Mosspa, I am interested in hearing your thought on this small study. I found it interesting, but am not convinced that in a larger study, gender brain function would not be that defined. I think some of us are wired a little differently.
YaleNews | Smoking lights up brain
As for the study, it seems reasonable. There have been a lot of differences reported between sexes in how things are processed by the brain. The biggest problem with this study is that it is based on the idea that nicotine is responsible for the activity they are measuring. Since they haven't isolated nicotine they have no way of knowing what is causing the effect. Any number of things associated with smoking behavior could account for it, even the completion of one chain of smoking behavior, itself (i.e., which would be what I would argue without seeing some convincing data to the contrary).
Another question I have for you is your opinion on food grade verses pharmaceutical grade PG or VG, as it related to "inhalation toxicity".
I buy my PG from the pharmacy but it seems to be a "cosmetic grade" maybe. There seems to be a difference, I assume in purity between that sold in 500 ml bottles and 473 ml bottles. A compounding pharmacy wanted $50 for 500 ml of pharmacy grade.
One bottle I have even says "Federal law prohibits dispensing without a prescription". Your thoughts?
Yes, that is an incredibly good question, and one that I can attempt to answer based on my experiences. If you have read about my personal experiences and decisions in this thread you will realize that I am different than most people who read this forum. When I started vaping last December, I had not smoked a cigarette in about 42 years. When I was between 32 and 45 I was in the best physical condition of my life and I try to continue to maintain a healthy lifestyle. As I aged to my present age of 60 I started noticing little cognitive defects that I didn't like. I found myself to pause more during oral presentations, and I found the occurrence of 'senior moments' seemed to introduce themselves into my well rehearsed lectures. I was never convinced that nicotine was particularly toxic (because it really isn't at any reasonable level one might attain by vaping), and due to my reading of the scientific literature and from experiments I performed in my research laboratories on rat models of dependence, I was also convinced that 'nicotine addiction' is a myth. Also, the links between cancer and nicotine have never been demonstrated to exist, so, if I didn't spend the last 16 years of my pre-academic career directing a major government toxicology lab with a sophisticated inhalation toxicology capability, I probably would have started vaping as soon as the e-cig was invented (circa 2008?). It took up to last December for me to actually try inhaling nicotine-laced vapors because I was concerned about the effects of deeply inhaling small atomized particles of ANYTHING into my lungs. I tried to apply lung models developed at the lab to the particles of propylene glycol and glycerol inhaled during vaping but I could never come to any firm conclusion. What enabled my first vaping was constant scrutiny of the epidemiology of vaping for adverse effects in lung toxicity endpoints, including irritation, blood oxygenation, and onset of COPD-like symptoms, and not finding any. My reasoning was that by the end of 2014, the overall population of vapers would be large enough for those kinds of adverse effects to start showing up if they were, in fact, there. That they hadn't gave me the green light to start vaping.
Now, to answer your question (and this is only my answer given my biases). Back to purity of lifestyle, the way I see it is: why introduce complicating variables like contaminants in juice into a prognosis situation that is still somewhat unknown. The USP grades reagents by levels of various contaminants in representative sampled batches. So, for whatever juice mixture I brew, I try to limit the impurities as best I can. So, for PG and VG I purchase only pharmaceutical grade alcohols, since these are the ones that have been used for decades in pharmaceutics, even in inhalers, without respiratory incident. Additionally, I use only pharmaceutical grade nicotine, because there are many known detrimental contaminants from various processing and oxidizing events that can result in plant extraction/distillation processes. As I said, I started using Vuse e-cigs from Winston-Reynolds because, believe it or not, I trusted the product to contain what the spectroanalyses the company was providing the government indicated they contained, in it's attempt to conquer the vaping market. The sprctrographs were pretty clean and they served to ease my paranoid mind

Since then, I have found one vape company that I will consistently use in the future, if for no other reason than my trust of the purity of their juices, alcohols, and nicotine (they even advertize the fact that they use pharmaceutical grade nicotine and why). The company I use is MyFreedomSmokes.com. However, I've only been at this for about 3 months, and my overall knowledge of vaping products available is somewhat lacking. I'm sure there are other suppliers of equally-pure stuffs out there, I just haven't looked for them because I'm satisfied with MFS. Note: I don't even including flavorings in my juices because I view them as additional contaminants.
There isn't any truly empirical reason for me to believe the way I do, but it makes me sleep easier. Experience would suggest, however, that to err on the side of caution is probably a good thing.