The effect of farm vehicle exhaust emissions on TSNAs
Even low concentrations of nitrogenous gases (NOx) produced during combustion in direct-fired flue-cured barns increase tobacco-specific nitrosamines (TSNAs) in the cured leaf. Previous work in France and Kentucky, and in our recent storage study, has demonstrated that air-cured leaf of stalk-cut plants left hanging on the stick in the barn accumulate more TSNAs than leaf stored in bales for the same amount of time. Air-cured barns are designed to allow farm equipment to drive into the barn to facilitate housing and take-down of the crop, and the NOx from the exhaust emissions from this equipment could be causing this increase in TSNAs. We did a proof of concept study to test whether this could be the case. A high converter selection of TN 90 was grown with normal crop production practices through curing. At the end of the cure, five-stick plots with six plants per stick were transferred from the air-curing barn to each of four sealed cabinets. Exhaust fumes from a 1970 model diesel tractor were ducted into each of three cabinets for 5, 15, or 45 minutes a day for nine days. The fourth cabinet was the untreated check. Leaf samples were collected from each treatment before the start of the gassing treatments, and then 24 hours after the first, third, and ninth exposure. Both 4-(methylnitrosamino)-1-(3-pyridyl)-1-(butanone) (NNK) and N’-nitrosonornicotine (NNN) increased as the cumulative exposure time increased. The rate of increase of NNN slowed after 135 minutes of exposure, but NNK appeared to increase exponentially as exposure increased. This marked increase of TSNAs, albeit under these extreme conditions, warrants further investigation in a more realistic farm situation.