Health effects of soy-biodiesel emissions: mutagenicity-emission factors^*

Abstract

Context: Soy biodiesel is the predominant biodiesel fuel used in the USA, but only a few, frequently conflicting studies have examined the potential health effects of its emissions.

Objective: We combusted petroleum diesel (B0) and fuels with increasing percentages of soy methyl esters (B20, B50 and B100) and determined the mutagenicity-emission factors expressed as revertants/megajoule of thermal energy consumed (rev/MJ_th).

Materials and Methods: We combusted each fuel in replicate in a small (4.3-kW) diesel engine without emission controls at a constant load, extracted organics from the particles with dichloromethane, determined the percentage of extractable organic material (EOM), and evaluated these extracts for mutagenicity in 16 strains/S9 combinations of Salmonella.

Results: Mutagenic potencies of the EOM did not differ significantly between replicate experiments for B0 and B100 but did for B20 and B50. B0 had the highest rev/MJ_th, and those of B20 and B100 were 50% and ∼85% lower, respectively, in strains that detect mutagenicity due to polycyclic aromatic hydrocarbons (PAHs), nitroarenes, aromatic amines or oxidative mutagens. For all strains, the rev/MJ_th decreased with increasing biodiesel in the fuel. The emission factor for the 16 EPA Priority PAHs correlated strongly (r²= 0.69) with the mutagenicity-emission factor in strain TA100 + S9, which detects PAHs.

Conclusions: Under a constant load, soy-biodiesel emissions were 50–85% less mutagenic than those of petroleum diesel. Without additional emission controls, petroleum and biodiesel fuels had mutagenicity-emission factors between those of large utility-scale combustors (e.g. natural gas, coal, or oil) and inefficient open-burning (e.g. residential wood fireplaces).

• Combustion emissions
• complex mixtures
• mutagenicity

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Acknowledgements

Funding for this research was provided by the intramural research program of the Office of Research and Development of the U.S. Environmental Protection Agency, Research Triangle Park, NC.

We thank C.D. Swartz and J.A. Ross for their helpful comments on this manuscript.

Declaration of interest

The authors declare that they have no financial interest associated with the subject of this work. This article was reviewed by the National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency and approved for publication. Approval does not signify that the contents reflect the views of the agency nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

Notes

* Dedicated to the memory of Dr. Joellen Lewtas (1944–2014) who was a pioneer in the fields of diesel-exhaust mutagenicity and bioassay-directed fractionation.