I'm no chemist either so don't quote me on this, but I suspect that it's from the heavy solvents used. PROPERLY made tren isn't bad at all. I have friends that abuse tren and have okay liver values and kidney function. However, so many of the UGLs out there absolutely blast their tren with BA and all that shit for sterility purposes. And that's because they're brewing that shit in a motel bath tub.
I tried some really shitty tren that made me break out in blisters all over. Filtered it and it was better, but still broke out. Got some fina online (pellets and cartridges) and brewed up some tren properly just following some douche bag guide on the internet and I was good to go. It takes a real bonehead to fuck something up as elementary as a tren kit.
Other blends like test/tren/masteron and other UGL "specials" can also be pretty brutal. I have a friend in another province who is an absolute guru. He used to post on the boards years ago and he explained it all to me. I haven't read a study or done much research in a long time but I don't have any reason not to believe him. Most UGL tren = shit. Home brewed tren isn't half as bad. Just goes to show how shitty most UGLs are out there.
When Bill's new book comes out, it's going to expose a lot of fuckers that need to have a bullet buried in their sorry asses. 
Making tren isnt a big deal … that is y I said I would rather make mine cause I can make sure it will b good stuff … and no I don’t make mine … nor do I sell steroids …
I am not on a lot of tren … I am not using anything at all … nor have I lifted since mid April … but hey look at me i am still smiling

The problem is when someone comes here and just wants to argue for the sake of arguing … what I said was it is kidney toxic … it doesn’t mean it will melt ur kidney as soon as u use it … as I said the side effect factor is related to genetics and how your body can handle a certain compound … yes there are people who stay on it for very long time and there are people who get problems at low doses and for a short period of time … I had people stopping tren cause there nuts hurt … now that is not so common but there every one response differently to each drug
Yes what I said is when u get dark urine (on same amount of drinking water daily), ur kidney hurts & get blood cells in ur urine (even if it is not visible) then it is –without having an MBBS- targeting the kidney … and some even get kidney pain because of that
What I said was advising some one to be on tren for “as long as they want” is risky and dangerous … staying 8-10 weeks is not a big deal at all … I had people on it for much longer time … but u cant apply that to everyone …
Explaining how something is toxic is nothing that u can put on paper
Bills new book will talk about purity and contamination in the UG labs products … and as I said that is what plays a big role in the quality of gains these days … as u cant trust labels
As for BA … some speculate that that is the reason of the cough … but a lot of other drugs do use BA as well …. So it could be the combination of tren + BA
Even though I never had a cough issue with human grade products … again depends on what u define as human grade … as having something that is made in Thailand but says made in Italy or uses a name of a reputed brand but is made in a china doesn’t define it as human if it says so …
There are a lot of bodybuilders who stay on test all year around … nothing happens to them … but I never recommended that … as I said in one of my radio shows … I have a standard for what I use (how much & how long) and I follow as I see fit … now in some unorthodox cases taking drastic measures is a must … aging with caution … that is y non of the people I trained ever got sick or fainted back stage