their potentially adverse health effects in workers. There is no evidence of significantly increased risk of cancer in petroleum refinery workers. Non cancer exposures cause skin irritation, skin sensitization, and dermatitis.

Refinery Process Diagram


  1. Work Safe: Occupational Disease Hazards in the Oil and Gas Industry.
  2. National Institute of Health: Crude Oil.
  3. Environmental Protection Agency: Addressing Air Emissions from the Petroleum Refinery Sector.
  4. United States Department of Transportation: Fact Sheet: Refineries.


This question prepared by:  Elmang Nchako, MD, MPH   (Occupational Medicine Resident-PGY 3)   Department of Family and Community Medicine   Meharry Medical College


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Medical Director

Tennessee Poison Center

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