Toxicologically Acceptable Levels of Methanol and Formaldehyde Emissions from Methanol-Fueled Vehicles

The increased interest in use of methanol makes it important to determine what levels of methanol and formaldehyde emissions may be acceptable. This paper reviews the available health data for methanol and formaldehyde to define what approximate ranges of concentrations, termed ranges of concern, could be acceptable from a toxicological viewpoint. Air quality models are then used to predict the in-use fleet average exhaust emission levels in localized situations (heavily impacted by mobile sources) corresponding to these ranges of concern. Using predicted fleet compositions, approximate target emission levels are given for the light-duty portion of the fleet which could yield these fleet averages. Finally, there is a brief summary of available methanol and formaldehyde emissions data from neat methanol-fueled vehicles which are compared to the target levels.

In general, most of the design targets have already been met by current neat methanol-fueled vehicles, but some situations may require specific attention with respect to the design of emission control systems (e.g., cold start exhaust and hot soak evaporative emissions).