Scannell has previously mentioned their modeling of exposure to particulates (PM). PMs are only one narrow slice of the the pie. While diesel particulates are a concern (and known carcinogen), exhaust presents many other compounds of interest.

 

As characterized by NIH, other major components of truck exhaust include:

 

Carbon Monoxide - https://pubchem.ncbi.nlm.nih.gov/compound/281

 

Extremely flammable. Toxic Acute Exposure: 420 ppm @ 10 mins causes irreversible damage or inability to escape. 27 ppm @ 8 hours. 130 ppm @ 8 hours is lethal.

 

Carbon Dioxide - https://pubchem.ncbi.nlm.nih.gov/compound/280

 

We are all familiar with CO2.

 

Nitric Oxide - https://pubchem.ncbi.nlm.nih.gov/compound/145068

Heavier than air, fire accelerant. Very toxic inhalant. Forms acid with moisture including lungs. 60-150 ppm causes immediate burning in throat and chest. 6-24 hours after exposure you've got labored breathing and possibly unconsciousness. Concentrations of more than 200 ppm are lethal.

 

Nitrogen Dioxide - https://pubchem.ncbi.nlm.nih.gov/compound/3032552

Forms nitric acid in soil and water, forms smog in atmosphere. Attacks and lingers in lungs.

 

0.5 ppm considered baseline Acute Exposure Level. 20 ppm @ 10 mins causes irreversible or serious long-lasting effects OR inability to escape. 34 ppm @ 10 mins is life threatening or 11 ppm @ 8 hours is lethal.

 

Sulfur Dioxide - https://pubchem.ncbi.nlm.nih.gov/compound/1119

Very toxic by inhalation. Heavier than air and water soluble. Strong irritating odor. Forms sulfuric acid with moisture in soil, water, and lungs.

 

Baseline acute exposure is 0.2 ppm @ 10 mins. Irreversible damage in 10 mins @ 0.75 ppm. Lethal at 30 ppm @ 10 mins or 9.6 ppm @ 8 hours.

 

There are dozens more trace compounds in diesel exhaust. Some notable compounds include Benzene and Formaldehyde.

 

It should be immediately obvious none of these compounds are great for the environment or people. They would not only be present but persistent. All day. Every day. Many are water soluble and heavier than air; meaning they will acidify soil and water. Changes to soil and water can alter productivity, behavior, and in more extreme cases, survival of plants and animals. Experiments such as those conducted by the USGS (https://pubs.er.usgs.gov/publication/ 5211119) have shown even small changes (pH 6.8 -> 5) have major impact. Diesel particulates are only ONE of the problematic compounds this project would introduce to the area. Scannell's statement on particulates was appreciated but limited and not realistic