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Background
Modern petroleum refining involves a complicated system of interrelated chemical reactions that produce a wide variety of petroleum-based products. Many of these reactions require precise temperature and pressure parameters. The equipment and monitoring required to ensure the proper progression of these processes is complex, and has evolved through the advancement of the scientific field of petroleum engineering.

The wide array of high pressure and/or high temperature reactions, along with the necessary chemical additives or extracted contaminants, produces an astonishing number of potential health hazards to the oil refinery worker. Through the advancement of technical chemical and petroleum engineering, the vast majority of these processes are automated and enclosed, thus greatly reducing the potential health impact to workers. However, depending on the specific process in which a worker is engaged, as well as the particular method employed by the refinery in which he/she works, significant health hazards remain.

Although U.S. occupational injuries were not routinely tracked/reported at the time, reports of the health impacts of working in an oil refinery can be found as early as the 1800's. For instance, an explosion in a Chicago refinery killed 20 workers in 1890. Since then, numerous fires, explosions, and other significant events have from time to time drawn the public's attention to the health of oil refinery workers. Such events continue today, with explosions reported in refineries in Wisconsin and Germany in 2018.

However, there are many less visible hazards that endanger oil refinery workers.

Chemical exposures
Given the highly automated and technically advanced nature of modern petroleum refineries, nearly all processes are contained within engineering controls and represent a substantially decreased risk of exposure to workers compared to earlier times. However, certain situations or work tasks may subvert these safety mechanisms, and expose workers to a number of chemical (see table above) or physical (described below) hazards. Examples of these scenarios include:


 * System failures (leaks, explosions, etc.).
 * Standard inspection, product sampling, process turnaround, or equipment maintenance/cleaning activities.

Cancer risks
Interestingly, even though petroleum refineries utilize and produce chemicals that are known carcinogens, the literature on cancer rates among refinery workers is mixed. For example, benzene has been shown to have a relationship with leukemia, however studies examining benzene exposure and resultant leukemia specifically in the context of oil refinery workers have come to opposing conclusions. Asbestos-related mesothelioma is another particular cancer-carcinogen relationship that has been investigated in the context of oil refinery workers. To date, this work has shown a marginally significant link to refinery employment and mesothelioma. Notably, a meta-analysis which included data on more than 350,000 refinery workers failed to find any statistically significant excess rates of cancer mortality, except for a marginally significant increase in melanoma deaths. An additional U.S.-based study included a follow-up period of 50 years among over 17,000 workers. This study concluded that there was no excess mortality among this cohort as a result of employment

BTX
This acronym stands for benzene, toluene, xylene. This is a group of common volatile organic compounds (VOC's) that are found in the oil refinery environment, and serve as a paradigm for more in depth discussion of occupational exposure limits, chemical exposure and surveillance among refinery workers.

Occupational Exposure Limits
OSHA, NIOSH, and ACGIH have all established occupational exposure limits (OEL's) for many of the chemicals above that workers may be exposed to in petroleum refineries.

Routes of Exposure
The most important route of exposure for BTEX chemicals is inhalation due to the low boiling point of these chemicals. The majority of the gaseous production of BTEX occurs during tank cleaning and fuel transfer, which causes offgassing of these chemicals into the air. It should be noted that exposure can also occur through ingestion via contaminated water, but this is unlikely in an occupational setting. Dermal exposure and absorption is also possible, but is again less likely in an occupational setting where appropriate personal protective equipment is in place.

Medical Surveillance
Benzene, in particular, has multiple biomarkers that can be measured to determine exposure. Benzene itself can be measured in the breath, blood, and urine, and metabolites such as phenol, t,t-muconic acid (t,tMA) and S-phenylmercapturic acid (sPMA) can be measured in urine. In addition to monitoring the exposure levels via these biomarkers, employers are required by OSHA to perform regular blood tests on workers to test for early signs of some of the feared hematologic outcomes, of which the most widely recognized is leukemia. Required testing includes complete blood count with cell differentials and peripheral blood smear "on a regular basis". The utility of these tests is supported by formal scientific studies.

Injuries
Workers are at risk of physical injuries due to the large number of high-powered machines in the relatively close proximity of the oil refinery. The high pressure required for many of the chemical reactions also presents the possibility of localized system failures resulting in blunt or penetrating trauma from exploding system components. However, Bureau of Labor (BLS) statistical reports indicate that petroleum refinery workers have a significantly lower rate of occupational injury (0.7 OSHA-recordable cases per 100 full-time workers) than all industries (3.1), oil and gas extraction (1.0), and petroleum manufacturing in general (1.6).

Heat
The temperature required for the proper progression of certain reactions in the refining process can reach 1600 degrees F. As with chemicals, the operating system is designed to safely contain this hazard without injury to the worker. However, in system failures this is a potent threat to workers’ health. Concerns include both direct injury through a heat illness or injury, as well as the potential for devastating burns should the worker come in contact with super-heated reagents/equipment.

Noise
Refineries can be very loud environments, and have previously been shown to be associated with hearing loss among workers. The interior environment of an oil refinery can reach levels in excess of 90 dB. An average of 90 dB is the OSHA Permissible Exposure Limit (PEL) for an 8 hour work-day. Noise exposures that average greater than 85 dB over an 8 hour require a hearing conservation program to regularly evaluate workers' hearing and to promote its protection. Regular evaluation of workers’ auditory capacity and faithful use of properly vetted hearing protection are essential parts of such programs.

Others
While not specific to the industry, oil refinery workers may also be at risk for hazards such as vehicle-related accidents, machinery-associated injuries, work in a confined space, explosions/fires, ergonomic hazards, shift-work related sleep disorders, and falls.

Controls
The theory of hierarchy of controls can be applied to petroleum refineries and their efforts to ensure worker safety.

Elimination/Substitution
This is unlikely in petroleum refineries, as many of the raw materials, waste products, and finished products are hazardous in one form or another (e.g. flammable, carcinogenic).

Engineering
Examples include a fire detection/extinguishing system, pressure/chemical sensors to detect/predict loss of structural integrity, and adequate maintenance of piping to prevent hydrocarbon-induced corrosion (leading to structural failure).

Other examples employed in petroleum refineries include the post-construction protection of steel components with vermiculite to improve heat/fire resistance. Compartmentalization can help to prevent a fire or other systems failure from spreading to affect other areas of the structure, and may help prevent dangerous reactions by keeping difference chemicals separate from one another until they can be safely combined in the proper environment.

Administrative
Careful planning and oversight of the refinery cleaning, maintenance, and turnaround processes. These occur when many of the engineering controls are shut down or suppressed, and may be especially dangerous to workers. Detailed coordination is necessary to ensure that maintenance of one part of the facility will not cause dangerous exposures to those performing the maintenance, or to workers in other areas of the plant. Due to the highly flammable nature of many of the involved chemical, smoking areas are tightly controlled and carefully placed.

Personal Protective Equipment
Depending on the specific chemical being processed or produced, personal protective equipment may be necessary. Particular care is needed during sampling of the partially-completed product, tank cleaning, and other high-risk tasks as mentioned above. Such activities may require the use of impervious outer wear, acid hood, disposable coveralls, etc. More generally, all personnel in operating areas should use appropriate hearing and vision protection, avoid clothes made of flammable material (nylon, Dacron, acrylic, or blends), and full-length pants/sleeves.

Policies/Regulations
Worker health and safety in oil refineries is closely monitored by both OSHA and NIOSH. CalOSHA has been particularly active in regulating worker health in this industry, and adopted a policy in 2017 that requires petroleum refineries to perform a Hierarchy of Hazard Controls Analysis (see above "Controls" section) for each process safety hazard.

Below is a list of the most common regulations referenced in petroleum refinery safety citations issued by OSHA:

Flammable and Combustible Liquids (29 CFR 1910.106)

The Hazard Communication (HazCom) standard (29 CFR 1910.1200)

Permit-Required Confined Spaces (29 CFR 1910.146)

Hazardous (Classified) Locations (29 CFR 1910.307)

The Personal Protective Equipment (PPE) standard (29 CFR 1910.132)

The Control of Hazardous Energy (Lockout/Tagout) standard (29 CFR 1910.147)