Diesel engines emit a complex mixture of air pollutants, composed of gaseous and solid material. The visible emissions in diesel exhaust are known as particulate matter (PM), which includes carbon particles or "soot." In 1998, ARB identified diesel PM as a toxic air contaminant. Health risks from diesel PM are highest in areas of concentrated emissions, such as near ports, rail yards or freeways.
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The Placer County Air Pollution Control District requested the California Air Resources Board (ARB) study on behalf of Placer county residents to learn the levels of diesel emissions from the J.R. Davis Rail Yard and their relative impact. The District requested the study because of residents' concerns and because the ARB had identified "diesel particulate matter" as a toxic air contaminant.
The study results indicate high concentrations of "diesel particulate matter" which can cause cancer, in an area surrounding the rail yard. The level of cancer risk associated with diesel emissions from the rail yard depends on length of exposure and proximity to the yard.
The District is committed to working with Union Pacific to reduce emissions at the rail yard. The Air Resources Board (ARB) is also involved in this effort. Both the District and ARB have formalized agreements with Union Pacific to take specific actions to reduce emission from the rail yard.
There are no practical personal protective measures recommended for healthy individuals. Individuals with unique sensitivities such as chronic lung disease or asthma may consider indoor air filtering units such as those described on the Air Resources Board website.