Excellent post with examples. You are right. But can you really say adding more toxins is still beneficial? Plus, I am sure if a study ensued that there would be evidence that direct inhalation of these substances with tar accumulation is still worse--resulting in soldiers having less endurance & energy..
Also, cigarette smoke actually adds more stress (cardiovascular stress). And it is the fine particles that are burned and inhaled that stick to your lungs, not the big particles (friend of mine did a study on WTC dust and cancer).
It's like drinking vodka in cold weather, you feel you warm up, but your body temperature actually drops.
If we go the route of less toxin exposure being beneficial for a soldiers health...what use would the e-cig be? Nicotine is considered a toxin despite the purity and route of delivery.
Aspiration of particulates, whether fine (smaller than 2.5 micrometers in diameter) or larger (over2.5), are a fact of life particularly in urban areas, one example is smog. The lungs are specifically equipped to remove this peril and achieve homeostasis to restore functionality. I submit the pervasive and repeated sandstorms our forces are exposed to are more of a health concern. These sandstorms have both types of particulate matter and as anthropologists/scientists have found....are present in the lungs of remains that were attributed to aspiration over time.
Stress is defined as any change from baseline in human physiological responses. Thus, it carries no value as to if it is judged to be good or bad. Positive changes in your life can overload one's senses and make your heart beat faster from excitement...that is called a stressor because of the change from resting heartbeat. Imagine the "stress" in the normal sexual encounter. Loads of changes from baseline (one hopes).