Mendocino County Air Quality Management District comments on air quality

Mendocino County Air Quality Management District saw a link to our post The bypass is good for the children, and here is what Bob Scaglione, Senior Air Quality Specialist and Acting Air pollution Control Officer, shared…

The Air District supports and encourages the Willits Bypass project, primarily because of the benefit of the significant reduction in air contaminants from idling vehicles and their impact on the local community.

Diesel particulate emissions have been identified by the Air Resources Board as a Toxic Air Contaminant, capable of increasing risks to human health. This risk is greater in children, with developing lungs, as well as older people and those with chronic respiratory symptoms. Further information concerning the health affects of diesel exhaust is available at the California Air Resources Board web site as well as the Office of Environmental Health Hazard Assessment at .

One of the factors of concern to the District is the affect of idling vehicles, especially heavy on-road trucks. The nature and constituents of diesel exhaust change during the idling process, producing greater levels of NOx, Particulate, and CO emissions at idle than an engine at full load. Research information at ARB’s web site indicate that particulate at idling is produced in greater quantities at much finer particle size per cylinder cycle than a normally operating engine. This allows for the particles to stay airborne longer and impact a larger portion of the surrounding community.

I have attached a brief summary of the information available at the ARB web site which outlines the District’s concerns. I believe you already have the OEHHA report of Health Effects of Diesel Exhaust. I hope this information is of value and should you need anything else, please let me know.


Bob Scaglione

Senior Air Quality Specialist

Acting Air Pollution Control Officer


Attachment – Effects of Idling Diesel Trucks