In recent years, cerium oxide has been used in many different applications, including as a nanoparticle fuel additive to lower particulate matter emissions and boost fuel economy.
ImageCredit/Shutterstock: Rainer Fuhrmann
Many uses of cerium oxide nanoparticles result in the particle making their way into nature, which increases the odds of exposure, potential health effects, and ecological implications. The health impacts of cerium oxide nanoparticles are not just due to their innate toxicity, but also on the degree of physical contact. Even though this may seem logical, several research studies have confirmed the deleterious health effects of cerium oxide nanoparticles on animals.
Cerium Oxide Fuel Additives as a Health Risk
A 2014 study by the United States Environmental Protection Agency (EPA) looked at toxicity differences between standard diesel exhaust and exhaust from diesel with a cerium oxide additive. The study scientists noted that by adding cerium oxide nanoparticles to diesel fuel, boosts fuel efficiency, but results in a transformation of emissions and possibly different health impacts.
To ascertain if cerium-additive diesel fuel causes more adverse effects on the lungs compared to conventional diesel, scientists exposed three different groups of lab rats to filtered air, diesel exhaust and cerium oxide diesel exhaust, for 5 hours daily over two days. The researchers found significant increases in N-acetyl glucosaminidase, a biomarker for lung damage, in the rats that were exposed to the cerium oxide exhaust. There were also minor, statistically insignificant rises in other biomarkers for lung injury in the additive group compared to the conventional diesel exhaust group.
In a separate study, EPA scientists also subjected two groups of lab rats to filtered air or additive exhaust for 5 hours per day, for 2 days or 4 weeks. Examinations of tissue samples indicated a quantity- and time-dependent build-up of cerium oxide in the lungs and liver. The study team also found a delayed clearance of cerium oxide by the lungs. The gas-phase and high levels of additive exhaust boosted lung inflammation at the 2-day mark, the researchers said, suggesting that gas-phase elements and particles influence lung toxicity. Histopathology and electron microscopy showed elevated alveolar septa density as a result of swelling, and heightened levels of macrophages after exposure to cerium oxide.
Taken together, these results reveal that additive exhausts trigger more adverse lung impacts than conventional diesel exhausts. Furthermore, lung and liver build-up of cerium, as well as delayed clearance, are major concerns, in addition to the health effects of standard diesel exhaust.
In a 2017 study, researchers looked specifically at the inhalation of cerium oxide nanoparticles. To reach their conclusion, the study team performed a toxicity study, involving exposing lab rats to aerosols of cerium oxide for 6 hours a day, 5 days a week and over 90 days.
Analyses of the test subjects revealed cerium oxide nanoparticles triggered chronic inflammation in the lungs. Also, the was a direct relationship between the size of nanoparticle dose and lung burden. At high doses, the lungs had difficulty clearing cerium. The study team said long-term damage due to exposure is possible.
Cerium Oxide as a Catalyst for Sustainable Fuels
The significant potential for cerium oxide as a catalyst for sustainable fuels could mean more prevalent use of the compound.
In a 2019 study, researchers from Stanford University described how cerium oxide could be used to more easily create carbon monoxide, a fuel precursor, from carbon dioxide. The key to the process described in the study was the stability of cerium oxide and its capacity to keep carbon in a steady oxidized form.
The study involved cerium oxide as an electrode and did not include an investigation of cerium oxide potentially being incorporated into a carbon monoxide fuel from this process.