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  • Jacob Sumner

Coke Oven Emissions: What's in Allegheny County's Air?

Updated: Jul 29, 2021

By Jacob Sumner

Photo by Vladimir from Pexels


Take a drive through the Mon Valley with your windows down. Smell something? The scent is foul, almost reminiscent of rotten eggs. Residents of the area near the Clairton Coke Works can tell you: they deal with this smell on a daily basis. Some have even smelled it so much that they have grown disconnected from it, only reminded of its presence when their eyes water or when they suddenly feel lightheaded. This begs several questions. What is in the air here? Is it dangerous to breathe? Why does this smell persist despite years of improvement to equipment within the Clairton Coke Works?

The main culprit behind the "rotten egg" smell is called hydrogen sulfide (H2S). Aside from producing a foul odor, H2S has been linked to respiratory illness and can prove to be particularly problematic for those with preexisting respiratory conditions. When considering that residents of Clairton are nearly twice as likely to develop asthma than other residents of Allegheny County, the issue begins to take shape. While there has been a safe H2S emissions limit set by the state, U.S. Steel's Clairton Coke Works has regularly violated this limit. The standard requires that entities do not exceed an average of .005 parts per million (ppm) of H2S in 24 hour period. The seven violations of this standard (this year alone) by the Clairton Coke Works ranged from .006 ppm to .009 ppm, with the high end of these concentrations almost doubling the acceptable limit (“Health Department Issues").

Hydrogen sulfide is not the only potentially harmful substance emitted by the coke production process. A more dangerous class of coke oven emissions, Polycyclic Aromatic Hydrocarbons (or PAH's, for short), are known human carcinogens, meaning they are known to cause certain types of cancer in people exposed to them. PAH's and other coke oven emissions are directly linked to the development of both kidney and lung cancer, and further research is being done to study their effects on the skin and pancreas (“Report on Carcinogens, Fourteenth Edition.”). If these effects sound familiar, it may be because cigarettes contain hundreds of these PAH's (Vu, An, et al).

There are several other compounds given off as byproducts of the coke-making process that are known to be dangerous. Nitrosamines, for instance, are thought to cause extensive DNA damage to those exposed to a heavy concentration or continuously over a long period of time. They are known to cause cancer in animals and possibly humans (Swager and Beard). Coal tar, although less of a threat to those outside of production sites, is known to cause skin cancer in workers. Furthermore, because it contains the carcinogenic compound benzene, prolonged exposure to coal tar is thought to be linked to lung cancer and certain urinary and digestive tract cancers (“Coal Tar and Coal-Tar Pitch.”). Benzene also causes a range of other serious problems. In the case of short-term exposure, it can cause drowsiness, vomiting, and irregular heartbeat, while long-term exposures can result in irreversible bone marrow damage, disrupted menstrual cycles in women, and immune system deficiencies.

The last few decades have forced polluters to alter their processes and equipment to keep the public safe from these harmful substances. As a result, plants often recycle several of the vapor, gas, and solid byproducts back into the process. However, even with these protocols, defects in the coke ovens and improper execution of these tasks expose both workers and nearby residents to unsafe levels of PAH's and H2S, among other potentially harmful substances.

Understanding the nature of these harmful emissions is important in understanding the danger posed to residents of the Mon Valley. For this reason, we will be posting more descriptive guides for each class of coke oven emissions. Hopefully, in doing so, we will allow those interested in joining our fight to see the true extent of the damage caused by polluters of the Mon Valley and the hardships faced by its residents every day.


Works Cited

“Coal Tar and Coal-Tar Pitch.” National Cancer Institute, 28 Dec. 2018,

“Coke Manufacturing.” World Bank Group, 1998.

“Coke Oven Emissions - Cancer-Causing Substances.” National Cancer Institute,

“Facts About Benzene.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 4 Apr. 2018,

“Health Department Issues Notice Of Violation to U.S. Steel Over Hydrogen-Sulfide Exceedances.” GASP, Group Against Smog and Pollution, 1 Apr. 2021,

“Hydrogen Sulfide (H2S).” Occupational Safety and Health Administration.

“Hydrogen Sulfide and Carbonyl Sulfide.” Center For Disease Control and Prevention.

“List of Alkylating Agents.”,

“Polycyclic Aromatic Hydrocarbons (PAHs) Factsheet.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 7 Apr. 2017,

“Report on Carcinogens, Fourteenth Edition.” National Toxicology Program, 1981.

Swager , Timothy M., and Jessica C. Beard. “An Organic Chemist's Guide to N-Nitrosamines: Their Structure, Reactivity, and Role as Contaminants.” ACS Publications, 21 Jan. 2021,

Vu, An T, et al. “Polycyclic Aromatic Hydrocarbons in the Mainstream Smoke of Popular U.S. Cigarettes.” Chemical Research in Toxicology, U.S. National Library of Medicine, 17 Aug. 2015,

Wereschagin, Mike. “Cokeless Steel?” Pittsburgh Quarterly, 20 Aug. 2017,

Yang, Kai, et al. “Effects of Coke Oven Emissions and Benzo[a]Pyrene on Blood Pressure and Electrocardiogram in Coke Oven Workers.” Journal of Occupational Health, Japan Society for Occupational Health, 24 Jan. 2017,

“GASP, Residents Hold Press Conference to Tell ACHD: Revise Coke Oven Regs & Get a Handle On H2S Violations: Group AGAINST Smog and Pollution.” GASP,

“Ambient Standards.” Department of Environmental Protection,

“Hydrogen Sulfide & Health.” California Air Resources Board,

“Hydrogen Sulfide - Hazards .” Occupational Safety and Health Administration, United State Department of Labor,

“Hydrogen Sulfide.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 21 Oct. 2014,

McDowell, Sandy. “What Is Methemoglobinemia>.” Healthline, Healthline Media, 1 Sept. 2018,

Saeedi, A, et al. “Effects of Long-Term Exposure to Hydrogen Sulfide on Human Red Blood Cells.” NCBI, US National Library of Medicine, 1 Jan. 2015,

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