Formaldehyde: environmental partitioning and vegetation exposed

The combustion of methanol fuels and methyl-t-butyl-ether (MTBE) may result in the release of significantly more formaldehyde into the environment than from the use of conventional fuels. The concern is that increased levels of atmospheric formaldehyde may be detrimental to vegetation. Models were used to simulate the environmental partitioning of formaldehyde and to compare changes in its atmospheric concentrations for three vehicle/fuel scenarios within the South Coast Air Quality Management District, California, USA. Scenario 1 assumed that all vehicles were powered with conventional fuels. Scenario 2 assumed that light- and medium-duty vehicles were flexible-fueled and powered with 100% methanol fuel (M100). Scenario 3 assumed that light- and medium-duty vehicles were dedicated M100 vehicles. The simulations predict that 96.2, 2.2, and 1.6% of ambient formaldehyde partitioned to the air, soil, and water, respectively. Scenario 2 represents the greatest risk to vegetation because atmospheric formaldehyde concentrations could reach 90 ppb. Formaldehyde concentrations in scenario 3 were the lowest and would not exceed 20 ppb. Atmospheric formaldehyde at concentrations that may occur with methanol flexible-fueled vehicles could affect certain plant species according to limited data from the literature.