Aerosolized Coal Fly Ash: Risk Factor for Lung Cancer

Introduction: Coal is burned by electric utilities, about 10% remains as ash. The heavy ash settles, while
the light coal fly ash (CFA) condenses and accumulates in the flue gases. In India and China CFA is
usually allowed to exit smokestacks, but in Western nations it is trapped and sequestered for public
health reasons. Epidemiological evidence indicates that aerosolized particulate pollution in the size range
≤ 2.5 μm is associated with numerous risks to health including, but not limited to lung cancer.
Aim: Coal fly ash (CFA) is a major contributor to ambient air pollution in China and India, but it is trapped
and sequestered in Western nations. Members of the public chronically exposed to aerosolized CFA are
likely to have an increased incidence of respiratory disease, including lung cancer. Our objective is to
review the multiple carcinogenic constituents of aerosolized coal fly ash in connection with their
potentiality to cause lung cancer.
Methods: We review the interdisciplinary scientific and medical literature.
Results: CFA contains a variety of potentially carcinogenic substances including aluminosilicates, an iron
oxide-containing magnetic fraction, several toxic trace elements, nanoparticles, and alpha-particleemitting
radionuclides. Silica, arsenic, cadmium, and hexavalent chromium are found in CFA and all
have been associated with increased lung cancer risk. Radical generation catalyzed by transition metals
associated with the particulate matter in CFA can result in a cascade of cell signaling, transcription factor
activation, and mediator release. Ferric iron in the aluminum-silicate glass phase of CFA is a source of
bioavailable iron. There is emerging evidence that reactive iron induces cancer stem cells and aggressive
phenotypes in lung cancer. The potential pulmonary toxicity and carcinogenicity of aerosolized CFA is
suggested by studies of asbestos, a fibrous silicate that also contains iron oxide. CFA contains an
abundance of ultrafine particles and nanoparticles, including magnetite (Fe3O4). These tiny particles are
toxic to lung cells, capable of producing oxidative stress, cytotoxicity, and genotoxicity. Radioactive
elements are concentrated in CFA. CFA can settle deep in the lungs where its alpha-particle-emitting
radionuclides pose significant risk factors for lung cancer.
Conclusion: Considering the well-known and manifold toxicities of CFA, the public should be made
aware of the potential risks for lung cancer and severe respiratory disease posed by aerosolized CFA
including its use in climate alteration activities. CFA contains a plethora of potentially carcinogenic agents
likely to have cumulative additive and/or synergistic interactions with long-term exposure. The CFA
industry can be diligent about minimizing the likelihood of CFA aerosolization for sake of workers and
those living in the proximity of CFA dumps. Jet-spraying of CFA into the regions where clouds form
represents a potential global and previously unrecognized long-term risk factor for respiratory disease
and lung cancer, especially in vulnerable populations.